# utils/guardrails.R
# 统计护栏函数库

library(glue)

# 大样本优化阈值
LARGE_SAMPLE_THRESHOLD <- 5000

# 护栏 Action 类型
ACTION_BLOCK <- "Block"    # 阻止执行
ACTION_WARN <- "Warn"      # 警告但继续
ACTION_SWITCH <- "Switch"  # 切换到备选方法

# 正态性检验（支持三种 Action）
check_normality <- function(values, alpha = 0.05, action = ACTION_SWITCH, action_target = NULL) {
  n <- length(values)
  
  # 样本量过小
  if (n < 3) {
    return(list(
      passed = TRUE, 
      action = NULL,
      action_target = NULL,
      reason = "样本量过小，跳过正态性检验", 
      skipped = TRUE
    ))
  }
  
  # 大样本优化：N > 5000 时使用抽样检验
  if (n > LARGE_SAMPLE_THRESHOLD) {
    set.seed(42)
    sampled_values <- sample(values, 1000)
    test <- shapiro.test(sampled_values)
    passed <- test$p.value >= alpha
    
    return(list(
      passed = passed,
      action = if (passed) NULL else action,
      action_target = if (passed) NULL else action_target,
      p_value = test$p.value,
      reason = glue("大样本(N={n})抽样检验，{if (passed) '满足正态性' else '不满足正态性'}"),
      sampled = TRUE,
      sample_size = 1000
    ))
  }
  
  # 常规检验
  test <- shapiro.test(values)
  passed <- test$p.value >= alpha
  
  return(list(
    passed = passed,
    action = if (passed) NULL else action,
    action_target = if (passed) NULL else action_target,
    p_value = test$p.value,
    reason = if (passed) "满足正态性" else "不满足正态性",
    sampled = FALSE
  ))
}

# 方差齐性检验 (Levene)
check_homogeneity <- function(df, group_var, value_var, alpha = 0.05, action = ACTION_WARN) {
  library(car)
  
  formula <- as.formula(paste(value_var, "~", group_var))
  test <- leveneTest(formula, data = df)
  p_val <- test$`Pr(>F)`[1]
  passed <- p_val >= alpha
  
  return(list(
    passed = passed,
    action = if (passed) NULL else action,
    p_value = p_val,
    reason = if (passed) "方差齐性满足" else "方差不齐性"
  ))
}

# 样本量检验
check_sample_size <- function(n, min_required = 3, action = ACTION_BLOCK) {
  passed <- n >= min_required
  return(list(
    passed = passed,
    action = if (passed) NULL else action,
    n = n,
    reason = if (passed) "样本量充足" else paste0("样本量不足, 需要至少 ", min_required)
  ))
}

# 执行护栏链（按 check_order 顺序执行）
run_guardrail_chain <- function(guardrail_results) {
  warnings <- c()
  
  for (result in guardrail_results) {
    if (!result$passed) {
      if (result$action == ACTION_BLOCK) {
        return(list(
          status = "blocked",
          reason = result$reason
        ))
      } else if (result$action == ACTION_SWITCH) {
        return(list(
          status = "switch",
          target_tool = result$action_target,
          reason = result$reason
        ))
      } else if (result$action == ACTION_WARN) {
        warnings <- c(warnings, result$reason)
      }
    }
  }
  
  return(list(
    status = "passed",
    warnings = warnings
  ))
}

# ========== JIT 护栏接口（Phase 2A） ==========
# 用于 WorkflowExecutor 在执行核心工具前调用

#' JIT 护栏检查：执行核心统计前检验假设
#' @param df 数据框
#' @param tool_code 目标工具代码
#' @param params 工具参数（group_var, value_var 等）
#' @return list(checks, suggested_tool, can_proceed)
run_jit_guardrails <- function(df, tool_code, params) {
  checks <- list()
  suggested_tool <- tool_code
  can_proceed <- TRUE
  
  # 根据工具类型执行不同的检验
  if (tool_code %in% c("ST_T_TEST_IND", "ST_MANN_WHITNEY")) {
    # 独立样本比较：需要正态性 + 方差齐性检验
    group_var <- params$group_var
    value_var <- params$value_var
    
    if (!is.null(group_var) && !is.null(value_var)) {
      groups <- unique(df[[group_var]])
      
      # 正态性检验（分组）
      for (g in groups) {
        vals <- df[df[[group_var]] == g, value_var]
        if (length(vals) >= 3) {
          norm_result <- check_normality(vals, alpha = 0.05)
          checks <- c(checks, list(list(
            check_name = glue("正态性检验 (组: {g})"),
            passed = norm_result$passed,
            p_value = norm_result$p_value,
            recommendation = if (norm_result$passed) "满足正态性" else "建议使用非参数方法"
          )))
          
          if (!norm_result$passed && tool_code == "ST_T_TEST_IND") {
            suggested_tool <- "ST_MANN_WHITNEY"
          }
        }
      }
      
      # 方差齐性检验
      if (length(groups) == 2) {
        tryCatch({
          homo_result <- check_homogeneity(df, group_var, value_var, alpha = 0.05)
          checks <- c(checks, list(list(
            check_name = "方差齐性检验 (Levene)",
            passed = homo_result$passed,
            p_value = homo_result$p_value,
            recommendation = if (homo_result$passed) "方差齐性满足" else "建议使用 Welch 校正"
          )))
        }, error = function(e) {
          message("方差齐性检验失败: ", e$message)
        })
      }
    }
    
  } else if (tool_code == "ST_T_TEST_PAIRED") {
    # 配对检验：需要差值正态性检验
    before_var <- params$before_var
    after_var <- params$after_var
    
    if (!is.null(before_var) && !is.null(after_var)) {
      diff_vals <- df[[after_var]] - df[[before_var]]
      diff_vals <- diff_vals[!is.na(diff_vals)]
      
      if (length(diff_vals) >= 3) {
        norm_result <- check_normality(diff_vals, alpha = 0.05)
        checks <- c(checks, list(list(
          check_name = "差值正态性检验",
          passed = norm_result$passed,
          p_value = norm_result$p_value,
          recommendation = if (norm_result$passed) "差值满足正态性" else "建议使用 Wilcoxon 符号秩检验"
        )))
        
        if (!norm_result$passed) {
          suggested_tool <- "Wilcoxon signed-rank test"
        }
      }
    }
    
  } else if (tool_code == "ST_CORRELATION") {
    # 相关分析：需要双变量正态性检验
    var_x <- params$var_x
    var_y <- params$var_y
    
    if (!is.null(var_x) && !is.null(var_y)) {
      x_vals <- df[[var_x]][!is.na(df[[var_x]])]
      y_vals <- df[[var_y]][!is.na(df[[var_y]])]
      
      if (length(x_vals) >= 3) {
        norm_x <- check_normality(x_vals, alpha = 0.05)
        checks <- c(checks, list(list(
          check_name = glue("正态性检验 ({var_x})"),
          passed = norm_x$passed,
          p_value = norm_x$p_value,
          recommendation = if (norm_x$passed) "满足正态性" else "建议使用 Spearman 秩相关"
        )))
      }
      
      if (length(y_vals) >= 3) {
        norm_y <- check_normality(y_vals, alpha = 0.05)
        checks <- c(checks, list(list(
          check_name = glue("正态性检验 ({var_y})"),
          passed = norm_y$passed,
          p_value = norm_y$p_value,
          recommendation = if (norm_y$passed) "满足正态性" else "建议使用 Spearman 秩相关"
        )))
        
        if (!norm_x$passed || !norm_y$passed) {
          suggested_tool <- "ST_CORRELATION (Spearman)"
        }
      }
    }
  }
  
  # 汇总
  all_passed <- all(sapply(checks, function(c) c$passed))
  
  return(list(
    checks = checks,
    suggested_tool = suggested_tool,
    can_proceed = TRUE,  # 即使检验不通过也允许继续，由用户/LLM 决定
    all_checks_passed = all_passed
  ))
}