# ==============================
# Load Libraries
# ==============================
library(shiny)
library(dplyr)
library(shinycssloaders)
library(shinyWidgets)
library(recosystem)
library(recommenderlab)  # যদি প্রয়োজন হয়

# ==============================
# Load Data & Models
# ==============================
movies <- readRDS("movies.rds")
ratings_filtered <- readRDS("ratings_filtered.rds")
rating_matrix <- readRDS("rating_matrix.rds")
r <- readRDS("svd_model.rds")
ubcf_model <- readRDS("ubcf_model.rds")
ibcf_model <- readRDS("ibcf_model.rds")
topN_svd_list <- readRDS("topN_svd.rds")

# Ensure poster_url exists
if(!"poster_url" %in% colnames(movies)){
  movies$poster_url <- "https://via.placeholder.com/150x225.png?text=No+Poster"
} else {
  movies$poster_url <- ifelse(is.na(movies$poster_url),
                              "https://via.placeholder.com/150x225.png?text=No+Poster",
                              movies$poster_url)
}

# ==============================
# Recommendation Function
# ==============================
recommend_movies <- function(user_id, N = 10, model_type = "SVD") {
  
  if(!(user_id %in% rownames(rating_matrix))) {
    return(data.frame(title="No recommendations available", 
                      poster_url="https://via.placeholder.com/150x225.png?text=No+Poster"))
  }
  
  if(model_type == "SVD") {
    user_movies <- ratings_filtered %>% filter(userId == user_id) %>% pull(movieId)
    unseen_movies <- setdiff(unique(ratings_filtered$movieId), user_movies)
    
    if(length(unseen_movies) == 0) {
      return(data.frame(title="No recommendations available", 
                        poster_url="https://via.placeholder.com/150x225.png?text=No+Poster"))
    }
    
    unseen_df <- data.frame(user = user_id, item = unseen_movies)
    pred_ratings <- r$predict(data_memory(user = unseen_df$user, item = unseen_df$item))
    
    top_n_df <- data.frame(movieId = unseen_movies, pred_rating = pred_ratings) %>%
      arrange(desc(pred_rating)) %>%
      head(N)
    
    recs <- movies %>% filter(movieId %in% top_n_df$movieId) %>%
      select(title, poster_url)
    
  } else if(model_type == "UBCF") {
    pred <- predict(ubcf_model, rating_matrix[user_id,], type="topNList", n=N)
    ids <- as(pred, "list")[[1]]
    recs <- movies %>% filter(movieId %in% as.numeric(ids)) %>%
      select(title, poster_url)
    
  } else if(model_type == "IBCF") {
    pred <- predict(ibcf_model, rating_matrix[user_id,], type="topNList", n=N)
    ids <- as(pred, "list")[[1]]
    recs <- movies %>% filter(movieId %in% as.numeric(ids)) %>%
      select(title, poster_url)
    
  } else {
    stop("Invalid model_type. Choose 'SVD', 'UBCF', or 'IBCF'.")
  }
  
  if(nrow(recs) == 0) {
    recs <- data.frame(title="No recommendations available", 
                       poster_url="https://via.placeholder.com/150x225.png?text=No+Poster")
  }
  
  return(recs)
}

# ==============================
# Shiny UI
# ==============================
ui <- fluidPage(
  tags$head(
    tags$style(HTML("
      .header-emoji { font-size:34px; font-weight:bold; background: linear-gradient(90deg, #ff4e50, #f9d423);
        -webkit-background-clip:text; -webkit-text-fill-color:transparent; animation:gradient 3s ease infinite;}
      @keyframes gradient {0% {background-position:0%} 50% {background-position:100%} 100% {background-position:0%}}
      body { background-color: #fff0f5; }
      .btn-success { background: linear-gradient(45deg, #ff6b6b, #fbc531); color: #fff; font-weight:bold; transition:transform 0.2s; }
      .btn-success:hover { transform:scale(1.05); box-shadow:0px 4px 20px rgba(0,0,0,0.4); }
      .poster img { transition: transform 0.3s; border-radius:10px; }
      .poster img:hover { transform: scale(1.1) rotate(-2deg); box-shadow:0px 4px 20px rgba(0,0,0,0.5); }
      .title { text-align:center; font-size:12px; font-weight:bold; margin-top:5px; }
      .recommendation-scroll { max-height:600px; overflow-y:auto; }
      .tags-overlay { position:relative; }
      .tags-overlay span { position:absolute; top:5px; left:5px; font-size:16px; animation:sparkle 1.5s infinite; }
      @keyframes sparkle { 0%,100% {opacity:1;} 50% {opacity:0.3;} }
    "))
  ),
  
  titlePanel(tags$div("🎥 MovieLens Recommendation System 🍿", class="header-emoji")),
  
  sidebarLayout(
    sidebarPanel(
      numericInput("user_id", "Enter User ID:", value = 1, min = 1, max = nrow(rating_matrix)),
      selectInput("model_type", "Select Model:", choices = c("SVD", "UBCF", "IBCF"), selected = "UBCF"),
      numericInput("top_n", "Number of Recommendations:", value = 10, min = 1, max = 20),
      actionBttn("recommend_btn", "GET RECOMMENDATIONS ✨", style="material-flat", color="success")
    ),
    
    mainPanel(
      h4("Recommended Movies 🎬:", style="color:darkblue;"),
      withSpinner(uiOutput("recommendations_ui"), type=6)
    )
  )
)

# ==============================
# Shiny Server
# ==============================
server <- function(input, output) {
  recommendations <- eventReactive(input$recommend_btn, {
    recommend_movies(user_id=input$user_id, N=input$top_n, model_type=input$model_type)
  })
  
  output$recommendations_ui <- renderUI({
    recs <- recommendations()
    div(class="recommendation-scroll",
        fluidRow(
          lapply(1:nrow(recs), function(i){
            column(2,
                   div(class="poster tags-overlay",
                       tags$img(src=recs$poster_url[i], width="150px", height="225px"),
                       tags$span("✨"),
                       tags$p(recs$title[i], class="title")
                   )
            )
          })
        )
    )
  })
}

# ==============================
# Run Shiny App
# ==============================
shinyApp(ui = ui, server = server)