package service

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"regexp"
	"strings"
	"time"

	"gorm.io/gorm"

	"wx_service/config"
	"wx_service/internal/model"
)

const removeWatermarkEndpoint = "https://api.23bt.cn/api/d1w/index"

var (
	// 从用户输入的文本里“抓取 URL”的简单正则（找到第一个 http/https 链接）
	urlPattern            = regexp.MustCompile(`https?://[^\s]+`)
	ErrURLNotFound        = errors.New("no valid url found in content")
	ErrShortVideoAPIKey   = errors.New("short video api key is not configured")
	ErrDailyQuotaExceeded = errors.New("daily free quota exceeded, please watch an ad to continue")
)

type VideoService struct {
	// VideoService 封装“去水印”相关业务：
	// - 限额（每天免费次数）
	// - 调用第三方解析接口
	// - 记录解析日志（便于排查问题/统计）
	db     *gorm.DB
	cfg    config.ShortVideoConfig
	client *http.Client
}

type RemoveWatermarkResult struct {
	// json.RawMessage 表示“原始 JSON 字节”，不强制把第三方返回结构定义成 Go struct。
	// 对接不稳定/字段多的第三方接口时，这种做法更灵活。
	Provider      string          `json:"provider"`
	Raw           json.RawMessage `json:"raw"`
	FreeQuotaUsed bool            `json:"free_quota_used"`
}

type ThirdPartyError struct {
	StatusCode int
	Message    string
}

func (e *ThirdPartyError) Error() string {
	return fmt.Sprintf("third-party api error: status=%d message=%s", e.StatusCode, e.Message)
}

func NewVideoService(db *gorm.DB, cfg config.ShortVideoConfig) (*VideoService, error) {
	timeout := cfg.RequestTimeout
	if timeout <= 0 {
		// 不配置就给一个默认超时，避免请求卡住占用 goroutine
		timeout = 5 * time.Second
	}

	client := &http.Client{
		Timeout: timeout,
	}

	return &VideoService{
		db:     db,
		cfg:    cfg,
		client: client,
	}, nil
}

func (s *VideoService) RemoveWatermark(ctx context.Context, user *model.User, content string) (*RemoveWatermarkResult, error) {
	// RemoveWatermark 的整体流程：
	// 1) 从 content 里提取链接
	// 2) 检查每日免费额度（或是否已解锁）
	// 3) 调用第三方接口解析
	// 4) 写入解析日志（无论成功/失败都记一条，方便定位问题）
	link, err := extractFirstURL(content)
	if err != nil {
		return nil, ErrURLNotFound
	}

	freeQuotaUsed, err := s.ensureQuota(ctx, user)
	if err != nil {
		return nil, err
	}

	now := time.Now()
	var (
		statusCode int
		body       []byte
		requestErr error
	)

	statusCode, body, requestErr = s.callThirdParty(ctx, link)

	duration := int(time.Since(now).Milliseconds())
	logEntry := model.VideoParseLog{
		MiniProgramID:    user.MiniProgramID,
		UserID:           user.ID,
		RequestContent:   content,
		ParsedURL:        link,
		ThirdPartyStatus: statusCode,
		FreeQuotaUsed:    freeQuotaUsed,
		DurationMs:       duration,
	}

	if requestErr == nil {
		logEntry.ThirdPartyPayload = body
	} else {
		logEntry.ErrorMessage = requestErr.Error()
	}

	if err := s.db.WithContext(ctx).Create(&logEntry).Error; err != nil {
		return nil, fmt.Errorf("save parse log: %w", err)
	}

	if requestErr != nil {
		return nil, requestErr
	}

	return &RemoveWatermarkResult{
		Provider:      "23bt",
		Raw:           json.RawMessage(body),
		FreeQuotaUsed: freeQuotaUsed,
	}, nil
}

func (s *VideoService) UnlockForToday(ctx context.Context, user *model.User) error {
	// “看广告解锁”的实现方式：在当天写一条 unlock 记录即可（存在则更新时间戳）
	startOfDay, _ := dayRange(time.Now())

	var unlock model.VideoParseUnlock
	tx := s.db.WithContext(ctx)
	err := tx.Where("user_id = ? AND mini_program_id = ? AND unlock_date = ?", user.ID, user.MiniProgramID, startOfDay).First(&unlock).Error
	if err == nil {
		return tx.Model(&unlock).Updates(map[string]interface{}{
			"ad_watched_at": time.Now(),
		}).Error
	}
	if err != nil && err != gorm.ErrRecordNotFound {
		return fmt.Errorf("load unlock record: %w", err)
	}

	record := model.VideoParseUnlock{
		MiniProgramID: user.MiniProgramID,
		UserID:        user.ID,
		UnlockDate:    startOfDay,
		AdWatchedAt:   time.Now(),
	}
	if err := tx.Create(&record).Error; err != nil {
		return fmt.Errorf("create unlock record: %w", err)
	}
	return nil
}

func (s *VideoService) ensureQuota(ctx context.Context, user *model.User) (bool, error) {
	// ensureQuota 返回值 freeQuotaUsed 的含义：
	// - true：这次调用会消耗一次“免费额度”
	// - false：不消耗（例如今日已解锁或未启用限额）
	if s.cfg.FreeDailyQuota <= 0 {
		return false, nil
	}

	startOfDay, endOfDay := dayRange(time.Now())
	tx := s.db.WithContext(ctx)

	var unlock model.VideoParseUnlock
	if err := tx.Where("user_id = ? AND mini_program_id = ? AND unlock_date = ?", user.ID, user.MiniProgramID, startOfDay).First(&unlock).Error; err == nil {
		return false, nil
	} else if err != gorm.ErrRecordNotFound {
		return false, fmt.Errorf("check unlock record: %w", err)
	}

	var count int64
	if err := tx.Model(&model.VideoParseLog{}).
		Where("user_id = ? AND mini_program_id = ? AND free_quota_used = ? AND created_at >= ? AND created_at < ?",
			user.ID, user.MiniProgramID, true, startOfDay, endOfDay).
		Count(&count).Error; err != nil {
		return false, fmt.Errorf("count user quota: %w", err)
	}

	if count >= int64(s.cfg.FreeDailyQuota) {
		return false, ErrDailyQuotaExceeded
	}
	return true, nil
}

func (s *VideoService) callThirdParty(ctx context.Context, link string) (int, []byte, error) {
	if s.cfg.APIKey == "" {
		return 0, nil, ErrShortVideoAPIKey
	}
	params := url.Values{}
	params.Set("key", s.cfg.APIKey)
	params.Set("url", link)

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, fmt.Sprintf("%s?%s", removeWatermarkEndpoint, params.Encode()), nil)
	if err != nil {
		return 0, nil, fmt.Errorf("build third-party request: %w", err)
	}

	resp, err := s.client.Do(req)
	if err != nil {
		return 0, nil, fmt.Errorf("call third-party api: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return resp.StatusCode, nil, fmt.Errorf("read third-party response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return resp.StatusCode, nil, &ThirdPartyError{
			StatusCode: resp.StatusCode,
			Message:    truncateString(string(body), 256),
		}
	}

	return resp.StatusCode, body, nil
}

func extractFirstURL(content string) (string, error) {
	// 从文本里提取第一个 URL，并做简单 trim，把末尾可能粘上的标点去掉。
	if content == "" {
		return "", ErrURLNotFound
	}
	match := urlPattern.FindString(content)
	if match == "" {
		return "", ErrURLNotFound
	}
	return strings.Trim(match, " \t\n\r,.;!\"'()[]{}<>"), nil
}

func dayRange(ts time.Time) (time.Time, time.Time) {
	// 计算“当天的起止时间”：[00:00, 次日00:00)
	// 用本地时区 loc，避免跨时区导致的日期偏移。
	loc := ts.Location()
	start := time.Date(ts.Year(), ts.Month(), ts.Day(), 0, 0, 0, 0, loc)
	end := start.Add(24 * time.Hour)
	return start, end
}

func truncateString(input string, max int) string {
	// 截断字符串，避免把第三方错误响应原样写入导致日志过大
	if len(input) <= max {
		return input
	}
	return input[:max]
}