import type { AsyncHandler } from '../../../../src/util/handlers/AsyncHandler';
import {
  CachedHandler,
} from '../../../../src/util/handlers/CachedHandler';

describe('A CachedHandler', (): void => {
  const input = { entry: { key: 'value' }};
  const output = 'response';
  let source: jest.Mocked<AsyncHandler<{ entry: { key: string }}, string>>;
  let handler: CachedHandler<{ entry: { key: string }}, string>;

  beforeEach(async(): Promise<void> => {
    source = {
      canHandle: jest.fn(),
      handle: jest.fn().mockResolvedValue(output),
    } as any;
    handler = new CachedHandler(source);
  });

  it('can handle input if its source can.', async(): Promise<void> => {
    await expect(handler.canHandle(input)).resolves.toBeUndefined();
    expect(source.canHandle).toHaveBeenCalledTimes(1);
    source.canHandle.mockRejectedValue(new Error('bad input'));
    await expect(handler.canHandle(input)).rejects.toThrow('bad input');
    expect(source.canHandle).toHaveBeenCalledTimes(2);
  });

  it('returns the source result.', async(): Promise<void> => {
    await expect(handler.handle(input)).resolves.toBe(output);
    expect(source.handle).toHaveBeenCalledTimes(1);
    expect(source.handle).toHaveBeenLastCalledWith(input);
  });

  it('caches the result.', async(): Promise<void> => {
    await expect(handler.handle(input)).resolves.toBe(output);
    await expect(handler.handle(input)).resolves.toBe(output);
    expect(source.handle).toHaveBeenCalledTimes(1);
  });

  it('caches on the object itself.', async(): Promise<void> => {
    const copy = { ...input };
    await expect(handler.handle(input)).resolves.toBe(output);
    await expect(handler.handle(copy)).resolves.toBe(output);
    expect(source.handle).toHaveBeenCalledTimes(2);
  });

  it('can handle the input if it has a cached result.', async(): Promise<void> => {
    await expect(handler.handle(input)).resolves.toBe(output);
    source.canHandle.mockRejectedValue(new Error('bad input'));
    await expect(handler.canHandle(input)).resolves.toBeUndefined();
    expect(source.canHandle).toHaveBeenCalledTimes(0);
  });

  it('can use a specific field of the input as key.', async(): Promise<void> => {
    handler = new CachedHandler(source, 'entry');

    const copy = { ...input };
    await expect(handler.handle(input)).resolves.toBe(output);
    await expect(handler.handle(copy)).resolves.toBe(output);
    expect(source.handle).toHaveBeenCalledTimes(1);
  });
});