// Copyright (C) 2024  Umorpha Systems
// SPDX-License-Identifier: AGPL-3.0-or-later

package main

import (
	"fmt"
	"net/http"
	"net/url"
	"regexp"
	"strings"
)

// - /HEAD
// - /objects/[0-9a-f]{2}/[0-9a-f]{38}
// - /objects/pack/
// - /objects/info/packs (*)
// - /objects/info/alternates
// - /objects/info/http-alternates
// - /info/refs (*)


var reGitHTTP = regexp.MustCompile(`^.*/(?:` +
	`HEAD` + `|` +
	`objects(?:/[/a-z0-9]*)?` + `|` +
	`info/refs(?:[?&](?:service=[-_a-z0-9]+)$` + `)` +
	`)$`)

// routeGitHTTP takes a gitprotocol-http(5) request and parses it into
// a repoPath component and a service query component.
//
//   - Returns ("", "", "", nil) if the request does not look like a
//     gitprotocol-http(5) request.
//
// Returns ("", "", err) if the request looks like a
// gitprotocol-http(5) request, but has a malformed query string.
func routeGitHTTP(r *http.Request) (repoPath, file, service string, err error) {
	idx := strings.LastIndex(r.RequestURI, "/info/refs")
	if idx < 0 {
		return "", "", "", nil
	}

	repoPath = r.RequestURI[:idx]
	rawQuery := r.RequestURI[idx+len("/info/refs"):]
	var query url.Values
	if rawQuery != "" {
		queryPrefix := "?"
		if strings.Contains(repoPath, "?") {
			queryPrefix = "&"
		}
		if !strings.HasPrefix(rawQuery, queryPrefix) {
			return "", "", "", nil
		}
		var err error
		query, err = url.ParseQuery(rawQuery[len(queryPrefix):])
		if err != nil {
			return "", "", "", fmt.Errorf("invalid query string: %w", err)
		}
		if len(query) > 1 || len(query["service"]) > 1 {
			return "", "", "", fmt.Errorf("invalid query string: too many query parameters")
		}
		if len(query) > 0 && query["service"] == nil {
			return "", "", "", fmt.Errorf("invalid query string: unexpected  query parameters")
		}
	}
	return repoPath, "TODO", query.Get("service"), nil
}