import { expect, tap } from '@git.zone/tstest/tapbundle';
import * as smartdb from '../ts/index.js';
import { MongoClient, Db } from 'mongodb';
import * as fs from 'fs';
import * as path from 'path';
import * as os from 'os';

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

let tmpDir: string;

function makeTmpDir(): string {
  return fs.mkdtempSync(path.join(os.tmpdir(), 'smartdb-migration-test-'));
}

function cleanTmpDir(dir: string): void {
  if (fs.existsSync(dir)) {
    fs.rmSync(dir, { recursive: true, force: true });
  }
}

/**
 * Create a v0 (legacy JSON) storage layout:
 *   {base}/{db}/{coll}.json
 *   {base}/{db}/{coll}.indexes.json
 */
function createV0Layout(basePath: string, dbName: string, collName: string, docs: any[]): void {
  const dbDir = path.join(basePath, dbName);
  fs.mkdirSync(dbDir, { recursive: true });

  // Convert docs to the extended JSON format that the old Rust engine wrote:
  // ObjectId is stored as { "$oid": "hex" }
  const jsonDocs = docs.map(doc => {
    const clone = { ...doc };
    if (!clone._id) {
      // Generate a fake ObjectId-like hex string
      const hex = [...Array(24)].map(() => Math.floor(Math.random() * 16).toString(16)).join('');
      clone._id = { '$oid': hex };
    }
    return clone;
  });

  const collPath = path.join(dbDir, `${collName}.json`);
  fs.writeFileSync(collPath, JSON.stringify(jsonDocs, null, 2));

  const indexPath = path.join(dbDir, `${collName}.indexes.json`);
  fs.writeFileSync(indexPath, JSON.stringify([
    { name: '_id_', key: { _id: 1 } },
  ], null, 2));
}

// ============================================================================
// Migration: v0 → v1 basic
// ============================================================================

tap.test('migration: detects v0 format and migrates on startup', async () => {
  tmpDir = makeTmpDir();

  // Create v0 layout with test data
  createV0Layout(tmpDir, 'mydb', 'users', [
    { name: 'Alice', age: 30, email: 'alice@test.com' },
    { name: 'Bob', age: 25, email: 'bob@test.com' },
    { name: 'Charlie', age: 35, email: 'charlie@test.com' },
  ]);

  createV0Layout(tmpDir, 'mydb', 'products', [
    { sku: 'W001', name: 'Widget', price: 9.99 },
    { sku: 'G001', name: 'Gadget', price: 19.99 },
  ]);

  // Verify v0 files exist
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'users.json'))).toBeTrue();
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'products.json'))).toBeTrue();

  // Start server — migration should run automatically
  const server = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server.start();

  // v1 directories should now exist
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'users', 'data.rdb'))).toBeTrue();
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'products', 'data.rdb'))).toBeTrue();

  // v0 files should still exist (not deleted)
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'users.json'))).toBeTrue();
  expect(fs.existsSync(path.join(tmpDir, 'mydb', 'products.json'))).toBeTrue();

  // Connect and verify data is accessible
  const client = new MongoClient(server.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client.connect();
  const db = client.db('mydb');

  // Users collection
  const users = await db.collection('users').find({}).toArray();
  expect(users.length).toEqual(3);
  const alice = users.find(u => u.name === 'Alice');
  expect(alice).toBeTruthy();
  expect(alice!.age).toEqual(30);
  expect(alice!.email).toEqual('alice@test.com');

  // Products collection
  const products = await db.collection('products').find({}).toArray();
  expect(products.length).toEqual(2);
  const widget = products.find(p => p.sku === 'W001');
  expect(widget).toBeTruthy();
  expect(widget!.price).toEqual(9.99);

  await client.close();
  await server.stop();
});

// ============================================================================
// Migration: migrated data survives another restart
// ============================================================================

tap.test('migration: migrated data persists across restart', async () => {
  const server = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server.start();

  const client = new MongoClient(server.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client.connect();
  const db = client.db('mydb');

  const users = await db.collection('users').find({}).toArray();
  expect(users.length).toEqual(3);

  const products = await db.collection('products').find({}).toArray();
  expect(products.length).toEqual(2);

  await client.close();
  await server.stop();
});

// ============================================================================
// Migration: can write new data after migration
// ============================================================================

tap.test('migration: new writes work after migration', async () => {
  const server = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server.start();

  const client = new MongoClient(server.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client.connect();
  const db = client.db('mydb');

  // Insert new documents
  await db.collection('users').insertOne({ name: 'Diana', age: 28 });
  const count = await db.collection('users').countDocuments();
  expect(count).toEqual(4);

  // Update existing migrated document
  await db.collection('users').updateOne(
    { name: 'Alice' },
    { $set: { age: 31 } }
  );
  const alice = await db.collection('users').findOne({ name: 'Alice' });
  expect(alice!.age).toEqual(31);

  // Delete a migrated document
  await db.collection('products').deleteOne({ sku: 'G001' });
  const prodCount = await db.collection('products').countDocuments();
  expect(prodCount).toEqual(1);

  await client.close();
  await server.stop();
  cleanTmpDir(tmpDir);
});

// ============================================================================
// Migration: skips already-migrated data
// ============================================================================

tap.test('migration: no-op for v1 format', async () => {
  tmpDir = makeTmpDir();

  // Start fresh to create v1 layout
  const server = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server.start();

  const client = new MongoClient(server.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client.connect();
  const db = client.db('v1test');
  await db.collection('items').insertOne({ x: 1 });
  await client.close();
  await server.stop();

  // Restart — migration should detect v1 and skip
  const server2 = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server2.start();

  const client2 = new MongoClient(server2.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client2.connect();
  const db2 = client2.db('v1test');
  const doc = await db2.collection('items').findOne({ x: 1 });
  expect(doc).toBeTruthy();

  await client2.close();
  await server2.stop();
  cleanTmpDir(tmpDir);
});

// ============================================================================
// Migration: empty storage is handled gracefully
// ============================================================================

tap.test('migration: empty storage directory works', async () => {
  tmpDir = makeTmpDir();

  const server = new smartdb.SmartdbServer({
    socketPath: path.join(os.tmpdir(), `smartdb-mig-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`),
    storage: 'file',
    storagePath: tmpDir,
  });
  await server.start();

  const client = new MongoClient(server.getConnectionUri(), {
    directConnection: true,
    serverSelectionTimeoutMS: 5000,
  });
  await client.connect();

  // Should work fine with empty storage
  const db = client.db('emptytest');
  await db.collection('first').insertOne({ hello: 'world' });
  const doc = await db.collection('first').findOne({ hello: 'world' });
  expect(doc).toBeTruthy();

  await client.close();
  await server.stop();
  cleanTmpDir(tmpDir);
});

export default tap.start();