package app

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

const (
	chatMediaCleanupLock = "im_chat_media_cleanup_v1"
	chatMediaBatchSize   = 200
)

type chatMediaCleanupSummary struct {
	Scanned int `json:"scanned"`
	Deleted int `json:"deleted"`
	Failed  int `json:"failed"`
}

type chatMediaTarget struct {
	MessageID       int64
	MediaAssetID    sql.NullInt64
	MediaType       string
	PublicURL       string
	ConversationID  int64
	Seq             int64
	StorageProvider string
	Bucket          string
	ObjectKey       string
	AssetStatus     int
}

type chatMediaEvent struct {
	MessageID      int64
	ConversationID int64
	Seq            int64
}

func clampChatMediaRetentionDays(days int) int {
	if days < 1 || days > 3650 {
		return 90
	}
	return days
}

func chatMediaObjectKeys(objectKey, mediaType string) []string {
	objectKey = strings.TrimSpace(objectKey)
	if objectKey == "" {
		return nil
	}
	keys := []string{objectKey}
	if mediaType == "image" {
		extension := filepath.Ext(objectKey)
		stem := strings.TrimSuffix(objectKey, extension)
		// Chat/post images uploaded by this service use the immutable -im1
		// suffix and always have a derived thumbnail sibling.
		if strings.HasSuffix(stem, "-im1") {
			keys = append(keys, stem+"-thumb.jpg")
		}
	}
	return keys
}

func chatMediaCleanupError(err error) string {
	if err == nil {
		return ""
	}
	message := strings.TrimSpace(err.Error())
	runes := []rune(message)
	if len(runes) > 480 {
		message = string(runes[:480])
	}
	return message
}

func isMissingMediaObject(err error) bool {
	if err == nil || errors.Is(err, os.ErrNotExist) {
		return true
	}
	message := strings.ToLower(err.Error())
	return strings.Contains(message, "nosuchkey") ||
		strings.Contains(message, "no such key") ||
		strings.Contains(message, "not found") ||
		strings.Contains(message, "status code: 404") ||
		strings.Contains(message, "statuscode=404")
}

func (a *App) adminChatMedia(w http.ResponseWriter, r *http.Request) {
	page, size, offset := pagination(r)
	keyword := strings.TrimSpace(r.URL.Query().Get("keyword"))
	mediaType := strings.TrimSpace(r.URL.Query().Get("type"))
	statusText := strings.TrimSpace(r.URL.Query().Get("status"))
	where := ` WHERE 1=1`
	args := []any{}
	if mediaType == "image" || mediaType == "voice" {
		where += ` AND mm.media_type=?`
		args = append(args, mediaType)
	}
	if statusText != "" {
		status, err := strconv.Atoi(statusText)
		if err == nil && status >= 0 && status <= 3 {
			where += ` AND mm.status=?`
			args = append(args, status)
		}
	}
	if keyword != "" {
		like := "%" + keyword + "%"
		where += ` AND (sp.nickname LIKE ? OR su.public_id LIKE ? OR mm.public_url LIKE ? OR CAST(mm.message_id AS CHAR) LIKE ? OR CAST(m.conversation_id AS CHAR) LIKE ?)`
		args = append(args, like, like, like, like, like)
	}
	base := ` FROM im_message_media mm JOIN im_messages m ON m.id=mm.message_id JOIN users su ON su.id=m.sender_id JOIN user_profiles sp ON sp.user_id=m.sender_id LEFT JOIN media_assets ma ON ma.id=mm.media_asset_id`
	var total int64
	if err := a.db.QueryRowContext(r.Context(), `SELECT COUNT(*)`+base+where, args...).Scan(&total); err != nil {
		fail(w, http.StatusInternalServerError, 50001, "查询聊天媒体失败")
		return
	}
	queryArgs := append(append([]any{}, args...), size, offset)
	rows, err := a.db.QueryContext(r.Context(), `SELECT mm.message_id,mm.media_asset_id,m.conversation_id,m.seq,m.sender_id,su.public_id,sp.nickname,sp.avatar_url,mm.media_type,mm.public_url,mm.duration_ms,mm.status,mm.delete_reason,mm.cleanup_error,mm.deleted_at,mm.created_at,COALESCE(ma.storage_provider,''),COALESCE(ma.bucket,''),COALESCE(ma.object_key,''),COALESCE(ma.mime_type,''),COALESCE(ma.file_size,0)`+base+where+` ORDER BY mm.created_at DESC,mm.message_id DESC LIMIT ? OFFSET ?`, queryArgs...)
	if err != nil {
		fail(w, http.StatusInternalServerError, 50001, "查询聊天媒体失败")
		return
	}
	defer rows.Close()
	items := []map[string]any{}
	for rows.Next() {
		var messageID, conversationID, seq, senderID, fileSize int64
		var assetID sql.NullInt64
		var durationMS sql.NullInt64
		var deletedAt sql.NullTime
		var publicID, nickname, avatar, typ, publicURL, reason, cleanupError, provider, bucket, objectKey, mimeType string
		var status int
		var createdAt time.Time
		if err = rows.Scan(&messageID, &assetID, &conversationID, &seq, &senderID, &publicID, &nickname, &avatar, &typ, &publicURL, &durationMS, &status, &reason, &cleanupError, &deletedAt, &createdAt, &provider, &bucket, &objectKey, &mimeType, &fileSize); err != nil {
			fail(w, http.StatusInternalServerError, 50001, "读取聊天媒体失败")
			return
		}
		items = append(items, map[string]any{
			"id": messageID, "messageId": messageID, "mediaAssetId": nullableInt64(assetID), "conversationId": conversationID, "seq": seq,
			"senderId": senderID, "senderPublicId": publicID, "senderNickname": nickname, "senderAvatar": avatar,
			"type": typ, "url": publicURL, "durationMs": nullableInt64(durationMS), "status": status, "deleteReason": reason,
			"cleanupError": cleanupError, "deletedAt": nullableTime(deletedAt), "createdAt": createdAt, "storageProvider": provider,
			"bucket": bucket, "objectKey": objectKey, "mimeType": mimeType, "fileSize": fileSize,
		})
	}
	if err = rows.Err(); err != nil {
		fail(w, http.StatusInternalServerError, 50001, "读取聊天媒体失败")
		return
	}

	stats := map[string]any{"total": 0, "active": 0, "deleted": 0, "failed": 0, "activeBytes": 0}
	var statsTotal, active, deleted, failed, activeBytes int64
	if scanErr := a.db.QueryRowContext(r.Context(), `SELECT COUNT(*),COALESCE(SUM(mm.status=1),0),COALESCE(SUM(mm.status=0),0),COALESCE(SUM(mm.status=3),0),COALESCE(SUM(IF(mm.status=1,ma.file_size,0)),0) FROM im_message_media mm LEFT JOIN media_assets ma ON ma.id=mm.media_asset_id`).Scan(&statsTotal, &active, &deleted, &failed, &activeBytes); scanErr == nil {
		stats = map[string]any{"total": statsTotal, "active": active, "deleted": deleted, "failed": failed, "activeBytes": activeBytes}
	}
	reply(w, map[string]any{
		"items": items, "total": total, "page": page, "size": size, "stats": stats,
		"retention": map[string]any{
			"enabled":    a.configBool(r.Context(), "im.chat_media_retention_enabled", false),
			"days":       clampChatMediaRetentionDays(a.configInt(r.Context(), "im.chat_media_retention_days", 90)),
			"lastAt":     a.configPlain(r.Context(), "im.chat_media_cleanup_last_at", ""),
			"lastResult": a.configPlain(r.Context(), "im.chat_media_cleanup_last_result", ""),
		},
	})
}

func (a *App) adminUpdateChatMediaRetention(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Enabled bool `json:"enabled"`
		Days    int  `json:"days"`
	}
	if decode(r, &req) != nil || req.Days < 1 || req.Days > 3650 {
		fail(w, http.StatusBadRequest, 20001, "保留天数应为 1 至 3650 天")
		return
	}
	tx, err := a.db.BeginTx(r.Context(), nil)
	if err == nil {
		_, err = tx.ExecContext(r.Context(), `UPDATE system_configs SET config_value=? WHERE config_key='im.chat_media_retention_enabled'`, strconv.FormatBool(req.Enabled))
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), `UPDATE system_configs SET config_value=? WHERE config_key='im.chat_media_retention_days'`, strconv.Itoa(req.Days))
	}
	if err != nil || tx.Commit() != nil {
		if tx != nil {
			_ = tx.Rollback()
		}
		fail(w, http.StatusInternalServerError, 50001, "保存聊天媒体清理策略失败")
		return
	}
	a.audit(r, "update_retention", "chat_media", 0, map[string]any{"enabled": req.Enabled, "days": req.Days})
	reply(w, map[string]any{"enabled": req.Enabled, "days": req.Days})
}

func (a *App) adminCleanupDueChatMedia(w http.ResponseWriter, r *http.Request) {
	days := clampChatMediaRetentionDays(a.configInt(r.Context(), "im.chat_media_retention_days", 90))
	result, acquired, err := a.withChatMediaCleanupLock(r.Context(), func(ctx context.Context) (chatMediaCleanupSummary, error) {
		return a.cleanupDueChatMedia(ctx, time.Now().Add(-time.Duration(days)*24*time.Hour))
	})
	if err != nil && !acquired {
		fail(w, http.StatusInternalServerError, 50001, "无法启动聊天媒体清理任务")
		return
	}
	if !acquired {
		fail(w, http.StatusConflict, 20001, "聊天媒体清理任务正在执行")
		return
	}
	if err != nil {
		fail(w, http.StatusBadGateway, 50001, "聊天媒体清理任务执行失败")
		return
	}
	a.recordChatMediaCleanupResult(r.Context(), result)
	a.audit(r, "cleanup_due", "chat_media", 0, map[string]any{"retentionDays": days, "result": result})
	reply(w, result)
}

func (a *App) adminDeleteChatMedia(w http.ResponseWriter, r *http.Request) {
	messageID, err := pathID(r)
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "聊天媒体编号无效")
		return
	}
	result, acquired, runErr := a.withChatMediaCleanupLock(r.Context(), func(ctx context.Context) (chatMediaCleanupSummary, error) {
		summary := chatMediaCleanupSummary{Scanned: 1}
		deleted, cleanupErr := a.cleanupChatMedia(ctx, messageID, "管理员手动清理")
		if cleanupErr != nil {
			summary.Failed = 1
			return summary, cleanupErr
		}
		if deleted {
			summary.Deleted = 1
		}
		return summary, nil
	})
	if runErr != nil && !acquired {
		fail(w, http.StatusInternalServerError, 50001, "无法启动聊天媒体清理任务")
		return
	}
	if !acquired {
		fail(w, http.StatusConflict, 20001, "聊天媒体清理任务正在执行")
		return
	}
	if runErr != nil {
		a.audit(r, "cleanup_failed", "chat_media", messageID, map[string]any{"error": chatMediaCleanupError(runErr)})
		fail(w, http.StatusBadGateway, 50001, "文件清理失败，记录已保留并可重试")
		return
	}
	a.audit(r, "cleanup", "chat_media", messageID, map[string]any{"result": result})
	reply(w, result)
}

func (a *App) withChatMediaCleanupLock(ctx context.Context, run func(context.Context) (chatMediaCleanupSummary, error)) (chatMediaCleanupSummary, bool, error) {
	conn, err := a.db.Conn(ctx)
	if err != nil {
		return chatMediaCleanupSummary{}, false, err
	}
	defer conn.Close()
	var acquired int
	if err = conn.QueryRowContext(ctx, `SELECT GET_LOCK(?,0)`, chatMediaCleanupLock).Scan(&acquired); err != nil || acquired != 1 {
		return chatMediaCleanupSummary{}, false, err
	}
	defer func() {
		releaseCtx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
		defer cancel()
		_, _ = conn.ExecContext(releaseCtx, `SELECT RELEASE_LOCK(?)`, chatMediaCleanupLock)
	}()
	result, err := run(ctx)
	return result, true, err
}

func (a *App) cleanupDueChatMedia(ctx context.Context, before time.Time) (chatMediaCleanupSummary, error) {
	result := chatMediaCleanupSummary{}
	a.recoverStuckChatMediaCleanups(ctx)
	for batch := 0; batch < 50; batch++ {
		retryBefore := time.Now().Add(-time.Hour)
		rows, err := a.db.QueryContext(ctx, `SELECT message_id FROM im_message_media WHERE created_at<? AND (status=1 OR (status=3 AND updated_at<?)) ORDER BY created_at,message_id LIMIT ?`, before, retryBefore, chatMediaBatchSize)
		if err != nil {
			return result, err
		}
		ids := []int64{}
		for rows.Next() {
			var id int64
			if scanErr := rows.Scan(&id); scanErr != nil {
				_ = rows.Close()
				return result, scanErr
			}
			ids = append(ids, id)
		}
		if err = rows.Close(); err != nil {
			return result, err
		}
		if len(ids) == 0 {
			break
		}
		for _, id := range ids {
			if ctx.Err() != nil {
				return result, ctx.Err()
			}
			result.Scanned++
			deleted, cleanupErr := a.cleanupChatMedia(ctx, id, "超过保留期限自动清理")
			if cleanupErr != nil {
				result.Failed++
				continue
			}
			if deleted {
				result.Deleted++
			}
		}
		if len(ids) < chatMediaBatchSize {
			break
		}
	}
	return result, nil
}

func (a *App) recoverStuckChatMediaCleanups(ctx context.Context) {
	_, _ = a.db.ExecContext(ctx, `UPDATE im_message_media SET status=3,cleanup_error='上次清理中断，可重试' WHERE status=2 AND updated_at<DATE_SUB(NOW(3),INTERVAL 10 MINUTE)`)
}

func (a *App) cleanupChatMedia(ctx context.Context, messageID int64, reason string) (bool, error) {
	var currentStatus int
	if err := a.db.QueryRowContext(ctx, `SELECT status FROM im_message_media WHERE message_id=?`, messageID).Scan(&currentStatus); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return false, fmt.Errorf("聊天媒体不存在")
		}
		return false, err
	}
	if currentStatus == 0 {
		return false, nil
	}
	claim, err := a.db.ExecContext(ctx, `UPDATE im_message_media SET status=2,cleanup_error='' WHERE message_id=? AND status IN (1,3)`, messageID)
	if err != nil {
		return false, err
	}
	if affected, _ := claim.RowsAffected(); affected == 0 {
		return false, fmt.Errorf("聊天媒体正在清理")
	}

	target := chatMediaTarget{MessageID: messageID}
	if err = a.db.QueryRowContext(ctx, `SELECT mm.media_asset_id,mm.media_type,mm.public_url,m.conversation_id,m.seq,COALESCE(ma.storage_provider,''),COALESCE(ma.bucket,''),COALESCE(ma.object_key,''),COALESCE(ma.status,-1) FROM im_message_media mm JOIN im_messages m ON m.id=mm.message_id LEFT JOIN media_assets ma ON ma.id=mm.media_asset_id WHERE mm.message_id=?`, messageID).Scan(
		&target.MediaAssetID, &target.MediaType, &target.PublicURL, &target.ConversationID, &target.Seq, &target.StorageProvider, &target.Bucket, &target.ObjectKey, &target.AssetStatus,
	); err != nil {
		a.failChatMediaCleanup(ctx, messageID, err)
		return false, err
	}
	if !target.MediaAssetID.Valid || target.ObjectKey == "" {
		err = fmt.Errorf("未找到关联的媒体上传记录，无法确认对象文件位置")
		a.failChatMediaCleanup(ctx, messageID, err)
		return false, err
	}
	if target.AssetStatus != 0 {
		if used, useErr := a.mediaUsedOutsideChat(ctx, target.PublicURL); useErr != nil {
			a.failChatMediaCleanup(ctx, messageID, useErr)
			return false, useErr
		} else if used {
			err = fmt.Errorf("该文件仍被动态、头像或认证材料使用，已跳过删除")
			a.failChatMediaCleanup(ctx, messageID, err)
			return false, err
		}
		storage, closeStorage, storageErr := a.newMediaObjectStorageForProvider(ctx, target.StorageProvider, target.Bucket)
		if storageErr != nil {
			a.failChatMediaCleanup(ctx, messageID, storageErr)
			return false, storageErr
		}
		defer closeStorage()
		for _, key := range chatMediaObjectKeys(target.ObjectKey, target.MediaType) {
			if deleteErr := storage.Delete(ctx, key); deleteErr != nil && !isMissingMediaObject(deleteErr) {
				err = fmt.Errorf("删除对象 %s 失败: %w", filepath.Base(key), deleteErr)
				a.failChatMediaCleanup(ctx, messageID, err)
				return false, err
			}
		}
	}
	if err = a.finishChatMediaCleanup(ctx, target, reason); err != nil {
		a.failChatMediaCleanup(ctx, messageID, err)
		return false, err
	}
	return true, nil
}

func (a *App) mediaUsedOutsideChat(ctx context.Context, publicURL string) (bool, error) {
	var used int
	err := a.db.QueryRowContext(ctx, `SELECT EXISTS(
		SELECT 1 FROM post_media WHERE media_url=?
		UNION ALL SELECT 1 FROM user_profiles WHERE avatar_url=? OR cover_url=?
		UNION ALL SELECT 1 FROM user_verifications WHERE JSON_CONTAINS(IF(JSON_VALID(evidence_json),evidence_json,'[]'),JSON_QUOTE(?))
	)`, publicURL, publicURL, publicURL, publicURL).Scan(&used)
	return used == 1, err
}

func (a *App) failChatMediaCleanup(ctx context.Context, messageID int64, cleanupErr error) {
	_, _ = a.db.ExecContext(context.WithoutCancel(ctx), `UPDATE im_message_media SET status=3,cleanup_error=? WHERE message_id=? AND status=2`, chatMediaCleanupError(cleanupErr), messageID)
}

func (a *App) finishChatMediaCleanup(ctx context.Context, target chatMediaTarget, reason string) error {
	tx, err := a.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() { _ = tx.Rollback() }()
	events := []chatMediaEvent{}
	rows, err := tx.QueryContext(ctx, `SELECT m.id,m.conversation_id,m.seq FROM im_message_media mm JOIN im_messages m ON m.id=mm.message_id WHERE mm.media_asset_id=? AND mm.status<>0`, target.MediaAssetID.Int64)
	if err != nil {
		return err
	}
	for rows.Next() {
		var event chatMediaEvent
		if err = rows.Scan(&event.MessageID, &event.ConversationID, &event.Seq); err != nil {
			_ = rows.Close()
			return err
		}
		events = append(events, event)
	}
	if err = rows.Close(); err != nil {
		return err
	}
	if _, err = tx.ExecContext(ctx, `UPDATE media_assets SET status=0,deleted_at=COALESCE(deleted_at,NOW(3)) WHERE id=?`, target.MediaAssetID.Int64); err != nil {
		return err
	}
	if _, err = tx.ExecContext(ctx, `UPDATE im_message_media SET status=0,delete_reason=?,cleanup_error='',deleted_at=COALESCE(deleted_at,NOW(3)) WHERE media_asset_id=? AND status<>0`, reason, target.MediaAssetID.Int64); err != nil {
		return err
	}
	if err = tx.Commit(); err != nil {
		return err
	}
	for _, event := range events {
		a.broadcastChatMediaDeleted(ctx, event)
	}
	return nil
}

func (a *App) broadcastChatMediaDeleted(ctx context.Context, event chatMediaEvent) {
	rows, err := a.db.QueryContext(ctx, `SELECT user_id FROM im_conversation_members WHERE conversation_id=? AND status=1`, event.ConversationID)
	if err != nil {
		return
	}
	members := []int64{}
	for rows.Next() {
		var id int64
		if rows.Scan(&id) == nil {
			members = append(members, id)
		}
	}
	_ = rows.Close()
	a.hub.broadcast(members, map[string]any{"command": "MESSAGE_MEDIA_DELETED", "data": map[string]any{"id": event.MessageID, "conversationId": event.ConversationID, "seq": event.Seq, "mediaDeleted": true}})
}

func (a *App) recordChatMediaCleanupResult(ctx context.Context, result chatMediaCleanupSummary) {
	lastAt := time.Now().Format(time.RFC3339)
	lastResult := fmt.Sprintf("检查 %d 个，清理 %d 个，失败 %d 个", result.Scanned, result.Deleted, result.Failed)
	_, _ = a.db.ExecContext(ctx, `UPDATE system_configs SET config_value=? WHERE config_key='im.chat_media_cleanup_last_at'`, lastAt)
	_, _ = a.db.ExecContext(ctx, `UPDATE system_configs SET config_value=? WHERE config_key='im.chat_media_cleanup_last_result'`, lastResult)
}

func (a *App) runChatMediaCleanupWorker(ctx context.Context) {
	run := func() {
		a.recoverStuckChatMediaCleanups(ctx)
		if !a.configBool(ctx, "im.chat_media_retention_enabled", false) {
			return
		}
		workerCtx, cancel := context.WithTimeout(ctx, 20*time.Minute)
		defer cancel()
		days := clampChatMediaRetentionDays(a.configInt(workerCtx, "im.chat_media_retention_days", 90))
		result, acquired, err := a.withChatMediaCleanupLock(workerCtx, func(runCtx context.Context) (chatMediaCleanupSummary, error) {
			return a.cleanupDueChatMedia(runCtx, time.Now().Add(-time.Duration(days)*24*time.Hour))
		})
		if err != nil && !acquired {
			log.Printf("chat media cleanup lock failed: %v", err)
			return
		}
		if !acquired {
			return
		}
		if err != nil {
			log.Printf("chat media cleanup failed: %v", err)
			return
		}
		a.recordChatMediaCleanupResult(workerCtx, result)
	}
	run()
	ticker := time.NewTicker(time.Hour)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			run()
		}
	}
}