phase 0 complete

internal/db/migrate.go

@@ -0,0 +1,73 @@
+// Package db holds the embedded golang-migrate migrations and the sqlc
+// generated query code (internal/db/sqlcgen).
+package db
+
+import (
+	"embed"
+	"errors"
+	"fmt"
+	"net/url"
+
+	"github.com/golang-migrate/migrate/v4"
+	_ "github.com/golang-migrate/migrate/v4/database/pgx/v5"
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+)
+
+//go:embed migrations/*.sql
+var migrationsFS embed.FS
+
+// newMigrate builds a *migrate.Migrate over the embedded migration files and
+// the given database connection string.
+func newMigrate(databaseURL string) (*migrate.Migrate, error) {
+	sourceDriver, err := iofs.New(migrationsFS, "migrations")
+	if err != nil {
+		return nil, fmt.Errorf("db: loading embedded migrations: %w", err)
+	}
+
+	m, err := migrate.NewWithSourceInstance("iofs", sourceDriver, wrapDatabaseURL(databaseURL))
+	if err != nil {
+		return nil, fmt.Errorf("db: initializing migrate: %w", err)
+	}
+	return m, nil
+}
+
+// wrapDatabaseURL swaps the postgres(ql):// scheme for pgx5:// as required
+// by golang-migrate's pgx/v5 database driver registration.
+func wrapDatabaseURL(databaseURL string) string {
+	u, err := url.Parse(databaseURL)
+	if err != nil {
+		return databaseURL
+	}
+	u.Scheme = "pgx5"
+	return u.String()
+}
+
+// MigrateUp applies all pending migrations. It returns nil if there is
+// nothing to do.
+func MigrateUp(databaseURL string) error {
+	m, err := newMigrate(databaseURL)
+	if err != nil {
+		return err
+	}
+	defer func() { _, _ = m.Close() }()
+
+	if err := m.Up(); err != nil && !errors.Is(err, migrate.ErrNoChange) {
+		return fmt.Errorf("db: migrate up: %w", err)
+	}
+	return nil
+}
+
+// MigrateDown rolls back all migrations. It returns nil if there is nothing
+// to do.
+func MigrateDown(databaseURL string) error {
+	m, err := newMigrate(databaseURL)
+	if err != nil {
+		return err
+	}
+	defer func() { _, _ = m.Close() }()
+
+	if err := m.Down(); err != nil && !errors.Is(err, migrate.ErrNoChange) {
+		return fmt.Errorf("db: migrate down: %w", err)
+	}
+	return nil
+}