lambda/cache.go

package main

// This file caches images in memory so we are not loading them from disk every time we need them
// It also does the same for images that need to be grabbed from HTTP.

import (
	"crypto/sha256"
	"fmt"
	"github.com/diamondburned/gotk4/pkg/gdk/v4"
	"github.com/diamondburned/gotk4/pkg/gtk/v4"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"github.com/kirsle/configdir"
)

// global or app-level map/cache
var textureCache = make(map[string]gdk.Paintabler)

func ensureCache() (string, error) {
	cachePath := configdir.LocalCache("lambda-im")
	err := configdir.MakePath(cachePath) // Ensure it exists.
	if err != nil {
		return "", err
	}

	return cachePath, nil
}

func getTexture(path string) gdk.Paintabler {
	if tex, exists := textureCache[path]; exists {
		return tex
	}
	tex, err := gdk.NewTextureFromFilename(path) // load once
	if err != nil {
		panic(err)
	}
	textureCache[path] = tex
	return tex
}

func newPictureFromPath(path string) *gtk.Picture {
	tex := getTexture(path)
	img := gtk.NewPictureForPaintable(tex)
	return img
}

func newImageFromPath(path string) *gtk.Image {
	tex := getTexture(path)
	img := gtk.NewImageFromPaintable(tex)
	return img
}

func newPictureFromWeb(url string) *gtk.Picture {
	pa, _ := ensureCache()
	// step 1: get a sha256 sum of the URL
	sum := fmt.Sprintf("%x", sha256.Sum256([]byte(url)))

	p, ok := textureCache[sum]
	if ok {
		return gtk.NewPictureForPaintable(p)
	}

	// step 2: download it
	resp, err := http.Get(url)
	if err != nil {
		return nil
	}

	b, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil
	}

	fullpath := filepath.Join(pa, sum)

	// step 3: save it
	err = os.WriteFile(fullpath, b, 0644)
	if err != nil {
		return nil
	}

	return newPictureFromPath(fullpath)
}

func newImageFromWeb(url string) *gtk.Image {
	pa, _ := ensureCache()
	// step 1: get a sha256 sum of the URL
	sum := fmt.Sprintf("%x", sha256.Sum256([]byte(url)))

	p, ok := textureCache[sum]
	if ok {
		return gtk.NewImageFromPaintable(p)
	}

	// step 2: download it
	resp, err := http.Get(url)
	if err != nil {
		return nil
	}

	b, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil
	}


	fullpath := filepath.Join(pa, sum)

	// step 3: save it
	err = os.WriteFile(fullpath, b, 0644)
	if err != nil {
		return nil
	}

	return newImageFromPath(fullpath)
}