# server.R for DWD App

# Helper function for label generation
generate_station_label <- function(name, id, state, start_date, end_date, detailed_summary,
                                   overall_start = NULL, overall_end = NULL, resolution = NULL) {
    tryCatch(
        {
            format_range <- function(start_val, end_val) {
                format_val <- function(value, is_end = FALSE) {
                    if (is.null(value) || is.na(value) || value == "") {
                        return("Unknown")
                    }

                    if (inherits(value, "Date")) {
                        return(format(value, "%Y-%m-%d"))
                    }

                    value <- as.character(value)
                    if (value == "99999999") {
                        return(if (is_end) "Present" else "Unknown")
                    }
                    if (value == "00000000") {
                        return("Unknown")
                    }

                    if (grepl("^\\d{4}-\\d{2}-\\d{2}$", value)) {
                        d <- as.Date(value)
                    } else {
                        d <- as.Date(value, format = "%Y%m%d")
                    }
                    if (is.na(d)) {
                        return("Unknown")
                    }
                    format(d, "%Y-%m-%d")
                }

                paste0(format_val(start_val, FALSE), " to ", format_val(end_val, TRUE))
            }

            res_label <- if (is.null(resolution) || is.na(resolution) || resolution == "") {
                "Data"
            } else {
                paste0(toupper(substr(resolution, 1, 1)), substr(resolution, 2, nchar(resolution)))
            }

            station_range <- format_range(start_date, end_date)
            coverage_start <- if (is.null(overall_start)) start_date else overall_start
            coverage_end <- if (is.null(overall_end)) end_date else overall_end
            coverage_range <- format_range(coverage_start, coverage_end)
            summary_text <- if (is.null(detailed_summary) || is.na(detailed_summary) || detailed_summary == "") {
                "No Data"
            } else {
                detailed_summary
            }

            paste0(
                "<div style='font-size:18px; max-width: 400px;'>",
                "<b>", htmltools::htmlEscape(name), "</b> (", id, ")<br>",
                "<span style='font-size:80%;'>State: ", htmltools::htmlEscape(state), "</span><br>",
                "<span style='font-size:80%; color:#555;'>",
                "Station Active: ", station_range,
                "</span><br>",
                "<span style='font-size:80%; color:#555;'>",
                res_label, " Coverage: ", coverage_range,
                "</span><br>",
                "<div style='font-size:80%; color:#333; font-weight:bold; margin-top:5px;'>",
                "Data Availability (", res_label, "):</div>",
                "<div style='font-size:75%; color:#333; line-height: 1.1;'>• ",
                paste0(
                    gsub(", ", "<br>• ", htmltools::htmlEscape(summary_text)),
                    "<br><small><i>Note: 'Present' indicates ongoing monitoring;<br>",
                    "some parameters may have<br>",
                    "upload delays.</i></small>"
                ),
                "</div>",
                "</div>"
            )
        },
        error = function(e) {
            paste0("<b>", htmltools::htmlEscape(name), "</b> (", id, ")")
        }
    )
}

server <- function(input, output, session) {
    # --- Reactive Values ---
    current_station_id <- reactiveVal(NULL)
    station_data <- reactiveVal(NULL) # The loaded data
    loading_status <- reactiveVal(FALSE)
    loading_diagnostics <- reactiveVal("")
    previous_station_choices <- reactiveVal(NULL) # Track previous choices to avoid blink
    previous_date_range <- reactiveVal(NULL) # Track previous date range for bi-directional sync
    url_initialized <- reactiveVal(FALSE)

    # MapLibre Reactive Values
    style_change_trigger <- reactiveVal(0) # Trigger station re-render after style change
    map_initialized <- reactiveVal(FALSE) # Track if map bounds have been set
    stations_before_id <- reactiveVal(NULL) # Layer ID for station ordering
    current_raster_layers <- reactiveVal(character(0)) # Track dynamically added raster layers

    # Map bounds for Germany
    map_bounds <- list(
        lng_min = 5.5,
        lat_min = 47.0,
        lng_max = 15.5,
        lat_max = 55.5
    )

    # --- URL Parameter Parsing ---
    parse_url_params <- function(query) {
        params <- list()
        if (length(query) == 0) {
            return(params)
        }

        # Helper to decode
        decode <- function(x) URLdecode(x)

        # Parse query string
        pairs <- strsplit(query, "&")[[1]]
        for (pair in pairs) {
            parts <- strsplit(pair, "=")[[1]]
            if (length(parts) == 2) {
                key <- parts[1]
                val <- decode(parts[2])
                params[[key]] <- val
            }
        }
        params
    }

    # Observer: Apply URL params on app startup
    observe({
        req(!url_initialized())
        query <- session$clientData$url_search
        # Wait for query to be available (it might be empty string initially)
        # But we also want to handle no-params case to set initialized=TRUE

        # Parse query (even if empty to confirm no params)
        # Note: session$clientData$url_search usually starts with "?"
        q_str <- sub("^\\?", "", query)
        params <- parse_url_params(q_str)

        # If params exist, apply them
        if (length(params) > 0) {
            # 1. Resolution
            if (!is.null(params$resolution)) {
                updateRadioButtons(session, "data_resolution", selected = params$resolution)
            }

            # 2. Date Range
            if (!is.null(params$start) && !is.null(params$end)) {
                updateDateRangeInput(session, "date_range", start = params$start, end = params$end)
            }

            # 3. State/Land Selection
            if (!is.null(params$landname)) {
                updateSelectizeInput(session, "state_selector", selected = params$landname)
            }

            # 4. Station Selection
            if (!is.null(params$station)) {
                station_ref <- params$station
                # We need to wait for stations to load?
                # The all_stations() reactive depends on resolution.
                # Just updating the input might trigger the search.
                # Note: station_selector choices are updated dynamically.
                # We might need to handle this carefully if stations aren't loaded yet.
                # However, updateSelectizeInput usually works nicely.

                # Check if we need to set selected
                shinyjs::delay(500, {
                    # Try to find ID if name was passed
                    # For now just set the value, assuming ID or Name match
                    # DWD station selector choices are "Name (ID)" = ID.

                    # If passed param is a name, we might need to lookup.
                    # But if we rely on broadcast sending Name, URL has Name.
                    # DWD selector needs ID.

                    # Search in current all_stations()
                    current_st <- isolate(all_stations())
                    if (!is.null(current_st)) {
                        # Try match ID
                        match <- current_st %>% filter(id == station_ref)
                        if (nrow(match) == 0) {
                            # Try match Name
                            match <- current_st %>% filter(name == station_ref)
                        }

                        if (nrow(match) > 0) {
                            target_id <- match$id[1]
                            updateSelectizeInput(session, "station_selector", selected = target_id)

                            # Also trigger details panel if view implies it
                            # The observer for station_selector will run and trigger map logic
                        }
                    }
                })
            }

            # 4. View/Tab
            if (!is.null(params$view)) {
                view <- params$view
                shinyjs::delay(800, {
                    if (view == "map") {
                        nav_select("main_nav", "Map View") # using bslib way or updateNavbarPage
                        # DWD ui uses page_navbar id="main_nav".
                        # updateNavbarPage(session, "main_nav", selected = "Map View") should work?
                        # Or custom message if updateNavbarPage isn't standard in bslib setups?
                        # UI line 3: id="main_nav".
                    } else if (view == "station-info") {
                        updateNavbarPage(session, "main_nav", selected = "Stations Info")
                    } else if (grepl("dashboard", view)) {
                        updateNavbarPage(session, "main_nav", selected = "Dashboard")

                        if (view == "dashboard-data") {
                            shinyjs::delay(200, {
                                nav_select("dashboard_subtabs", "Data")
                                # navset_card_pill id="dashboard_subtabs"
                            })
                        }
                    }
                })
            }
        }

        url_initialized(TRUE)
    })

    # --- Reactive Data Sources (Resolution Dependent) ---
    observeEvent(input$data_resolution,
        {
            session$sendCustomMessage("freezeUI", list(text = "Switching resolution..."))

            # Update date range based on resolution
            res <- tolower(input$data_resolution)

            tryCatch(
                {
                    new_end <- Sys.Date()
                    if (res %in% c("monthly", "daily")) {
                        # For Monthly/Daily: default to last 6 years
                        new_start <- new_end - (365 * 6)
                    } else {
                        # For Hourly: default to last 1 year (366 days)
                        new_start <- new_end - 366
                    }
                    updateDateRangeInput(session, "date_range", start = new_start, end = new_end)
                },
                error = function(e) {
                    message("Note: Could not update date range: ", e$message)
                }
            )
        },
        priority = 1000,
        ignoreInit = TRUE
    )

    current_index <- reactive({
        req(input$data_resolution)
        # Identify resolution (default hourly)
        res <- tolower(input$data_resolution)
        # Load File Index (for data fetching only)
        load_dwd_index(res)
    })

    all_stations <- reactive({
        req(input$data_resolution)
        res <- tolower(input$data_resolution)
        # Load enriched stations from pre-generated cache
        load_enriched_stations(res)
    })

    # Observe and Update State Selector
    observe({
        st <- all_stations()
        req(st)
        # Get unique states
        states <- sort(unique(st$state))

        # Update choice - preserve selection if possible (handled by Shiny usually)
        # We use server=TRUE for performance if list is long (states is short but good practice)
        updateSelectizeInput(session, "state_selector", choices = states, server = TRUE)
    })

    # --- Freeze UI During Data Loading ---
    # Disable all interactive controls (except map hovering) while parsing data
    observe({
        is_loading <- loading_status()

        # List of input IDs to disable/enable
        inputs_to_toggle <- c(
            "state_selector",
            "station_selector",
            "date_range",
            "zoom_home",
            "main_nav",
            "download_hourly"
        )

        if (is_loading) {
            for (inp in inputs_to_toggle) {
                shinyjs::disable(inp)
            }
        } else {
            for (inp in inputs_to_toggle) {
                shinyjs::enable(inp)
            }
        }
    })

    # Filtered stations based on Sidebar inputs
    filtered_stations <- reactive({
        req(all_stations(), input$date_range)
        df <- all_stations()

        # Filter by Date (Strict File Availability)
        # We check if the station has specific data files overlapping the range
        range_start <- as.numeric(format(input$date_range[1], "%Y%m%d"))
        range_end <- as.numeric(format(input$date_range[2], "%Y%m%d"))

        # Filter by State
        if (!is.null(input$state_selector) && length(input$state_selector) > 0) {
            df <- df %>% filter(state %in% input$state_selector)
        }

        df <- df %>% filter(
            as.numeric(station_overall_start) <= range_end &
                as.numeric(station_overall_end) >= range_start
        )

        # Defensive: atomic data.frame to prevent tibble/rowwise issues
        as.data.frame(df)
    })

    # Initialize / Update Station Selector Choices
    observe({
        df <- filtered_stations()
        req(df)

        # Create choices: "Station Name (ID)" = "ID"
        # Defensive: Ensure atomic vectors
        ids <- as.character(df$id)
        names <- paste0(as.character(df$name), " (", ids, ")")

        if (length(ids) > 0) {
            new_choices <- setNames(ids, names)
        } else {
            new_choices <- character(0)
        }

        # Only update if choices have actually changed (compare IDs)
        prev_choices <- previous_station_choices()
        new_ids <- sort(unname(new_choices))
        prev_ids <- if (!is.null(prev_choices)) sort(unname(prev_choices)) else NULL

        if (is.null(prev_ids) || !identical(new_ids, prev_ids)) {
            # Preserve selection if still in filtered list
            current_sel <- input$station_selector

            updateSelectizeInput(session, "station_selector",
                choices = new_choices,
                selected = current_sel,
                server = TRUE
            )
            previous_station_choices(new_choices)
        }
    })


    # Helper: Broadcast current state to parent page
    broadcast_state <- function(view_override = NULL) {
        # Get active station
        sid <- current_station_id()
        st_meta <- NULL
        if (!is.null(sid)) {
            all <- isolate(all_stations()) # Use isolate to avoid dependency loop if called inside observer?
            # Actually active observers call this, so it's fine.
            if (!is.null(all)) {
                st_meta <- all %>%
                    filter(id == sid) %>%
                    head(1)
            }
        }

        station_id <- if (!is.null(st_meta) && nrow(st_meta) > 0) as.character(st_meta$id) else NULL
        station_name <- if (!is.null(st_meta) && nrow(st_meta) > 0) as.character(st_meta$name) else NULL
        landname <- if (!is.null(st_meta) && nrow(st_meta) > 0) as.character(st_meta$state) else NULL

        # Ensure we have a valid resolution string (Capitalized from UI?)
        resolution <- input$data_resolution

        # Determine current view
        main_tab <- input$main_nav
        view <- if (!is.null(view_override)) {
            view_override
        } else if (!is.null(main_tab)) {
            if (main_tab == "Map View") {
                "map"
            } else if (main_tab == "Stations Info") {
                "station-info"
            } else if (main_tab == "Dashboard") {
                subtab <- input$dashboard_subtabs
                # If subtab is NULL/loading, default to plots
                if (!is.null(subtab) && subtab == "Data") {
                    "dashboard-data"
                } else {
                    "dashboard-plots"
                }
            } else {
                "map"
            }
        } else {
            "map"
        }

        start_date <- if (!is.null(input$date_range)) as.character(input$date_range[1]) else NULL
        end_date <- if (!is.null(input$date_range)) as.character(input$date_range[2]) else NULL

        session$sendCustomMessage("updateParentURL", list(
            station = station_id,
            stationName = station_name,
            landname = landname,
            resolution = resolution,
            view = view,
            start = start_date,
            end = end_date
        ))
        # Debug notification
        # showNotification(paste("Broadcasting:", station_name), duration = 3, type = "message")
    }

    # --- Selection Logic via Dropdown ---
    observeEvent(input$station_selector, {
        req(input$station_selector)
        id_val <- input$station_selector

        # Find station details
        s_meta <- all_stations() %>% filter(id == id_val)
        req(nrow(s_meta) > 0)

        lat_val <- s_meta$latitude[1]
        lng_val <- s_meta$longitude[1]

        # Set ID
        # Optimization: If ID is same as current, do not re-trigger date resets or map moves
        # This prevents circular loops where Date Filter -> Filtered List -> Update Selector -> Trigger Observer -> Reset Date
        prev_id <- current_station_id()
        if (!is.null(prev_id) && prev_id == id_val) {
            return()
        }

        current_station_id(id_val)

        # Highlight & Zoom
        # Generate Label
        res <- if (is.null(input$data_resolution)) NULL else tolower(input$data_resolution)
        overall_start <- if ("station_overall_start" %in% names(s_meta)) s_meta$station_overall_start[1] else s_meta$start_date[1]
        overall_end <- if ("station_overall_end" %in% names(s_meta)) s_meta$station_overall_end[1] else s_meta$end_date[1]
        lbl <- generate_station_label(
            s_meta$name[1], s_meta$id[1], s_meta$state[1],
            s_meta$start_date[1], s_meta$end_date[1], s_meta$detailed_summary[1],
            overall_start, overall_end, res
        )

        highlight_selected_station(maplibre_proxy("map"), lng_val, lat_val, lbl)

        # Trigger Panel
        output$show_details_panel <- reactive(TRUE)
        outputOptions(output, "show_details_panel", suspendWhenHidden = FALSE)

        # NOTE: Date reset removed to preserve user context
    })

    # Station Count
    output$station_count_filtered <- renderText({
        n <- nrow(filtered_stations())
        paste(n, "stations found")
    })

    # --- Map ---
    output$map <- renderMaplibre({
        maplibre(
            style = "https://basemaps.cartocdn.com/gl/positron-gl-style/style.json",
            center = c(10.45, 51.16),
            zoom = 6
        ) %>%
            add_navigation_control(show_compass = FALSE, visualize_pitch = FALSE, position = "top-left")
    })

    # Initialize map bounds only once
    observe({
        req(!map_initialized())
        req(input$map_zoom)

        maplibre_proxy("map") %>%
            fit_bounds(
                c(map_bounds$lng_min, map_bounds$lat_min, map_bounds$lng_max, map_bounds$lat_max)
            )

        map_initialized(TRUE)
    })

    # Zoom to extent of all filtered stations
    observeEvent(input$zoom_home, {
        df <- filtered_stations()
        req(df)
        if (nrow(df) > 0) {
            # Calculate bounds
            lons <- range(df$longitude, na.rm = TRUE)
            lats <- range(df$latitude, na.rm = TRUE)

            # If only one station, zoom to it with a small buffer
            if (nrow(df) == 1) {
                maplibre_proxy("map") %>%
                    fly_to(center = c(df$longitude[1], df$latitude[1]), zoom = 12)
            } else {
                maplibre_proxy("map") %>%
                    fit_bounds(c(lons[1], lats[1], lons[2], lats[2]), animate = TRUE)
            }
        }
    })

    # Zoom to extent when state selection changes
    observeEvent(input$state_selector,
        {
            df <- filtered_stations()
            req(df)
            if (nrow(df) > 0) {
                # Calculate bounds
                lons <- range(df$longitude, na.rm = TRUE)
                lats <- range(df$latitude, na.rm = TRUE)

                if (nrow(df) == 1) {
                    maplibre_proxy("map") %>%
                        fly_to(center = c(df$longitude[1], df$latitude[1]), zoom = 12)
                } else {
                    maplibre_proxy("map") %>%
                        fit_bounds(c(lons[1], lats[1], lons[2], lats[2]), animate = TRUE)
                }
            }
        },
        ignoreInit = TRUE
    )

    # Fix Map Rendering on Tab Switch
    observeEvent(input$main_nav, {
        if (input$main_nav == "Map View") {
            # Slight delay to ensure tab is visible - MapLibre handles resize automatically
            shinyjs::runjs("
                setTimeout(function() {
                    var map = document.getElementById('map');
                    if (map && map.__mapgl) {
                        map.__mapgl.resize();
                    }
                }, 200);
            ")
        }
    })

    # --- Basemap Switching ---
    observeEvent(input$basemap, {
        proxy <- maplibre_proxy("map")

        # Explicitly remove any previously added raster layers
        old_layers <- isolate(current_raster_layers())
        if (length(old_layers) > 0) {
            for (layer_id in old_layers) {
                proxy %>% clear_layer(layer_id)
            }
            current_raster_layers(character(0))
        }

        if (input$basemap %in% c("carto_positron", "carto_voyager", "esri_imagery")) {
            # VECTOR LOGIC (Carto-based styles)
            style_url <- switch(input$basemap,
                "carto_positron" = "https://basemaps.cartocdn.com/gl/positron-gl-style/style.json",
                "carto_voyager" = "https://basemaps.cartocdn.com/gl/voyager-gl-style/style.json",
                "esri_imagery" = "https://basemaps.cartocdn.com/gl/voyager-gl-style/style.json"
            )

            proxy %>%
                set_style(style_url)

            # For vector sandwich, we want stations below labels
            stations_before_id("watername_ocean")

            # For Esri Imagery: Insert satellite raster layer below the vector style's features
            if (input$basemap == "esri_imagery") {
                current_session <- shiny::getDefaultReactiveDomain()
                selected_basemap <- input$basemap

                later::later(function() {
                    shiny::withReactiveDomain(current_session, {
                        # Race condition check
                        current_basemap <- isolate(input$basemap)
                        if (current_basemap != selected_basemap) {
                            return()
                        }

                        unique_suffix <- as.numeric(Sys.time()) * 1000
                        source_id <- paste0("esri_imagery_source_", unique_suffix)
                        layer_id <- paste0("esri_imagery_layer_", unique_suffix)

                        esri_url <- "https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}"

                        maplibre_proxy("map") %>%
                            add_raster_source(id = source_id, tiles = c(esri_url), tileSize = 256) %>%
                            add_layer(
                                id = layer_id,
                                type = "raster",
                                source = source_id,
                                paint = list("raster-opacity" = 1),
                                before_id = "watername_ocean"
                            )

                        current_raster_layers(c(layer_id))
                        style_change_trigger(isolate(style_change_trigger()) + 1)
                    })
                }, delay = 0.5)
            } else {
                style_change_trigger(isolate(style_change_trigger()) + 1)
            }
        } else {
            # RASTER LOGIC (Esri Topo, OSM)
            tile_url <- if (input$basemap %in% c("osm", "osm_gray")) {
                "https://tile.openstreetmap.org/{z}/{x}/{y}.png"
            } else {
                "https://server.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer/tile/{z}/{y}/{x}"
            }

            attribution_text <- if (input$basemap %in% c("osm", "osm_gray")) {
                '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
            } else {
                "Tiles &copy; Esri"
            }

            paint_props <- list("raster-opacity" = 1)
            if (input$basemap == "osm_gray") {
                paint_props[["raster-saturation"]] <- -0.9
                paint_props[["raster-contrast"]] <- 0.3
            }

            # Use blank style + raster layer
            blank_style <- list(
                version = 8,
                sources = list(),
                layers = list(),
                metadata = list(timestamp = as.numeric(Sys.time()))
            )
            json_blank <- jsonlite::toJSON(blank_style, auto_unbox = TRUE)
            blank_uri <- paste0("data:application/json,", URLencode(as.character(json_blank), reserved = TRUE))

            proxy %>%
                set_style(blank_uri)

            current_session <- shiny::getDefaultReactiveDomain()
            selected_basemap <- input$basemap

            later::later(function() {
                shiny::withReactiveDomain(current_session, {
                    current_basemap <- isolate(input$basemap)
                    if (current_basemap != selected_basemap) {
                        return()
                    }

                    unique_suffix <- as.numeric(Sys.time()) * 1000
                    source_id <- paste0("raster_source_", unique_suffix)
                    layer_id <- paste0("raster_layer_", unique_suffix)

                    maplibre_proxy("map") %>%
                        add_raster_source(id = source_id, tiles = c(tile_url), tileSize = 256, attribution = attribution_text) %>%
                        add_layer(
                            id = layer_id,
                            type = "raster",
                            source = source_id,
                            paint = paint_props
                        )

                    stations_before_id(NULL)
                    current_raster_layers(c(layer_id))
                    style_change_trigger(isolate(style_change_trigger()) + 1)
                })
            }, delay = 0.5)
        }
    })

    # Toggle Labels visibility
    observeEvent(input$show_labels,
        {
            visibility <- if (input$show_labels) "visible" else "none"

            label_layers <- c(
                "place_villages", "place_town", "place_country_2", "place_country_1",
                "place_state", "place_continent",
                "place_city_r6", "place_city_r5", "place_city_dot_r7", "place_city_dot_r4",
                "place_city_dot_r2", "place_city_dot_z7",
                "place_capital_dot_z7", "place_capital",
                "roadname_minor", "roadname_sec", "roadname_pri", "roadname_major",
                "motorway_name",
                "watername_ocean", "watername_sea", "watername_lake", "watername_lake_line",
                "poi_stadium", "poi_park", "poi_zoo",
                "airport_label",
                "country-label", "state-label", "settlement-major-label", "settlement-minor-label",
                "settlement-subdivision-label", "road-label", "waterway-label", "natural-point-label",
                "poi-label", "airport-label"
            )

            proxy <- maplibre_proxy("map")

            for (layer_id in label_layers) {
                tryCatch(
                    {
                        proxy <- proxy %>% set_layout_property(layer_id, "visibility", visibility)
                    },
                    error = function(e) {
                        # Layer may not exist in current style, ignore silently
                    }
                )
            }
        },
        ignoreInit = TRUE
    )

    # Update Markers
    # Optimize: Only update when data actually changes, not on tab switch
    # Also depends on style_change_trigger to re-add layer after style change
    observe({
        df <- filtered_stations()
        req(df, input$data_resolution)

        # Wait for map to be ready before adding markers
        req(map_initialized())

        # Add dependency on style_change_trigger to re-add layer after style change
        style_change_trigger()

        # We do NOT check input$main_nav here. We want markers to persist/update
        # regardless of view, so they are ready when user switches back.
        # This prevents the "reload" (clear + re-add) effect on tab switch.

        res <- tolower(input$data_resolution)
        n_rows <- nrow(df)
        coverage_start <- if ("station_overall_start" %in% names(df)) df$station_overall_start else df$start_date
        coverage_end <- if ("station_overall_end" %in% names(df)) df$station_overall_end else df$end_date

        # Pre-process label with HTML using Helper
        df$popup_content <- purrr::pmap_chr(
            list(
                df$name, df$id, df$state, df$start_date, df$end_date,
                df$detailed_summary, coverage_start, coverage_end, rep(res, n_rows)
            ),
            generate_station_label
        )

        if (nrow(df) > 0) {
            # Standard styling for all stations (selection is handled by separate highlight layer)
            df <- df %>%
                mutate(
                    circle_color = "navy",
                    circle_radius = 6,
                    circle_stroke_color = "#00000000",
                    circle_stroke_width = 0
                )

            # Convert to sf
            map_data <- st_as_sf(df, coords = c("longitude", "latitude"), crs = 4326)

            # Apply to map
            maplibre_proxy("map") %>%
                clear_layer("stations") %>%
                add_circle_layer(
                    id = "stations",
                    source = map_data,
                    circle_color = get_column("circle_color"),
                    circle_radius = get_column("circle_radius"),
                    circle_stroke_color = get_column("circle_stroke_color"),
                    circle_stroke_width = get_column("circle_stroke_width"),
                    circle_opacity = 0.7,
                    tooltip = get_column("popup_content"),
                    before_id = stations_before_id()
                )

            # Re-highlight selected station if present (to update label with new resolution)
            sid <- isolate(current_station_id())
            if (!is.null(sid)) {
                sel_row <- df %>% filter(id == sid)
                if (nrow(sel_row) > 0) {
                    highlight_selected_station(maplibre_proxy("map"), sel_row$longitude[1], sel_row$latitude[1], sel_row$popup_content[1], move_map = FALSE)
                } else {
                    # Station no longer in filtered set, clear highlight
                    maplibre_proxy("map") %>% clear_layer("selected-highlight")
                }
            }
        }

        # Unfreeze after markers are updated
        session$sendCustomMessage("unfreezeUI", list())
    })

    # --- Selection Logic ---
    observeEvent(input$map_feature_click, {
        clicked_data <- input$map_feature_click

        # Check if the click was on the "stations" layer
        if (!is.null(clicked_data) && (isTRUE(clicked_data$layer_id == "stations") || isTRUE(clicked_data$layer == "stations"))) {
            # The ID is in the properties
            id_val <- clicked_data$properties$id

            if (!is.null(id_val)) {
                # Set ID
                current_station_id(id_val)

                # Highlight & Zoom
                # Fetch meta for label
                s_meta <- all_stations() %>% filter(id == id_val)

                if (nrow(s_meta) > 0) {
                    lng <- s_meta$longitude[1]
                    lat <- s_meta$latitude[1]

                    res <- if (is.null(input$data_resolution)) NULL else tolower(input$data_resolution)
                    overall_start <- if ("station_overall_start" %in% names(s_meta)) s_meta$station_overall_start[1] else s_meta$start_date[1]
                    overall_end <- if ("station_overall_end" %in% names(s_meta)) s_meta$station_overall_end[1] else s_meta$end_date[1]
                    lbl <- generate_station_label(
                        s_meta$name[1], s_meta$id[1], s_meta$state[1],
                        s_meta$start_date[1], s_meta$end_date[1], s_meta$detailed_summary[1],
                        overall_start, overall_end, res
                    )

                    highlight_selected_station(maplibre_proxy("map"), lng, lat, lbl)
                }

                # Sync dropdown
                updateSelectizeInput(session, "station_selector", selected = id_val)
            }
        }
    })

    # --- Date Synchronization (Sliding Window & Bi-Directional) ---

    # 2. Sidebar constraints: 28 <= days <= max (366 for hourly/daily, 3652 for monthly)
    observeEvent(input$date_range, {
        req(input$date_range)
        d_start <- input$date_range[1]
        d_end <- input$date_range[2]

        # Validate inputs are not NA
        if (any(is.na(c(d_start, d_end)))) {
            return()
        }
        req(input$data_resolution)

        # Get previous values for change detection
        prev <- previous_date_range()

        # If this is the first observation, just store the current values and return
        if (is.null(prev)) {
            previous_date_range(c(d_start, d_end))
            return()
        }

        prev_start <- prev[1]
        prev_end <- prev[2]

        # Calculate current diff
        diff <- as.numeric(difftime(d_end, d_start, units = "days"))

        # Defensive check for NA diff
        if (is.na(diff)) {
            return()
        }

        # Max window depends on resolution:
        # Monthly/Daily: ~10 years (3652 days) to allow 6-year views
        # Hourly: 1 year (366 days)
        res <- tolower(input$data_resolution)
        is_extended <- res %in% c("monthly", "daily")
        max_days <- if (is_extended) 3652 else 366
        min_days <- 28

        if (diff > max_days || diff < min_days) {
            # Detect which date changed
            start_changed <- !isTRUE(all.equal(d_start, prev_start))
            end_changed <- !isTRUE(all.equal(d_end, prev_end))

            if (end_changed && !start_changed) {
                # User changed end date -> adjust start date
                target_diff <- if (diff > max_days) max_days else min_days
                new_start <- d_end - target_diff

                freezeReactiveValue(input, "date_range")
                updateDateRangeInput(session, "date_range", start = new_start, end = d_end)

                # Update tracked state
                previous_date_range(c(new_start, d_end))
            } else {
                # User changed start date (or both) -> adjust end date
                target_diff <- if (diff > max_days) max_days else min_days
                new_end <- d_start + target_diff

                freezeReactiveValue(input, "date_range")
                updateDateRangeInput(session, "date_range", start = d_start, end = new_end)

                # Update tracked state
                previous_date_range(c(d_start, new_end))
            }
        } else {
            # Update tracked state
            previous_date_range(c(d_start, d_end))
        }
    })

    # --- Async Fetching State Machine ---

    # State Variables
    fetch_stage <- reactiveVal(0) # 0=Idle, 1=Init, 2=NextFile, 3=Head, 4=Download, 5=Parse, 6=Merge
    fetch_message <- reactiveVal("Idle")
    fetch_queue <- reactiveVal(list()) # List of targets (url, etc.)
    fetch_queue_idx <- reactiveVal(0)
    parsed_data_list <- reactiveVal(list()) # Accumulate dataframes

    # Progress Tracking
    fetch_total_size <- reactiveVal(0)
    fetch_current_pos <- reactiveVal(0)
    fetch_current_token <- reactiveVal(NULL) # To invalidate stale sessions
    fetch_temp_file <- reactiveVal(NULL)

    # --- Immediate State Clearing to Prevent Main Thread Blocking ---
    # When inputs change, clear data IMMEDIATELY to prevent plots from
    # rendering old data with new settings (e.g. Daily data -> Hourly plots = 3000+ traces)
    # This covers the 500ms debounce gap.
    observeEvent(input$data_resolution,
        {
            station_data(NULL)
            parsed_data_list(list())

            # Only block UI if we have a station selected (fetch will occur)
            if (!is.null(current_station_id())) {
                loading_status(TRUE)
            }
        },
        priority = 1000,
        ignoreInit = TRUE
    )

    observeEvent(current_station_id(),
        {
            station_data(NULL)
            parsed_data_list(list())

            # Only block UI if a valid station is selected
            if (!is.null(current_station_id())) {
                loading_status(TRUE)
            }
        },
        priority = 1000,
        ignoreInit = TRUE
    )

    # Initial Trigger (Debounced Window)
    window_reactive <- reactive({
        req(input$date_range)
        list(id = current_station_id(), start = input$date_range[1], end = input$date_range[2])
    })
    window_debounced <- window_reactive %>% debounce(500)

    reset_fetch <- function(msg = NULL) {
        fetch_stage(0)
        # Invalidate token to kill pending async tasks
        fetch_current_token(as.numeric(Sys.time()))

        loading_status(FALSE)
        if (!is.null(msg)) loading_diagnostics(msg)
        tmp <- fetch_temp_file()
        if (!is.null(tmp) && file.exists(tmp)) unlink(tmp)
        fetch_temp_file(NULL)
        parsed_data_list(list())
        # Unfreeze UI when fetch is reset/cancelled
        session$sendCustomMessage("unfreezeUI", list())
    }

    # Handle Cancel from Freeze Window
    observeEvent(input$cancel_loading, {
        reset_fetch("Cancelled by user")
        showNotification("Loading cancelled by user.", type = "warning")
    })

    # Stage 1: Initialization
    observe({
        req(window_debounced()$id, window_debounced()$start, window_debounced()$end)

        # Prevent re-triggering if already running for same params (optional logic could go here)
        # For now, any change restarts fetch.

        station_id <- window_debounced()$id
        loading_status(TRUE)

        # Get station name for display
        station_meta <- all_stations() %>% filter(id == station_id)
        station_name <- if (nrow(station_meta) > 0) station_meta$name[1] else station_id

        msg <- "Initializing data fetch..."
        loading_diagnostics(msg)
        fetch_message(msg)
        # Freeze UI during download and parsing - include station name
        session$sendCustomMessage("freezeUI", list(text = msg, station = station_name))

        # Generate Filtered Index - Optimize based on Date Range
        req_start_date <- as.Date(window_debounced()$start)
        req_end_date <- as.Date(window_debounced()$end)

        # Helper to convert YYYYMMDD string to Date
        parse_dwd_date <- function(x) {
            as.Date(x, format = "%Y%m%d")
        }

        targets <- current_index() %>%
            filter(id == station_id) %>%
            filter(
                # Logic: Keep file if (FileStart <= ReqEnd) AND (FileEnd >= ReqStart)
                # Handle cases where start/end might be NA or "recent" type implies checking
                type == "recent" | # Always check recent files as they might have fresh data
                    type == "solar" | # Solar usually has one file or simple structure, keep safe
                    (
                        !is.na(start_date) & !is.na(end_date) &
                            parse_dwd_date(start_date) <= req_end_date &
                            parse_dwd_date(end_date) >= req_start_date
                    )
            )

        if (nrow(targets) == 0) {
            # Fallback/Debug: check if we filtered out everything
            raw_targets <- current_index() %>% filter(id == station_id)
            msg <- "No data found in index for this station."

            if (nrow(raw_targets) > 0) {
                # Data exists but was filtered out by date range
                msg <- "No data found for the selected date range."
            }

            reset_fetch(msg)
            return()
        }

        # Setup Queue
        # We convert targets to a list of rows for easier iteration
        q <- split(targets, seq(nrow(targets)))
        fetch_queue(q)
        fetch_queue_idx(1)
        parsed_data_list(list()) # Clear previous

        # New Token
        token <- as.numeric(Sys.time())
        fetch_current_token(token)

        fetch_stage(2) # Go to Next File
    })

    # Stage 2: Next File
    observe({
        req(fetch_stage() == 2)
        idx <- fetch_queue_idx()
        q <- fetch_queue()

        if (idx > length(q)) {
            # All files done -> Merge
            fetch_stage(6)
        } else {
            # Setup next file
            target <- q[[idx]]
            msg <- paste0("Downloading file ", idx, "/", length(q), "...")
            loading_diagnostics(msg)
            session$sendCustomMessage("freezeUI", list(text = msg))
            fetch_message(msg)

            # Initialize tracking for new file
            fetch_total_size(0) # Unknown initially
            fetch_current_pos(0)

            # Prep Temp File
            tmp <- tempfile(fileext = ".zip")
            fetch_temp_file(tmp)
            file.create(tmp)

            fetch_stage(4) # Go directly to Download Loop
        }
    })

    # Stage 3: REMOVED (Head Check caused blocking)

    # Stage 4: Download Chunk
    observe({
        req(fetch_stage() == 4)

        # Settings - Increased to 50MB to reduce loop overhead
        chunk_size <- 50 * 1024 * 1024
        total <- fetch_total_size()
        current <- fetch_current_pos()
        tmp <- fetch_temp_file()
        idx <- fetch_queue_idx()
        q <- fetch_queue()
        target <- q[[idx]]

        # If total unknown, we assume we want next chunk
        if (total > 0) {
            end <- min(current + chunk_size - 1, total - 1)
        } else {
            end <- current + chunk_size - 1
        }

        token <- fetch_current_token()
        message(paste0("[Debug] Stage 4: Starting chunk download. Range: ", current, "-", end, " Total: ", total))

        later::later(function() {
            if (!identical(isolate(fetch_current_token()), token)) {
                message("[Debug] Stage 4: Token mismatch in later callback. Aborting.")
                return()
            }

            tryCatch(
                {
                    isolate({
                        h <- curl::new_handle()
                        curl::handle_setopt(
                            h,
                            range = paste0(current, "-", end),
                            # Robustness: Timeout if connection hangs or speed is too low
                            connecttimeout = 10,
                            low_speed_time = 30, # Abort if speed < 100 B/s for 30s
                            low_speed_limit = 100
                        )

                        message(paste0("[Debug] Stage 4: Executing curl for ", target$url))

                        tryCatch(
                            {
                                resp <- curl::curl_fetch_memory(target$url, handle = h)
                                message(paste0("[Debug] Stage 4: Curl finished. Status: ", resp$status_code))

                                if (resp$status_code == 200) {
                                    # 200 OK means server sent the whole file (or ignored range)
                                    con <- file(tmp, open = "wb")
                                    writeBin(resp$content, con)
                                    close(con)

                                    new_pos <- length(resp$content)
                                    fetch_current_pos(new_pos)
                                    fetch_total_size(new_pos)

                                    msg <- paste0("Downloaded file ", idx, "/", length(q), ": ", format_bytes(new_pos), " (Finished)")
                                    loading_diagnostics(msg)
                                    session$sendCustomMessage("freezeUI", list(text = msg))
                                    fetch_message(msg)

                                    fetch_stage(5) # Parse
                                } else if (resp$status_code == 206) {
                                    # 206 Partial Content
                                    con <- file(tmp, open = "ab")
                                    writeBin(resp$content, con)
                                    close(con)

                                    bytes_received <- length(resp$content)
                                    new_pos <- current + bytes_received
                                    fetch_current_pos(new_pos)

                                    # Try to guess total from header if unknown
                                    if (total == 0) {
                                        headers <- curl::parse_headers_list(resp$headers)
                                        if (!is.null(headers[["content-range"]])) {
                                            cr <- headers[["content-range"]]
                                            parts <- strsplit(cr, "/")[[1]]
                                            if (length(parts) == 2 && parts[2] != "*") {
                                                t_val <- as.numeric(parts[2])
                                                if (!is.na(t_val)) fetch_total_size(t_val)
                                            }
                                        }
                                    }

                                    total <- fetch_total_size()

                                    done <- FALSE
                                    percent_str <- ""

                                    if (total > 0) {
                                        if (new_pos >= total) done <- TRUE
                                        pct <- round(new_pos / total * 100)
                                        percent_str <- paste0(" / ", format_bytes(total), " (", pct, "%)")
                                    } else {
                                        if (bytes_received < chunk_size) done <- TRUE
                                        percent_str <- " (Unknown total)"
                                    }

                                    msg <- paste0(
                                        "Downloading file ", idx, "/", length(q), ": ",
                                        format_bytes(new_pos), percent_str
                                    )
                                    loading_diagnostics(msg)
                                    session$sendCustomMessage("freezeUI", list(text = msg))
                                    fetch_message(msg)

                                    if (done) {
                                        if (total == 0) fetch_total_size(new_pos)
                                        fetch_stage(5) # Parse
                                    } else {
                                        fetch_stage(4) # Next Chunk
                                    }
                                } else if (resp$status_code == 416) {
                                    # Range Not Satisfiable
                                    if (total == 0 && current > 0) {
                                        fetch_stage(5)
                                    } else {
                                        loading_diagnostics(paste("Download Error HTTP", resp$status_code))
                                        fetch_stage(0)
                                    }
                                } else {
                                    loading_diagnostics(paste("Download Error HTTP", resp$status_code))
                                    fetch_stage(0)
                                }
                            },
                            error = function(e) {
                                # Handle Timeout/Connection Errors
                                message(paste0("[Debug] Download Failed: ", e$message))
                                loading_diagnostics(paste("Download Failed:", e$message))
                                session$sendCustomMessage("unfreezeUI", list())
                                showNotification(
                                    paste("Download stopped: Connection timed out or stuck. Please try again later. (File ", idx, ")"),
                                    type = "error",
                                    duration = NULL # Persistent until clicked
                                )
                                fetch_stage(0)
                            }
                        )
                    })
                },
                error = function(e) {
                    message(paste0("[Debug] Critical Async Error: ", e$message))
                    msg <- paste("Critical Async Error:", e$message)

                    loading_diagnostics(msg)
                    loading_status(FALSE)
                    session$sendCustomMessage("unfreezeUI", list())
                    fetch_stage(0)
                }
            )
        }, 0.05)

        fetch_stage(-1)
    })

    # Stage 5: Parse
    observe({
        req(fetch_stage() == 5)
        token <- fetch_current_token()

        idx <- fetch_queue_idx()
        len <- length(fetch_queue())
        msg <- paste0("Parsing file ", idx, "/", len, "...")
        loading_diagnostics(msg)
        session$sendCustomMessage("freezeUI", list(text = msg))
        fetch_message(msg)

        later::later(function() {
            if (!identical(isolate(fetch_current_token()), token)) {
                return()
            }

            isolate({
                tmp <- fetch_temp_file()

                # We reuse read_dwd_data logic
                # We need start/end dates for efficient parsing if supported
                s_date <- window_debounced()$start
                e_date <- window_debounced()$end

                # Call parser (from global environment)
                parsed <- tryCatch(read_dwd_data(tmp, s_date, e_date), error = function(e) NULL)

                if (!is.null(parsed)) {
                    # Add to list
                    plist <- parsed_data_list()
                    plist[[length(plist) + 1]] <- parsed
                    parsed_data_list(plist)
                }

                unlink(tmp)
                fetch_temp_file(NULL)

                # Next file
                fetch_queue_idx(idx + 1)
                fetch_stage(2)
            })
        }, 0.1)

        fetch_stage(-1)
    })

    # Stage 6: Merge
    observe({
        req(fetch_stage() == 6)

        token <- fetch_current_token()
        msg <- "Merging and finalizing data..."
        loading_diagnostics(msg)
        session$sendCustomMessage("freezeUI", list(text = msg))
        fetch_message(msg)

        later::later(function() {
            if (!identical(isolate(fetch_current_token()), token)) {
                return()
            }

            isolate({
                plist <- parsed_data_list()

                if (length(plist) == 0) {
                    loading_diagnostics("No valid data found.")
                    loading_status(FALSE)
                    station_data(NULL)
                    fetch_stage(0)
                    return()
                }

                # Merge Logic (simplified from parse_dwd.R)
                final_df <- purrr::reduce(plist, full_join, by = "datetime")

                # Coalesce
                weather_vars <- c(
                    "temp", "temp_min", "temp_max", "temp_min_avg", "temp_max_avg", "rh", "dew_point",
                    "abs_humidity", "vapor_pressure", "wet_bulb_temp",
                    "precip", "wind_speed", "wind_dir", "pressure", "station_pressure", "cloud_cover", "cloud_cover_indicator",
                    "wind_gust_max", "solar_global", "sunshine_duration",
                    "soil_temp_2cm", "soil_temp_5cm", "soil_temp_10cm", "soil_temp_20cm", "soil_temp_50cm", "soil_temp_100cm",
                    "soil_temp_min_5cm",
                    "snow_depth", "snow_water_equiv", "snow_fresh_sum", "snow_depth_sum",
                    "thunderstorm", "glaze", "graupel", "hail", "fog", "frost", "storm_6", "storm_8", "dew",
                    "precip_net_thunderstorm", "precip_net_graupel", "precip_net_hail", "precip_net_fog",
                    "visibility", "visibility_indicator", "weather_code", "weather_text",
                    "cloud_layer1_code", "cloud_layer1_abbrev", "cloud_layer1_height", "cloud_layer1_amount",
                    "cloud_layer2_code", "cloud_layer2_abbrev", "cloud_layer2_height", "cloud_layer2_amount",
                    "cloud_layer3_code", "cloud_layer3_abbrev", "cloud_layer3_height", "cloud_layer3_amount",
                    "cloud_layer4_code", "cloud_layer4_abbrev", "cloud_layer4_height", "cloud_layer4_amount"
                )
                available_cols <- names(final_df)
                clean_df <- final_df %>% select(datetime)

                for (v in weather_vars) {
                    v_cols <- available_cols[grepl(paste0("^", v, "(\\.|$)"), available_cols)]
                    if (length(v_cols) > 0) {
                        clean_df[[v]] <- do.call(coalesce, final_df[v_cols])
                    }
                }

                # Cleanup
                clean_df <- clean_df %>%
                    distinct(datetime, .keep_all = TRUE) %>%
                    arrange(datetime)

                # Final Window Filter (safety) with Auto-Correction
                s_date <- window_debounced()$start
                e_date <- window_debounced()$end

                if (!is.null(s_date) && !is.null(e_date)) {
                    req_start <- as.POSIXct(s_date)
                    req_end <- as.POSIXct(e_date) + days(1)

                    filtered_df <- clean_df %>%
                        filter(datetime >= req_start, datetime <= req_end)

                    # Check for mismatch: Data exists but not in window
                    if (nrow(filtered_df) == 0 && nrow(clean_df) > 0) {
                        data_max <- max(clean_df$datetime, na.rm = TRUE)
                        data_min <- min(clean_df$datetime, na.rm = TRUE)

                        # If the requested window is completely outside the data range
                        if (req_start > data_max || req_end < data_min) {
                            msg <- paste0("Warning: No data in selected range. Available data ends: ", format(data_max, "%Y-%m-%d"), ". Displaying available data.")
                            loading_diagnostics(msg)

                            # Do NOT auto-adjust dates (user preference)
                            # We just let it filter (which yields 0 rows) or show what we have
                        }
                    }

                    clean_df <- filtered_df
                }

                # If after filtering we have 0 rows, but we had data before, it means window is empty
                if (nrow(clean_df) == 0 && nrow(final_df) > 0) {
                    msg <- "No data found for the selected date range."
                    loading_diagnostics(msg)
                }


                station_data(clean_df)
                loading_diagnostics(paste0("Success: ", nrow(clean_df), " rows loaded."))
                loading_status(FALSE)
                fetch_stage(0)

                # Navigate to Dashboard tab
                if (input$main_nav != "Dashboard") {
                    updateNavbarPage(session, "main_nav", selected = "Dashboard")
                }

                # Show rendering message and then unfreeze after delay
                session$sendCustomMessage("freezeUI", list(text = "Rendering plots..."))
                later::later(function() {
                    session$sendCustomMessage("unfreezeUI", list())
                }, 2.0) # Give 2 seconds for plots to render
            })
        }, 0.1)

        fetch_stage(-1)
    })

    # Output logic for Panel
    output$is_loading <- reactive({
        loading_status()
    })
    outputOptions(output, "is_loading", suspendWhenHidden = FALSE)

    output$station_ready <- reactive({
        !is.null(station_data())
    })
    outputOptions(output, "station_ready", suspendWhenHidden = FALSE)

    output$data_diagnostics <- renderUI({
        HTML(loading_diagnostics())
    })

    output$has_diag <- reactive({
        nzchar(loading_diagnostics())
    })
    outputOptions(output, "has_diag", suspendWhenHidden = FALSE)

    # --- Plot Outputs (Top-Level Reactivity) ---
    # These are defined outside of observers to ensure they invalidate immediately when station_data() changes.

    output$temp_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_temperature_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$humidity_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_humidity_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$wind_overview_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_wind_overview_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$pressure_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_pressure_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$cloud_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_cloud_cover_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$precip_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_precipitation_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$wind_rose <- renderPlotly({
        df <- station_data()
        req(df)
        create_wind_rose_plot(df)
    })

    output$solar_radiation_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_solar_radiation_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$sunshine_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_sunshine_duration_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$snow_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_snow_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$soil_temp_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_soil_temp_plot(df, resolution = isolate(tolower(input$data_resolution)))
    })

    output$diurnal_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_diurnal_plot(df)
    })

    output$weathergami_plot <- renderPlotly({
        df <- station_data()
        req(df)
        create_weathergami_plot(df)
    })

    # Tables
    output$hourly_data_table <- DT::renderDataTable({
        req(!loading_status())
        df <- station_data()
        req(df)

        # Format datetime
        df <- df %>% mutate(datetime = format(datetime, "%Y-%m-%d %H:%M"))

        # Rename columns using global mapping
        # We use any_of() to safely select/rename only columns that exist in the data
        # Note: rename(new = old) syntax, so we need to invert our named vector or use any_of matching
        # rename(df, any_of(dwd_column_labels)) works if vector is NewName = OldName?
        # dwd_column_labels is "old_code" = "New Name"
        # dplyr::rename(df, any_of(dwd_column_labels)) expects c("New Name" = "old_code")?
        # actually rename accepts named vector c(New = Old).
        # Our vector is Old = New? No, it's c("temp" = "Air Temp").
        # If we use rename(!!dwd_column_labels), it expects c(New = Old).
        # So we likely need to invert the vector for rename, OR use label substitution.
        # Actually, let's just use data.table or setNames for simplicity on the display DF.

        # Invert the mapping: c("Air Temp" = "temp")
        renaming_vec <- setNames(names(dwd_column_labels), dwd_column_labels)

        # But wait, dwd_column_labels is defined as c("temp" = "Air Temp").
        # dplyr::rename(df, !!!dwd_column_labels) -> this would try to rename column "Air Temp" to "temp"?
        # No, rename(new = old).
        # If I hav c(a = b), rename(!!!x) means rename b to a.
        # So if dwd_column_labels is c("temp" = "Air Temp"), it means rename "Air Temp" to "temp".
        # That is the Opposite of what we want. We have "temp" in DF, want "Air Temp".
        # So we need c("Air Temp" = "temp").

        display_labels <- setNames(names(dwd_column_labels), dwd_column_labels)
        # Wait, names(dwd_column_labels) is "temp". dwd_column_labels is "Air Temp".
        # setNames("temp", "Air Temp") -> c("Air Temp" = "temp")
        # This is correct for rename(new = old).

        cols_to_rename <- dwd_column_labels[names(dwd_column_labels) %in% names(df)]
        # This gives c("temp" = "Air Temp") subset.
        # We need to construct the rename vector: "Air Temp" = "temp"
        rename_map <- setNames(names(cols_to_rename), cols_to_rename)

        # Actually, much simpler:
        req(df)

        # Use simple column replacement for display
        df_display <- df
        for (col in names(dwd_column_labels)) {
            if (col %in% names(df_display)) {
                names(df_display)[names(df_display) == col] <- dwd_column_labels[[col]]
            }
        }

        datatable(df_display,
            options = list(pageLength = 15, scrollX = TRUE)
        )
    })

    # Download Handler
    output$download_hourly <- downloadHandler(
        filename = function() {
            id <- current_station_id()
            res <- if (!is.null(input$data_resolution)) tolower(input$data_resolution) else "data"
            if (is.null(id)) {
                paste0("dwd_data_", res, ".xlsx")
            } else {
                paste0("dwd_station_", id, "_", res, ".xlsx")
            }
        },
        content = function(file) {
            req(station_data())
            # Ensure proper datetime formatting for Excel (writexl handles POSIXct, but text might be safer for strict format)
            # Actually writexl handles dates nicely natively.
            out_df <- station_data()
            write_xlsx(out_df, path = file)
        }
    )

    # Data Tab Header - Info Callout Card
    output$station_info_header <- renderUI({
        id <- current_station_id()
        if (is.null(id)) {
            return(NULL)
        }

        # Metadata
        meta <- all_stations() %>% dplyr::filter(id == !!id)
        if (nrow(meta) == 0) {
            return(NULL)
        }

        s_name <- meta$name[1]
        s_state <- meta$state[1]
        s_elev <- meta$elevation[1]

        # Dynamic Badge Logic
        res_label <- input$data_resolution
        res_class <- if (tolower(res_label) == "hourly") "bg-primary" else "bg-success"

        # Data Range
        df <- station_data()
        if (is.null(df) || nrow(df) == 0) {
            dates_text <- "No data loaded"
        } else {
            date_range <- range(as.Date(df$datetime), na.rm = TRUE)
            dates_text <- paste(date_range[1], "to", date_range[2])
        }

        # Unified Info Card
        card(
            style = "margin-bottom: 20px; border-left: 5px solid #007bff;",
            card_body(
                padding = 15,
                layout_columns(
                    fill = FALSE,
                    # Col 1: Station
                    div(
                        strong("Station"), br(),
                        span(s_name, style = "font-size: 1.1rem;"), br(),
                        tags$small(class = "text-muted", paste("ID:", id))
                    ),
                    # Col 2: Location
                    div(
                        strong("Location"), br(),
                        span(s_state), br(),
                        tags$small(class = "text-muted", paste0(meta$latitude[1], "°N, ", meta$longitude[1], "°E"))
                    ),
                    # Col 3: Elevation & Resolution
                    div(
                        strong("Technical"), br(),
                        span(paste0(s_elev, " m")), br(),
                        span(class = paste("badge", res_class), res_label)
                    ),
                    # Col 4: Period
                    div(
                        strong("Data Selection"), br(),
                        span(dates_text)
                    ),
                    # Col 5: Actions
                    div(
                        class = "d-flex align-items-center justify-content-end",
                        downloadButton(
                            "download_hourly",
                            label = "Export Excel",
                            class = "btn-sm btn-primary",
                            icon = icon("file-excel")
                        )
                    )
                )
            )
        )
    })

    output$table <- DT::renderDataTable({
        # Mirror MeteoFrance: Select specific columns and disable row names
        # This ensures rowData[0] in JS is the Station ID
        df_display <- filtered_stations() %>%
            select(
                "ID" = id,
                "Name" = name,
                "State" = state,
                "Elev." = elevation,
                "Status" = detailed_summary
            )

        datatable(df_display,
            selection = "none",
            rownames = FALSE,
            callback = JS("
                table.on('dblclick', 'tr', function() {
                    var rowData = table.row(this).data();
                    if (rowData !== undefined && rowData !== null) {
                        var stationId = rowData[0];
                        Shiny.setInputValue('table_station_dblclick', stationId, {priority: 'event'});
                    }
                });
            ")
        )
    })

    # Selection from Table - Double Click
    observeEvent(input$table_station_dblclick, {
        id_val <- input$table_station_dblclick
        req(id_val)

        # Get station metadata
        # Using filtered_stations ensures we respect current context, but ID lookup is robust
        s <- filtered_stations() %>% filter(id == id_val)

        # Fallback to all stations if filter changed momentarily (unlikely but safe)
        if (nrow(s) == 0) {
            s <- all_stations() %>% filter(id == id_val)
        }

        req(nrow(s) > 0)

        current_station_id(id_val)

        # Sync dropdown (sidebar)
        updateSelectizeInput(session, "station_selector", selected = id_val)

        # Highlight on map (data fetch triggered by current_station_id change will navigate to Dashboard)
        lat_val <- s$latitude[1]
        lng_val <- s$longitude[1]
        # Highlight & Zoom
        # Generate Label
        res <- if (is.null(input$data_resolution)) NULL else tolower(input$data_resolution)
        overall_start <- if ("station_overall_start" %in% names(s)) s$station_overall_start[1] else s$start_date[1]
        overall_end <- if ("station_overall_end" %in% names(s)) s$station_overall_end[1] else s$end_date[1]
        lbl <- generate_station_label(
            s$name[1], s$id[1], s$state[1],
            s$start_date[1], s$end_date[1], s$detailed_summary[1],
            overall_start, overall_end, res
        )

        highlight_selected_station(maplibre_proxy("map"), lng_val, lat_val, lbl)

        # NOTE: Data parsing and Dashboard navigation are automatically triggered
        # by the change in current_station_id() through window_debounced -> fetch state machine
    })

    # Dynamic Plots Panel - All plots in grid format (no tabs)
    # Only display plots that have data available
    output$details_tabs <- renderUI({
        req(input$data_resolution)

        # Don't render if we are currently loading/fetching new data
        if (isTRUE(loading_status())) {
            return(NULL)
        }

        res <- isolate(tolower(input$data_resolution))
        df <- station_data()
        req(df)

        # Clean data once for checking
        df_clean <- clean_dwd_data(df)

        # Check data availability for each parameter
        has_temp <- ("temp" %in% names(df_clean) && any(!is.na(df_clean$temp))) ||
            ("temp_min" %in% names(df_clean) && any(!is.na(df_clean$temp_min))) ||
            ("temp_max" %in% names(df_clean) && any(!is.na(df_clean$temp_max)))

        has_humidity <- ("rh" %in% names(df_clean) && any(!is.na(df_clean$rh))) ||
            ("dew_point" %in% names(df_clean) && any(!is.na(df_clean$dew_point)))

        has_wind <- ("wind_speed" %in% names(df_clean) && any(!is.na(df_clean$wind_speed))) ||
            ("wind_gust_max" %in% names(df_clean) && any(!is.na(df_clean$wind_gust_max)))

        has_pressure <- ("pressure" %in% names(df_clean) && any(!is.na(df_clean$pressure))) ||
            ("station_pressure" %in% names(df_clean) && any(!is.na(df_clean$station_pressure)))

        has_cloud <- ("cloud_cover" %in% names(df_clean) && any(!is.na(df_clean$cloud_cover)))

        has_precip <- ("precip" %in% names(df_clean) && any(!is.na(df_clean$precip)))

        has_solar <- ("solar_global" %in% names(df_clean) && any(!is.na(df_clean$solar_global)))

        has_sunshine <- ("sunshine_duration" %in% names(df_clean) && any(!is.na(df_clean$sunshine_duration)))

        has_wind_dir <- ("wind_dir" %in% names(df_clean) && any(!is.na(df_clean$wind_dir))) && has_wind

        has_daily_temp <- ("temp_min" %in% names(df_clean) && any(!is.na(df_clean$temp_min))) &&
            ("temp_max" %in% names(df_clean) && any(!is.na(df_clean$temp_max)))

        has_snow <- ("snow_depth" %in% names(df_clean) && any(!is.na(df_clean$snow_depth))) ||
            ("snow_water_equiv" %in% names(df_clean) && any(!is.na(df_clean$snow_water_equiv))) ||
            ("snow_fresh_sum" %in% names(df_clean) && any(!is.na(df_clean$snow_fresh_sum))) ||
            ("snow_depth_sum" %in% names(df_clean) && any(!is.na(df_clean$snow_depth_sum)))

        has_soil_temp <- ("soil_temp_2cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_2cm))) ||
            ("soil_temp_5cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_5cm))) ||
            ("soil_temp_10cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_10cm))) ||
            ("soil_temp_20cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_20cm))) ||
            ("soil_temp_50cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_50cm))) ||
            ("soil_temp_100cm" %in% names(df_clean) && any(!is.na(df_clean$soil_temp_100cm)))

        # Build list of available plots
        plot_list <- tagList()

        if (has_temp) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("temp_plot", height = "320px")))
        }
        if (has_humidity) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("humidity_plot", height = "320px")))
        }
        if (has_wind) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("wind_overview_plot", height = "320px")))
        }
        if (has_pressure) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("pressure_plot", height = "320px")))
        }
        if (has_cloud) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("cloud_plot", height = "320px")))
        }
        if (has_precip) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("precip_plot", height = "320px")))
        }
        if (has_solar) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("solar_radiation_plot", height = "320px")))
        }
        if (has_sunshine) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("sunshine_plot", height = "320px")))
        }

        # Conditional: Wind Rose for hourly, Weathergami for daily
        if (res == "hourly" && has_wind_dir) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("wind_rose", height = "320px")))
        }
        if (res == "daily" && has_daily_temp) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("weathergami_plot", height = "320px")))
        }
        if (has_snow) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("snow_plot", height = "320px")))
        }
        if (has_soil_temp) {
            plot_list <- tagList(plot_list, div(class = "col-12 col-lg-6", plotlyOutput("soil_temp_plot", height = "320px")))
        }

        # Wrap in grid container
        div(
            class = "row g-3",
            style = "padding: 10px;",
            plot_list
        )
    })
    # --- URL Synchronization Observers ---

    # 1. Tab changes
    observeEvent(input$main_nav,
        {
            broadcast_state()
        },
        ignoreInit = TRUE
    )

    # 2. Station ID change (covers map click and selector)
    observeEvent(current_station_id(),
        {
            broadcast_state()
        },
        ignoreInit = TRUE
    )

    # 3. Dashboard subtab changes
    observeEvent(input$dashboard_subtabs,
        {
            broadcast_state()
        },
        ignoreInit = TRUE
    )

    # 4. Resolution changes
    observeEvent(input$data_resolution,
        {
            broadcast_state()
        },
        ignoreInit = TRUE
    )

    # 5. Date Range changes
    observeEvent(input$date_range,
        {
            broadcast_state()
        },
        ignoreInit = TRUE
    )
}