import { assign } from './utils.js';
export * from './dom.js';
export * from './transitions.js';
export * from './utils.js';

export function differs(a, b) {
	return a !== b || ((a && typeof a === 'object') || typeof a === 'function');
}

export function dispatchObservers(component, group, newState, oldState) {
	for (var key in group) {
		if (!(key in newState)) continue;

		var newValue = newState[key];
		var oldValue = oldState[key];

		if (differs(newValue, oldValue)) {
			var callbacks = group[key];
			if (!callbacks) continue;

			for (var i = 0; i < callbacks.length; i += 1) {
				var callback = callbacks[i];
				if (callback.__calling) continue;

				callback.__calling = true;
				callback.call(component, newValue, oldValue);
				callback.__calling = false;
			}
		}
	}
}

export function get(key) {
	return key ? this._state[key] : this._state;
}

export function fire(eventName, data) {
	var handlers =
		eventName in this._handlers && this._handlers[eventName].slice();
	if (!handlers) return;

	for (var i = 0; i < handlers.length; i += 1) {
		handlers[i].call(this, data);
	}
}

export function observe(key, callback, options) {
	var group = options && options.defer
		? this._observers.post
		: this._observers.pre;

	(group[key] || (group[key] = [])).push(callback);

	if (!options || options.init !== false) {
		callback.__calling = true;
		callback.call(this, this._state[key]);
		callback.__calling = false;
	}

	return {
		cancel: function() {
			var index = group[key].indexOf(callback);
			if (~index) group[key].splice(index, 1);
		}
	};
}

export function observeDev(key, callback, options) {
	var c = (key = '' + key).search(/[^\w]/);
	if (c > -1) {
		var message =
			'The first argument to component.observe(...) must be the name of a top-level property';
		if (c > 0)
			message += ", i.e. '" + key.slice(0, c) + "' rather than '" + key + "'";

		throw new Error(message);
	}

	return observe.call(this, key, callback, options);
}

export function on(eventName, handler) {
	if (eventName === 'teardown') return this.on('destroy', handler);

	var handlers = this._handlers[eventName] || (this._handlers[eventName] = []);
	handlers.push(handler);

	return {
		cancel: function() {
			var index = handlers.indexOf(handler);
			if (~index) handlers.splice(index, 1);
		}
	};
}

export function onDev(eventName, handler) {
	if (eventName === 'teardown') {
		console.warn(
			"Use component.on('destroy', ...) instead of component.on('teardown', ...) which has been deprecated and will be unsupported in Svelte 2"
		);
		return this.on('destroy', handler);
	}

	return on.call(this, eventName, handler);
}

export function set(newState) {
	this._set(assign({}, newState));
	callAll(this._root._oncreate);
}

export function callAll(fns) {
	while (fns && fns.length) fns.pop()();
}

export var proto = {
	get: get,
	fire: fire,
	observe: observe,
	on: on,
	set: set
};

export var protoDev = {
	get: get,
	fire: fire,
	observe: observeDev,
	on: onDev,
	set: set
};