// GoCheese -- Python private package repository and caching proxy
// Copyright (C) 2019-2024 Sergey Matveev <stargrave@stargrave.org>
//               2019-2024 Elena Balakhonova <balakhonova_e@riseup.net>
//
// 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, version 3 of the License.
//
// 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/>.

package main

import (
	"bufio"
	"context"
	"errors"
	"log"
	"net/http"
	"os"
	"strings"
	"sync"
)

var (
	Passwords  map[string]*User = make(map[string]*User)
	PasswordsM sync.RWMutex
)

type CtxUserKeyType struct{}

var CtxUserKey CtxUserKeyType

type Auther interface {
	Auth(password string) bool
}

type User struct {
	name   string
	ro     bool
	auther Auther
}

func strToAuther(verifier string) (string, Auther, error) {
	st := strings.SplitN(verifier, "$", 3)
	if len(st) != 3 || st[0] != "" {
		return "", nil, errors.New("invalid verifier structure")
	}
	algorithm := st[1]
	var auther Auther
	var err error
	switch algorithm {
	case "argon2i":
		auther, err = parseArgon2i(st[2])
	case "sha256":
		auther, err = parseSHA256(st[2])
	default:
		err = errors.New("unknown hashing algorithm")
	}
	return algorithm, auther, err
}

func passwdReader(fd *os.File) bool {
	isGood := true
	scanner := bufio.NewScanner(fd)
	for scanner.Scan() {
		t := scanner.Text()
		if len(t) == 0 {
			continue
		}
		splitted := strings.Split(t, ":")
		if len(splitted) < 2 {
			log.Println("wrong login:password[:ro] format:", t)
			isGood = false
			continue
		}
		login := splitted[0]
		passwd := splitted[1]
		if passwd == "" {
			log.Println("deleting login:", login)
			PasswordsM.Lock()
			delete(Passwords, login)
			PasswordsM.Unlock()
			continue
		}
		_, auther, err := strToAuther(passwd)
		if err != nil {
			log.Println("login:", login, "invalid password:", err)
			isGood = false
			continue
		}
		var ro bool
		if len(splitted) > 2 {
			switch splitted[2] {
			case "ro":
				ro = true
			default:
				log.Println("wrong format of optional field:", t)
				isGood = false
				continue
			}
		}
		log.Println("adding password for:", login)
		PasswordsM.Lock()
		Passwords[login] = &User{name: login, ro: ro, auther: auther}
		PasswordsM.Unlock()
	}
	return isGood
}

func passwdLister(fd *os.File) {
	PasswordsM.RLock()
	logins := make([]string, 0, len(Passwords))
	for login := range Passwords {
		logins = append(logins, login)
	}
	PasswordsM.RUnlock()
	for _, login := range logins {
		fd.WriteString(login + "\n")
	}
}

func checkAuth(handler http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		username, password, gotAuth := r.BasicAuth()
		var user *User
		if gotAuth {
			PasswordsM.RLock()
			user = Passwords[username]
			PasswordsM.RUnlock()
		}
		var passwordValid bool
		if gotAuth && user != nil {
			passwordValid = user.auther.Auth(password)
		}
		if (gotAuth && user == nil) ||
			(user != nil && !passwordValid) ||
			(*AuthRequired && !gotAuth) {
			log.Println(r.RemoteAddr, "unauthenticated", username)
			http.Error(w, "unauthenticated", http.StatusUnauthorized)
			return
		}
		handler(w, r.WithContext(context.WithValue(r.Context(), CtxUserKey, user)))
	}
}