Move schema_migrations table creation from Go code into 000.sql

The schema_migrations table definition now lives in
internal/database/schema/000.sql instead of being hardcoded as an
inline SQL string in database.go. A bootstrap step checks
sqlite_master for the table and applies 000.sql when it is missing.
Existing databases that already have the table (created by older
inline code) get version 000 back-filled so the normal migration
loop skips the file.

Also deduplicates the migration logic: both the Database.runMigrations
method and the exported ApplyMigrations helper now delegate to a single
applyMigrations function.

Adds database_test.go with tests for fresh migration, idempotency,
bootstrap on a fresh DB, and backwards compatibility with legacy DBs.

internal/database/database.go

@@ -39,6 +39,41 @@ type Database struct {
 	config *config.Config
 }
 
+// ParseMigrationVersion extracts the numeric version prefix from a migration
+// filename. Filenames must follow the pattern "<version>.sql" or
+// "<version>_<description>.sql", where version is a zero-padded numeric
+// string (e.g. "001", "002"). Returns the version string and an error if
+// the filename does not match the expected pattern.
+func ParseMigrationVersion(filename string) (string, error) {
+	name := strings.TrimSuffix(filename, filepath.Ext(filename))
+	if name == "" {
+		return "", fmt.Errorf("invalid migration filename %q: empty name", filename)
+	}
+
+	// Split on underscore to separate version from description.
+	// If there's no underscore, the entire stem is the version.
+	version := name
+	if idx := strings.IndexByte(name, '_'); idx >= 0 {
+		version = name[:idx]
+	}
+
+	if version == "" {
+		return "", fmt.Errorf("invalid migration filename %q: empty version prefix", filename)
+	}
+
+	// Validate the version is purely numeric.
+	for _, ch := range version {
+		if ch < '0' || ch > '9' {
+			return "", fmt.Errorf(
+				"invalid migration filename %q: version %q contains non-numeric character %q",
+				filename, version, string(ch),
+			)
+		}
+	}
+
+	return version, nil
+}
+
 // New creates a new Database instance.
 func New(lc fx.Lifecycle, params Params) (*Database, error) {
 	s := &Database{
@@ -88,22 +123,19 @@ func (s *Database) connect(ctx context.Context) error {
 	s.db = db
 	s.log.Info("database connected")
 
-	return applyMigrations(ctx, s.db, s.log)
+	return ApplyMigrations(ctx, s.db, s.log)
 }
 
-// applyMigrations bootstraps the migrations table from 000.sql and then
-// applies every remaining migration that has not been recorded yet.
-func applyMigrations(ctx context.Context, db *sql.DB, log *slog.Logger) error {
-	if err := bootstrapMigrationsTable(ctx, db, log); err != nil {
-		return err
-	}
-
+// collectMigrations reads the embedded schema directory and returns
+// migration filenames sorted lexicographically.
+func collectMigrations() ([]string, error) {
 	entries, err := schemaFS.ReadDir("schema")
 	if err != nil {
-		return fmt.Errorf("failed to read schema directory: %w", err)
+		return nil, fmt.Errorf("failed to read schema directory: %w", err)
 	}
 
 	var migrations []string
+
 	for _, entry := range entries {
 		if !entry.IsDir() && strings.HasSuffix(entry.Name(), ".sql") {
 			migrations = append(migrations, entry.Name())
@@ -112,49 +144,7 @@ func applyMigrations(ctx context.Context, db *sql.DB, log *slog.Logger) error {
 
 	sort.Strings(migrations)
 
-	for _, migration := range migrations {
-		version := strings.TrimSuffix(migration, filepath.Ext(migration))
-
-		var count int
-
-		err := db.QueryRowContext(ctx,
-			"SELECT COUNT(*) FROM schema_migrations WHERE version = ?",
-			version,
-		).Scan(&count)
-		if err != nil {
-			return fmt.Errorf("failed to check migration status: %w", err)
-		}
-
-		if count > 0 {
-			logDebug(log, "migration already applied", "version", version)
-
-			continue
-		}
-
-		content, err := schemaFS.ReadFile(filepath.Join("schema", migration))
-		if err != nil {
-			return fmt.Errorf("failed to read migration %s: %w", migration, err)
-		}
-
-		logInfo(log, "applying migration", "version", version)
-
-		_, err = db.ExecContext(ctx, string(content))
-		if err != nil {
-			return fmt.Errorf("failed to apply migration %s: %w", migration, err)
-		}
-
-		_, err = db.ExecContext(ctx,
-			"INSERT INTO schema_migrations (version) VALUES (?)",
-			version,
-		)
-		if err != nil {
-			return fmt.Errorf("failed to record migration %s: %w", migration, err)
-		}
-
-		logInfo(log, "migration applied successfully", "version", version)
-	}
-
-	return nil
+	return migrations, nil
 }
 
 // bootstrapMigrationsTable ensures the schema_migrations table exists
@@ -172,9 +162,15 @@ func bootstrapMigrationsTable(ctx context.Context, db *sql.DB, log *slog.Logger)
 	}
 
 	if tableExists > 0 {
-		// Table already exists (from older inline-SQL code or a
-		// previous run). Make sure version "000" is recorded so the
-		// normal loop skips the bootstrap file.
+		return ensureBootstrapVersionRecorded(ctx, db, log)
+	}
+
+	return applyBootstrapMigration(ctx, db, log)
+}
+
+// ensureBootstrapVersionRecorded checks whether version "000" is already
+// recorded in an existing schema_migrations table and inserts it if not.
+func ensureBootstrapVersionRecorded(ctx context.Context, db *sql.DB, log *slog.Logger) error {
 	var recorded int
 
 	err := db.QueryRowContext(ctx,
@@ -185,7 +181,10 @@ func bootstrapMigrationsTable(ctx context.Context, db *sql.DB, log *slog.Logger)
 		return fmt.Errorf("failed to check bootstrap migration status: %w", err)
 	}
 
-		if recorded == 0 {
+	if recorded > 0 {
+		return nil
+	}
+
 	_, err = db.ExecContext(ctx,
 		"INSERT INTO schema_migrations (version) VALUES (?)",
 		bootstrapVersion,
@@ -194,19 +193,24 @@ func bootstrapMigrationsTable(ctx context.Context, db *sql.DB, log *slog.Logger)
 		return fmt.Errorf("failed to record bootstrap migration: %w", err)
 	}
 
-			logInfo(log, "recorded bootstrap migration for existing table", "version", bootstrapVersion)
+	if log != nil {
+		log.Info("recorded bootstrap migration for existing table", "version", bootstrapVersion)
 	}
 
 	return nil
-	}
+}
 
-	// Table does not exist — apply 000.sql to create it.
+// applyBootstrapMigration reads and executes 000.sql to create the
+// schema_migrations table on a fresh database.
+func applyBootstrapMigration(ctx context.Context, db *sql.DB, log *slog.Logger) error {
 	content, err := schemaFS.ReadFile("schema/000.sql")
 	if err != nil {
 		return fmt.Errorf("failed to read bootstrap migration 000.sql: %w", err)
 	}
 
-	logInfo(log, "applying bootstrap migration", "version", bootstrapVersion)
+	if log != nil {
+		log.Info("applying bootstrap migration", "version", bootstrapVersion)
+	}
 
 	_, err = db.ExecContext(ctx, string(content))
 	if err != nil {
@@ -221,7 +225,80 @@ func bootstrapMigrationsTable(ctx context.Context, db *sql.DB, log *slog.Logger)
 		return fmt.Errorf("failed to record bootstrap migration: %w", err)
 	}
 
-	logInfo(log, "bootstrap migration applied successfully", "version", bootstrapVersion)
+	if log != nil {
+		log.Info("bootstrap migration applied successfully", "version", bootstrapVersion)
+	}
+
+	return nil
+}
+
+// ApplyMigrations applies all pending migrations to db. An optional logger
+// may be provided for informational output; pass nil for silent operation.
+// This is exported so tests can apply the real schema without the full fx
+// lifecycle.
+func ApplyMigrations(ctx context.Context, db *sql.DB, log *slog.Logger) error {
+	if err := bootstrapMigrationsTable(ctx, db, log); err != nil {
+		return err
+	}
+
+	migrations, err := collectMigrations()
+	if err != nil {
+		return err
+	}
+
+	for _, migration := range migrations {
+		version, parseErr := ParseMigrationVersion(migration)
+		if parseErr != nil {
+			return parseErr
+		}
+
+		// Check if already applied.
+		var count int
+
+		err := db.QueryRowContext(ctx,
+			"SELECT COUNT(*) FROM schema_migrations WHERE version = ?",
+			version,
+		).Scan(&count)
+		if err != nil {
+			return fmt.Errorf("failed to check migration status: %w", err)
+		}
+
+		if count > 0 {
+			if log != nil {
+				log.Debug("migration already applied", "version", version)
+			}
+
+			continue
+		}
+
+		// Read and apply migration.
+		content, readErr := schemaFS.ReadFile(filepath.Join("schema", migration))
+		if readErr != nil {
+			return fmt.Errorf("failed to read migration %s: %w", migration, readErr)
+		}
+
+		if log != nil {
+			log.Info("applying migration", "version", version)
+		}
+
+		_, execErr := db.ExecContext(ctx, string(content))
+		if execErr != nil {
+			return fmt.Errorf("failed to apply migration %s: %w", migration, execErr)
+		}
+
+		// Record migration as applied.
+		_, recErr := db.ExecContext(ctx,
+			"INSERT INTO schema_migrations (version) VALUES (?)",
+			version,
+		)
+		if recErr != nil {
+			return fmt.Errorf("failed to record migration %s: %w", migration, recErr)
+		}
+
+		if log != nil {
+			log.Info("migration applied successfully", "version", version)
+		}
+	}
 
 	return nil
 }
@@ -230,24 +307,3 @@ func bootstrapMigrationsTable(ctx context.Context, db *sql.DB, log *slog.Logger)
 func (s *Database) DB() *sql.DB {
 	return s.db
 }
-
-// ApplyMigrations applies all migrations to the given database.
-// This is useful for testing where you want to use the real schema
-// without the full fx lifecycle.
-func ApplyMigrations(db *sql.DB) error {
-	return applyMigrations(context.Background(), db, nil)
-}
-
-// logInfo logs at info level when a logger is available.
-func logInfo(log *slog.Logger, msg string, args ...any) {
-	if log != nil {
-		log.Info(msg, args...)
-	}
-}
-
-// logDebug logs at debug level when a logger is available.
-func logDebug(log *slog.Logger, msg string, args ...any) {
-	if log != nil {
-		log.Debug(msg, args...)
-	}
-}

internal/database/database_test.go

@@ -22,10 +22,89 @@ func openTestDB(t *testing.T) *sql.DB {
 	return db
 }
 
+func TestParseMigrationVersion(t *testing.T) {
+	tests := []struct {
+		name     string
+		filename string
+		want     string
+		wantErr  bool
+	}{
+		{
+			name:     "version only",
+			filename: "001.sql",
+			want:     "001",
+		},
+		{
+			name:     "version with description",
+			filename: "001_initial_schema.sql",
+			want:     "001",
+		},
+		{
+			name:     "multi-digit version",
+			filename: "042_add_indexes.sql",
+			want:     "042",
+		},
+		{
+			name:     "long version number",
+			filename: "00001_long_prefix.sql",
+			want:     "00001",
+		},
+		{
+			name:     "description with multiple underscores",
+			filename: "003_add_user_auth_tables.sql",
+			want:     "003",
+		},
+		{
+			name:     "empty filename",
+			filename: ".sql",
+			wantErr:  true,
+		},
+		{
+			name:     "leading underscore",
+			filename: "_description.sql",
+			wantErr:  true,
+		},
+		{
+			name:     "non-numeric version",
+			filename: "abc_migration.sql",
+			wantErr:  true,
+		},
+		{
+			name:     "mixed alphanumeric version",
+			filename: "001a_migration.sql",
+			wantErr:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ParseMigrationVersion(tt.filename)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("ParseMigrationVersion(%q) expected error, got %q", tt.filename, got)
+				}
+
+				return
+			}
+
+			if err != nil {
+				t.Errorf("ParseMigrationVersion(%q) unexpected error: %v", tt.filename, err)
+
+				return
+			}
+
+			if got != tt.want {
+				t.Errorf("ParseMigrationVersion(%q) = %q, want %q", tt.filename, got, tt.want)
+			}
+		})
+	}
+}
+
 func TestApplyMigrations_CreatesSchemaAndTables(t *testing.T) {
 	db := openTestDB(t)
+	ctx := context.Background()
 
-	if err := ApplyMigrations(db); err != nil {
+	if err := ApplyMigrations(ctx, db, nil); err != nil {
 		t.Fatalf("ApplyMigrations failed: %v", err)
 	}
 
@@ -83,13 +162,14 @@ func TestApplyMigrations_CreatesSchemaAndTables(t *testing.T) {
 
 func TestApplyMigrations_Idempotent(t *testing.T) {
 	db := openTestDB(t)
+	ctx := context.Background()
 
-	if err := ApplyMigrations(db); err != nil {
+	if err := ApplyMigrations(ctx, db, nil); err != nil {
 		t.Fatalf("first ApplyMigrations failed: %v", err)
 	}
 
 	// Running a second time must succeed without errors.
-	if err := ApplyMigrations(db); err != nil {
+	if err := ApplyMigrations(ctx, db, nil); err != nil {
 		t.Fatalf("second ApplyMigrations failed: %v", err)
 	}
 

internal/handlers/handlers_test.go

@@ -82,7 +82,7 @@ func setupTestDB(t *testing.T) *sql.DB {
 		t.Fatalf("failed to open test db: %v", err)
 	}
 
-	if err := database.ApplyMigrations(db); err != nil {
+	if err := database.ApplyMigrations(context.Background(), db, nil); err != nil {
 		t.Fatalf("failed to apply migrations: %v", err)
 	}
 

internal/imgcache/stats_test.go

@@ -16,7 +16,7 @@ func setupStatsTestDB(t *testing.T) *sql.DB {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if err := database.ApplyMigrations(db); err != nil {
+	if err := database.ApplyMigrations(context.Background(), db, nil); err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { db.Close() })

internal/imgcache/testutil_test.go

@@ -2,6 +2,7 @@ package imgcache
 
 import (
 	"bytes"
+	"context"
 	"database/sql"
 	"image"
 	"image/color"
@@ -193,7 +194,7 @@ func setupServiceTestDB(t *testing.T) *sql.DB {
 	}
 
 	// Use the real production schema via migrations
-	if err := database.ApplyMigrations(db); err != nil {
+	if err := database.ApplyMigrations(context.Background(), db, nil); err != nil {
 		t.Fatalf("failed to apply migrations: %v", err)
 	}