import * as bluebird from 'bluebird';
import {ChildProcess} from 'child_process';
import * as net from 'net';
import * as path from 'path';
import {ConnectionOptions} from 'typeorm';

/**
 * Promisify a node-style callback function. E.g.
 *    fromCallback(cb => someAsyncFunc(someArgs, cb));
 * This is merely a type-checked version of bluebird.fromCallback().
 * (Note that providing it using native Promises is also easy, but bluebird's big benefit is
 * support of long stack traces (when enabled for debugging).
 */
type NodeCallback<T> = (err: Error|undefined|null, value?: T) => void;
type NodeCallbackFunc<T> = (cb: NodeCallback<T>) => void;
const _fromCallback = bluebird.fromCallback;
export function fromCallback<T>(nodeFunc: NodeCallbackFunc<T>): Promise<T> {
  return _fromCallback(nodeFunc);
}


/**
 * Finds and returns a promise for the first available TCP port.
 * @param {Number} firstPort: First port number to check, defaults to 8000.
 * @param {Number} optCount: Number of ports to check, defaults to 200.
 * @returns Promise<Number>: Promise for an available port.
 */
export function getAvailablePort(firstPort: number = 8000, optCount: number = 200) {
  const lastPort = firstPort + optCount - 1;
  function checkNext(port: number): Promise<number> {
    if (port > lastPort) {
      throw new Error("No available ports between " + firstPort + " and " + lastPort);
    }
    return new bluebird((resolve: (p: number) => void, reject: (e: Error) => void) => {
      const server = net.createServer();
      server.on('error', reject);
      server.on('close', () => resolve(port));
      server.listen(port, 'localhost', () => server.close());
    })
    .catch(() => checkNext(port + 1));
  }
  return bluebird.try(() => checkNext(firstPort));
}

/**
 * Promisified version of net.connect(). Takes the same arguments, and returns a Promise for the
 * connected socket. (Types are specified as in @types/node.)
 */
export function connect(options: { port: number, host?: string, localAddress?: string, localPort?: string,
                                   family?: number, allowHalfOpen?: boolean; }): Promise<net.Socket>;
export function connect(port: number, host?: string): Promise<net.Socket>;
export function connect(path: string): Promise<net.Socket>;   // tslint:disable-line:unified-signatures
export function connect(arg: any, ...moreArgs: any[]): Promise<net.Socket> {
  return new Promise((resolve, reject) => {
    const s = net.connect(arg, ...moreArgs, () => resolve(s));
    s.on('error', reject);
  });
}

/**
 * Returns whether the path `inner` is contained within the directory `outer`.
 */
export function isPathWithin(outer: string, inner: string): boolean {
  const rel = path.relative(outer, inner);
  const index = rel.indexOf(path.sep);
  const firstDir = index < 0 ? rel : rel.slice(0, index);
  return firstDir !== "..";
}


/**
 * Returns a promise that's resolved when `child` exits, or rejected if it could not be started.
 * The promise resolves to the numeric exit code, or the string signal that terminated the child.
 *
 * Note that this must be called synchronously after creating the ChildProcess, since a delay may
 * cause the 'error' or 'exit' message from the child to be missed, and the resulting exitPromise
 * would then hang forever.
 */
export function exitPromise(child: ChildProcess): Promise<number|string> {
  return new Promise((resolve, reject) => {
    // Called if process could not be spawned, or could not be killed(!), or sending a message failed.
    child.on('error', reject);
    child.on('exit', (code: number, signal: string) => resolve(signal || code));
  });
}

/**
 * Resolves to true if promise is still pending after msec milliseconds have passed. Otherwise
 * returns false, including when promise is rejected.
 */
export function timeoutReached<T>(msec: number, promise: Promise<T>): Promise<boolean> {
  const timedOut = {};
  // Be careful to clean up the timer after ourselves, so it doesn't remain in the event loop.
  let timer: NodeJS.Timer;
  const delayPromise = new Promise<any>((resolve) => (timer = setTimeout(() => resolve(timedOut), msec)));
  return Promise.race([promise, delayPromise])
  .then((res) => { clearTimeout(timer); return res === timedOut; })
  .catch(() => false);
}

/**
 * Get database url in DATABASE_URL format popularized by heroku, suitable for
 * use by psql, sqlalchemy, etc.
 */
export function getDatabaseUrl(options: ConnectionOptions, includeCredentials: boolean): string {
  if (options.type === 'sqlite') {
    return `sqlite://${options.database}`;
  } else if (options.type === 'postgres') {
    const pass = options.password ? `:${options.password}` : '';
    const creds = includeCredentials && options.username ? `${options.username}${pass}@` : '';
    const port = options.port ? `:${options.port}` : '';
    return `postgres://${creds}${options.host}${port}/${options.database}`;
  } else {
    return `${options.type}://?`;
  }
}