package service

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"image/png"
	"os"
	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
	config := &Config{
		BarcodeHeight: 120,
		ModuleWidth:   2,
		Padding:       20,
		FontPath:      "fonts/youaimoshouheiti-regular.ttf",
		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") {
		config.FontSize = 35
	}

	// 生成条形码图片的Base64
	base64Image, err := generateBase64Barcode(content, config)
	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, config *Config) (string, error) {
	// 1. 生成条形码图像
	barcodeImg, err := generateBarcodeImage(content, config)
	if err != nil {
		return "", err
	}

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

	// 2. 加载字体
	face, err := loadFont(config)
	if err != nil {
		return "", err
	}
	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

	maxContentWidth := barcodeWidth
	if textWidth > maxContentWidth {
		maxContentWidth = textWidth
	}
	finalWidth := maxContentWidth + config.Padding*2
	finalHeight := barcodeHeight + gapBetween + textHeight + config.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{config.BgColor}, image.Point{}, draw.Src)

	// 6. 绘制条形码(居中)
	barcodeStartX := (finalWidth - barcodeWidth) / 2
	barcodeStartY := config.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)
	textAreaTop := barcodeStartY + barcodeHeight + gapBetween
	textAreaHeight := textHeight + textBottomPadding
	baselineY := textAreaTop + (textAreaHeight / 2) + (ascent / 2) - 2

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

	textDrawer := &font.Drawer{
		Dst:  finalImg,
		Src:  image.NewUniform(config.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 加载加粗TrueType字体
func loadFont(config *Config) (font.Face, error) {
	fontBytes, err := os.ReadFile(config.FontPath)
	if err != nil {
		return nil, fmt.Errorf("读取字体文件失败: %w", err)
	}

	parsedFont, err := opentype.Parse(fontBytes)
	if err != nil {
		return nil, fmt.Errorf("解析字体失败: %w", err)
	}

	face, err := opentype.NewFace(parsedFont, &opentype.FaceOptions{
		Size:    config.FontSize,
		DPI:     96,
		Hinting: font.HintingFull,
	})
	if err != nil {
		return nil, fmt.Errorf("创建字体失败: %w", err)
	}
	return face, nil
}