package logger

import (
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"douyu_go/internal/constants"
)

// AsyncLogWriter 异步日志写入器，队列满时丢弃日志以保护主链路。
type AsyncLogWriter struct {
	dst     io.Writer
	ch      chan []byte
	wg      sync.WaitGroup
	closed  uint32
	dropped uint64
}

// NewAsyncLogWriter 创建异步日志写入器。
func NewAsyncLogWriter(dst io.Writer, buffer int) *AsyncLogWriter {
	if buffer <= 0 {
		buffer = 1024
	}
	w := &AsyncLogWriter{
		dst: dst,
		ch:  make(chan []byte, buffer),
	}
	w.wg.Add(1)
	go w.run()
	return w
}

// Write 异步写日志；队列满时丢弃，避免抢购请求被磁盘 I/O 阻塞。
func (w *AsyncLogWriter) Write(p []byte) (int, error) {
	if w == nil {
		return len(p), nil
	}
	if atomic.LoadUint32(&w.closed) == 1 {
		return len(p), nil
	}
	buf := append([]byte(nil), p...)
	select {
	case w.ch <- buf:
	default:
		atomic.AddUint64(&w.dropped, 1)
	}
	return len(p), nil
}

func (w *AsyncLogWriter) run() {
	defer w.wg.Done()
	for p := range w.ch {
		_, _ = w.dst.Write(p)
	}
	if dropped := atomic.LoadUint64(&w.dropped); dropped > 0 {
		_, _ = fmt.Fprintf(w.dst, "%s [日志][warn] 日志队列已丢弃 %d 条，已优先保护抢购链路\n",
			time.Now().In(constants.CST).Format("2006/01/02 15:04:05.000000"), dropped)
	}
}

// Close 关闭写入器，等待队列清空。
func (w *AsyncLogWriter) Close() error {
	if w == nil {
		return nil
	}
	if atomic.CompareAndSwapUint32(&w.closed, 0, 1) {
		close(w.ch)
		w.wg.Wait()
	}
	return nil
}

// InitLogging 初始化日志输出：终端、日志文件、内存缓冲三处同时写入。
func InitLogging(store *MemoryLogStore, logDir string) func() {
	if logDir == "" {
		logDir = constants.DefaultLogDir
	}
	if err := os.MkdirAll(logDir, 0755); err != nil {
		async := NewAsyncLogWriter(io.MultiWriter(os.Stdout, store), 2048)
		log.SetOutput(async)
		log.Printf("日志目录创建失败，仅写入终端和内存: %v", err)
		return func() { _ = async.Close() }
	}

	filePath := filepath.Join(logDir, "douyu_"+time.Now().In(constants.CST).Format("20060102_150405")+".log")
	file, err := os.OpenFile(filePath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
	if err != nil {
		async := NewAsyncLogWriter(io.MultiWriter(os.Stdout, store), 2048)
		log.SetOutput(async)
		log.Printf("日志文件创建失败，仅写入终端和内存: %v", err)
		return func() { _ = async.Close() }
	}

	store.SetFilePath(filePath)
	async := NewAsyncLogWriter(io.MultiWriter(os.Stdout, file, store), 2048)
	log.SetOutput(async)
	log.Printf("日志文件已启用: %s", filePath)
	return func() {
		_ = async.Close()
		_ = file.Close()
	}
}

// LogEvent 输出带分类和级别的结构化文本日志。
func LogEvent(category, level, format string, args ...any) {
	if category == "" {
		category = "系统"
	}
	if level == "" {
		level = "info"
	}
	log.Printf("[%s][%s] %s", category, level, fmt.Sprintf(format, args...))
}

// ParseLogMeta 从标准日志行中提取类似 [网络][warn] 的分类和级别。
func ParseLogMeta(line string) (string, string) {
	idx := strings.Index(line, "[")
	if idx < 0 {
		return "", ""
	}
	category, rest, ok := cutBracket(line[idx:])
	if !ok {
		return "", ""
	}
	level, _, ok := cutBracket(rest)
	if !ok || !IsLogLevel(level) {
		return category, ""
	}
	return category, level
}

func cutBracket(s string) (string, string, bool) {
	if !strings.HasPrefix(s, "[") {
		return "", s, false
	}
	end := strings.Index(s, "]")
	if end <= 1 {
		return "", s, false
	}
	return s[1:end], s[end+1:], true
}

// IsLogLevel 判断是否为有效日志级别。
func IsLogLevel(level string) bool {
	switch strings.ToLower(level) {
	case "success", "error", "warn", "info":
		return true
	default:
		return false
	}
}

// DetectLogLevel 根据日志文本粗略分类，方便前端染色。
func DetectLogLevel(line string) string {
	lower := strings.ToLower(line)
	switch {
	case strings.Contains(lower, "[success]"):
		return "success"
	case strings.Contains(lower, "[error]"):
		return "error"
	case strings.Contains(lower, "[warn]"):
		return "warn"
	case strings.Contains(lower, "[info]"):
		return "info"
	case strings.Contains(line, "成功"):
		return "success"
	case strings.Contains(line, "失败") || strings.Contains(line, "错误") || strings.Contains(lower, "error") || strings.Contains(lower, "panic"):
		return "error"
	case strings.Contains(line, "降级") || strings.Contains(line, "跳过") || strings.Contains(line, "不存在") || strings.Contains(lower, "warn"):
		return "warn"
	default:
		return "info"
	}
}