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// TODO this is out of date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 destroy(detach) {
	this.destroy = this.set = this.get = noop;
	this.fire('destroy');

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

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

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

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

		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));
	if (this._root._lock) return;
	this._root._lock = true;
	callAll(this._root._beforecreate);
	callAll(this._root._oncreate);
	callAll(this._root._aftercreate);
	this._root._lock = false;
}

function _set(newState) {
	var oldState = this._state,
		changed = {},
		dirty = false;

	for (var key in newState) {
		if (differs(newState[key], oldState[key])) changed[key] = dirty = true;
	}
	if (!dirty) return;

	this._state = assign({}, oldState, newState);
	this._recompute(changed, this._state, oldState, false);
	if (this._bind) this._bind(changed, this._state);
	dispatchObservers(this, this._observers.pre, changed, this._state, oldState);
	this._fragment.update(changed, this._state);
	dispatchObservers(this, this._observers.post, changed, this._state, oldState);
}

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

var proto = {
	destroy: destroy,
	get: get,
	fire: fire,
	observe: observe,
	on: on,
	set: set,
	teardown: destroy,
	_recompute: noop,
	_set: _set
};

function create_main_fragment ( state, component ) {
	var text, p, 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( 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 ( changed.comments || changed.elapsed || changed.time ) {
				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 ( changed.foo ) {
				text_1.data = state.foo;
			}
		},

		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, text_1, span, text_2_value = comment.author, text_2, text_3, text_4_value = state.elapsed(comment.time, state.time), text_4, text_5, text_6, raw_value = comment.html, raw_before, raw_after;

	return {
		create: function () {
			div = createElement( 'div' );
			strong = createElement( 'strong' );
			text = createText( i );
			text_1 = createText( "\n\n\t\t" );
			span = createElement( 'span' );
			text_2 = createText( text_2_value );
			text_3 = createText( " wrote " );
			text_4 = createText( text_4_value );
			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 );
		},

		update: function ( changed, state, each_block_value, comment, i ) {
			if ( ( changed.comments ) && text_2_value !== ( text_2_value = comment.author ) ) {
				text_2.data = text_2_value;
			}

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

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

		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._bind = options._bind;

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

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

assign( SvelteComponent.prototype, proto );

export default SvelteComponent;