package export

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/xuri/excelize/v2"
)

// 配色跟随管理端 MIUIx 令牌，导出件与界面观感一致；字体用 Windows 自带的微软雅黑，
// 现场机器不需要额外装字体就能正确显示。
const (
	colorPrimary    = "3482FF"
	colorHeaderText = "FFFFFF"
	colorBorder     = "D0D7E5"
	colorBand       = "F5F8FF"
	colorMuted      = "6B7280"
	fontFamily      = "微软雅黑"
)

// 每张表的固定版式：1 标题 / 2 副标题 / 3 空行 / 4 表头 / 5 起为数据。
const (
	rowTitle    = 1
	rowSubtitle = 2
	rowHeader   = 4
)

// maxSheetName 是 Excel 对工作表名的硬限制。
const maxSheetName = 31

// cellKind 决定单元格的对齐方式与数字格式。
type cellKind int

const (
	kindText cellKind = iota
	kindCenter
	kindNumber
	kindInt
)

// column 是一列的展示定义；宽度按内容预留，导出即可打印，不用再手工调列宽。
type column struct {
	title string
	width float64
	kind  cellKind
}

type dataKey struct {
	kind cellKind
	band bool
}

// styleSet 是一份工作簿内复用的样式集合；excelize 的样式 id 与工作簿绑定，
// 因此每打开一份新工作簿都要重建一次。
type styleSet struct {
	title    int
	subtitle int
	header   int
	data     map[dataKey]int
}

func newStyleSet(f *excelize.File) (*styleSet, error) {
	border := []excelize.Border{
		{Type: "left", Color: colorBorder, Style: 1},
		{Type: "right", Color: colorBorder, Style: 1},
		{Type: "top", Color: colorBorder, Style: 1},
		{Type: "bottom", Color: colorBorder, Style: 1},
	}

	st := &styleSet{data: make(map[dataKey]int, 8)}
	var err error
	if st.title, err = f.NewStyle(&excelize.Style{
		Font:      &excelize.Font{Bold: true, Size: 16, Family: fontFamily},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
	}); err != nil {
		return nil, fmt.Errorf("export: 创建标题样式: %w", err)
	}
	if st.subtitle, err = f.NewStyle(&excelize.Style{
		Font:      &excelize.Font{Size: 10, Family: fontFamily, Color: colorMuted},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
	}); err != nil {
		return nil, fmt.Errorf("export: 创建副标题样式: %w", err)
	}
	if st.header, err = f.NewStyle(&excelize.Style{
		Font:      &excelize.Font{Bold: true, Size: 11, Family: fontFamily, Color: colorHeaderText},
		Fill:      excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{colorPrimary}},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center", WrapText: true},
		Border:    border,
	}); err != nil {
		return nil, fmt.Errorf("export: 创建表头样式: %w", err)
	}

	for _, kind := range []cellKind{kindText, kindCenter, kindNumber, kindInt} {
		for _, band := range []bool{false, true} {
			id, err := f.NewStyle(&excelize.Style{
				Font:         &excelize.Font{Size: 11, Family: fontFamily},
				Alignment:    &excelize.Alignment{Horizontal: horizontal(kind), Vertical: "center", WrapText: kind == kindText},
				Border:       border,
				Fill:         fill(band),
				CustomNumFmt: numFmt(kind),
			})
			if err != nil {
				return nil, fmt.Errorf("export: 创建数据样式: %w", err)
			}
			st.data[dataKey{kind: kind, band: band}] = id
		}
	}
	return st, nil
}

func horizontal(kind cellKind) string {
	if kind == kindText {
		return "left"
	}
	return "center"
}

func fill(band bool) excelize.Fill {
	if !band {
		return excelize.Fill{}
	}
	return excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{colorBand}}
}

// numFmt 让积分最多保留两位小数、不显示多余的 0；整数列固定不带小数。
func numFmt(kind cellKind) *string {
	switch kind {
	case kindNumber:
		return strPtr("0.##")
	case kindInt:
		return strPtr("0")
	default:
		return nil
	}
}

func (s *styleSet) cell(kind cellKind, band bool) int {
	return s.data[dataKey{kind: kind, band: band}]
}

// buildWorkbook 建好工作簿与样式后交给 build 填充。
// build 若不新建任何工作表，就把默认工作表改名为 defaultSheet，避免出现空白的 "Sheet1"。
func buildWorkbook(defaultSheet string, build func(f *excelize.File, st *styleSet) error) (*excelize.File, error) {
	f := excelize.NewFile()
	st, err := newStyleSet(f)
	if err != nil {
		return nil, err
	}
	if err := build(f, st); err != nil {
		return nil, err
	}

	sheets := f.GetSheetList()
	if len(sheets) == 1 && sheets[0] == "Sheet1" {
		if err := f.SetSheetName("Sheet1", sanitizeSheetName(defaultSheet)); err != nil {
			return nil, fmt.Errorf("export: 重命名工作表: %w", err)
		}
		return f, nil
	}
	if idx, err := f.GetSheetIndex("Sheet1"); err == nil && idx >= 0 {
		_ = f.DeleteSheet("Sheet1")
	}
	return f, nil
}

func addSheet(f *excelize.File, name string) error {
	if _, err := f.NewSheet(name); err != nil {
		return fmt.Errorf("export: 新建工作表 %s: %w", name, err)
	}
	return nil
}

// writeSheet 按统一版式写一张表：合并标题、副标题、带底色的表头、斑马纹数据行、
// 冻结表头，并预设 A4 横向、按宽度缩放、每页重复表头，导出后可直接打印。
func writeSheet(f *excelize.File, st *styleSet, sheet string, meta Meta, title string, cols []column, rows [][]any) error {
	if len(cols) == 0 {
		return fmt.Errorf("export: 工作表 %s 没有列定义", sheet)
	}
	lastCol := colName(len(cols))

	if err := f.SetCellValue(sheet, "A1", title); err != nil {
		return err
	}
	if err := f.MergeCell(sheet, "A1", lastCol+"1"); err != nil {
		return err
	}
	if err := f.SetCellStyle(sheet, "A1", lastCol+"1", st.title); err != nil {
		return err
	}
	if err := f.SetRowHeight(sheet, rowTitle, 32); err != nil {
		return err
	}

	if sub := metaSubtitle(meta); sub != "" {
		if err := f.SetCellValue(sheet, "A2", sub); err != nil {
			return err
		}
		if err := f.MergeCell(sheet, "A2", lastCol+"2"); err != nil {
			return err
		}
		if err := f.SetCellStyle(sheet, "A2", lastCol+"2", st.subtitle); err != nil {
			return err
		}
	}

	for i, c := range cols {
		name := colName(i + 1)
		if err := f.SetCellValue(sheet, name+strconv.Itoa(rowHeader), c.title); err != nil {
			return err
		}
		if err := f.SetColWidth(sheet, name, name, c.width); err != nil {
			return err
		}
	}
	if err := f.SetCellStyle(sheet, "A"+strconv.Itoa(rowHeader), lastCol+strconv.Itoa(rowHeader), st.header); err != nil {
		return err
	}
	if err := f.SetRowHeight(sheet, rowHeader, 26); err != nil {
		return err
	}

	for r, row := range rows {
		excelRow := rowHeader + 1 + r
		for i, c := range cols {
			var v any = ""
			if i < len(row) && row[i] != nil {
				v = row[i]
			}
			cell := colName(i+1) + strconv.Itoa(excelRow)
			if err := f.SetCellValue(sheet, cell, v); err != nil {
				return err
			}
			if err := f.SetCellStyle(sheet, cell, cell, st.cell(c.kind, r%2 == 1)); err != nil {
				return err
			}
		}
	}

	if err := f.SetPanes(sheet, &excelize.Panes{
		Freeze:      true,
		YSplit:      rowHeader,
		TopLeftCell: "A" + strconv.Itoa(rowHeader+1),
		ActivePane:  "bottomLeft",
	}); err != nil {
		return err
	}
	if err := f.SetPageLayout(sheet, &excelize.PageLayoutOptions{
		Size:        intPtr(9), // 9 = A4
		Orientation: strPtr("landscape"),
		FitToWidth:  intPtr(1),
		FitToHeight: intPtr(0),
	}); err != nil {
		return err
	}
	// 打印标题与页码是「锦上添花」，失败不影响文件可用性，故忽略错误。
	_ = f.SetDefinedName(&excelize.DefinedName{
		Name:     "_xlnm.Print_Titles",
		RefersTo: fmt.Sprintf("'%s'!$1:$%d", sheet, rowHeader),
		Scope:    sheet,
	})
	_ = f.SetHeaderFooter(sheet, &excelize.HeaderFooterOptions{
		OddHeader: "&C" + title,
		OddFooter: "&C第 &P 页 / 共 &N 页",
	})
	return nil
}

// saveWorkbook 落盘；目录不存在时自动创建，避免调用方先手工 mkdir。
func saveWorkbook(f *excelize.File, dst string) error {
	if strings.TrimSpace(dst) == "" {
		return errors.New("export: 导出路径为空")
	}
	if dir := filepath.Dir(dst); dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return fmt.Errorf("export: 创建导出目录 %s: %w", dir, err)
		}
	}
	if err := f.SaveAs(dst); err != nil {
		return fmt.Errorf("export: 保存 xlsx %s: %w", dst, err)
	}
	return nil
}

// sheetTitle 把赛事名拼在表名前面，打印出来一眼能看出是哪场赛事。
func sheetTitle(meta Meta, name string) string {
	if meta.EventName == "" {
		return name
	}
	return meta.EventName + " · " + name
}

func metaSubtitle(m Meta) string {
	parts := make([]string, 0, 4)
	if m.Organizer != "" {
		parts = append(parts, m.Organizer)
	}
	if m.Subtitle != "" {
		parts = append(parts, m.Subtitle)
	}
	if !m.GeneratedAt.IsZero() {
		parts = append(parts, "导出时间 "+m.GeneratedAt.Format("2006-01-02 15:04"))
	}
	if m.GeneratedBy != "" {
		parts = append(parts, "导出人 "+m.GeneratedBy)
	}
	return strings.Join(parts, " · ")
}

// sanitizeSheetName 替换 Excel 不允许的字符并截断到 31 字符。
func sanitizeSheetName(name string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		name = "成绩"
	}
	name = strings.NewReplacer(
		"[", "（", "]", "）", ":", "：", "*", "＊",
		"?", "？", "/", "／", "\\", "＼",
	).Replace(name)
	if rs := []rune(name); len(rs) > maxSheetName {
		name = string(rs[:maxSheetName])
	}
	return name
}

// sheetNamer 保证同一工作簿内的工作表名唯一（Excel 不允许重名）。
type sheetNamer struct {
	used map[string]bool
}

func (n *sheetNamer) add(base string) string {
	base = sanitizeSheetName(base)
	if n.used == nil {
		n.used = make(map[string]bool)
	}
	name := base
	for i := 2; n.used[name]; i++ {
		suffix := fmt.Sprintf("(%d)", i)
		rs := []rune(base)
		if keep := maxSheetName - len([]rune(suffix)); len(rs) > keep {
			rs = rs[:keep]
		}
		name = string(rs) + suffix
	}
	n.used[name] = true
	return name
}

func colName(n int) string {
	name, _ := excelize.ColumnNumberToName(n)
	return name
}

func intPtr(v int) *int       { return &v }
func strPtr(v string) *string { return &v }

// nowOr 让测试可以注入固定时间；零值取当前时间。
func nowOr(t time.Time) time.Time {
	if t.IsZero() {
		return time.Now()
	}
	return t
}