library(shiny)
library(DT)
library(readxl)
library(haven)
library(openxlsx)
library(expss)
library(dplyr)

ui <- fluidPage(
  titlePanel("Shiny App: Cross Tabulation"),
  
  sidebarLayout(
    sidebarPanel(
      fileInput("file", "Upload File (CSV, XLSX, SAV)", accept = c(".csv", ".xlsx", ".sav")),
      
      # Input for R script
      textAreaInput(
        "r_script",
        label = "Write R Script to Modify Data:",
        #value = "data$New_Column <- data$Score * 2",  # Example default script
        rows = 10,
        placeholder = "Write R code here to modify the dataframe, example: data$New_Column <- data$Score * 2"
      ),
      actionButton("apply_script", "Apply Script"),
      br(),
      
      # Select the data source for the crosstab
      selectInput("data_source", "Select Data Source for Crosstab", 
                  choices = c("Original Data" = "original", "Modified Data" = "modified")),
      
      # Crosstab selections
      selectInput("col_vars", "Select Column Variables", choices = NULL, multiple = TRUE),
      selectInput("row_vars", "Select Row Variables", choices = NULL, multiple = TRUE),
      selectInput("crosstab_type", "Crosstab Type", 
                  choices = c("Absolute Values", "Percentage", "Mean Score")),
      actionButton("generate_crosstab", "Generate Crosstab"),
      
      # Download Crosstab
      downloadButton("download_crosstab", "Download Crosstab")
    ),
    
    mainPanel(
      tabsetPanel(
        tabPanel("Original Data", DTOutput("original_data_table")),
        tabPanel("Modified Data", DTOutput("modified_data_table")),
        tabPanel("Crosstab Output", DTOutput("crosstab_table"))
      )
    )
  )
)

server <- function(input, output, session) {
  # Reactive values for data
  original_data <- reactiveVal(NULL)
  modified_data <- reactiveVal(NULL)
  
  # Load original data
  observeEvent(input$file, {
    req(input$file)
    
    file_ext <- tools::file_ext(input$file$name)
    if (file_ext == "csv") {
      df <- read.csv(input$file$datapath)
    } else if (file_ext == "xlsx") {
      df <- read_excel(input$file$datapath)
    } else if (file_ext == "sav") {
      df <- haven::read_sav(input$file$datapath)
      for (var in names(df)) {
        var_lab(df[[var]]) <- var_lab(df[[var]])  # Keep variable labels
      }
    } else {
      showNotification("Unsupported file format!", type = "error")
      return()
    }
    
    original_data(df)
    
    # Display the original data in the Original Data tab
    output$original_data_table <- renderDT({
      datatable(original_data(), options = list(pageLength = 10, scrollX = TRUE))
    })
    
    # Update dropdown variabel
    updateSelectInput(session, "col_vars", choices = names(df))
    updateSelectInput(session, "row_vars", choices = names(df))
    
    showNotification("Original data loaded successfully!", type = "message")
  })
  
  # Apply R script to modify data
  observeEvent(input$apply_script, {
  req(input$r_script)
  req(original_data())  # Ensure that the original data has been loaded
  
  tryCatch({
    # Take the original data
    df <- original_data()
    
    # Evaluate the script in a specific environment
    env <- new.env()
    env$data <- df  # The original data is stored in the evaluation environment
    
    eval(parse(text = input$r_script), envir = env)  # Evaluate the script
    
    # Take the modification results from the environment
    modified_data(env$data)
    
    # Display the modified data in the Modified Data tab
    output$modified_data_table <- renderDT({
      datatable(modified_data(), options = list(pageLength = 10, scrollX = TRUE))
    })
    
    showNotification("Script applied successfully!", type = "message")
  }, error = function(e) {
    showNotification(paste("Error in script:", e$message), type = "error")
  })
  })

  
  # Generate Crosstab
  crosstab <- eventReactive(input$generate_crosstab, {
    req(input$col_vars, input$row_vars)
    
    # Select data based on the selected source
    df <- if (input$data_source == "original") {
      original_data()
    } else {
      modified_data()
    }
    
    # Prepare row and column variables
    row_result <- df %>% select(all_of(input$row_vars))
    column_result <- df %>% select(all_of(input$col_vars))
    
    # Crosstab calculation based on type
    if (input$crosstab_type == "Absolute Values") {
      cro_cases(row_result, list(total(), column_result))
    } else if (input$crosstab_type == "Percentage") {
      cro_cpct(row_result, list(total(), column_result))
    } else {
      cro_mean_sd_n(row_result, list(total(), column_result))
    }
  })
  
  # Render Crosstab
  output$crosstab_table <- renderDT({
    req(crosstab())
    datatable(crosstab(), options = list(pageLength = 10, scrollX = TRUE))
  })
  
  # Download Crosstab
  output$download_crosstab <- downloadHandler(
    filename = function() {
      paste("crosstab-", Sys.Date(), ".xlsx", sep = "")
    },
    content = function(file) {
      wb <- createWorkbook()
      sh1 <- addWorksheet(wb, "Crosstab")
      xl_write(crosstab(), wb, sh1)
      saveWorkbook(wb, file, overwrite = TRUE)
    }
  )
}

shinyApp(ui, server)