import { readFileSync } from 'fs';
import path from 'path';
import { pool } from '../../src/db';
import { closeDb } from './setup/testDb';

afterAll(async () => {
  await pool.end();
  await closeDb();
});

const SCHEMA = readFileSync(
  path.join(__dirname, '..', '..', 'src', 'db-drizzle', 'schema.ts'),
  'utf8'
);

/** Every table name the generated mirror declares. */
function mirroredTables(): string[] {
  return [...SCHEMA.matchAll(/pgTable\("([a-z_]+)"/g)].map((m) => m[1]!).sort();
}

async function liveTables(): Promise<string[]> {
  const { rows } = await pool.query<{ table_name: string }>(
    `SELECT table_name FROM information_schema.tables
     WHERE table_schema = 'public' AND table_type = 'BASE TABLE'
       AND table_name <> 'pgmigrations'
     ORDER BY table_name`
  );
  return rows.map((r) => r.table_name);
}

/**
 * The guard for #217.
 *
 * `src/db-drizzle/schema.ts` is generated by `drizzle-kit pull` and is a
 * read-only mirror of the real schema, which `backend/migrations` owns. Nothing
 * makes anyone re-pull after writing a migration, and that is not hypothetical:
 * the mirror sat missing `item_drafts` and `upload_links` from the moment #222
 * landed until #217, because it had been copied into src/ by hand and nobody
 * had reason to look at it.
 *
 * A stale mirror is worse than no mirror. Drizzle infers row types from it, so
 * a converted query would type-check against a schema the database does not
 * have and fail at run time with a column that does not exist — the exact class
 * of drift the adoption was meant to close.
 */
describe('the Drizzle schema mirror', () => {
  it('declares every table the migrations create', async () => {
    const live = await liveTables();
    const mirrored = mirroredTables();

    const missing = live.filter((name) => !mirrored.includes(name));
    expect(missing).toEqual([]);
  });

  it('declares no table the database does not have', async () => {
    const live = await liveTables();
    const mirrored = mirroredTables();

    const extra = mirrored.filter((name) => !live.includes(name));
    expect(extra).toEqual([]);
  });

  // pgmigrations is node-pg-migrate's bookkeeping, excluded by tablesFilter in
  // drizzle.config.ts. A re-pull without that filter would quietly put it back.
  it('excludes node-pg-migrate bookkeeping', () => {
    expect(mirroredTables()).not.toContain('pgmigrations');
  });

  // Columns, not just tables: a migration that adds a column to a table the
  // mirror already knows about is the likelier drift, and the one a table-level
  // check would wave through.
  it('declares every column of every table it mirrors', async () => {
    const { rows } = await pool.query<{ table_name: string; column_name: string }>(
      `SELECT table_name, column_name FROM information_schema.columns
       WHERE table_schema = 'public' AND table_name <> 'pgmigrations'
       ORDER BY table_name, column_name`
    );

    // The mirror names a column either as a bare camelCase key or, when the
    // database name differs, as an explicit string argument. Checking the
    // snake_case name appears anywhere in the file is deliberately loose: it
    // catches a column the mirror has never heard of, which is the failure that
    // matters, without re-implementing drizzle-kit's naming rules.
    const missing = rows
      .filter((row) => !SCHEMA.includes(`"${row.column_name}"`))
      .filter((row) => !SCHEMA.includes(snakeToCamel(row.column_name)))
      .map((row) => `${row.table_name}.${row.column_name}`);

    expect(missing).toEqual([]);
  });
});

function snakeToCamel(name: string): string {
  return name.replace(/_([a-z])/g, (_, c: string) => c.toUpperCase());
}