rewrote cache to work better

internal/cache/cache.go

@@ -0,0 +1,97 @@
+package cache
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"errors"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+
+	"github.com/labstack/echo/v4"
+)
+
+type Cache struct {
+	CacheDir string
+	Disabled bool
+}
+
+func getCacheDir() (string, error) {
+	baseDir, err := os.UserCacheDir()
+	if err != nil {
+		baseDir = "/tmp"
+	}
+	cacheDir := filepath.Join(baseDir, "startpage")
+	err = os.MkdirAll(cacheDir, 0o755)
+	if err != nil {
+		return "", err
+	}
+	return cacheDir, nil
+}
+
+func getProfileCacheDir(profile string) (string, error) {
+	var profileCacheDir string
+
+	cacheDir, err := getCacheDir()
+	if err != nil {
+		return profileCacheDir, err
+	}
+
+	profileCacheDir = filepath.Join(cacheDir, profile)
+	err = os.MkdirAll(cacheDir, 0o755)
+	return profileCacheDir, err
+}
+
+func NewCache(profile string) Cache {
+	cacheDir, err := getProfileCacheDir(profile)
+
+	return Cache{
+		CacheDir: cacheDir,
+		Disabled: err != nil,
+	}
+}
+
+const baseCacheUrl = "cache"
+
+func (c Cache) StartStaticServer(e *echo.Echo) error {
+	e.Static("/"+baseCacheUrl, c.CacheDir)
+	return nil
+}
+
+func hashUrl(url string) string {
+	h := sha1.New()
+	io.WriteString(h, url)
+	return hex.EncodeToString(h.Sum(nil))
+}
+
+func (c Cache) CacheUrl(urlString string) (string, error) {
+	filename := hashUrl(urlString) + filepath.Ext(urlString)
+	targetPath := filepath.Join(c.CacheDir, filename)
+
+	// if the file was already downloaded it doesn't need to be downloaded again
+	if _, err := os.Stat(targetPath); errors.Is(err, os.ErrNotExist) {
+		resp, err := http.Get(urlString)
+		if !errors.Is(err, os.ErrNotExist) {
+			return urlString, err
+		}
+		defer resp.Body.Close()
+
+		file, err := os.Create(targetPath)
+		if err != nil {
+			return urlString, err
+		}
+		defer file.Close()
+
+		_, err = io.Copy(file, resp.Body)
+
+		if err != nil {
+			return urlString, err
+		}
+	} else {
+		return url.JoinPath(baseCacheUrl, filename)
+	}
+
+	return url.JoinPath(baseCacheUrl, filename)
+}