import {isEmpty} from "@/utils"
import request from "@/config/request"
import {elError} from "@/utils/message"
import {download} from "@/utils/file"

/**
 * 搜索表格页导出excel
 * 响应头为json时进行前端导出，否则直接下载文件
 *
 * @param url              搜索的请求地址
 * @param searchForm       搜索参数
 * @param options          合并选项{column, merge}，只有前端导出时才需要
 * @param json2workbook
 * @param exportExcelByJs
 */
export function abstractExportExcel(url, searchForm, options, json2workbook, exportExcelByJs) {
    request({url, method: 'post', responseType: 'blob', data: searchForm})
        .then(({headers, data}) => {
            const contentType = headers['content-type']
            const contentDisposition = headers['content-disposition']
            const filename = window.decodeURI(contentDisposition.split('=')[1])

            if (contentType.includes('json')) {
                const reader = new FileReader()
                reader.onload = () => {
                    const response = JSON.parse(reader.result)
                    if (response.status !== 200) return elError(response.msg)
                    const {column, merge} = options
                    const workbook = json2workbook(column, response.data, merge)
                    exportExcelByJs(workbook, filename)
                }
                reader.readAsText(data)
            }
            else download(data, filename)
        })
        .catch(e => elError(e))
}

/**
 * 合并excel
 * 此方法会修改原始json数据（重写序号）
 *
 * @param props        需要合并的字段数组，用于映射json
 * @param data         json数组
 * @param primaryKey   该行json的唯一标识字段名
 * @param orderKey     该行json的序号字段名
 * @param ignoreRows   忽略的行数，默认为1（忽略表头）
 * @return 包含合并信息的数组，形如['A1:A10',...]
 */
export function mergeExcel(props, data, primaryKey, orderKey, ignoreRows = 1) {
    const result = [], merge = [], temp = []

    props.forEach((prop, index) => {
        merge[index] = prop ? [1] : undefined
        temp[index] = prop ? 1 : undefined
    })

    //序号从1开始
    let indexAfterMerge = data[0][orderKey] = 1

    function compare(currentRow, lastRow, nextRow, colIndex) {
        const attr = props[colIndex]

        //若与上一行的primaryKey相同且属性相同，则temp对应项+1
        if (currentRow[primaryKey] === lastRow[primaryKey]
            && currentRow[attr] === lastRow[attr]) {
            temp[colIndex]++
            //最后一行特殊处理
            if (!nextRow) return merge[colIndex].push(temp[colIndex])

            //若与下一行相同
            if (currentRow[primaryKey] === nextRow[primaryKey]
                && currentRow[attr] === nextRow[attr]) {
                merge[colIndex].push(1)
            }
            //否则存入
            else merge[colIndex].push(temp[colIndex])
        }
        //否则清零
        else {
            temp[colIndex] = 1
            merge[colIndex].push(1)
        }
    }

    for (let i = 1; i < data.length; i++) {
        const currentRow = data[i]
        const lastRow = data[i - 1]
        const nextRow = data[i + 1]

        //重写序号
        if (currentRow[primaryKey] === lastRow[primaryKey]) {
            currentRow[orderKey] = lastRow[orderKey]
        }
        else currentRow[orderKey] = ++indexAfterMerge
        if (nextRow && nextRow[primaryKey] === currentRow[primaryKey]) {
            nextRow[orderKey] = currentRow[orderKey]
        }

        props.forEach((_, colIndex) => !isEmpty(_) && compare(currentRow, lastRow, nextRow, colIndex))
    }

    function mergeResultConstructor(arr, colIndex) {
        const colHeader = number2excelColumnHeader(colIndex)
        const startRows = ignoreRows + 1

        arr.forEach((rowspan, rowIndex) => {
            if (rowspan > 1) {
                const start = colHeader + (startRows + rowIndex - (rowspan - 1))
                const end = colHeader + (startRows + rowIndex)
                result.push(`${start}:${end}`)
            }
        })
    }

    merge.forEach((arr, index) => arr && mergeResultConstructor(arr, index))

    return result
}

/**
 * 生成二维数组，例如json为[{id:1,name:'x'}]，结果为[[1,'x']]
 *
 * @param data    json数组
 * @param propMap 表头和字段名的映射表
 */
export function jsonArray2rowArray(data, propMap) {
    return data.map(i => Object.keys(i)
        .reduce((arr, key) => {
            arr[propMap[key]] = i[key]
            return arr
        }, []))
}

//数字转excel列名
export function number2excelColumnHeader(n) {
    let s = ""
    while (n >= 0) {
        s = String.fromCharCode(n % 26 + 65) + s
        n = Math.floor(n / 26) - 1
    }
    return s
}