package shareser

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strings"
	"time"

	"91porn-server/models/v/vidmod"

	"go.mongodb.org/mongo-driver/bson/primitive"
)

const (
	recommendShareEventIDMaxLength = 128
	recommendShareEventDedupTTL    = 7 * 24 * time.Hour
	recommendShareDailyDedupTTL    = 48 * time.Hour
	recommendShareCleanupTimeout   = 5 * time.Second
)

type recommendShareDeduper interface {
	SetNXContext(
		ctx context.Context,
		key string,
		value interface{},
		expiration time.Duration,
	) (bool, error)
	DelContext(ctx context.Context, keys ...string) (int64, error)
}

type recommendShareIncrement func(context.Context, primitive.ObjectID) error

func incrementRecommendShareOnce(
	ctx context.Context,
	deduper recommendShareDeduper,
	uid uint64,
	videoID primitive.ObjectID,
	eventID string,
	now time.Time,
) error {
	return incrementRecommendShareOnceWith(
		ctx,
		deduper,
		uid,
		videoID,
		eventID,
		now,
		func(ctx context.Context, id primitive.ObjectID) error {
			return vidmod.IncrementRecommendInteractionContext(
				ctx,
				id,
				vidmod.RecommendInteractionShare,
			)
		},
	)
}

func incrementRecommendShareOnceWith(
	ctx context.Context,
	deduper recommendShareDeduper,
	uid uint64,
	videoID primitive.ObjectID,
	eventID string,
	now time.Time,
	increment recommendShareIncrement,
) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	if deduper == nil {
		return fmt.Errorf("recommend share deduper is nil")
	}
	if uid == 0 || videoID.IsZero() {
		return nil
	}
	eventID = strings.TrimSpace(eventID)
	if len(eventID) > recommendShareEventIDMaxLength {
		return fmt.Errorf("share eventId exceeds %d characters", recommendShareEventIDMaxLength)
	}

	// 无论客户端是否提供 eventId，同一用户、视频、自然日只累计一次推荐分享分，
	// 避免客户端通过不断生成新 eventId 刷高权重。eventId 仍用于跨日重试幂等。
	day := now.In(time.FixedZone("CST", 8*60*60)).Format("20060102")
	dailyKey := recommendShareDedupKey(uid, videoID, "day:"+day)
	dailyAcquired, err := deduper.SetNXContext(
		ctx, dailyKey, "1", recommendShareDailyDedupTTL,
	)
	if err != nil || !dailyAcquired {
		return err
	}

	keysToRelease := []string{dailyKey}
	if eventID != "" {
		eventKey := recommendShareDedupKey(uid, videoID, "event:"+eventID)
		eventAcquired, eventErr := deduper.SetNXContext(
			ctx, eventKey, "1", recommendShareEventDedupTTL,
		)
		if eventErr != nil || !eventAcquired {
			releaseRecommendShareKeys(deduper, keysToRelease...)
			return eventErr
		}
		keysToRelease = append(keysToRelease, eventKey)
	}

	err = increment(ctx, videoID)
	if err != nil {
		// 推荐累计失败时释放幂等标记，使同一事件后续重试仍有补偿机会。
		releaseRecommendShareKeys(deduper, keysToRelease...)
		return err
	}
	return nil
}

func releaseRecommendShareKeys(deduper recommendShareDeduper, keys ...string) {
	if deduper == nil || len(keys) == 0 {
		return
	}
	cleanupCtx, cancel := context.WithTimeout(
		context.Background(), recommendShareCleanupTimeout,
	)
	defer cancel()
	_, _ = deduper.DelContext(cleanupCtx, keys...)
}

func recommendShareDedupKey(uid uint64, videoID primitive.ObjectID, scope string) string {
	sum := sha256.Sum256([]byte(fmt.Sprintf("%d:%s:%s", uid, videoID.Hex(), scope)))
	return "recommend:short:share-dedup:" + hex.EncodeToString(sum[:])
}