import { Watcher } from '../src/watcher.js';

describe('A watcher', () => {
	const selector = {};
	const opts = {};

	it('initially does nothing.', () => {
		const db = {
			changes: () => fail('Watcher should not call changes until the first subscription.')
		};

		const w = Watcher(db, selector, opts);
		expect().nothing();
	});

	it('calls PouchDB.change API on the first subscription.', () => {
		let state = 0;
		const db = {
			changes: options => {
				expect(state).toEqual(1);
				expect(options.live).toEqual(true);
				expect(options.since).toEqual('now');
				expect(options.selector).toBe(selector);
				return db;
			},
			on: (eventName, callback) => {
				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
				return db;
			},
			cancel: () => {}
		};

		const w = Watcher(db, selector, opts);
		state = 1;
		w(() => fail('Subscription callback should not be called until data changes.'));
	});

	it('cancels change subscription when the last subscriber unsubscribes', () => {
		let state = 0;
		const db = {
			changes: options => {
				expect(state).toEqual(1);
				expect(options.live).toEqual(true);
				expect(options.since).toEqual('now');
				expect(options.selector).toBe(selector);
				return db;
			},
			on: (eventName, callback) => {
				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
				return db;
			},
			cancel: () => {
				expect(state).toEqual(2);
				state = 3;
			}
		};

		const w = Watcher(db, selector, opts);
		state = 1;
		const unsub = w(() => fail('Subscription callback should not be called until data changes.'));
		state = 2;
		unsub();
		expect(state).toEqual(3);
	});

	it('passes change events to subscribers.', () => {
		let state = 0;
		const changes = {
			234: { id: 234, deleted: false, doc: { _id: 234 } },
			34: { id: 34, deleted: true, doc: { _id: 34 } },
			4564565: { id: 4564565, deleted: false, doc: { _id: 4564565 } }
		};
		let sub = null;
		const db = {
			changes: options => {
				expect(state).toEqual(1);
				expect(options.live).toEqual(true);
				expect(options.since).toEqual('now');
				expect(options.selector).toBe(selector);
				return db;
			},
			on: (eventName, callback) => {
				if (eventName == 'change') {
					sub = callback;
				}
				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
				return db;
			},
			cancel: () => (sub = null)
		};

		const w = Watcher(db, selector, opts);
		state = 1;
		w((id, deleted, doc) => {
			expect(changes.hasOwnProperty(id)).toBeTruthy();
			expect(changes[id].doc).toBe(doc);
			expect(changes[id].deleted).toEqual(deleted);
		});

		Object.values(changes).forEach(sub);
	});

	it('dumps subscribers when an error event happens.', () => {
		let state = 0;
		const changes = {
			234: { id: 234, deleted: false, doc: { _id: 234 } },
			34: { id: 34, deleted: true, doc: { _id: 34 } },
			4564565: { id: 4564565, deleted: false, doc: { _id: 4564565 } }
		};
		let sub = null;
		let errorSub = null;
		const db = {
			changes: options => {
				expect(state).toEqual(1);
				expect(options.live).toEqual(true);
				expect(options.since).toEqual('now');
				expect(options.selector).toBe(selector);
				return db;
			},
			on: (eventName, callback) => {
				if (eventName == 'change') {
					sub = callback;
				}
				if (eventName == 'error') {
					errorSub = callback;
				}
				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
				return db;
			},
			cancel: () => {
				sub = null;
				errorSub = null;
			}
		};

		const w = Watcher(db, selector, opts);
		state = 1;
		w(() => fail('Subscription callback should not be called until data changes.'));

		const error = new Error('TestError');
		try {
			errorSub(error);
		} catch (e) {
			expect(e).toBe(error);
		}
		Object.values(changes).forEach(sub);
	});
});