package logic

import (
	"context"

	"spark-server/internal/module/moment/entity"
	userentity "spark-server/internal/module/user/entity"
)

func (s *Service) attachViews(ctx context.Context, viewer int64, posts []*entity.Post, full bool) ([]*View, error) {
	if len(posts) == 0 {
		return []*View{}, nil
	}
	ids := postIDs(posts)
	likes, err := s.repo.ListLikes(ctx, ids)
	if err != nil {
		return nil, err
	}
	comments, err := s.repo.ListComments(ctx, ids)
	if err != nil {
		return nil, err
	}
	uids := collectUIDs(posts, likes, comments, viewer)
	users := s.loadUsers(ctx, uids)
	remarks := s.loadRemarks(ctx, viewer, uids)
	friendIDs, err := s.friends.ListFriendIDs(ctx, viewer)
	if err != nil {
		return nil, err
	}
	friends := idSet(friendIDs)
	out := make([]*View, 0, len(posts))
	for _, p := range posts {
		out = append(out, s.oneView(viewer, p, likes[p.ID], comments[p.ID], users, remarks, friends, full))
	}
	return out, nil
}

func (s *Service) oneView(viewer int64, p *entity.Post, likes []*entity.Like, comments []*entity.Comment, users map[int64]*userentity.User, remarks map[int64]string, friends map[int64]bool, full bool) *View {
	likeCards, liked, likeN := filterLikes(viewer, p.UserID, likes, users, remarks, friends, full)
	commentViews, commentN := filterComments(viewer, p.UserID, comments, users, remarks, friends, full)
	return &View{
		ID: p.ID, User: cardOf(users[p.UserID], remarks[p.UserID]), Kind: p.Kind, Text: p.Text,
		Content: contentJSON(p.Content), POI: poiPtr(p.POI), Visibility: p.Visibility,
		LikeCount: likeN, CommentCount: commentN,
		Liked: liked, Likes: likeCards, Comments: commentViews, CreatedAt: p.CreatedAtMS,
	}
}

func filterLikes(viewer, author int64, likes []*entity.Like, users map[int64]*userentity.User, remarks map[int64]string, friends map[int64]bool, full bool) ([]UserCard, bool, int) {
	out := make([]UserCard, 0)
	liked := false
	visible := 0
	for _, like := range likes {
		if like == nil {
			continue
		}
		if like.UserID == viewer {
			liked = true
		}
		if !seeInteract(viewer, author, like.UserID, friends) {
			continue
		}
		visible++
		if full || len(out) < entity.LikePreviewMax {
			out = append(out, cardOf(users[like.UserID], remarks[like.UserID]))
		}
	}
	return out, liked, visible
}

func filterComments(viewer, author int64, comments []*entity.Comment, users map[int64]*userentity.User, remarks map[int64]string, friends map[int64]bool, full bool) ([]*CommentView, int) {
	out := make([]*CommentView, 0)
	alive := 0
	for _, c := range comments {
		if c == nil || !seeInteract(viewer, author, c.UserID, friends) {
			continue
		}
		cv := &CommentView{
			ID: c.ID, User: cardOf(users[c.UserID], remarks[c.UserID]),
			ReplyToID: c.ReplyToID, ReplyToUID: c.ReplyToUID, Text: c.Text, CreatedAt: c.CreatedAtMS,
		}
		if c.Status == entity.StatusDeleted {
			cv.Deleted = true
			cv.Text = ""
		} else {
			alive++
		}
		if full || len(out) < entity.CommentPreviewMax {
			out = append(out, cv)
		}
	}
	return out, alive
}

func seeInteract(viewer, author, actor int64, friends map[int64]bool) bool {
	if viewer == author || actor == viewer {
		return true
	}
	return friends[actor]
}

func postIDs(posts []*entity.Post) []int64 {
	out := make([]int64, 0, len(posts))
	for _, p := range posts {
		if p != nil {
			out = append(out, p.ID)
		}
	}
	return out
}

func collectUIDs(posts []*entity.Post, likes map[int64][]*entity.Like, comments map[int64][]*entity.Comment, viewer int64) []int64 {
	seen := map[int64]struct{}{viewer: {}}
	add := func(id int64) {
		if id > 0 {
			seen[id] = struct{}{}
		}
	}
	for _, p := range posts {
		if p != nil {
			add(p.UserID)
		}
	}
	for _, rows := range likes {
		for _, like := range rows {
			if like != nil {
				add(like.UserID)
			}
		}
	}
	for _, rows := range comments {
		for _, c := range rows {
			if c != nil {
				add(c.UserID)
			}
		}
	}
	out := make([]int64, 0, len(seen))
	for id := range seen {
		out = append(out, id)
	}
	return out
}

func (s *Service) loadUsers(ctx context.Context, ids []int64) map[int64]*userentity.User {
	out := make(map[int64]*userentity.User, len(ids))
	for _, id := range ids {
		u, err := s.users.Get(ctx, id)
		if err != nil {
			continue
		}
		out[id] = u
	}
	return out
}

func (s *Service) loadRemarks(ctx context.Context, viewer int64, ids []int64) map[int64]string {
	out := make(map[int64]string)
	for _, id := range ids {
		if id == viewer {
			continue
		}
		rel, err := s.friends.Relation(ctx, viewer, id)
		if err != nil || rel == nil {
			continue
		}
		out[id] = rel.Remark
	}
	return out
}