Enhancement/http (#32)

* added HTTP debug logging using `-d` or `DEBUGHTTP=1` (headers only)

http.go

@@ -0,0 +1,66 @@
+/*
+Copyright © 2023-2024 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+// FIXME: we could also incorporate
+// https://github.com/kdkumawat/golang/blob/main/http-retry/http/retry-client.go
+
+package main
+
+import (
+	"fmt"
+	"log/slog"
+	"math/rand"
+	"net/http"
+	"net/http/httputil"
+	"os"
+)
+
+type loggingTransport struct{}
+
+var letters = []rune("ABCDEF0123456789")
+
+func getid() string {
+	b := make([]rune, 8)
+	for i := range b {
+		b[i] = letters[rand.Intn(len(letters))]
+	}
+	return string(b)
+}
+
+func (s *loggingTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	resp, err := http.DefaultTransport.RoundTrip(req)
+
+	// just requred for debugging
+	id := getid()
+	slog.Debug("REQUEST", "id", id, "uri", req.URL, "host", req.Host)
+	slog.Debug("RESPONSE", "id", id, "status", resp.StatusCode, "contentlength", resp.ContentLength)
+
+	if len(os.Getenv("DEBUGHTTP")) > 0 {
+		fmt.Println("DEBUGHTTP Request ===>")
+		bytes, _ := httputil.DumpRequestOut(req, true)
+		fmt.Printf("%s\n", bytes)
+
+		fmt.Println("<=== DEBUGHTTP Response")
+		for header, value := range resp.Header {
+			fmt.Printf("%s: %s\n", header, value)
+		}
+		fmt.Printf("Status: %s %s\nContent-Length: %d\n\n\n", resp.Proto, resp.Status, resp.ContentLength)
+
+	}
+
+	return resp, err
+}