// Copyright 2022 Cloudbase Solutions SRL
//
//    Licensed under the Apache License, Version 2.0 (the "License"); you may
//    not use this file except in compliance with the License. You may obtain
//    a copy of the License at
//
//         http://www.apache.org/licenses/LICENSE-2.0
//
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
//    License for the specific language governing permissions and limitations
//    under the License.

package auth

import (
	"context"
	"errors"
	"fmt"
	"time"

	jwt "github.com/golang-jwt/jwt/v5"
	"github.com/nbutton23/zxcvbn-go"
	"golang.org/x/crypto/bcrypt"

	runnerErrors "github.com/cloudbase/garm-provider-common/errors"
	"github.com/cloudbase/garm-provider-common/util"
	"github.com/cloudbase/garm/config"
	"github.com/cloudbase/garm/database/common"
	"github.com/cloudbase/garm/params"
)

func NewAuthenticator(cfg config.JWTAuth, store common.Store) *Authenticator {
	return &Authenticator{
		cfg:   cfg,
		store: store,
	}
}

type Authenticator struct {
	store common.Store
	cfg   config.JWTAuth
}

func (a *Authenticator) IsInitialized() bool {
	return a.store.HasAdminUser(context.Background())
}

func (a *Authenticator) GetJWTToken(ctx context.Context) (string, error) {
	tokenID, err := util.GetRandomString(16)
	if err != nil {
		return "", fmt.Errorf("error generating random string: %w", err)
	}
	expireToken := time.Now().Add(a.cfg.TimeToLive.Duration())
	expires := &jwt.NumericDate{
		Time: expireToken,
	}
	generation := PasswordGeneration(ctx)
	claims := JWTClaims{
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: expires,
			// nolint:golangci-lint,godox
			// TODO: make this configurable
			Issuer: "garm",
		},
		UserID:     UserID(ctx),
		TokenID:    tokenID,
		IsAdmin:    IsAdmin(ctx),
		FullName:   FullName(ctx),
		Generation: generation,
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString([]byte(a.cfg.Secret))
	if err != nil {
		return "", fmt.Errorf("error fetching token string: %w", err)
	}

	return tokenString, nil
}

// GetJWTMetricsToken returns a JWT token that can be used to read metrics.
// This token is not tied to a user, no user is stored in the db.
func (a *Authenticator) GetJWTMetricsToken(ctx context.Context) (string, error) {
	if !IsAdmin(ctx) {
		return "", runnerErrors.ErrUnauthorized
	}

	tokenID, err := util.GetRandomString(16)
	if err != nil {
		return "", fmt.Errorf("error generating random string: %w", err)
	}
	// nolint:golangci-lint,godox
	// TODO: currently this is the same TTL as the normal Token
	// maybe we should make this configurable
	// it's usually pretty nasty if the monitoring fails because the token expired
	expireToken := time.Now().Add(a.cfg.TimeToLive.Duration())
	expires := &jwt.NumericDate{
		Time: expireToken,
	}
	claims := JWTClaims{
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: expires,
			// nolint:golangci-lint,godox
			// TODO: make this configurable
			Issuer: "garm",
		},
		TokenID:     tokenID,
		IsAdmin:     false,
		ReadMetrics: true,
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString([]byte(a.cfg.Secret))
	if err != nil {
		return "", fmt.Errorf("error fetching token string: %w", err)
	}

	return tokenString, nil
}

func (a *Authenticator) InitController(ctx context.Context, param params.NewUserParams) (params.User, error) {
	_, err := a.store.ControllerInfo()
	if err != nil {
		if !errors.Is(err, runnerErrors.ErrNotFound) {
			return params.User{}, fmt.Errorf("error initializing controller: %w", err)
		}
	}
	if a.store.HasAdminUser(ctx) {
		return params.User{}, runnerErrors.ErrNotFound
	}

	if param.Email == "" || param.Username == "" {
		return params.User{}, runnerErrors.NewBadRequestError("missing username or email")
	}

	if !util.IsValidEmail(param.Email) {
		return params.User{}, runnerErrors.NewBadRequestError("invalid email address")
	}

	// username is varchar(64)
	if len(param.Username) > 64 || !util.IsAlphanumeric(param.Username) {
		return params.User{}, runnerErrors.NewBadRequestError("invalid username")
	}

	param.IsAdmin = true
	param.Enabled = true

	passwordStenght := zxcvbn.PasswordStrength(param.Password, nil)
	if passwordStenght.Score < 4 {
		return params.User{}, runnerErrors.NewBadRequestError("password is too weak")
	}

	hashed, err := util.PaswsordToBcrypt(param.Password)
	if err != nil {
		return params.User{}, fmt.Errorf("error creating user: %w", err)
	}

	param.Password = hashed

	return a.store.CreateUser(ctx, param)
}

func (a *Authenticator) AuthenticateUser(ctx context.Context, info params.PasswordLoginParams) (context.Context, error) {
	if info.Username == "" || info.Password == "" {
		return ctx, runnerErrors.ErrUnauthorized
	}

	user, err := a.store.GetUser(ctx, info.Username)
	if err != nil {
		if errors.Is(err, runnerErrors.ErrNotFound) {
			return ctx, runnerErrors.ErrUnauthorized
		}
		return ctx, fmt.Errorf("error authenticating: %w", err)
	}

	if !user.Enabled {
		return ctx, runnerErrors.ErrUnauthorized
	}

	if user.Password == "" {
		return ctx, runnerErrors.ErrUnauthorized
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(info.Password)); err != nil {
		return ctx, runnerErrors.ErrUnauthorized
	}

	return PopulateContext(ctx, user, nil), nil
}