var Excel = 
{
    open : function(data, filename, sheetname) {
        this.name = sheetname || 'sheet1';
        this.sheet = XLSX.utils.aoa_to_sheet(data, {raw: true});
        this.autoWidthFunc(this.sheet, data);
        if (filename.substr(-5).toLowerCase() !== '.xlsx') {
            filename += '.xlsx';
        }
        this.openDownloadDialog(this.sheet2blob(this.sheet, this.name), filename);
    },

    autoWidthFunc : function (ws, data) {
      // set worksheet max width per col
      const colWidth = data.map(row =>
        row.map(val => {
          // if null/undefined
          if (val == null) {
            return { wch: 10 };
          } else if (val.toString().charCodeAt(0) > 255) {
            // if chinese
            var l = val.toString().length;
            var n = l + l*0.5;
            return { wch: n * 2 };
          } else {
            var l = val.toString().length;
            var n = l + l*0.5;
            return { wch: n };
          }
        })
      );
      // start in the first row
      const result = colWidth[0];
      for (let i = 1; i < colWidth.length; i++) {
        for (let j = 0; j < colWidth[i].length; j++) {
          if (result[j].wch < colWidth[i][j].wch) {
            result[j].wch = colWidth[i][j].wch;
          }
        }
      }
      ws['!cols'] = result;
    },

    export : function (url, data) {
    	var self = this;
        var filename = '';
        var head = [];
		var alldata = [];
	    var loading = layer.msg('正在加载 <span data-upload-page></span>，完成<span data-upload-progress>0</span>%', {time:0,icon: 1});
	    nextPage(1, 1);

	    function nextPage(curPage, maxPage) {
	        if (curPage > maxPage) {
	        	alldata.unshift(head);
	            this.result = alldata;
                if (this.result !== false) {
                    self.open(this.result, filename || '文件下载.xlsx');
                } else {
                    console.log('格式化函数返回`false`，已终止数据导出操作', alldata, this.result);
                }
	            layer.close(loading);
	        } else {
	            $.post(url, {excel_type:1,pg:curPage,json:1}, function (ret) {
	            	var ret = eval('(' + ret + ')');
	                if (ret.status == 1 && ret.data) {
	                	filename = ret.data.filename;
	                	head = ret.data.head;
	                    alldata = alldata.concat(ret.data.body);

	                    curPage = ret.page.current_page;
	                    maxPage = ret.page.total_page;
	                    $('[data-upload-page]').html(curPage + '/' + maxPage);
	            		$('[data-upload-progress]').html((curPage / maxPage * 100).toFixed(2));

	                    return nextPage(curPage + 1, maxPage, false);
	                } else {
                        layer.close(loading);
                        layer.alert(ret.msg);
                    }
	            }, false);
	        }
	    }
    },

    /*! Sheet 转下载对象 */
    sheet2blob : function(sheet, name) {
        this.workbook = {SheetNames: [name], Sheets: {}};
        this.workbook.Sheets[name] = sheet;
        this.content = XLSX.write(this.workbook, {
            type: 'binary', bookSST: false, bookType: 'xlsx',
        });
        return new Blob([this.toArrayBuffer(this.content)], {
            type: "application/octet-stream"
        });
    },

    /*! 字符串转 ArrayBuffer */
    toArrayBuffer : function(s) {
        this.buff = new ArrayBuffer(s.length);
        this.view = new Uint8Array(this.buff);
        for (this.index = 0; this.index !== s.length; ++this.index) {
            this.view[this.index] = s.charCodeAt(this.index) & 0xFF;
        }
        return this.buff;
    },

    /*! 通用的打开下载对话框方法 */
    openDownloadDialog : function(location, filename) {
        if (typeof location == 'object' && location instanceof Blob) {
            location = URL.createObjectURL(location);
        }
        this.link = document.createElement('a');
        this.link.download = filename || Date.now() + '.xlsx';
        this.link.href = location;
        if (window.MouseEvent) {
            this.event = new MouseEvent('click');
        } else {
            this.event = document.createEvent('MouseEvents');
            this.event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
        }
        this.link.dispatchEvent(this.event);
    }
}