const { reg } = require('lib/registry.js');

class BaseSyncTarget {

	constructor(db, options = null) {
		this.db_ = db;
		this.synchronizer_ = null;
		this.initState_ = null;
		this.logger_ = null;
		this.options_ = options;
	}

	option(name, defaultValue = null) {
		return this.options_ && (name in this.options_) ? this.options_[name] : defaultValue;
	}

	logger() {
		return this.logger_;
	}

	setLogger(v) {
		this.logger_ = v;
	}

	db() {
		return this.db_;
	}

	isAuthenticated() {
		return false;
	}

	static id() {
		throw new Error('id() not implemented');
	}

	// Note: it cannot be called just "name()" because that's a reserved keyword and
	// it would throw an obscure error in React Native.
	static targetName() {
		throw new Error('targetName() not implemented');
	}

	static label() {
		throw new Error('label() not implemented');
	}

	async initSynchronizer() {
		throw new Error('initSynchronizer() not implemented');
	}

	async initFileApi() {
		throw new Error('initFileApi() not implemented');
	}

	async fileApi() {
		if (this.fileApi_) return this.fileApi_;
		this.fileApi_ = await this.initFileApi();
		return this.fileApi_;
	}

	// Usually each sync target should create and setup its own file API via initFileApi()
	// but for testing purposes it might be convenient to provide it here so that multiple
	// clients can share and sync to the same file api (see test-utils.js)
	setFileApi(v) {
		this.fileApi_ = v;
	}

	async synchronizer() {
		if (this.synchronizer_) return this.synchronizer_;

		if (this.initState_ == 'started') {
			// Synchronizer is already being initialized, so wait here till it's done.
			return new Promise((resolve, reject) => {
				const iid = setInterval(() => {
					if (this.initState_ == 'ready') {
						clearInterval(iid);
						resolve(this.synchronizer_);
					}
					if (this.initState_ == 'error') {
						clearInterval(iid);
						reject(new Error('Could not initialise synchroniser'));
					}
				}, 1000);
			});
		} else {
			this.initState_ = 'started';

			try {
				this.synchronizer_ = await this.initSynchronizer();
				this.synchronizer_.setLogger(this.logger());
				this.synchronizer_.dispatch = BaseSyncTarget.dispatch;
				this.initState_ = 'ready';
				return this.synchronizer_;
			} catch (error) {
				this.initState_ = 'error';
				throw error;
			}
		}
	}

	async syncStarted() {
		if (!this.synchronizer_) return false;
		if (!this.isAuthenticated()) return false;
		const sync = await this.synchronizer();
		return sync.state() != 'idle';
	}

}

BaseSyncTarget.dispatch = (action) => {};

module.exports = BaseSyncTarget;