package main

import (
	"encoding/json"
	"fmt"
	"log"
	"maps"
	"os"
	"path/filepath"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
)

// -----------------------------------------------------------------------------
// 审计日志 (JSON Lines, 一行一条事件, 落盘到 *auditDir/YYYY-MM-DD.log, 跨日自动轮转)
// -----------------------------------------------------------------------------

var (
	auditMu     sync.Mutex
	auditFile   *os.File
	auditCurDay string // 当前打开文件对应的日期 (YYYY-MM-DD)
)

// initAudit 创建目录, 打开今天的日志文件
func initAudit() error {
	if *auditDir == "" {
		log.Println("[audit] disabled (audit dir is empty)")
		return nil
	}
	if err := os.MkdirAll(*auditDir, 0o755); err != nil {
		return fmt.Errorf("create audit dir: %w", err)
	}
	if err := openAuditFor(time.Now()); err != nil {
		return err
	}
	log.Printf("[audit] writing to %s/%s.log", *auditDir, auditCurDay)
	return nil
}

// openAuditFor 为指定时间打开对应日期的日志文件. 调用方需持有 auditMu.
func openAuditFor(t time.Time) error {
	day := t.Format("2006-01-02")
	if day == auditCurDay && auditFile != nil {
		return nil
	}
	if auditFile != nil {
		_ = auditFile.Close()
	}
	path := filepath.Join(*auditDir, day+".log")
	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		return fmt.Errorf("open %s: %w", path, err)
	}
	auditFile = f
	auditCurDay = day
	return nil
}

// audit 写一条审计事件. fields 里的键会合并到事件 JSON 中.
// 写入失败仅记录到 stdout, 不会影响主流程.
func audit(c *gin.Context, action string, fields map[string]any) {
	if *auditDir == "" {
		return
	}
	entry := map[string]any{
		"ts":      time.Now().Format(time.RFC3339),
		"action":  action,
		"ip":      c.ClientIP(),
		"method":  c.Request.Method,
		"path":    c.Request.URL.Path,
		"ua":      c.Request.UserAgent(),
		"status":  c.Writer.Status(),
		"latency": time.Since(c.GetTime("t0")).String(),
	}
	maps.Copy(entry, fields)
	b, err := json.Marshal(entry)
	if err != nil {
		log.Printf("[audit] marshal err: %v", err)
		return
	}
	b = append(b, '\n')

	auditMu.Lock()
	defer auditMu.Unlock()
	if err := openAuditFor(time.Now()); err != nil {
		log.Printf("[audit] open err: %v", err)
		return
	}
	if _, err := auditFile.Write(b); err != nil {
		log.Printf("[audit] write err: %v", err)
	}
}

// auditT0 记录请求进入时间, 供 audit() 计算 latency
func auditT0() gin.HandlerFunc {
	return func(c *gin.Context) {
		c.Set("t0", time.Now())
		c.Next()
	}
}