package logic

import (
	"bytes"
	"math"
	"regexp"
	"strconv"

	"github.com/signintech/gopdf"
	"golang.org/x/image/font/sfnt"
)

var (
	embeddedFont []byte
	fontMap      = make(map[string]string)
	sfntMap      = make(map[string]*sfnt.Font)
)

func SetFontData(data []byte) { embeddedFont = data }
func RegisterFontPath(id, path string) { fontMap[id] = path }
func RegisterFontSFNT(id string, f *sfnt.Font) { sfntMap[id] = f }

// HasGlyph 检查字体是否包含某个字符
func HasGlyph(fontId string, char rune) bool {
	f, ok := sfntMap[fontId]
	if !ok { return false }
	var buffer sfnt.Buffer
	idx, err := f.GlyphIndex(&buffer, char)
	return err == nil && idx != 0
}

// GeneratePDFExtended 支持动态字体切换和缺字降级
func GeneratePDFExtended(chars []HanziData, mode, paperSize, fontId string) ([]byte, error) {
	pdf := &gopdf.GoPdf{}
	rect := gopdf.Rect{W: 595.28, H: 841.89}
	if paperSize == "Letter" { rect = gopdf.Rect{W: 612, H: 792} }
	pdf.Start(gopdf.Config{PageSize: rect})

	if len(embeddedFont) > 0 { _ = pdf.AddTTFFontData("font", embeddedFont) }

	// 注册所有可用字体
	for id, path := range fontMap {
		_ = pdf.AddTTFFont(id, path)
	}

	switch mode {
	case "step":
		addStepPages(pdf, chars, true, rect.W, rect.H)
	case "manuscript":
		addManuscriptPages(pdf, chars, rect.W, rect.H, fontId)
	default:
		addTeachingPages(pdf, chars, true, rect.W, rect.H)
	}

	var buf bytes.Buffer
	_, err := pdf.WriteTo(&buf)
	return buf.Bytes(), err
}

func addTeachingPages(pdf *gopdf.GoPdf, chars []HanziData, flipY bool, pW, pH float64) {
	cols := 2; gap, margin := 17.0, 40.0
	size := math.Min((pW-2*margin-gap)/2, (pH-2*margin-2*gap)/3)
	totalW, totalH := 2*size+gap, 3*size+2*gap
	marginX, marginY := (pW-totalW)/2, (pH-totalH)/2
	for i := 0; i < len(chars); i += 6 {
		pdf.AddPage()
		end := i + 6; if end > len(chars) { end = len(chars) }
		for idx, data := range chars[i:end] {
			drawCharacter(pdf, data, marginX+float64(idx%cols)*(size+gap), marginY+float64(idx/cols)*(size+gap), size, flipY, len(data.Strokes), true)
		}
	}
}

func addStepPages(pdf *gopdf.GoPdf, chars []HanziData, flipY bool, pW, pH float64) {
	cols, margin := 9, 30.0; size := (pW - 2*margin) / float64(cols)
	pdf.AddPage(); currY := margin
	for _, data := range chars {
		numS := len(data.Strokes); rowsN := 1; if numS > 8 { rowsN = 1 + (numS - 8 + 7) / 8 }
		if currY + float64(rowsN)*size > pH - margin { pdf.AddPage(); currY = margin }
		totalG := rowsN * cols; strokeC := 0 
		for gIdx := 0; gIdx < totalG; gIdx++ {
			r, c := gIdx/cols, gIdx%cols; x, y := margin+float64(c)*size, currY+float64(r)*size
			if r == 0 && c == 0 { drawCharacter(pdf, data, x, y, size, flipY, len(data.Strokes), false); strokeC = 1
			} else if r > 0 && c == 0 { drawMiZiGe(pdf, x, y, size)
			} else if strokeC <= numS { drawStepBox(pdf, data, x, y, size, flipY, strokeC); strokeC++
			} else { drawMiZiGe(pdf, x, y, size) }
		}
		currY += float64(rowsN) * size
	}
}

func addManuscriptPages(pdf *gopdf.GoPdf, chars []HanziData, pW, pH float64, targetFont string) {
	margin := 40.0; cols, rows := 10, 15
	colW, rowH := (pW-2*margin)/float64(cols), (pH-2*margin)/float64(rows)
	fontSize := colW * 0.75

	pdf.AddPage(); drawManuscriptGrid(pdf, pW, pH, margin, cols, colW)
	cIdx, rIdx := 0, 0
	
	for _, data := range chars {
		if data.Character == "\n" {
			cIdx++; rIdx = 0
			if cIdx >= cols { pdf.AddPage(); cIdx = 0; drawManuscriptGrid(pdf, pW, pH, margin, cols, colW) }
			continue
		}
		if rIdx >= rows {
			cIdx++; rIdx = 0
			if cIdx >= cols { pdf.AddPage(); cIdx = 0; drawManuscriptGrid(pdf, pW, pH, margin, cols, colW) }
		}

		x, y := pW - margin - float64(cIdx+1)*colW, margin + float64(rIdx)*rowH
		charRune := []rune(data.Character)[0]

		// 智能字体选择
		renderFont := targetFont
		isFallback := false
		
		if !HasGlyph(targetFont, charRune) {
			// 尝试降级到字库最全的宋体或楷体
			if HasGlyph("songti", charRune) {
				renderFont = "songti"; isFallback = true
			} else if HasGlyph("kaiti", charRune) {
				renderFont = "kaiti"; isFallback = true
			} else {
				// 全部缺失，保留空白
				rIdx++; continue
			}
		}

		pdf.SetFillColor(200, 200, 200)
		if isFallback {
			// 降级显示：小字 (1/2 大小)，右上角对齐
			smallSize := fontSize * 0.5
			_ = pdf.SetFont(renderFont, "", smallSize)
			// 计算右上角位置：X靠右，Y靠上
			pdf.SetXY(x + colW - smallSize - 2, y + 2)
			_ = pdf.Cell(nil, data.Character)
		} else {
			// 正常显示
			_ = pdf.SetFont(renderFont, "", fontSize)
			pdf.SetXY(x + (colW-fontSize*0.9)/2, y + (rowH-fontSize)/2)
			_ = pdf.Cell(nil, data.Character)
		}
		rIdx++
	}
}

func drawManuscriptGrid(pdf *gopdf.GoPdf, pW, pH, margin float64, cols int, colW float64) {
	pdf.SetStrokeColor(200, 0, 0); pdf.SetLineWidth(0.6)
	for c := 0; c <= cols; c++ { x := pW - margin - float64(c)*colW; pdf.Line(x, margin, x, pH-margin) }
	pdf.Line(margin, margin, pW-margin, margin); pdf.Line(margin, pH-margin, pW-margin, pH-margin)
}

func drawCharacter(pdf *gopdf.GoPdf, data HanziData, x, y, size float64, flipY bool, strokeLimit int, showAnnotations bool) {
	if showAnnotations { drawGrid(pdf, x, y, size) } else { drawMiZiGe(pdf, x, y, size) }
	p, drawS := size*0.12, size-(size*0.12*2); scale := drawS/1024.0
	if strokeLimit == len(data.Strokes) {
		if showAnnotations { pdf.SetFillColor(240, 240, 240) } else { pdf.SetFillColor(0, 0, 0) }
	} else { pdf.SetFillColor(180, 180, 180) }
	for sIdx := 0; sIdx < len(data.Strokes); sIdx++ {
		if sIdx >= strokeLimit && strokeLimit != len(data.Strokes) { break }
		pts := parseSVGPath(data.Strokes[sIdx], scale, x+p, y+p, flipY)
		if len(pts) > 2 { pdf.Polygon(pts, "F") }
	}
	if showAnnotations && strokeLimit == len(data.Strokes) {
		fS := size * 0.035
		_ = pdf.SetFont("font", "", fS)
		for idx, median := range data.Medians {
			mP := transformPoints(median, scale, x+p, y+p, flipY); if len(mP) < 2 { continue }
			pdf.SetStrokeColor(255, 0, 0); pdf.SetLineWidth(0.6)
			for j := 0; j < len(mP)-1; j++ { pdf.Line(mP[j].X, mP[j].Y, mP[j+1].X, mP[j+1].Y) }
			pdf.SetFillColor(255, 0, 0); drawArrow(pdf, mP[len(mP)-1], mP[len(mP)-2], size*0.035)
			r := size*0.025; dx, dy := mP[1].X-mP[0].X, mP[1].Y-mP[0].Y; dist := math.Sqrt(dx*dx+dy*dy); ux, uy := -1.0, -1.0
			if dist > 0.001 { ux, uy = dx/dist, dy/dist }; cX, cY := mP[0].X-ux*r, mP[0].Y-uy*r
			pdf.SetStrokeColor(255, 0, 0); pdf.SetLineWidth(0.5); pdf.Oval(cX-r, cY-r, cX+r, cY+r)
			numS := strconv.Itoa(idx+1); tw := fS*0.6*float64(len(numS))/2; if len(numS) > 1 { tw = fS*0.5 }
			pdf.SetFillColor(255, 0, 0); pdf.SetXY(cX-tw/2, cY-fS/2); _ = pdf.Cell(nil, numS)
		}
	}
}

func drawStepBox(pdf *gopdf.GoPdf, data HanziData, x, y, size float64, flipY bool, limit int) {
	drawMiZiGe(pdf, x, y, size); p, scale := size*0.12, (size-(size*0.12*2))/1024.0
	pdf.SetFillColor(180, 180, 180); for i := 0; i < limit; i++ {
		pts := parseSVGPath(data.Strokes[i], scale, x+p, y+p, flipY); if len(pts) > 2 { pdf.Polygon(pts, "F") }
	}
}

func drawGrid(pdf *gopdf.GoPdf, x, y, size float64) {
	pdf.SetStrokeColor(220, 220, 220); pdf.SetLineWidth(0.4); pdf.RectFromUpperLeft(x, y, size, size)
	mid := size/2; drawDashedLine(pdf, x, y+mid, x+size, y+mid); drawDashedLine(pdf, x+mid, y, x+mid, y+size)
}

func drawMiZiGe(pdf *gopdf.GoPdf, x, y, size float64) {
	pdf.SetStrokeColor(220, 220, 220); pdf.SetLineWidth(0.4); pdf.RectFromUpperLeft(x, y, size, size)
	mid := size/2; drawDashedLine(pdf, x, y+mid, x+size, y+mid); drawDashedLine(pdf, x+mid, y, x+mid, y+size); drawDashedLine(pdf, x, y, x+size, y+size); drawDashedLine(pdf, x, y+size, x+size, y)
}

func drawDashedLine(pdf *gopdf.GoPdf, x1, y1, x2, y2 float64) {
	dash := 2.0; dx, dy := x2-x1, y2-y1; dist := math.Sqrt(dx*dx + dy*dy); if dist < 0.001 { return }
	ux, uy := dx/dist, dy/dist; for i := 0.0; i < dist; i += dash * 2 { end := i + dash; if end > dist { end = dist }; pdf.Line(x1+ux*i, y1+uy*i, x1+ux*end, y1+uy*end) }
}

func drawArrow(pdf *gopdf.GoPdf, target, prev gopdf.Point, length float64) {
	angle := math.Atan2(target.Y-prev.Y, target.X-prev.X); arrowA := math.Pi/6
	p1X := target.X+length*math.Cos(angle+math.Pi+arrowA); p1Y := target.Y+length*math.Sin(angle+math.Pi+arrowA)
	p2X := target.X+length*math.Cos(angle+math.Pi-arrowA); p2Y := target.Y+length*math.Sin(angle+math.Pi-arrowA)
	pdf.Polygon([]gopdf.Point{target, {X: p1X, Y: p1Y}, {X: p2X, Y: p2Y}}, "F")
}

func transformPoints(pts []Point, scale, ox, oy float64, flipY bool) []gopdf.Point {
	res := make([]gopdf.Point, len(pts)); for i, p := range pts { y := p[1]; if flipY { y = 1024-y }; res[i] = gopdf.Point{X: ox+p[0]*scale, Y: oy+y*scale} }
	return res
}

var reSVG = regexp.MustCompile(`([MLQCZ])|(-?\d+\.?\d*)`)

func parseSVGPath(path string, scale, ox, oy float64, flipY bool) []gopdf.Point {
	var pts []gopdf.Point; matches := reSVG.FindAllStringSubmatch(path, -1); var lastX, lastY float64
	for idx := 0; idx < len(matches); {
		item := matches[idx][0]
		if item == "M" || item == "L" {
			if idx+2 < len(matches) {
				x, _ := strconv.ParseFloat(matches[idx+1][0], 64); y, _ := strconv.ParseFloat(matches[idx+2][0], 64); lastX, lastY = x, y
				if flipY { y = 1024 - y }; pts = append(pts, gopdf.Point{X: ox + x*scale, Y: oy + y*scale}); idx += 3
			} else { idx++ }
		} else if item == "C" {
			if idx+6 < len(matches) {
				x1, _ := strconv.ParseFloat(matches[idx+1][0], 64); y1, _ := strconv.ParseFloat(matches[idx+2][0], 64)
				x2, _ := strconv.ParseFloat(matches[idx+3][0], 64); y2, _ := strconv.ParseFloat(matches[idx+4][0], 64)
				x, _ := strconv.ParseFloat(matches[idx+5][0], 64); y, _ := strconv.ParseFloat(matches[idx+6][0], 64)
				for t := 0.2; t <= 1.0; t += 0.2 {
					tx := math.Pow(1-t, 3)*lastX + 3*math.Pow(1-t, 2)*t*x1 + 3*(1-t)*math.Pow(t, 2)*x2 + math.Pow(t, 3)*x
					ty := math.Pow(1-t, 3)*lastY + 3*math.Pow(1-t, 2)*t*y1 + 3*(1-t)*math.Pow(t, 2)*y2 + math.Pow(t, 3)*y
					ty_f := ty; if flipY { ty_f = 1024 - ty }; pts = append(pts, gopdf.Point{X: ox + tx*scale, Y: oy + ty_f*scale})
				}
				lastX, lastY = x, y; idx += 7
			} else { idx++ }
		} else if item == "Q" {
			if idx+4 < len(matches) {
				x1, _ := strconv.ParseFloat(matches[idx+1][0], 64); y1, _ := strconv.ParseFloat(matches[idx+2][0], 64)
				x, _ := strconv.ParseFloat(matches[idx+3][0], 64); y, _ := strconv.ParseFloat(matches[idx+4][0], 64)
				for t := 0.2; t <= 1.0; t += 0.2 {
					tx := math.Pow(1-t, 2)*lastX + 2*(1-t)*t*x1 + math.Pow(t, 2)*x
					ty := math.Pow(1-t, 2)*lastY + 2*(1-t)*t*y1 + math.Pow(t, 2)*y
					ty_f := ty; if flipY { ty_f = 1024 - ty }; pts = append(pts, gopdf.Point{X: ox + tx*scale, Y: oy + ty_f*scale})
				}
				lastX, lastY = x, y; idx += 5
			} else { idx++ }
		} else { idx++ }
	}
	return pts
}