package service

import (
	"context"
	"fmt"
	"log"
	"slices"

	"with_you/internal/dto"
	"with_you/internal/model"
	"with_you/internal/repository"
)

type PostRefService interface {
	ProcessPostReferences(ctx context.Context, sourcePostID string, segments model.MessageSegments) error
	EnrichPostRefSegments(ctx context.Context, segments model.MessageSegments, currentUserID string) (model.MessageSegments, error)
	RecordClick(ctx context.Context, sourcePostID, targetPostID string) error
	HandlePostDeleted(ctx context.Context, postID string) error
	HandlePostRecovered(ctx context.Context, postID string) error
	HandlePostHidden(ctx context.Context, postID string) error
	GetRelatedPosts(ctx context.Context, postID string, page, pageSize int) ([]*model.Post, int64, error)
	GetReferencedPosts(ctx context.Context, postID string) ([]*model.Post, error)
	SuggestPosts(ctx context.Context, keyword string, limit int) ([]dto.PostRefBrief, error)
}

type postRefServiceImpl struct {
	refRepo  repository.PostRefRepository
	postRepo repository.PostRepository
}

func NewPostRefService(refRepo repository.PostRefRepository, postRepo repository.PostRepository) PostRefService {
	return &postRefServiceImpl{
		refRepo:  refRepo,
		postRepo: postRepo,
	}
}

func (s *postRefServiceImpl) ProcessPostReferences(ctx context.Context, sourcePostID string, segments model.MessageSegments) error {
	targetIDs := dto.ExtractReferencedPosts(segments)
	if len(targetIDs) == 0 {
		return nil
	}

	validIDs := make([]string, 0, len(targetIDs))
	for _, tid := range targetIDs {
		post, err := s.postRepo.GetByID(tid)
		if err != nil {
			log.Printf("[WARN] post_ref target %s not found for source %s: %v", tid, sourcePostID, err)
			continue
		}
		if post.Status == model.PostStatusPublished && !post.IsDeleted {
			validIDs = append(validIDs, tid)
		}
	}

	if len(validIDs) == 0 {
		return nil
	}

	return s.refRepo.BatchUpsert(ctx, sourcePostID, validIDs)
}

func (s *postRefServiceImpl) EnrichPostRefSegments(ctx context.Context, segments model.MessageSegments, currentUserID string) (model.MessageSegments, error) {
	postIDs := dto.ExtractReferencedPosts(segments)
	if len(postIDs) == 0 {
		return segments, nil
	}

	posts, err := s.postRepo.GetByIDs(postIDs)
	if err != nil {
		log.Printf("[WARN] failed to get referenced posts: %v", err)
		return segments, nil
	}

	postMap := make(map[string]*model.Post, len(posts))
	for _, p := range posts {
		postMap[p.ID] = p
	}

	enriched := make(model.MessageSegments, len(segments))
	for i, seg := range segments {
		enriched[i] = seg
		if seg.Type == string(dto.SegmentTypePostRef) {
			postID, _ := seg.Data["post_id"].(string)
			enriched[i] = s.enrichSegment(seg, postID, postMap, currentUserID)
		}
	}

	return enriched, nil
}

func (s *postRefServiceImpl) enrichSegment(seg model.MessageSegment, postID string, postMap map[string]*model.Post, currentUserID string) model.MessageSegment {
	newSeg := model.MessageSegment{
		Type: seg.Type,
		Data: map[string]any{"post_id": postID},
	}

	post, ok := postMap[postID]
	if !ok || post == nil {
		newSeg.Data["status"] = "deleted"
		newSeg.Data["title"] = "该帖子已删除"
		newSeg.Data["accessible"] = false
		return newSeg
	}

	if post.IsDeleted {
		newSeg.Data["status"] = "deleted"
		newSeg.Data["title"] = "该帖子已删除"
		newSeg.Data["accessible"] = false
		return newSeg
	}

	if post.Status != model.PostStatusPublished {
		if currentUserID == post.UserID {
			newSeg.Data["status"] = string(post.Status)
			newSeg.Data["title"] = post.Title
			newSeg.Data["accessible"] = true
		} else {
			newSeg.Data["status"] = "hidden"
			newSeg.Data["title"] = "该帖子不可见"
			newSeg.Data["accessible"] = false
		}
		return newSeg
	}

	newSeg.Data["status"] = "published"
	newSeg.Data["title"] = post.Title
	newSeg.Data["accessible"] = true

	if post.User != nil {
		newSeg.Data["author"] = map[string]any{
			"id":       post.User.ID,
			"nickname": post.User.Nickname,
			"avatar":   post.User.Avatar,
		}
	}

	return newSeg
}

func (s *postRefServiceImpl) RecordClick(ctx context.Context, sourcePostID, targetPostID string) error {
	return s.refRepo.IncrementClickCount(ctx, sourcePostID, targetPostID)
}

func (s *postRefServiceImpl) HandlePostDeleted(ctx context.Context, postID string) error {
	return s.refRepo.MarkStatusByTargetPostID(ctx, postID, model.PostRefDead)
}

func (s *postRefServiceImpl) HandlePostRecovered(ctx context.Context, postID string) error {
	return s.refRepo.MarkStatusByTargetPostID(ctx, postID, model.PostRefActive)
}

func (s *postRefServiceImpl) HandlePostHidden(ctx context.Context, postID string) error {
	return s.refRepo.MarkStatusByTargetPostID(ctx, postID, model.PostRefHidden)
}

func (s *postRefServiceImpl) GetRelatedPosts(ctx context.Context, postID string, page, pageSize int) ([]*model.Post, int64, error) {
	refs, total, err := s.refRepo.GetSourcesByTargetPostID(ctx, postID, page, pageSize)
	if err != nil {
		return nil, 0, err
	}

	posts := make([]*model.Post, 0, len(refs))
	for _, ref := range refs {
		if ref.SourcePost != nil {
			posts = append(posts, ref.SourcePost)
		}
	}

	return posts, total, nil
}

func (s *postRefServiceImpl) GetReferencedPosts(ctx context.Context, postID string) ([]*model.Post, error) {
	refs, err := s.refRepo.GetTargetsBySourcePostID(ctx, postID)
	if err != nil {
		return nil, err
	}

	posts := make([]*model.Post, 0, len(refs))
	for _, ref := range refs {
		if ref.TargetPost != nil && ref.TargetPost.Status == model.PostStatusPublished && !ref.TargetPost.IsDeleted {
			posts = append(posts, ref.TargetPost)
		}
	}

	return posts, nil
}

func (s *postRefServiceImpl) SuggestPosts(ctx context.Context, keyword string, limit int) ([]dto.PostRefBrief, error) {
	if limit <= 0 {
		limit = 10
	}

	posts, _, err := s.postRepo.Search(keyword, 1, limit)
	if err != nil {
		return nil, fmt.Errorf("search posts for suggest: %w", err)
	}

	result := make([]dto.PostRefBrief, 0, len(posts))
	for _, p := range posts {
		brief := dto.PostRefBrief{
			ID:    p.ID,
			Title: p.Title,
		}
		if p.ChannelID != nil {
			brief.Channel = *p.ChannelID
		}
		result = append(result, brief)
	}

	slices.SortFunc(result, func(a, b dto.PostRefBrief) int {
		if len(a.Title) < len(b.Title) {
			return -1
		}
		if len(a.Title) > len(b.Title) {
			return 1
		}
		return 0
	})

	return result, nil
}