tsk-8: Create Message endpoint (#15)

Closes #8

Reviewed-on: phoenix/textsender-api#15
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

internal/store/message.go

@@ -0,0 +1,47 @@
+package store
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.kundeng.us/phoenix/textsender-models/pkg/message"
+)
+
+type MessageStore interface {
+	CreateMessage(ctx context.Context, msg *message.Message) error
+	MessageExists(ctx context.Context, msg *message.Message) (bool, error)
+}
+
+type PGMessageStore struct {
+	db *pgxpool.Pool
+}
+
+func NewMessageStore(db *pgxpool.Pool) *PGMessageStore {
+	return &PGMessageStore{db: db}
+}
+
+func (m *PGMessageStore) CreateMessage(ctx context.Context, msg *message.Message) error {
+	query := `
+	INSERT INTO messages (content, user_id)
+	VALUES ($1, $2)
+	RETURNING id
+	`
+
+	return m.db.QueryRow(ctx, query, msg.Content, msg.UserId).Scan(
+		&msg.Id,
+	)
+}
+
+func (m *PGMessageStore) MessageExists(ctx context.Context, msg *message.Message) (bool, error) {
+	query := `SELECT EXISTS(SELECT 1 FROM messages WHERE content = $1 AND user_id = $2)`
+
+	var exists bool
+	err := m.db.QueryRow(ctx, query, msg.Content, msg.UserId).Scan(&exists)
+	if err != nil {
+		return false, fmt.Errorf("checking if message exists: %w", err)
+	} else {
+		return exists, nil
+	}
+}