package service

import (
	"errors"
	"fmt"
	"io"
	"strings"

	"github.com/wmms/wmms/internal/model"
	"github.com/xuri/excelize/v2"
)

const (
	// MaterialImportSheetData 是填写数据的表名，「物料数据」。
	MaterialImportSheetData = "物料数据"
	// MaterialImportSheetGuide 是填写说明的表名。
	MaterialImportSheetGuide = "填写说明"
	// MaterialImportMaxRows 是数据区最大行数（不含表头）。
	MaterialImportMaxRows = 20000
	// MaterialImportMaxBytes 是上传文件大小上限。
	MaterialImportMaxBytes = 5 << 20
)

var (
	// ErrImportTemplateInvalid 表示上传的文件不是本功能的模板。
	ErrImportTemplateInvalid = errors.New("模板格式不正确，请重新下载最新模板")
	// ErrImportTooManyRows 表示数据行数超出上限。
	ErrImportTooManyRows = fmt.Errorf("导入行数超过 %d 行上限", MaterialImportMaxRows)
)

// materialImportHeaders 是生成模板时的列顺序（含选填列）。
var materialImportHeaders = []string{"物料名称", "规格", "单位", "大类", "小类"}

// materialImportRequiredHeaders 是表头里必须存在的列；缺任何一列都判定为
// 模板不合法。规格和单位是选填，用户删掉这两个空列是合理操作，不拦。
var materialImportRequiredHeaders = []string{"物料名称", "大类", "小类"}

// BuildMaterialImportTemplate 生成说明在前、空白数据表在后的导入模板。
func BuildMaterialImportTemplate() ([]byte, error) {
	f := excelize.NewFile()
	defer f.Close()
	if err := f.SetSheetName("Sheet1", MaterialImportSheetGuide); err != nil {
		return nil, err
	}
	if _, err := f.NewSheet(MaterialImportSheetData); err != nil {
		return nil, err
	}
	f.SetActiveSheet(0)

	rules := [][]string{
		{"物料名称", "必填", "内六角螺栓", "不超过 200 字，不可留空。"},
		{"规格", "选填", "M8×30", "不超过 200 字，可留空；含前导零的规格按文本填写。"},
		{"单位", "选填", "个 / kg", "填写当前组织已启用的单位名称或编码；留空默认「个」。"},
		{"大类", "必填", "机械结构类", "填写当前组织已启用的大类名称、编码或「编码 名称」。"},
		{"小类", "必填", "标准件", "填写所选大类下的小类名称、编码或「编码 名称」；小类须配置启用的编码规则。"},
	}
	sections := map[int]string{1: "物料批量导入 · 填写说明", 4: "一、字段填写规则", 12: "二、填写与上传步骤", 18: "三、导入注意事项", 25: "四、填写示例（仅供参考）"}
	notes := map[int]string{
		2:  "先阅读本页，再切换到第二个工作表「物料数据」填写。",
		13: "1. 确认页面当前组织，核对该组织的分类、单位及小类编码规则。",
		14: "2. 在「物料数据」从第 2 行开始填写；第 1 行表头及工作表名称请保留。",
		15: "3. 保存为 .xlsx 文件，回到「物料」页面点击「批量导入」并选择文件。",
		16: "4. 有错误时查看行号和原因，可导出错误明细；修正原 .xlsx 后重新上传。",
		19: "文件限制：仅支持 .xlsx，大小不超过 5MB；非空数据最多 20000 行，表头和全空行不计数。",
		20: "整批校验：任意一行校验失败，本次所有物料均不导入；请全部修正后重传。",
		21: "编码与库存：物料编码由系统生成，无需填写；仅新增物料，不增加库存，也不更新已有物料。",
		22: "重复导入：同名同规格不会自动去重；成功后重复上传同一文件，会再次新增物料。",
		23: "默认单位：单位留空时使用「个」；当前组织未启用「个」时，请填写其他有效单位。",
		30: "示例只展示写法，请替换为当前组织实际启用的分类与单位；示例不在数据页，不会自动导入。",
	}
	for row, text := range sections {
		if err := f.MergeCell(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), fmt.Sprintf("E%d", row)); err != nil {
			return nil, err
		}
		if err := f.SetCellValue(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), text); err != nil {
			return nil, err
		}
	}
	for row, text := range notes {
		if err := f.MergeCell(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), fmt.Sprintf("E%d", row)); err != nil {
			return nil, err
		}
		if err := f.SetCellValue(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), text); err != nil {
			return nil, err
		}
	}
	guideRows := append([][]string{{"字段", "是否必填", "示例", "填写规则"}}, rules...)
	for i, row := range guideRows {
		for j, text := range row {
			cell, _ := excelize.CoordinatesToCellName(j+1, i+5)
			if err := f.SetCellValue(MaterialImportSheetGuide, cell, text); err != nil {
				return nil, err
			}
		}
		if err := f.MergeCell(MaterialImportSheetGuide, fmt.Sprintf("D%d", i+5), fmt.Sprintf("E%d", i+5)); err != nil {
			return nil, err
		}
	}
	sampleRows := [][]string{materialImportHeaders, {"内六角螺栓", "M8×30", "个", "机械结构类", "标准件"}, {"六角螺母", "M8", "个", "机械结构类", "标准件"}}
	for i, row := range sampleRows {
		for j, text := range row {
			cell, _ := excelize.CoordinatesToCellName(j+1, i+26)
			if err := f.SetCellValue(MaterialImportSheetGuide, cell, text); err != nil {
				return nil, err
			}
		}
	}
	for i, header := range materialImportHeaders {
		cell, _ := excelize.CoordinatesToCellName(i+1, 1)
		if err := f.SetCellValue(MaterialImportSheetData, cell, header); err != nil {
			return nil, err
		}
	}
	if err := styleMaterialImportTemplate(f); err != nil {
		return nil, err
	}
	buf, err := f.WriteToBuffer()
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func styleMaterialImportTemplate(f *excelize.File) error {
	styles := []excelize.Style{
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Color: "334155"}, Alignment: &excelize.Alignment{Vertical: "center", WrapText: true}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 20, Bold: true, Color: "FFFFFF"}, Fill: excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"17365D"}}, Alignment: &excelize.Alignment{Vertical: "center"}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 12, Bold: true, Color: "17365D"}, Fill: excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"E8EFF7"}}, Alignment: &excelize.Alignment{Vertical: "center"}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Bold: true, Color: "FFFFFF"}, Fill: excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"345D87"}}, Alignment: &excelize.Alignment{Vertical: "center", Horizontal: "left", WrapText: true}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Color: "1D4ED8"}, NumFmt: 49, Alignment: &excelize.Alignment{Vertical: "center", Horizontal: "left", WrapText: true}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Bold: true, Italic: true, Color: "334155"}, Fill: excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"FFC000"}}, Alignment: &excelize.Alignment{Vertical: "center", WrapText: true}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Bold: true, Color: "334155"}, Alignment: &excelize.Alignment{Vertical: "center", WrapText: true}},
		{Font: &excelize.Font{Family: "Microsoft YaHei", Size: 11, Bold: true, Color: "FF0000"}, Alignment: &excelize.Alignment{Vertical: "center", WrapText: true}},
	}
	ids := make([]int, len(styles))
	for i := range styles {
		id, err := f.NewStyle(&styles[i])
		if err != nil {
			return err
		}
		ids[i] = id
	}
	if err := f.SetCellStyle(MaterialImportSheetGuide, "A1", "E30", ids[0]); err != nil {
		return err
	}
	if err := f.SetCellStyle(MaterialImportSheetGuide, "A2", "E2", ids[5]); err != nil {
		return err
	}
	if err := f.SetCellStyle(MaterialImportSheetGuide, "A1", "E1", ids[1]); err != nil {
		return err
	}
	for _, row := range []int{4, 12, 18, 25} {
		if err := f.SetCellStyle(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), fmt.Sprintf("E%d", row), ids[2]); err != nil {
			return err
		}
	}
	for _, row := range []int{5, 26} {
		if err := f.SetCellStyle(MaterialImportSheetGuide, fmt.Sprintf("A%d", row), fmt.Sprintf("E%d", row), ids[3]); err != nil {
			return err
		}
	}
	if err := f.SetCellStyle(MaterialImportSheetGuide, "A6", "A10", ids[6]); err != nil {
		return err
	}
	for _, cell := range []string{"B6", "B9", "B10"} {
		if err := f.SetCellStyle(MaterialImportSheetGuide, cell, cell, ids[7]); err != nil {
			return err
		}
	}
	for i, width := range []float64{20, 12, 24, 34} {
		col, _ := excelize.ColumnNumberToName(i + 1)
		if err := f.SetColWidth(MaterialImportSheetGuide, col, col, width); err != nil {
			return err
		}
	}
	for row := 1; row <= 30; row++ {
		height := 30.0
		if row == 1 {
			height = 42
		}
		if row >= 6 && row <= 10 {
			height = 54
		}
		if row >= 19 && row <= 23 || row == 30 {
			height = 42
		}
		if err := f.SetRowHeight(MaterialImportSheetGuide, row, height); err != nil {
			return err
		}
	}
	if err := f.SetColStyle(MaterialImportSheetData, "A:E", ids[4]); err != nil {
		return err
	}
	if err := f.SetCellStyle(MaterialImportSheetData, "A1", "E1", ids[3]); err != nil {
		return err
	}
	if err := f.SetRowHeight(MaterialImportSheetData, 1, 32); err != nil {
		return err
	}
	for i, width := range []float64{34, 28, 16, 26} {
		col, _ := excelize.ColumnNumberToName(i + 1)
		if err := f.SetColWidth(MaterialImportSheetData, col, col, width); err != nil {
			return err
		}
	}
	if err := f.SetColWidth(MaterialImportSheetData, "E", "E", 13); err != nil {
		return err
	}
	return f.SetPanes(MaterialImportSheetData, &excelize.Panes{Freeze: true, YSplit: 1, TopLeftCell: "A2", ActivePane: "bottomLeft"})
}

// ParseMaterialImportFile 解析上传的 xlsx，返回带 Excel 行号的数据行。
// 列按表头名定位：列顺序可调、选填列可整列删掉、多余列忽略；只有缺少必填列
// 或缺少「物料数据」表时才判定模板不合法。
// 整行为空的行会被跳过；只要任一列有内容就保留，交给后续校验报错。
func ParseMaterialImportFile(r io.Reader) ([]model.MaterialImportRow, error) {
	// 较大的工作表 XML 使用临时文件，避免压缩后很小的工作簿整表驻留内存。
	f, err := excelize.OpenReader(r, excelize.Options{UnzipXMLSizeLimit: 1 << 20})
	if err != nil {
		if f != nil {
			_ = f.Close()
		}
		return nil, ErrImportTemplateInvalid
	}
	defer f.Close()

	idx, err := f.GetSheetIndex(MaterialImportSheetData)
	if err != nil || idx < 0 {
		return nil, ErrImportTemplateInvalid
	}

	iterator, err := f.Rows(MaterialImportSheetData)
	if err != nil {
		return nil, err
	}
	defer iterator.Close()
	if !iterator.Next() {
		return nil, ErrImportTemplateInvalid
	}
	header, err := iterator.Columns()
	if err != nil {
		return nil, err
	}
	columns := materialImportColumnIndex(header)
	for _, required := range materialImportRequiredHeaders {
		if _, ok := columns[required]; !ok {
			return nil, ErrImportTemplateInvalid
		}
	}

	rows := make([]model.MaterialImportRow, 0, 256)
	rowNumber := 1
	for iterator.Next() {
		rowNumber++
		raw, err := iterator.Columns()
		if err != nil {
			return nil, err
		}
		row := model.MaterialImportRow{
			Row:       rowNumber, // 包含被跳过的空行，保留真实 Excel 行号。
			Name:      materialImportColumnValue(raw, columns, "物料名称"),
			Spec:      materialImportColumnValue(raw, columns, "规格"),
			Unit:      materialImportColumnValue(raw, columns, "单位"),
			MajorName: materialImportColumnValue(raw, columns, "大类"),
			MinorName: materialImportColumnValue(raw, columns, "小类"),
		}
		if row.Name == "" && row.Spec == "" && row.Unit == "" && row.MajorName == "" && row.MinorName == "" {
			continue
		}
		if len(rows) == MaterialImportMaxRows {
			return nil, ErrImportTooManyRows
		}
		rows = append(rows, row)
	}

	if err := iterator.Error(); err != nil {
		return nil, err
	}
	if err := iterator.Close(); err != nil {
		return nil, err
	}
	return rows, nil
}

// materialImportColumnIndex 把表头行转成「列名 → 列号」。允许用户在表头里加
// 首尾空格、末尾加 * 标记必填；不认识的列忽略，重复列名取第一列。
func materialImportColumnIndex(header []string) map[string]int {
	index := make(map[string]int, len(header))
	for i, cell := range header {
		name := strings.TrimSpace(strings.TrimSuffix(strings.TrimSpace(cell), "*"))
		if name == "" {
			continue
		}
		if _, exists := index[name]; !exists {
			index[name] = i
		}
	}
	return index
}

// materialImportColumnValue 按列名取值；选填列被整列删掉时返回空串。
func materialImportColumnValue(row []string, columns map[string]int, name string) string {
	index, ok := columns[name]
	if !ok {
		return ""
	}
	return materialImportCell(row, index)
}

func materialImportCell(row []string, index int) string {
	if index >= len(row) {
		return ""
	}
	return strings.TrimSpace(row[index])
}