import { format } from 'sql-formatter';

const GRAFANA_TEMPLATE_VARIABLE_REGEX = String.raw`\$[a-zA-Z_][a-zA-Z0-9_]*(?:\.[a-zA-Z_][a-zA-Z0-9_]*)*`;
const GRAFANA_MACRO_REGEX = String.raw`\$__[a-zA-Z_][a-zA-Z0-9_]*`;

export function formatSql(sql: string): string {
  try {
    const formatted = format(sql, {
      tabWidth: 2,
      keywordCase: 'upper',
      // Treat Grafana-style variables/macros as placeholders so the formatter can
      // parse expressions like $database.cpu and $__timeFilter(ts).
      paramTypes: {
        custom: [{ regex: GRAFANA_TEMPLATE_VARIABLE_REGEX }],
      },
    });
    // sql-formatter treats $__xxx as a placeholder and inserts a space before '('.
    // Remove that extra space so $__timeFilter( stays intact as a function call.
    return formatted.replace(new RegExp(`(${GRAFANA_MACRO_REGEX})\\s+\\(`, 'g'), '$1(');
  } catch {
    // If formatting fails, return the original SQL
    return sql;
  }
}