#' @tool_code ST_CHI_SQUARE
#' @name 卡方检验
#' @version 1.0.0
#' @description 两个分类变量的独立性检验
#' @author SSA-Pro Team

library(glue)
library(ggplot2)
library(base64enc)

run_analysis <- function(input) {
  # ===== 初始化 =====
  logs <- c()
  log_add <- function(msg) { logs <<- c(logs, paste0("[", Sys.time(), "] ", msg)) }
  
  on.exit({}, add = TRUE)
  
  # ===== 数据加载 =====
  log_add("开始加载输入数据")
  df <- tryCatch(
    load_input_data(input),
    error = function(e) {
      log_add(paste("数据加载失败:", e$message))
      return(NULL)
    }
  )
  
  if (is.null(df)) {
    return(make_error(ERROR_CODES$E100_INTERNAL_ERROR, details = "数据加载失败"))
  }
  log_add(glue("数据加载成功: {nrow(df)} 行, {ncol(df)} 列"))
  
  p <- input$params
  var1 <- p$var1
  var2 <- p$var2
  
  # ===== 参数校验 =====
  if (!(var1 %in% names(df))) {
    return(make_error(ERROR_CODES$E001_COLUMN_NOT_FOUND, col = var1))
  }
  if (!(var2 %in% names(df))) {
    return(make_error(ERROR_CODES$E001_COLUMN_NOT_FOUND, col = var2))
  }
  
  # ===== 数据清洗 =====
  original_rows <- nrow(df)
  df <- df[!is.na(df[[var1]]) & trimws(as.character(df[[var1]])) != "", ]
  df <- df[!is.na(df[[var2]]) & trimws(as.character(df[[var2]])) != "", ]
  
  removed_rows <- original_rows - nrow(df)
  if (removed_rows > 0) {
    log_add(glue("数据清洗: 移除 {removed_rows} 行缺失值 (剩余 {nrow(df)} 行)"))
  }
  
  # ===== 护栏检查 =====
  guardrail_results <- list()
  warnings_list <- c()
  
  # 样本量检查
  sample_check <- check_sample_size(nrow(df), min_required = 10, action = ACTION_BLOCK)
  guardrail_results <- c(guardrail_results, list(sample_check))
  log_add(glue("样本量检查: N = {nrow(df)}, {sample_check$reason}"))
  
  guardrail_status <- run_guardrail_chain(guardrail_results)
  
  if (guardrail_status$status == "blocked") {
    return(list(
      status = "blocked",
      message = guardrail_status$reason,
      trace_log = logs
    ))
  }
  
  # ===== 构建列联表 =====
  contingency_table <- table(df[[var1]], df[[var2]])
  log_add(glue("列联表维度: {nrow(contingency_table)} x {ncol(contingency_table)}"))
  
  # 检查列联表有效性
  if (nrow(contingency_table) < 2 || ncol(contingency_table) < 2) {
    return(make_error(ERROR_CODES$E003_INSUFFICIENT_GROUPS,
                      col = paste(var1, "或", var2),
                      expected = 2,
                      actual = min(nrow(contingency_table), ncol(contingency_table))))
  }
  
  # ===== 期望频数检查（决定使用卡方还是 Fisher） =====
  expected <- chisq.test(contingency_table)$expected
  low_expected_count <- sum(expected < 5)
  total_cells <- length(expected)
  low_expected_pct <- low_expected_count / total_cells
  
  use_fisher <- FALSE
  is_2x2 <- nrow(contingency_table) == 2 && ncol(contingency_table) == 2
  
  if (low_expected_pct > 0.2) {
    warnings_list <- c(warnings_list, glue("期望频数 < 5 的格子占 {round(low_expected_pct * 100, 1)}%"))
    if (is_2x2) {
      use_fisher <- TRUE
      log_add("2x2 表且期望频数不足，自动切换为 Fisher 精确检验")
    } else {
      log_add("期望频数不足，但非 2x2 表，继续使用卡方检验（结果需谨慎解读）")
    }
  }
  
  # ===== 核心计算 =====
  if (use_fisher) {
    log_add("执行 Fisher 精确检验")
    result <- fisher.test(contingency_table)
    method_used <- "Fisher's Exact Test"
    
    output_results <- list(
      method = method_used,
      p_value = jsonlite::unbox(as.numeric(result$p.value)),
      p_value_fmt = format_p_value(result$p.value),
      odds_ratio = if (!is.null(result$estimate)) jsonlite::unbox(as.numeric(result$estimate)) else NULL,
      conf_int = if (!is.null(result$conf.int)) as.numeric(result$conf.int) else NULL
    )
  } else {
    log_add("执行 Pearson 卡方检验")
    result <- chisq.test(contingency_table, correct = is_2x2)  # 2x2表使用Yates连续性校正
    method_used <- if (is_2x2) "Pearson's Chi-squared test with Yates' continuity correction" else "Pearson's Chi-squared test"
    
    # 计算 Cramér's V
    n <- sum(contingency_table)
    k <- min(nrow(contingency_table), ncol(contingency_table))
    cramers_v <- sqrt(result$statistic / (n * (k - 1)))
    
    # 效应量解释
    v_interpretation <- if (cramers_v < 0.1) "微小" else if (cramers_v < 0.3) "小" else if (cramers_v < 0.5) "中等" else "大"
    
    log_add(glue("χ² = {round(result$statistic, 3)}, df = {result$parameter}, p = {round(result$p.value, 4)}, Cramér's V = {round(cramers_v, 3)}"))
    
    output_results <- list(
      method = method_used,
      statistic = jsonlite::unbox(as.numeric(result$statistic)),
      df = jsonlite::unbox(as.numeric(result$parameter)),
      p_value = jsonlite::unbox(as.numeric(result$p.value)),
      p_value_fmt = format_p_value(result$p.value),
      effect_size = list(
        cramers_v = jsonlite::unbox(round(as.numeric(cramers_v), 4)),
        interpretation = v_interpretation
      )
    )
  }
  
  # 添加列联表信息（精简版，不含原始数据）
  # 将 table 转为纯数值矩阵以便 JSON 序列化
  observed_matrix <- matrix(
    as.numeric(contingency_table),
    nrow = nrow(contingency_table),
    ncol = ncol(contingency_table),
    dimnames = list(rownames(contingency_table), colnames(contingency_table))
  )
  
  output_results$contingency_table <- list(
    row_var = var1,
    col_var = var2,
    row_levels = as.character(rownames(contingency_table)),
    col_levels = as.character(colnames(contingency_table)),
    observed = observed_matrix,
    row_totals = as.numeric(rowSums(contingency_table)),
    col_totals = as.numeric(colSums(contingency_table)),
    grand_total = jsonlite::unbox(sum(contingency_table))
  )
  
  # ===== 生成图表 =====
  log_add("生成马赛克图")
  plot_base64 <- tryCatch({
    generate_mosaic_plot(contingency_table, var1, var2)
  }, error = function(e) {
    log_add(paste("图表生成失败:", e$message))
    NULL
  })
  
  # ===== 生成可复现代码 =====
  original_filename <- if (!is.null(input$original_filename) && nchar(input$original_filename) > 0) {
    input$original_filename
  } else {
    "data.csv"
  }
  
  reproducible_code <- glue('
# SSA-Pro 自动生成代码
# 工具: 卡方检验
# 时间: {Sys.time()}
# ================================

library(ggplot2)

# 数据准备
df <- read.csv("{original_filename}")
var1 <- "{var1}"
var2 <- "{var2}"

# 数据清洗
df <- df[!is.na(df[[var1]]) & !is.na(df[[var2]]), ]

# 构建列联表
contingency_table <- table(df[[var1]], df[[var2]])
print(contingency_table)

# 卡方检验
result <- chisq.test(contingency_table)
print(result)

# 计算 Cramer V (效应量)
n <- sum(contingency_table)
k <- min(nrow(contingency_table), ncol(contingency_table))
cramers_v <- sqrt(result$statistic / (n * (k - 1)))
cat("Cramer V =", round(cramers_v, 3), "\\n")

# 可视化（马赛克图）
mosaicplot(contingency_table, main = "Mosaic Plot", color = TRUE)
')
  
  # ===== 返回结果 =====
  log_add("分析完成")
  
  return(list(
    status = "success",
    message = "分析完成",
    warnings = if (length(warnings_list) > 0) warnings_list else NULL,
    results = output_results,
    plots = if (!is.null(plot_base64)) list(plot_base64) else list(),
    trace_log = logs,
    reproducible_code = as.character(reproducible_code)
  ))
}

# 辅助函数：生成马赛克图（使用 ggplot2 模拟）
generate_mosaic_plot <- function(contingency_table, var1, var2) {
  # 转换为长格式数据
  df_plot <- as.data.frame(contingency_table)
  names(df_plot) <- c("Var1", "Var2", "Freq")
  
  p <- ggplot(df_plot, aes(x = Var1, y = Freq, fill = Var2)) +
    geom_bar(stat = "identity", position = "fill") +
    scale_y_continuous(labels = scales::percent) +
    theme_minimal() +
    labs(
      title = paste("Association between", var1, "and", var2),
      x = var1,
      y = "Proportion",
      fill = var2
    ) +
    scale_fill_brewer(palette = "Set2")
  
  tmp_file <- tempfile(fileext = ".png")
  ggsave(tmp_file, p, width = 7, height = 5, dpi = 100)
  base64_str <- base64encode(tmp_file)
  unlink(tmp_file)
  
  return(paste0("data:image/png;base64,", base64_str))
}