Messenger/server/internal/store/messages.go

package store

import (
	"context"
	"errors"

	"github.com/jackc/pgx/v5"
)

// InsertMessage creates a new message in a conversation and returns it.
// mediaID, when non-nil, attaches a previously uploaded media object.
func (s *Store) InsertMessage(ctx context.Context, conversationID, senderID int64, body string, mediaID *int64) (*Message, error) {
	var m Message
	err := s.pool.QueryRow(ctx, `
       INSERT INTO messages(conversation_id, sender_id, body, media_id)
       VALUES($1, $2, $3, $4)
       RETURNING id, conversation_id, sender_id, body, media_id, created_at, edited_at, deleted_at
   `, conversationID, senderID, body, mediaID).Scan(
		&m.ID, &m.ConversationID, &m.SenderID, &m.Body, &m.MediaID,
		&m.CreatedAt, &m.EditedAt, &m.DeletedAt,
	)
	if err != nil {
		return nil, err
	}
	return &m, nil
}

// GetMessageByID retrieves a message by ID or returns ErrNotFound.
func (s *Store) GetMessageByID(ctx context.Context, id int64) (*Message, error) {
	var m Message
	err := s.pool.QueryRow(ctx, `
       SELECT id, conversation_id, sender_id, body, media_id, created_at, edited_at, deleted_at
       FROM messages WHERE id=$1
   `, id).Scan(
		&m.ID, &m.ConversationID, &m.SenderID, &m.Body, &m.MediaID,
		&m.CreatedAt, &m.EditedAt, &m.DeletedAt,
	)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrNotFound
		}
		return nil, err
	}
	return &m, nil
}

// ListMessages returns messages for a conversation in reverse chronological order.
// If before > 0, only messages with ID less than before are returned.
func (s *Store) ListMessages(ctx context.Context, conversationID int64, before int64, limit int) ([]Message, error) {
	var rows pgx.Rows
	var err error
	if before > 0 {
		rows, err = s.pool.Query(ctx, `
           SELECT id, conversation_id, sender_id, body, media_id, created_at, edited_at, deleted_at
           FROM messages
           WHERE conversation_id=$1 AND id<$2
           ORDER BY id DESC LIMIT $3
       `, conversationID, before, limit)
	} else {
		rows, err = s.pool.Query(ctx, `
           SELECT id, conversation_id, sender_id, body, media_id, created_at, edited_at, deleted_at
           FROM messages
           WHERE conversation_id=$1
           ORDER BY id DESC LIMIT $2
       `, conversationID, limit)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var msgs []Message
	for rows.Next() {
		var m Message
		if err := rows.Scan(
			&m.ID, &m.ConversationID, &m.SenderID, &m.Body, &m.MediaID,
			&m.CreatedAt, &m.EditedAt, &m.DeletedAt,
		); err != nil {
			return nil, err
		}
		msgs = append(msgs, m)
	}
	return msgs, nil
}