package imglib

import (
	"fmt"
	"os"
	"runtime"
	"sync"

	"github.com/golang/freetype/truetype"
)

var (
	fontCacheOnce sync.Once
	cachedFont    *truetype.Font
	cachedFontErr error
)

// GetFont 获取系统默认中文字体（全局缓存，仅首次加载时读取磁盘）
func GetFont() (*truetype.Font, error) {
	fontCacheOnce.Do(func() {
		path := getDefaultFontPath()
		if path == "" {
			cachedFontErr = fmt.Errorf("未找到系统字体文件")
			return
		}
		data, err := os.ReadFile(path)
		if err != nil {
			cachedFontErr = fmt.Errorf("读取字体文件失败: %v", err)
			return
		}
		cachedFont, cachedFontErr = truetype.Parse(data)
	})
	return cachedFont, cachedFontErr
}

func getDefaultFontPath() string {
	switch runtime.GOOS {
	case "windows":
		paths := []string{
			"C:/Windows/Fonts/simhei.ttf",
			"C:/Windows/Fonts/simsun.ttc",
			"C:/Windows/Fonts/msyh.ttc",
		}
		for _, p := range paths {
			if _, err := os.Stat(p); err == nil {
				return p
			}
		}
	case "darwin":
		return "/System/Library/Fonts/PingFang.ttc"
	case "linux":
		paths := []string{
			"/usr/share/fonts/truetype/wqy/wqy-microhei.ttc",
			"/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc",
		}
		for _, p := range paths {
			if _, err := os.Stat(p); err == nil {
				return p
			}
		}
	}
	return ""
}