package social

import (
	"context"

	"github.com/google/uuid"
	"pipu/api/internal/api/gen"
)

// Read all previews in one query. Recheck friendship and both block directions
// here so a removed relationship cannot expose history through the inbox.
func (s *Store) attachLastMessages(ctx context.Context, viewer uuid.UUID, people []gen.SocialPerson) error {
	positions := map[uuid.UUID]int{}
	ids := []uuid.UUID{}
	for i, p := range people {
		if p.Relationship == "friend" {
			positions[p.Id] = i
			ids = append(ids, p.Id)
		}
	}
	if len(ids) == 0 {
		return nil
	}
	rows, e := s.pool.Query(ctx, `SELECT p.peer_id,m.id,m.sender_id,
 CASE WHEN m.deleted_at IS NULL THEN left(m.text,160) ELSE '' END,
 m.attachment_kind,m.created_at,m.deleted_at IS NOT NULL
 FROM unnest($2::uuid[]) AS p(peer_id)
 JOIN friendships f ON f.low_id=LEAST($1::uuid,p.peer_id) AND f.high_id=GREATEST($1::uuid,p.peer_id) AND f.accepted
 JOIN LATERAL (SELECT * FROM direct_messages
 WHERE LEAST(sender_id,recipient_id)=LEAST($1::uuid,p.peer_id)
 AND GREATEST(sender_id,recipient_id)=GREATEST($1::uuid,p.peer_id)
 ORDER BY seq DESC LIMIT 1) m ON true
 WHERE NOT EXISTS(SELECT 1 FROM social_blocks b WHERE (b.user_id=$1 AND b.peer_id=p.peer_id) OR (b.peer_id=$1 AND b.user_id=p.peer_id))`, viewer, ids)
	if e != nil {
		return e
	}
	defer rows.Close()
	for rows.Next() {
		var peer uuid.UUID
		var preview gen.SocialMessagePreview
		if e = rows.Scan(&peer, &preview.Id, &preview.SenderId, &preview.Text, &preview.AttachmentKind, &preview.CreatedAt, &preview.Deleted); e != nil {
			return e
		}
		people[positions[peer]].LastMessage = &preview
	}
	return rows.Err()
}