chore: initial commit of ai site platform

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/internal/schema/runner.go

@@ -0,0 +1,92 @@
+package schema
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+var dbNameRe = regexp.MustCompile(`^[a-z][a-z0-9_]{1,47}$`)
+
+type Runner interface {
+	ExecDDL(ctx context.Context, stmts []string) error
+	EnsureDatabase(ctx context.Context, dbName string) error
+}
+
+type NoopRunner struct{}
+
+func (NoopRunner) ExecDDL(context.Context, []string) error   { return nil }
+func (NoopRunner) EnsureDatabase(context.Context, string) error { return nil }
+
+type PostgresRunner struct {
+	DB          *sql.DB
+	AdminDSN    string // 用于 CREATE DATABASE（连到 postgres 库）
+}
+
+func (r *PostgresRunner) ExecDDL(ctx context.Context, stmts []string) error {
+	tx, err := r.DB.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = tx.Rollback() }()
+	for _, s := range stmts {
+		if _, err := tx.ExecContext(ctx, s); err != nil {
+			return fmt.Errorf("ddl failed: %w\nsql: %s", err, s)
+		}
+	}
+	return tx.Commit()
+}
+
+func (r *PostgresRunner) EnsureDatabase(ctx context.Context, dbName string) error {
+	if !dbNameRe.MatchString(dbName) {
+		return fmt.Errorf("invalid database name: %s", dbName)
+	}
+	admin := r.DB
+	var err error
+	if r.AdminDSN != "" {
+		admin, err = sql.Open("postgres", r.AdminDSN)
+		if err != nil {
+			return err
+		}
+		defer admin.Close()
+	}
+	var exists bool
+	if err := admin.QueryRowContext(ctx,
+		`SELECT EXISTS(SELECT 1 FROM pg_database WHERE datname=$1)`, dbName,
+	).Scan(&exists); err != nil {
+		return err
+	}
+	if exists {
+		return nil
+	}
+	// CREATE DATABASE 不能在事务中
+	_, err = admin.ExecContext(ctx, fmt.Sprintf(`CREATE DATABASE %s`, quoteIdent(dbName)))
+	return err
+}
+
+// DSNForDatabase 把原 DSN 的库名替换为目标库。
+func DSNForDatabase(baseDSN, dbName string) (string, error) {
+	if !dbNameRe.MatchString(dbName) {
+		return "", fmt.Errorf("invalid database name")
+	}
+	u, err := url.Parse(baseDSN)
+	if err != nil {
+		return "", err
+	}
+	u.Path = "/" + dbName
+	return u.String(), nil
+}
+
+func QuoteIdentExport(name string) string { return quoteIdent(name) }
+
+func SanitizeDBName(tenantID int64, slug string) string {
+	name := fmt.Sprintf("appdb_t%d_%s", tenantID, slug)
+	name = strings.ToLower(name)
+	if len(name) > 48 {
+		name = name[:48]
+	}
+	return name
+}