implmented fetch on cache miss

handlerPkgs.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"errors"
+	"net/http"
+	"os"
+	"path/filepath"
+
+	"gitea.ewpt3ch.dev/ewpt3ch/pkgstash/internal/cache"
+)
+
+func handlePackage(w http.ResponseWriter, req *http.Request, c *cache.Cache) {
+	// build file paths from the request, they follow archlinux repo
+	// <reporoot>/[core, extra, etc]/os/[x86_64, arm, etc]/package.pkg.tar.zst[.sig]
+	repo := req.PathValue("repo")
+	arch := req.PathValue("arch")
+	file := req.PathValue("file")
+	relPath := filepath.Join(repo, "os", arch, file) //path from repo root to pkg or db file
+	pkgPath := filepath.Join(repoRoot, relPath)      //path for local read of the file
+
+	if _, err := os.Stat(pkgPath); err != nil {
+		err = c.Fetch(relPath)
+		if err != nil {
+			var upstreamErr *cache.UpstreamError
+			if errors.As(err, &upstreamErr) {
+				http.Error(w, "Not found upstream", upstreamErr.StatusCode)
+				return
+			}
+			http.Error(w, "Failed to fetch from upstream", http.StatusBadGateway)
+
+		}
+	}
+
+	http.ServeFile(w, req, pkgPath)
+}