package service

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"image/png"
	"os"
	"path/filepath"
	systemRes "psi/models/response"
	"strings"

	"github.com/boombuler/barcode"
	"github.com/boombuler/barcode/code128"
	"golang.org/x/image/font"
	"golang.org/x/image/font/opentype"
	"golang.org/x/image/math/fixed"
)

type BarcodeService struct{}

// Config 条形码配置
type Config struct {
	BarcodeHeight int
	ModuleWidth   int
	Padding       int
	FontPath      string
	FontSize      float64
	BgColor       color.Color
	BarColor      color.Color
}

// GenerateBarcode 根据货号生成条形码图片(Base64)
func (s *BarcodeService) GenerateBarcode(content string) (systemRes.BarcodeResponse, error) {
	// 配置参数
	cfg := &Config{
		BarcodeHeight: 120,
		ModuleWidth:   2,
		Padding:       20,
		FontSize:      50,
		BgColor:       color.White,
		BarColor:      color.Black,
	}

	// 若内容包含isbn，则使用较小字号且不加粗
	if strings.Contains(strings.ToLower(content), "9787") {
		cfg.FontSize = 35
	}

	// 生成条形码图片的Base64
	base64Image, err := generateBase64Barcode(content, cfg)
	if err != nil {
		return systemRes.BarcodeResponse{}, fmt.Errorf("生成条形码失败: %w", err)
	}

	return systemRes.BarcodeResponse{
		ImageBase64: base64Image,
		Content:     content,
	}, nil
}

func generateBase64Barcode(content string, cfg *Config) (string, error) {
	// 1. 生成条形码图像
	barcodeImg, err := generateBarcodeImage(content, cfg)
	if err != nil {
		return "", err
	}

	barcodeBounds := barcodeImg.Bounds()
	barcodeWidth := barcodeBounds.Dx()
	barcodeHeight := barcodeBounds.Dy()

	// 2. 尝试加载字体（自定义字体 -> 系统字体 -> 跳过文字）
	face, fontErr := loadFont(cfg.FontSize)
	var textHeight, ascent, descent int
	var textWidth int
	if fontErr == nil && face != nil {
		defer face.Close()
		// 3. 获取文字度量信息
		metrics := face.Metrics()
		ascent = metrics.Ascent.Ceil()
		descent = metrics.Descent.Ceil()
		textHeight = ascent + descent

		// 计算文字宽度
		drawer := &font.Drawer{Face: face}
		advance := drawer.MeasureString(content)
		textWidth = advance.Ceil()
	}

	// 4. 计算最终图片尺寸
	gapBetween := 12
	textBottomPadding := 12

	finalWidth := barcodeWidth + cfg.Padding*2
	finalHeight := barcodeHeight + cfg.Padding*2
	if face != nil {
		maxContentWidth := barcodeWidth
		if textWidth > maxContentWidth {
			maxContentWidth = textWidth
		}
		finalWidth = maxContentWidth + cfg.Padding*2
		finalHeight = barcodeHeight + gapBetween + textHeight + cfg.Padding*2 + textBottomPadding
	}

	// 5. 创建最终图片
	finalImg := image.NewRGBA(image.Rect(0, 0, finalWidth, finalHeight))
	draw.Draw(finalImg, finalImg.Bounds(), &image.Uniform{cfg.BgColor}, image.Point{}, draw.Src)

	// 6. 绘制条形码(居中)
	barcodeStartX := (finalWidth - barcodeWidth) / 2
	barcodeStartY := cfg.Padding
	draw.Draw(finalImg,
		image.Rect(barcodeStartX, barcodeStartY, barcodeStartX+barcodeWidth, barcodeStartY+barcodeHeight),
		barcodeImg,
		image.Point{},
		draw.Over)

	// 7. 绘制货号文字(居中，加粗字体)
	if face != nil {
		textAreaTop := barcodeStartY + barcodeHeight + gapBetween
		textAreaHeight := textHeight + textBottomPadding
		baselineY := textAreaTop + (textAreaHeight / 2) + (ascent / 2) - 2

		textX := (finalWidth - textWidth) / 2
		if textX < 0 {
			textX = cfg.Padding
		}

		textDrawer := &font.Drawer{
			Dst:  finalImg,
			Src:  image.NewUniform(cfg.BarColor),
			Face: face,
			Dot: fixed.Point26_6{
				X: fixed.I(textX),
				Y: fixed.I(baselineY),
			},
		}
		textDrawer.DrawString(content)
	}

	// 8. 转换为Base64
	buf := new(bytes.Buffer)
	if err := png.Encode(buf, finalImg); err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(buf.Bytes()), nil
}

// generateBarcodeImage 生成条形码图像
func generateBarcodeImage(content string, config *Config) (image.Image, error) {
	// 使用Code128编码
	code128Barcode, err := code128.Encode(content)
	if err != nil {
		return nil, fmt.Errorf("编码失败: %w", err)
	}

	rawBounds := code128Barcode.Bounds()
	rawWidth := rawBounds.Dx()
	targetWidth := rawWidth * config.ModuleWidth
	targetHeight := config.BarcodeHeight

	return barcode.Scale(code128Barcode, targetWidth, targetHeight)
}

// loadFont 尝试加载字体，按优先级：项目字体目录 -> Windows系统字体 -> Linux系统字体
// 如果都失败，返回 nil（调用方会跳过文字绘制）
func loadFont(fontSize float64) (font.Face, error) {
	// 按优先级尝试的字体路径列表
	fontPaths := []string{
		"fonts/youaimoshouheiti-regular.ttf",                              // 项目自定义字体
		"C:\\Windows\\Fonts\\arial.ttf",                                   // Windows Arial
		"C:\\Windows\\Fonts\\simhei.ttf",                                  // Windows 黑体（支持中文）
		"/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",                 // Linux DejaVu
		"/usr/share/fonts/truetype/liberation/LiberationSans-Regular.ttf", // Linux Liberation
	}

	// 如果是相对路径，尝试基于可执行文件目录解析
	exePath, exeErr := os.Executable()
	for i, p := range fontPaths {
		if !filepath.IsAbs(p) && exeErr == nil {
			fontPaths[i] = filepath.Join(filepath.Dir(exePath), p)
		}
	}

	for _, fontPath := range fontPaths {
		fontBytes, err := os.ReadFile(fontPath)
		if err != nil {
			continue
		}
		parsedFont, err := opentype.Parse(fontBytes)
		if err != nil {
			continue
		}
		face, err := opentype.NewFace(parsedFont, &opentype.FaceOptions{
			Size:    fontSize,
			DPI:     96,
			Hinting: font.HintingFull,
		})
		if err != nil {
			continue
		}
		return face, nil
	}

	return nil, nil // 所有字体都加载失败，返回 nil（不绘制文字）
}