backend barebone done, big chunk of work done

server/internal/store/messages.go

@@ -0,0 +1,83 @@
+package store
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+)
+
+// InsertMessage creates a new message in a conversation and returns it.
+func (s *Store) InsertMessage(ctx context.Context, conversationID, senderID int64, body string) (*Message, error) {
+	var m Message
+	err := s.pool.QueryRow(ctx, `
+       INSERT INTO messages(conversation_id, sender_id, body)
+       VALUES($1, $2, $3)
+       RETURNING id, conversation_id, sender_id, body, created_at, edited_at, deleted_at
+   `, conversationID, senderID, body).Scan(
+		&m.ID, &m.ConversationID, &m.SenderID, &m.Body,
+		&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, created_at, edited_at, deleted_at
+       FROM messages WHERE id=$1
+   `, id).Scan(
+		&m.ID, &m.ConversationID, &m.SenderID, &m.Body,
+		&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, 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, 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.CreatedAt, &m.EditedAt, &m.DeletedAt,
+		); err != nil {
+			return nil, err
+		}
+		msgs = append(msgs, m)
+	}
+	return msgs, nil
+}