mcg/internal/gui/coverloader.go

package gui

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"sync"

	"github.com/diamondburned/gotk4/pkg/core/gerror"
	"github.com/diamondburned/gotk4/pkg/gdkpixbuf/v2"
	"github.com/diamondburned/gotk4/pkg/glib/v2"
	"suruatoel.xyz/mcg/internal/client"
	"suruatoel.xyz/mcg/internal/common"
)

type CoverLoader struct {
	hostDir string
	size    int
	mutex   sync.Mutex
}

func NewCoverLoader(host string) *CoverLoader {
	loader := CoverLoader{}
	loader.hostDir = loader.getHostDir(host)
	loader.size = loader.readCacheSize()

	return &loader
}

func (l *CoverLoader) SetSize(size int) {
	if l.size != size {
		log.Println("cache size has changed from", l.size, "to", size)
		l.clearCache()
		l.writeCacheSize(size)
		l.size = size
	}
}

func (l *CoverLoader) LoadThumbnail(album *common.Album) *gdkpixbuf.Pixbuf {
	// Load cover from cache
	pixbuf := l.getCached(album)
	if pixbuf != nil {
		return pixbuf
	}

	// Load cover from server
	albumart := client.Instance().LoadAlbumartNow(album)
	if albumart != nil {
		pixbuf = l.loadImage(albumart)
	}
	if pixbuf != nil {
		pixbuf = pixbuf.ScaleSimple(l.size, l.size, gdkpixbuf.InterpHyper)
		if pixbuf != nil {
			l.setCached(album, pixbuf)
		}
	}

	return pixbuf
}

func (l *CoverLoader) getHostDir(host string) string {
	cacheDir, cacheDirErr := os.UserCacheDir()
	if cacheDirErr != nil {
		log.Println("failed to detect user cache directory:", cacheDirErr)
		return ""
	}

	hostDir := filepath.Join(cacheDir, "mcg", host)

	return hostDir
}

func (l *CoverLoader) ensureHostDir() {
	hostDirErr := os.MkdirAll(l.hostDir, 0o750)
	if hostDirErr != nil {
		log.Println("failed to create cache folder for host", l.hostDir, ":", hostDirErr)
	}
}

func (l *CoverLoader) readCacheSize() int {
	sizeFile := l.getCacheSizeFile()
	if sizeFile == "" {
		return 100
	}

	l.mutex.Lock()
	defer l.mutex.Unlock()

	content, readErr := os.ReadFile(sizeFile)
	if readErr != nil {
		log.Println("failed to read cache size file for host", l.hostDir, ":", readErr)
		return 100
	}

	size, sizeErr := strconv.Atoi(string(content[:]))
	if sizeErr != nil {
		log.Println("invalid content of cache size file for host", l.hostDir, ":", readErr)
	}

	return size
}

func (l *CoverLoader) writeCacheSize(size int) {
	l.ensureHostDir()
	sizeFile := l.getCacheSizeFile()
	if sizeFile == "" {
		return
	}

	writeErr := os.WriteFile(sizeFile, []byte(fmt.Sprintf("%d", size)), 0o644)
	if writeErr != nil {
		log.Println("failed to write cache size file for host", l.hostDir, ":", writeErr)
	}
}

func (l *CoverLoader) getCacheFile(album *common.Album) string {
	if l.hostDir == "" {
		return ""
	}

	return filepath.Join(l.hostDir, album.ID())
}

func (l *CoverLoader) getCacheSizeFile() string {
	if l.hostDir == "" {
		return ""
	}

	return filepath.Join(l.hostDir, "size")
}

func (l *CoverLoader) clearCache() {
	if l.hostDir == "" {
		return
	}

	removeErr := os.RemoveAll(l.hostDir)
	if removeErr != nil {
		log.Println("failed to clear cache folder for host", l.hostDir, ":", removeErr)
	}
}

func (l *CoverLoader) getCached(album *common.Album) *gdkpixbuf.Pixbuf {
	cacheFile := l.getCacheFile(album)
	if cacheFile == "" {
		return nil
	}

	pixbuf, pixbufErr := gdkpixbuf.NewPixbufFromFile(cacheFile)
	if pixbufErr != nil {
		if !isFileNotFoundError(pixbufErr) {
			log.Println("failed to read cached thumbnail for host", l.hostDir, ":", pixbufErr)
		}
		return nil
	}

	return pixbuf
}

func isFileNotFoundError(err error) bool {
	if gerr, isGerror := err.(*gerror.GError); isGerror {
		return gerr.Quark() == uint32(glib.FileErrorQuark()) && gerr.ErrorCode() == int(glib.FileErrorNoent)
	}

	return false
}

func (l *CoverLoader) setCached(album *common.Album, pixbuf *gdkpixbuf.Pixbuf) {
	cacheFile := l.getCacheFile(album)
	if cacheFile == "" {
		return
	}

	l.ensureHostDir()
	pixbuf.Savev(cacheFile, "jpeg", []string{}, []string{})
}

func (l *CoverLoader) loadImage(file []byte) *gdkpixbuf.Pixbuf {
	pixbufLoader, loaderErr := loadPixbuf(file)
	if loaderErr != nil {
		log.Println("failed to load image:", loaderErr)
		return nil
	}

	return pixbufLoader.Pixbuf()
}