import { Pool } from 'pg';

export const pool = new Pool({
  host: process.env.PGHOST,
  port: parseInt(process.env.PGPORT || '5432', 10),
  user: process.env.PGUSER,
  password: process.env.PGPASSWORD,
  database: process.env.PGDATABASE
});

/**
 * The single row a query is guaranteed to have returned.
 *
 * For `INSERT ... RETURNING` and `UPDATE ... WHERE id = $1 RETURNING` after the
 * row's existence has already been established: Postgres returns exactly one
 * row, so there is nothing to branch on, but `noUncheckedIndexedAccess` is right
 * that `rows[0]` is `T | undefined` and the compiler cannot know better.
 *
 * A thrown error rather than a non-null assertion. If the assumption is ever
 * wrong the assertion would hand `undefined` to the next line and fail somewhere
 * unrelated, whereas this fails here and says which query. `asyncRoute` turns it
 * into a 500, which is the right answer for "the database did not do what the
 * statement says it does".
 *
 * Reads that legitimately might find nothing do not use this — they destructure
 * and branch, so the check and the use are the same thing.
 */
export function requireRow<T>(rows: T[], what: string): T {
  const row = rows[0];
  if (!row) {
    throw new Error(`expected ${what} to return a row, got none`);
  }
  return row;
}