import XLSX from "xlsx";
import ajax from '@/utils/ajax'
import {
    Message
} from 'element-ui';
const excelHeaderName = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"];
/**
 * excel导出默认选项
 */
const exportOptionDefault = {
    url: "",//*必填，导出请求地址
    tableRef: undefined,//#1组合必填 导出数据对应列信息，el-table引用
    columnMapping: undefined,//#1组合必填 自定义导出列映射
    fileName: "export.xlsx",//导出文件名
    params: {},//导出请求参数
    rowFetcher: res => {//从请求结果中获取导出行的方式，默认取请求结果中的data作为导出数据
        return (res || {data: []}).data;
    },
    columnFormatter: [],//需要格式化的列
    mergeSetting: {
        refs: [], //检测需要合并的数据列属性名
        columns: [] //检测需要合并后，要合并的列，以第一条数据为准合并
    },
  dropColumns: [],//导出时需要过滤掉的列
};
let HEADERS = [];
for (let i =0;i< 200;i++) {
    let c = parseInt(i / 26);
    let m = i % 26;
    HEADERS.push((c > 0 ? excelHeaderName[c - 1] : "") + excelHeaderName[m]);
}
let validOption = opt => {
    let option = Object.assign({}, opt);
    if (!option.url) {
        throw new Error("request url is required.");
    }
    if (!option.tableRef && !option.columnMapping) {
        throw new Error("element table ref object or columnMapping is required.");
    }
    if (option.rowFetcher != undefined && typeof option.rowFetcher != "function") {
        throw new Error("rowFetcher must be a function with one param.");
    }
}

let getMergeSetting = (data, s, allCols) => {
    let refCols = s.refs;
    let mcols = s.columns;
    let mergeList = [];

    let refRow = data[0];
    let mergeSetting = {
        s: 0,
        e: 0
    };
    for (let i = 0; i < data.length; i++) {
        let same = refCols.map(c => data[i][c] === refRow[c]).filter(r => !!r).length == refCols.length;
        if (!same) {
            mergeSetting.e > mergeSetting.s && (mergeList.push(mergeSetting));
            refRow = data[i];
            mergeSetting = {
                s: i,
                e: i
            };
        } else {
            i > mergeSetting.e && (mergeSetting.e = i);
            i == data.length - 1 && (mergeList.push(mergeSetting));
        }

    }

    let setting = [];
    mergeList.forEach(e => {
        mcols.forEach(c => {
            let ci = allCols.indexOf(c);
            setting.push({
                s: {
                    r: e.s + 1,
                    c: ci
                },
                e: {
                    r: e.e + 1,
                    c: ci
                }
            });
        });
    });
    return setting;
}

let setStyle = (ws, s) => {}

let getColSetting = (mapping,dropColums) => {
    let columns = [];
    for (let i = 0; i < mapping.length; i++) {
        let c = mapping[i];
      if (dropColums.indexOf(c.columnProp) == -1) {
        columns.push({
          property: c.columnProp || c.property,
          label: c.columnLabel,
          type: "default"
        });
      }
    }
    return {
        columns: columns
    };
}
let export2Excel = opt => {
    validOption(opt);
    let options = Object.assign({}, exportOptionDefault, opt);
    let expColSetting = !!options.tableRef ? options.tableRef : getColSetting(options.columnMapping, options.dropColumns);
    ajax.$post(options.url, options.params, resp => {
        if (resp.status !== 200) {
            Message.error({
                message: resp.description
            });
        }
        let rows = !!resp.data.rows?options.rowFetcher(resp).rows:resp.data.page.list;
        var columns = [
            []
        ];
        var keys = [];
        let formaters = new Array();
        expColSetting.columns.forEach(column => {
            if (!!column.label && column.type === "default") {
                columns[0].push(column.label);
                keys.push(column.property);
                let formater = options.columnFormatter.find(f => !!f[column.property] && typeof f[column.property] == 'function');
                !!formater && (formaters[column.property] = formater[column.property]);
            }
        });
        rows.forEach(o => {
            let list = [];
            keys.forEach(k => {
                let formater = formaters[k];
                if (!!formater) {
                    list.push(formater(o[k]));
                } else {
                    list.push(o[k]);
                }
            });
            columns.push(list);
        });
        const ws = XLSX.utils.aoa_to_sheet(columns);
        if (!!options.mergeSetting && !!options.mergeSetting.refs && options.mergeSetting.refs.length > 0) {
            let merges = getMergeSetting(rows, options.mergeSetting, keys);
            ws["!merges"] = merges;
            setStyle(ws, merges);
        }
        // console.log(ws);
        const wb = XLSX.utils.book_new();
        XLSX.utils.book_append_sheet(wb, ws, options.fileName.replace(/\.xlsx/, ""));
        XLSX.writeFile(wb, options.fileName);
    });
}

export default {
    exportTable: export2Excel
}