function noop() {}

function assign(target) {
	var k,
		source,
		i = 1,
		len = arguments.length;
	for (; i < len; i++) {
		source = arguments[i];
		for (k in source) target[k] = source[k];
	}

	return target;
}

function appendNode(node, target) {
	target.appendChild(node);
}

function insertNode(node, target, anchor) {
	target.insertBefore(node, anchor);
}

function detachNode(node) {
	node.parentNode.removeChild(node);
}

function detachBetween(before, after) {
	while (before.nextSibling && before.nextSibling !== after) {
		before.parentNode.removeChild(before.nextSibling);
	}
}

// TODO this is out of date
function destroyEach(iterations, detach, start) {
	for (var i = start; i < iterations.length; i += 1) {
		if (iterations[i]) iterations[i].destroy(detach);
	}
}

function createElement(name) {
	return document.createElement(name);
}

function createText(data) {
	return document.createTextNode(data);
}

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

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;
			}
		}
	}
}

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

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);
	}
}

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);
		}
	};
}

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);
		}
	};
}

function set(newState) {
	this._set(assign({}, newState));
	this._root._flush();
}

function _flush() {
	if (!this._oncreate) return;

	while (this._oncreate.length) {
		this._oncreate.pop()();
	}
}

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

function create_main_fragment ( state, component ) {
	var text, p, text_1_value, text_1;

	var each_block_value = state.comments;

	var each_block_iterations = [];

	for ( var i = 0; i < each_block_value.length; i += 1 ) {
		each_block_iterations[i] = create_each_block( state, each_block_value, each_block_value[i], i, component );
	}

	return {
		create: function () {
			for ( var i = 0; i < each_block_iterations.length; i += 1 ) {
				each_block_iterations[i].create();
			}

			text = createText( "\n\n" );
			p = createElement( 'p' );
			text_1 = createText( text_1_value = state.foo );
		},

		mount: function ( target, anchor ) {
			for ( var i = 0; i < each_block_iterations.length; i += 1 ) {
				each_block_iterations[i].mount( target, anchor );
			}

			insertNode( text, target, anchor );
			insertNode( p, target, anchor );
			appendNode( text_1, p );
		},

		update: function ( changed, state ) {
			var each_block_value = state.comments;

			if ( 'comments' in changed || 'elapsed' in changed || 'time' in changed ) {
				for ( var i = 0; i < each_block_value.length; i += 1 ) {
					if ( each_block_iterations[i] ) {
						each_block_iterations[i].update( changed, state, each_block_value, each_block_value[i], i );
					} else {
						each_block_iterations[i] = create_each_block( state, each_block_value, each_block_value[i], i, component );
						each_block_iterations[i].create();
						each_block_iterations[i].mount( text.parentNode, text );
					}
				}

				for ( ; i < each_block_iterations.length; i += 1 ) {
					each_block_iterations[i].unmount();
					each_block_iterations[i].destroy();
				}
				each_block_iterations.length = each_block_value.length;
			}

			if ( text_1_value !== ( text_1_value = state.foo ) ) {
				text_1.data = text_1_value;
			}
		},

		unmount: function () {
			for ( var i = 0; i < each_block_iterations.length; i += 1 ) {
				each_block_iterations[i].unmount();
			}

			detachNode( text );
			detachNode( p );
		},

		destroy: function () {
			destroyEach( each_block_iterations, false, 0 );
		}
	};
}

function create_each_block ( state, each_block_value, comment, i, component ) {
	var div, strong, text_value, text, text_1, span, text_2_value, text_2, text_3, text_4_value, text_4, text_5, text_6, raw_value, raw_before, raw_after;

	return {
		create: function () {
			div = createElement( 'div' );
			strong = createElement( 'strong' );
			text = createText( text_value = i );
			text_1 = createText( "\n\n\t\t" );
			span = createElement( 'span' );
			text_2 = createText( text_2_value = comment.author );
			text_3 = createText( " wrote " );
			text_4 = createText( text_4_value = state.elapsed(comment.time, state.time) );
			text_5 = createText( " ago:" );
			text_6 = createText( "\n\n\t\t" );
			raw_before = createElement( 'noscript' );
			raw_after = createElement( 'noscript' );
			this.hydrate();
		},

		hydrate: function ( nodes ) {
			div.className = "comment";
			span.className = "meta";
		},

		mount: function ( target, anchor ) {
			insertNode( div, target, anchor );
			appendNode( strong, div );
			appendNode( text, strong );
			appendNode( text_1, div );
			appendNode( span, div );
			appendNode( text_2, span );
			appendNode( text_3, span );
			appendNode( text_4, span );
			appendNode( text_5, span );
			appendNode( text_6, div );
			appendNode( raw_before, div );
			appendNode( raw_after, div );
			raw_before.insertAdjacentHTML( 'afterend', raw_value = comment.html );
		},

		update: function ( changed, state, each_block_value, comment, i ) {
			if ( text_value !== ( text_value = i ) ) {
				text.data = text_value;
			}

			if ( text_2_value !== ( text_2_value = comment.author ) ) {
				text_2.data = text_2_value;
			}

			if ( text_4_value !== ( text_4_value = state.elapsed(comment.time, state.time) ) ) {
				text_4.data = text_4_value;
			}

			if ( raw_value !== ( raw_value = comment.html ) ) {
				detachBetween( raw_before, raw_after );
				raw_before.insertAdjacentHTML( 'afterend', raw_value = comment.html );
			}
		},

		unmount: function () {
			detachBetween( raw_before, raw_after );

			detachNode( div );
		},

		destroy: noop
	};
}

function SvelteComponent ( options ) {
	options = options || {};
	this._state = options.data || {};

	this._observers = {
		pre: Object.create( null ),
		post: Object.create( null )
	};

	this._handlers = Object.create( null );

	this._root = options._root || this;
	this._yield = options._yield;

	this._torndown = false;

	this._fragment = create_main_fragment( this._state, this );

	if ( options.target ) {
		this._fragment.create();
		this._fragment.mount( options.target, null );
	}
}

assign( SvelteComponent.prototype, proto );

SvelteComponent.prototype._set = function _set ( newState ) {
	var oldState = this._state;
	this._state = assign( {}, oldState, newState );
	dispatchObservers( this, this._observers.pre, newState, oldState );
	this._fragment.update( newState, this._state );
	dispatchObservers( this, this._observers.post, newState, oldState );
};

SvelteComponent.prototype.teardown = SvelteComponent.prototype.destroy = function destroy ( detach ) {
	this.fire( 'destroy' );

	if ( detach !== false ) this._fragment.unmount();
	this._fragment.destroy();
	this._fragment = null;

	this._state = {};
	this._torndown = true;
};

export default SvelteComponent;