package threadsapi

import (
	"context"
	"fmt"
	"strings"

	"haixun-backend/internal/library/threadspost"
)

const maxCarouselItems = 20

type publishMediaInput struct {
	ThreadsUserID string
	AccessToken   string
	Text          string
	TopicTag      string
	ReplyToID     string
	ImageURLs     []string
}

func normalizeImageURLs(urls []string) []string {
	out := make([]string, 0, len(urls))
	seen := make(map[string]struct{}, len(urls))
	for _, raw := range urls {
		url := strings.TrimSpace(raw)
		if url == "" {
			continue
		}
		if _, ok := seen[url]; ok {
			continue
		}
		seen[url] = struct{}{}
		out = append(out, url)
		if len(out) >= maxCarouselItems {
			break
		}
	}
	return out
}

func publishMedia(ctx context.Context, in publishMediaInput) (*PublishResult, error) {
	userID := strings.TrimSpace(in.ThreadsUserID)
	token := strings.TrimSpace(in.AccessToken)
	text := strings.TrimSpace(in.Text)
	replyTo := strings.TrimSpace(in.ReplyToID)
	imageURLs := normalizeImageURLs(in.ImageURLs)

	if userID == "" || token == "" {
		return nil, fmt.Errorf("threads api credentials incomplete")
	}
	if replyTo == "" && text == "" && len(imageURLs) == 0 {
		return nil, fmt.Errorf("post text or image is required")
	}
	if replyTo != "" && text == "" && len(imageURLs) == 0 {
		return nil, fmt.Errorf("reply text or image is required")
	}
	if replyTo != "" && len(imageURLs) > 1 {
		return nil, fmt.Errorf("Threads API 目前不支援多圖回覆，請只附一張圖")
	}
	if replyTo != "" {
		if err := verifyReplyTarget(ctx, replyTo, token); err != nil {
			return nil, err
		}
	}
	if replyTo == "" {
		if err := threadspost.ValidatePublishContent(text, len(imageURLs) > 0); err != nil {
			return nil, err
		}
	} else if err := threadspost.ValidateReplyContent(text, len(imageURLs) > 0); err != nil {
		return nil, err
	}

	var containerID string
	var err error
	switch len(imageURLs) {
	case 0:
		if replyTo != "" {
			containerID, err = createReplyContainer(ctx, userID, token, replyTo, text)
		} else {
			containerID, err = createTextContainer(ctx, userID, token, text, in.TopicTag)
		}
	case 1:
		if replyTo == "" {
			containerID, err = createImageContainer(ctx, userID, token, text, imageURLs[0], in.TopicTag)
		} else {
			containerID, err = createImageReplyContainer(ctx, userID, token, replyTo, text, imageURLs[0])
		}
	default:
		containerID, err = createCarouselContainer(ctx, userID, token, text, in.TopicTag, replyTo, imageURLs)
	}
	if err != nil {
		return nil, err
	}

	waitAttempts := containerWaitAttempts(len(imageURLs))
	if err := waitForContainerReady(ctx, containerID, token, waitAttempts); err != nil {
		return nil, err
	}
	mediaID, err := publishContainer(ctx, userID, token, containerID)
	if err != nil {
		return nil, err
	}
	permalink, _ := fetchPermalink(ctx, mediaID, token)
	return &PublishResult{MediaID: mediaID, Permalink: permalink}, nil
}

func containerWaitAttempts(imageCount int) int {
	if imageCount == 0 {
		return 12
	}
	if imageCount == 1 {
		return 30
	}
	return 30 + imageCount*2
}

func createCarouselContainer(ctx context.Context, userID, token, text, topicTag, replyTo string, imageURLs []string) (string, error) {
	if len(imageURLs) < 2 {
		return "", fmt.Errorf("carousel requires at least two images")
	}
	childIDs := make([]string, 0, len(imageURLs))
	for _, imageURL := range imageURLs {
		childID, err := createCarouselItemContainer(ctx, userID, token, imageURL)
		if err != nil {
			return "", err
		}
		if err := waitForContainerReady(ctx, childID, token, 30); err != nil {
			return "", err
		}
		childIDs = append(childIDs, childID)
	}

	params := urlValues(token)
	params.Set("media_type", "CAROUSEL")
	params.Set("children", strings.Join(childIDs, ","))
	if text != "" {
		params.Set("text", text)
	}
	if tag := normalizeTopicTag(topicTag); tag != "" {
		params.Set("topic_tag", tag)
	}
	if replyTo != "" {
		params.Set("reply_to_id", replyTo)
	}
	return postThreadsContainer(ctx, userID, params)
}

func createCarouselItemContainer(ctx context.Context, userID, token, imageURL string) (string, error) {
	params := urlValues(token)
	params.Set("is_carousel_item", "true")
	params.Set("media_type", "IMAGE")
	params.Set("image_url", imageURL)
	return postThreadsContainer(ctx, userID, params)
}