import { TDTrinoClient } from '../client/trino';
import { AuditLogger } from '../security/audit-logger';
export interface ColumnInfo {
column_name: string;
data_type: string;
is_nullable: boolean;
}
export interface DescribeTableResult {
columns: ColumnInfo[];
}
/**
* MCP tool for describing table schema
*/
export class DescribeTableTool {
constructor(
private readonly client: TDTrinoClient,
private readonly auditLogger: AuditLogger
) {}
/**
* Gets column information for a specific table
* @param database - Database name
* @param table - Table name
* @returns Object containing array of column information
* @throws {Error} If parameters are invalid or query fails
*/
async execute(database: string, table: string): Promise<DescribeTableResult> {
if (!database || typeof database !== 'string') {
throw new Error('Database parameter is required');
}
if (!table || typeof table !== 'string') {
throw new Error('Table parameter is required');
}
const escapedDatabase = this.client.escapeStringLiteral(database);
const escapedTable = this.client.escapeStringLiteral(table);
const query = `
SELECT
column_name,
data_type,
is_nullable
FROM td.information_schema.columns
WHERE table_catalog = 'td'
AND table_schema = ${escapedDatabase}
AND table_name = ${escapedTable}
ORDER BY ordinal_position
`.trim();
const startTime = Date.now();
try {
// First verify the table exists
const tableCheckQuery = `
SELECT 1
FROM td.information_schema.tables
WHERE table_catalog = 'td'
AND table_schema = ${escapedDatabase}
AND table_name = ${escapedTable}
`.trim();
const tableExists = await this.client.query(tableCheckQuery);
if (tableExists.data.length === 0) {
throw new Error(`Table '${database}.${table}' does not exist`);
}
// Execute the main query
const result = await this.client.query(query);
const duration = Date.now() - startTime;
// Format column information
const columns: ColumnInfo[] = result.data.map((row: Record<string, unknown>) => ({
column_name: row.column_name as string,
data_type: row.data_type as string,
is_nullable: row.is_nullable === 'YES',
}));
this.auditLogger.logSuccess('SELECT', query, database, duration, columns.length);
return { columns };
} catch (error) {
const duration = Date.now() - startTime;
const errorMessage = error instanceof Error ? error.message : 'Unknown error';
this.auditLogger.logFailure('SELECT', query, errorMessage, database, duration);
throw new Error(`Failed to describe table: ${errorMessage}`);
}
}
}
