var isOutRange = function (x1, y1, x2, y2, x3, y3) {
	return x1 < 0 || x1 >= y1 || x2 < 0 || x2 >= y2 || x3 < 0 || x3 >= y3
};

var sortCore = function (sKey, eKey, st) {
	var _ = st.baseData;

	var excludeFix = function (cKey, type) {
		if (st.list[cKey].fixed) { // fixed 元素位置不会变化, 这里直接用 cKey(sortKey) 获取, 更加快捷
			type ? --cKey : ++cKey;
			return excludeFix(cKey, type);
		}
		return cKey;
	}

	// 先获取到 endKey 对应的 realKey, 防止下面排序过程中该 realKey 被修改
	var endRealKey = -1;
	st.list.forEach(function (item) {
		if(item.sortKey === eKey) endRealKey = item.realKey;
	});

	return st.list.map(function (item) {
		if (item.fixed) return item;
		var cKey = item.sortKey;
		var rKey = item.realKey;

		if (sKey < eKey) {
			// 正序拖动
			if (cKey > sKey && cKey <= eKey) {
				--rKey;
				cKey = excludeFix(--cKey, true);
			} else if (cKey === sKey) {
				rKey = endRealKey;
				cKey = eKey;
			}
		} else if (sKey > eKey) {
			// 倒序拖动
			if (cKey >= eKey && cKey < sKey) {
				++rKey
				cKey = excludeFix(++cKey, false);
			} else if (cKey === sKey) {
				rKey = endRealKey;
				cKey = eKey;
			}
		}

		if (item.sortKey !== cKey) {
			item.tranX = (cKey % _.columns) * 100 + "%";
			item.tranY = Math.floor(cKey / _.columns) * 100 + "%";
			item.sortKey = cKey;
			item.realKey = rKey;
		}
		return item;
	});
}

var triggerCustomEvent = function(list, type, ins) {
	var _list = [], listData = [];

	list.forEach(function (item) {
		_list[item.sortKey] = item;
	});

	_list.forEach(function (item) {
		if (!item.extraNode) {
			listData.push(item.data);
		}
	});

	ins.triggerEvent(type, {listData: listData});
}

var longPress = function (event, ownerInstance) {
	var ins = event.instance;
	var st = ownerInstance.getState();
	var _ = st.baseData;

	var sTouch = event.changedTouches[0];
	if (!sTouch) return;

	st.cur = ins.getDataset().index;

	// 初始项是固定项则返回
	var item = st.list[st.cur];
	if (item && item.fixed) return;

	// 如果已经在 drag 中则返回, 防止多指触发 drag 动作, touchstart 事件中有效果
	if (st.dragging) return;
	st.dragging = true;
	ownerInstance.callMethod("drag", {dragging: true});

	// 计算X,Y轴初始位移, 使 item 中心移动到点击处, 单列时候X轴初始不做位移
	st.tranX = _.columns === 1 ? 0 : sTouch.pageX - (_.itemWidth / 2 + _.wrapLeft);
	st.tranY = sTouch.pageY - (_.itemHeight / 2 + _.wrapTop);
	st.sId = sTouch.identifier;

	ins.setStyle({
		'transform': 'translate3d(' + st.tranX + 'px, ' + st.tranY + 'px, 0)'
	});

	st.itemsInstance.forEach(function (item, index) {
		item.removeClass("tran").removeClass("cur");
		item.addClass(index === st.cur ? "cur" : "tran");
	})

	ownerInstance.callMethod("vibrate");
};

var touchMove = function (event, ownerInstance) {
	var ins = event.instance;
	var st = ownerInstance.getState();
	var _ = st.baseData;

	var mTouch = event.changedTouches[0];
	if (!mTouch) return;

	if (!st.dragging) return;

	// 如果不是同一个触发点则返回
	if (st.sId !== mTouch.identifier) return;

	// 计算X,Y轴位移, 单列时候X轴初始不做位移
	var tranX = _.columns === 1 ? 0 : mTouch.pageX - (_.itemWidth / 2 + _.wrapLeft);
	var tranY = mTouch.pageY - (_.itemHeight / 2 + _.wrapTop);

	// 到顶到底自动滑动
	if (mTouch.clientY > _.windowHeight - _.itemHeight - _.realBottomSize) {
		// 当前触摸点pageY + item高度 - (屏幕高度 - 底部固定区域高度)
		ownerInstance.callMethod("pageScroll", {
			scrollTop: mTouch.pageY + _.itemHeight - (_.windowHeight - _.realBottomSize)
		});
	} else if (mTouch.clientY < _.itemHeight + _.realTopSize) {
		// 当前触摸点pageY - item高度 - 顶部固定区域高度
		ownerInstance.callMethod("pageScroll", {
			scrollTop: mTouch.pageY - _.itemHeight - _.realTopSize
		});
	}

	// 设置当前激活元素偏移量
	ins.setStyle({
		'transform': 'translate3d(' + tranX + 'px, ' + tranY + 'px, 0)'
	})

	var startKey = st.list[st.cur].sortKey;
	var curX = Math.round(tranX / _.itemWidth);
	var curY = Math.round(tranY / _.itemHeight);
	var endKey = curX + _.columns * curY;

	// 目标项是固定项则返回
	var item = st.list[endKey];
	if (item && item.fixed) return;

	// X轴或Y轴超出范围则返回
	if (isOutRange(curX, _.columns, curY, _.rows, endKey, st.list.length)) return;

	// 防止拖拽过程中发生乱序问题
	if (startKey === endKey || startKey === st.preStartKey) return;
	st.preStartKey = startKey;

	var list = sortCore(startKey, endKey, st);
	st.itemsInstance.forEach(function (itemIns, index) {
		var item = list[index];
		if (index !== st.cur) {
			itemIns.setStyle({
				'transform': 'translate3d(' + item.tranX + ',' + item.tranY + ', 0)'
			});
		}
	});

	ownerInstance.callMethod("vibrate");
	ownerInstance.callMethod("listChange", {list: list});
	triggerCustomEvent(list, "change", ownerInstance);
}

var touchEnd = function (event, ownerInstance) {
	var ins = event.instance;
	var st = ownerInstance.getState();

	if (!st.dragging) return;
	triggerCustomEvent(st.list, "sortend", ownerInstance);

	ins.addClass("tran");
	ins.setStyle({
		'transform': 'translate3d(' + st.list[st.cur].tranX + ',' + st.list[st.cur].tranY + ', 0)'
	});

	st.preStartKey = -1;
	st.dragging = false;
	ownerInstance.callMethod("drag", {dragging: false});
	st.cur = -1;
	st.tranX = 0;
	st.tranY = 0;
}

var baseDataObserver = function (newVal, oldVal, ownerInstance, ins) {
	var st = ownerInstance.getState();
	st.baseData = newVal;
}

var listObserver = function (newVal, oldVal, ownerInstance, ins) {
	var st = ownerInstance.getState();
	st.itemsInstance = ownerInstance.selectAllComponents('.item');

	st.list = newVal || [];

	st.list.forEach(function (item, index) {
		var itemIns = st.itemsInstance[index];
		if (item && itemIns) {
			itemIns.setStyle({
				'transform': 'translate3d(' + item.tranX + ',' + item.tranY + ', 0)'
			});
			if (item.fixed) itemIns.addClass("fixed");
		}
	})
}

module.exports = {
	longPress: longPress,
	touchMove: touchMove,
	touchEnd: touchEnd,
	baseDataObserver: baseDataObserver,
	listObserver: listObserver
}
