package parking

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/gofrs/uuid/v5"
	"go.uber.org/zap"
	"wails-app/internal/dao"
	"wails-app/internal/global"
)

const cameraStreamTokenTTL = 2 * time.Minute

type cameraStreamToken struct {
	DeviceCode string
	ExpiresAt  time.Time
}

var cameraStreamTokens sync.Map

func isSystemMJPEG(protocol string) bool {
	protocol = strings.ToLower(strings.TrimSpace(protocol))
	return protocol == "system-mjpeg" || protocol == "rtsp" || protocol == "system"
}

func issueCameraStreamToken(deviceCode string) string {
	for {
		id, err := uuid.NewV4()
		if err != nil {
			continue
		}
		token := id.String()
		cameraStreamTokens.Store(token, cameraStreamToken{
			DeviceCode: deviceCode,
			ExpiresAt:  time.Now().Add(cameraStreamTokenTTL),
		})
		return token
	}
}

func validateCameraStreamToken(deviceCode, token string) bool {
	value, ok := cameraStreamTokens.Load(token)
	if !ok {
		return false
	}
	entry := value.(cameraStreamToken)
	if entry.DeviceCode != deviceCode || time.Now().After(entry.ExpiresAt) {
		cameraStreamTokens.Delete(token)
		return false
	}
	return true
}

// StreamCameraMJPEG 在系统端把摄像头原始 RTSP/HTTP 流转换为 multipart MJPEG。
// 该输出可由 WebView 的 <img> 直接播放，不要求边缘端实现 WHEP。
func (s *PassageService) StreamCameraMJPEG(deviceCode, token string, writer http.ResponseWriter, ctx context.Context) error {
	if !validateCameraStreamToken(deviceCode, token) {
		return errors.New("摄像头播放令牌无效或已过期")
	}
	if global.GVA_DB == nil {
		return errors.New("数据库未初始化")
	}
	var camera dao.Camera
	if err := global.GVA_DB.Where("device_code = ? AND is_active = ?", deviceCode, true).First(&camera).Error; err != nil {
		return fmt.Errorf("摄像头不存在或未启用: %w", err)
	}
	if !isSystemMJPEG(camera.StreamProtocol) {
		return errors.New("当前摄像头未启用系统侧转换")
	}
	sourceURL := strings.TrimSpace(camera.SourceURL)
	if sourceURL == "" {
		sourceURL = strings.TrimSpace(camera.StreamURL)
	}
	if sourceURL == "" {
		return errors.New("摄像头未配置原始视频地址")
	}

	ffmpegPath := strings.TrimSpace(global.GVA_CONFIG.Camera.FFmpegPath)
	if ffmpegPath == "" {
		ffmpegPath = "ffmpeg"
	} else if info, statErr := os.Stat(ffmpegPath); statErr == nil && info.IsDir() {
		// Accept a configured FFmpeg bin directory for compatibility with older config files.
		ffmpegPath = filepath.Join(ffmpegPath, "ffmpeg.exe")
	}
	fps := global.GVA_CONFIG.Camera.MJPEGFPS
	if fps < 1 || fps > 25 {
		fps = 8
	}
	quality := global.GVA_CONFIG.Camera.JPEGQuality
	if quality < 2 || quality > 31 {
		quality = 5
	}
	args := []string{"-hide_banner", "-loglevel", "error"}
	if strings.HasPrefix(strings.ToLower(sourceURL), "rtsp://") {
		args = append(args, "-rtsp_transport", "tcp")
	}
	args = append(args, "-i", sourceURL, "-an", "-vf", fmt.Sprintf("fps=%d", fps), "-q:v", fmt.Sprintf("%d", quality), "-f", "mpjpeg", "pipe:1")

	cmd := exec.CommandContext(ctx, ffmpegPath, args...)
	if global.GVA_LOG != nil {
		global.GVA_LOG.Info("启动摄像头 FFmpeg 转码", zap.String("device_code", deviceCode), zap.String("ffmpeg", ffmpegPath), zap.String("source", redactCameraURL(sourceURL)))
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return fmt.Errorf("创建视频转换输出失败: %w", err)
	}
	cmd.Stderr = io.Discard
	if err := cmd.Start(); err != nil {
		if global.GVA_LOG != nil {
			global.GVA_LOG.Error("摄像头 FFmpeg 启动失败", zap.String("device_code", deviceCode), zap.String("ffmpeg", ffmpegPath), zap.Error(err))
		}
		return fmt.Errorf("启动 FFmpeg 失败（%s）: %w", ffmpegPath, err)
	}

	writer.Header().Set("Content-Type", "multipart/x-mixed-replace; boundary=ffmpeg")
	writer.Header().Set("Cache-Control", "no-store, no-cache, must-revalidate")
	writer.Header().Set("X-Content-Type-Options", "nosniff")
	if flusher, ok := writer.(http.Flusher); ok {
		flusher.Flush()
	}
	_, copyErr := io.Copy(&flushWriter{writer: writer}, stdout)
	waitErr := cmd.Wait()
	if copyErr != nil && !errors.Is(copyErr, context.Canceled) {
		return fmt.Errorf("视频流传输失败: %w", copyErr)
	}
	if ctx.Err() != nil {
		return nil
	}
	if waitErr != nil {
		if global.GVA_LOG != nil {
			global.GVA_LOG.Error("摄像头 FFmpeg 转码进程退出", zap.String("device_code", deviceCode), zap.Error(waitErr))
		}
		return fmt.Errorf("FFmpeg 进程退出: %w", waitErr)
	}
	return nil
}

func redactCameraURL(raw string) string {
	u, err := url.Parse(raw)
	if err != nil || u.User == nil {
		return raw
	}
	return strings.Replace(raw, u.User.String()+"@", "***@", 1)
}

type flushWriter struct {
	writer http.ResponseWriter
}

func (w *flushWriter) Write(data []byte) (int, error) {
	n, err := w.writer.Write(data)
	if flusher, ok := w.writer.(http.Flusher); ok {
		flusher.Flush()
	}
	return n, err
}