import { promisify } from 'util';
import { expect } from 'chai';
import { describe } from 'mocha';
import { SimpleMutex } from './simple-mutex';

describe('Simple Mutex', () => {
  it('executes code after acquiring lock', () => {
    const mutex = new SimpleMutex();

    return mutex.acquire().then(() => {
      const x = 1;
      expect(x).eq(1);
    });
  });

  it('correctly locks a resource', async () => {
    const mutex = new SimpleMutex();

    let inUse = false;

    const useResource = () => {
      expect(inUse).to.be.false;
      inUse = true;
      return promisify(setTimeout)(1).then(() => {
        inUse = false;
      });
    };

    const acquireOne = mutex.acquire();
    const acquireTwo = mutex.acquire();
    const acquireThree = mutex.acquire();
    void acquireOne.then(async (release) => {
      await useResource();
      release();
    });
    void acquireTwo.then(async (release) => {
      await useResource();
      release();
    });
    return acquireThree.then(async (release) => {
      await useResource();
      release();
    });
  });

  it('executes consumers in the right order', async () => {
    const mutex = new SimpleMutex();

    let counter = 0;

    const useResource = (expectValue: number) => {
      counter++;
      expect(counter).to.equal(expectValue);
      return promisify(setTimeout)(1);
    };

    const acquireOne = mutex.acquire();
    const acquireTwo = mutex.acquire();
    const acquireThree = mutex.acquire();
    void acquireOne.then(async (release) => {
      await useResource(1);
      release();
    });
    void acquireTwo.then(async (release) => {
      await useResource(2);
      release();
    });
    return acquireThree.then(async (release) => {
      await useResource(3);
      release();
    });
  });

  it('correctly informs if it is currently locked', async () => {
    const mutex = new SimpleMutex();

    const release = await mutex.acquire();
    expect(mutex.isLocked()).to.be.true;
    release();
    expect(mutex.isLocked()).to.be.false;
  });
});