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

package gitcache

import (
	_url "net/url"
	"path"
	"path/filepath"
	"regexp"
	"strings"
)

// reIsURL mimics git's url.c:is_url()
var reIsURL = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9+.-]*://`)

// NormalizeURL parses a URL in accordance with the "GIT URLS"
// section of git-fetch(1), and normalizes it.
func NormalizeURL(url string) (string, bool) {
	switch {
	case reIsURL.MatchString(url):
		u, err := _url.Parse(url)
		if err != nil {
			return "", false
		}

		// work this left-to-right

		// 1. scheme
		switch u.Scheme {
		case "ssh",
			"git",
			"http", "https",
			"ftp", "ftps",
			"file":
			// OK
		default:
			return "", false
		}

		// 2. userinfo
		if u.User != nil {
			if u.Scheme == "ssh" {
				u.User = _url.User(u.User.Username())
			} else {
				u.User = nil
			}
		}

		// 3. host[:port]
		if u.Host == "" && u.Scheme != "file" {
			return "", false
		}
		u.Host = strings.ToLower(u.Host)

		// 4. path
		u.Path = path.Clean(u.Path)
		switch u.Path {
		case ".", "/":
			u.Path = ""
		}
		if u.Host == "" && u.Path == "" {
			u.Path = "/"
		}

		// 5. query
		switch u.Scheme {
		case "http", "https":
			// > Clients MUST strip a trailing `/`, if present, from the
			// > user supplied `$GIT_URL` string
			// -- gitprotocol-http(5)
			//
			// ... and that might include the query
			u.RawQuery = strings.TrimRight(u.RawQuery, "/")
		}

		// 6. fragment
		u.Fragment = ""

		return u.String(), true
	case filepath.IsAbs(url):
		u := &_url.URL{
			Scheme: "file",
			Path:   filepath.ToSlash(url),
		}
		url, ok := NormalizeURL(u.String())
		if !ok {
			panic("should not happen")
		}
		return url, true
	default: // scp-like
		uauth, upath, ok := strings.Cut(url, ":")
		if !ok {
			return "", false
		}
		if strings.Contains(uauth, "/") {
			return "", false
		}
		if !path.IsAbs(upath) {
			if strings.HasPrefix(upath, "~") {
				upath = "/" + upath
			} else {
				upath = "/~/" + upath
			}
		}
		u := &_url.URL{
			Scheme: "ssh",
			Path:   path.Clean(upath),
		}
		atIdx := strings.LastIndex(uauth, "@")
		if atIdx < 0 {
			u.Host = uauth
		} else {
			u.User = _url.User(uauth[:atIdx])
			u.Host = uauth[atIdx+1:]
		}
		return NormalizeURL(u.String())
	}
}