初版功能完成

internal/database/migrate.go

@@ -0,0 +1,95 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"embed"
+	"fmt"
+	"io/fs"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+//go:embed migrations/*.sql
+var migrationFiles embed.FS
+
+// Migrate applies each embedded numbered migration exactly once.
+func Migrate(ctx context.Context, db *sql.DB) error {
+	if _, err := db.ExecContext(ctx, `
+        CREATE TABLE IF NOT EXISTS schema_migrations (
+            version INTEGER PRIMARY KEY,
+            name TEXT NOT NULL,
+            applied_at TEXT NOT NULL
+        )
+    `); err != nil {
+		return fmt.Errorf("create schema_migrations: %w", err)
+	}
+
+	entries, err := fs.ReadDir(migrationFiles, "migrations")
+	if err != nil {
+		return fmt.Errorf("read embedded migrations: %w", err)
+	}
+	sort.Slice(entries, func(i, j int) bool { return entries[i].Name() < entries[j].Name() })
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".sql") {
+			continue
+		}
+		versionText, _, ok := strings.Cut(entry.Name(), "_")
+		if !ok {
+			return fmt.Errorf("migration %q lacks numeric prefix", entry.Name())
+		}
+		version, err := strconv.Atoi(versionText)
+		if err != nil {
+			return fmt.Errorf("migration %q has invalid version: %w", entry.Name(), err)
+		}
+		applied, err := migrationApplied(ctx, db, version)
+		if err != nil {
+			return err
+		}
+		if applied {
+			continue
+		}
+		body, err := fs.ReadFile(migrationFiles, "migrations/"+entry.Name())
+		if err != nil {
+			return fmt.Errorf("read migration %q: %w", entry.Name(), err)
+		}
+		if err := applyMigration(ctx, db, version, entry.Name(), string(body)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func migrationApplied(ctx context.Context, db *sql.DB, version int) (bool, error) {
+	var count int
+	if err := db.QueryRowContext(ctx, `SELECT COUNT(*) FROM schema_migrations WHERE version = ?`, version).Scan(&count); err != nil {
+		return false, fmt.Errorf("query migration %d: %w", version, err)
+	}
+	return count != 0, nil
+}
+
+func applyMigration(ctx context.Context, db *sql.DB, version int, name string, body string) error {
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf("begin migration %q: %w", name, err)
+	}
+	defer tx.Rollback()
+	if _, err := tx.ExecContext(ctx, body); err != nil {
+		return fmt.Errorf("apply migration %q: %w", name, err)
+	}
+	if _, err := tx.ExecContext(
+		ctx,
+		`INSERT INTO schema_migrations(version, name, applied_at) VALUES(?, ?, ?)`,
+		version,
+		name,
+		time.Now().UTC().Format(time.RFC3339Nano),
+	); err != nil {
+		return fmt.Errorf("record migration %q: %w", name, err)
+	}
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("commit migration %q: %w", name, err)
+	}
+	return nil
+}