import ExcelJS from 'exceljs'

function normalizeCellValue(value) {
    if (value == null) {
        return value
    }
    if (typeof value === 'object') {
        if (value instanceof Date) {
            return value
        }
        if ('result' in value) {
            return value.result
        }
        if ('text' in value) {
            return value.text
        }
        if ('richText' in value && Array.isArray(value.richText)) {
            return value.richText.map((part) => part.text).join('')
        }
    }
    return value
}

function downloadBuffer(buffer, filename) {
    const blob = new Blob([buffer], {
        type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
    })
    const url = URL.createObjectURL(blob)
    const anchor = document.createElement('a')
    anchor.href = url
    anchor.download = filename
    anchor.click()
    URL.revokeObjectURL(url)
}

/**
 * 读取 Excel 首个工作表，返回与 sheet_to_json 等价的对象数组
 * @param {ArrayBuffer} arrayBuffer
 * @returns {Promise<{ rows: Array<Record<string, unknown>>, columns: string[] }>}
 */
export async function readExcelAsJson(arrayBuffer) {
    const workbook = new ExcelJS.Workbook()
    await workbook.xlsx.load(arrayBuffer)
    const worksheet = workbook.worksheets[0]

    if (!worksheet || worksheet.rowCount === 0) {
        return { rows: [], columns: [] }
    }

    const headerRow = worksheet.getRow(1)
    const headers = []
    headerRow.eachCell({ includeEmpty: true }, (cell, colNumber) => {
        const header = normalizeCellValue(cell.value)
        headers[colNumber - 1] = header != null && header !== ''
            ? String(header)
            : `Column${colNumber}`
    })

    const rows = []
    worksheet.eachRow({ includeEmpty: false }, (row, rowNumber) => {
        if (rowNumber === 1) {
            return
        }

        const record = {}
        row.eachCell({ includeEmpty: true }, (cell, colNumber) => {
            const header = headers[colNumber - 1]
            if (header) {
                record[header] = normalizeCellValue(cell.value)
            }
        })
        rows.push(record)
    })

    return {
        rows,
        columns: rows.length > 0 ? Object.keys(rows[0]) : headers.filter(Boolean)
    }
}

/**
 * 将对象数组导出为 Excel 文件
 * @param {Array<Record<string, unknown>>} rows
 * @param {string} filename
 * @param {string} sheetName
 */
export async function writeJsonToExcel(rows, filename, sheetName = 'Sheet1') {
    const workbook = new ExcelJS.Workbook()
    const worksheet = workbook.addWorksheet(sheetName)

    if (rows.length === 0) {
        const buffer = await workbook.xlsx.writeBuffer()
        downloadBuffer(buffer, filename)
        return
    }

    const columns = Object.keys(rows[0])
    worksheet.columns = columns.map((key) => ({ header: key, key }))
    rows.forEach((row) => worksheet.addRow(row))

    const buffer = await workbook.xlsx.writeBuffer()
    downloadBuffer(buffer, filename)
}

/**
 * 将二维数组导出为 Excel 文件
 * @param {Array<Array<unknown>>} data
 * @param {string} filename
 * @param {string} sheetName
 */
export async function writeAoaToExcel(data, filename, sheetName = 'Sheet1') {
    const workbook = new ExcelJS.Workbook()
    const worksheet = workbook.addWorksheet(sheetName)
    data.forEach((row) => worksheet.addRow(row))

    const buffer = await workbook.xlsx.writeBuffer()
    downloadBuffer(buffer, filename)
}