package api

import (
	"context"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"encoding/base64"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"

	"golang.org/x/oauth2"

	"github.com/grafana/grafana/pkg/bus"
	"github.com/grafana/grafana/pkg/log"
	"github.com/grafana/grafana/pkg/metrics"
	"github.com/grafana/grafana/pkg/middleware"
	m "github.com/grafana/grafana/pkg/models"
	"github.com/grafana/grafana/pkg/setting"
	"github.com/grafana/grafana/pkg/social"
)

var (
	ErrProviderDeniedRequest = errors.New("Login provider denied login request")
	ErrEmailNotAllowed       = errors.New("Required email domain not fulfilled")
	ErrSignUpNotAllowed      = errors.New("Signup is not allowed for this adapter")
	ErrUsersQuotaReached     = errors.New("Users quota reached")
	ErrNoEmail               = errors.New("Login provider didn't return an email address")
	oauthLogger              = log.New("oauth")
)

func GenStateString() string {
	rnd := make([]byte, 32)
	rand.Read(rnd)
	return base64.URLEncoding.EncodeToString(rnd)
}

func OAuthLogin(ctx *middleware.Context) {
	if setting.OAuthService == nil {
		ctx.Handle(404, "OAuth not enabled", nil)
		return
	}

	name := ctx.Params(":name")
	connect, ok := social.SocialMap[name]
	if !ok {
		ctx.Handle(404, fmt.Sprintf("No OAuth with name %s configured", name), nil)
		return
	}

	errorParam := ctx.Query("error")
	if errorParam != "" {
		errorDesc := ctx.Query("error_description")
		oauthLogger.Error("failed to login ", "error", errorParam, "errorDesc", errorDesc)
		redirectWithError(ctx, ErrProviderDeniedRequest, "error", errorParam, "errorDesc", errorDesc)
		return
	}

	code := ctx.Query("code")
	if code == "" {
		state := GenStateString()
		ctx.Session.Set(middleware.SESS_KEY_OAUTH_STATE, state)
		if setting.OAuthService.OAuthInfos[name].HostedDomain == "" {
			ctx.Redirect(connect.AuthCodeURL(state, oauth2.AccessTypeOnline))
		} else {
			ctx.Redirect(connect.AuthCodeURL(state, oauth2.SetAuthURLParam("hd", setting.OAuthService.OAuthInfos[name].HostedDomain), oauth2.AccessTypeOnline))
		}
		return
	}

	savedState, ok := ctx.Session.Get(middleware.SESS_KEY_OAUTH_STATE).(string)
	if !ok {
		ctx.Handle(500, "login.OAuthLogin(missing saved state)", nil)
		return
	}

	queryState := ctx.Query("state")
	if savedState != queryState {
		ctx.Handle(500, "login.OAuthLogin(state mismatch)", nil)
		return
	}

	// handle call back
	tr := &http.Transport{
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: setting.OAuthService.OAuthInfos[name].TlsSkipVerify,
		},
	}
	oauthClient := &http.Client{
		Transport: tr,
	}

	if setting.OAuthService.OAuthInfos[name].TlsClientCert != "" || setting.OAuthService.OAuthInfos[name].TlsClientKey != "" {
		cert, err := tls.LoadX509KeyPair(setting.OAuthService.OAuthInfos[name].TlsClientCert, setting.OAuthService.OAuthInfos[name].TlsClientKey)
		if err != nil {
			ctx.Logger.Error("Failed to setup TlsClientCert", "oauth", name, "error", err)
			ctx.Handle(500, "login.OAuthLogin(Failed to setup TlsClientCert)", nil)
			return
		}

		tr.TLSClientConfig.Certificates = append(tr.TLSClientConfig.Certificates, cert)
	}

	if setting.OAuthService.OAuthInfos[name].TlsClientCa != "" {
		caCert, err := ioutil.ReadFile(setting.OAuthService.OAuthInfos[name].TlsClientCa)
		if err != nil {
			ctx.Logger.Error("Failed to setup TlsClientCa", "oauth", name, "error", err)
			ctx.Handle(500, "login.OAuthLogin(Failed to setup TlsClientCa)", nil)
			return
		}
		caCertPool := x509.NewCertPool()
		caCertPool.AppendCertsFromPEM(caCert)

		tr.TLSClientConfig.RootCAs = caCertPool
	}

	oauthCtx := context.WithValue(context.Background(), oauth2.HTTPClient, oauthClient)

	// get token from provider
	token, err := connect.Exchange(oauthCtx, code)
	if err != nil {
		ctx.Handle(500, "login.OAuthLogin(NewTransportWithCode)", err)
		return
	}
	// token.TokenType was defaulting to "bearer", which is out of spec, so we explicitly set to "Bearer"
	token.TokenType = "Bearer"

	oauthLogger.Debug("OAuthLogin Got token", "token", token)

	// set up oauth2 client
	client := connect.Client(oauthCtx, token)

	// get user info
	userInfo, err := connect.UserInfo(client, token)
	if err != nil {
		if sErr, ok := err.(*social.Error); ok {
			redirectWithError(ctx, sErr)
		} else {
			ctx.Handle(500, fmt.Sprintf("login.OAuthLogin(get info from %s)", name), err)
		}
		return
	}

	oauthLogger.Debug("OAuthLogin got user info", "userInfo", userInfo)

	// validate that we got at least an email address
	if userInfo.Email == "" {
		redirectWithError(ctx, ErrNoEmail)
		return
	}

	// validate that the email is allowed to login to grafana
	if !connect.IsEmailAllowed(userInfo.Email) {
		redirectWithError(ctx, ErrEmailNotAllowed)
		return
	}

	userQuery := m.GetUserByEmailQuery{Email: userInfo.Email}
	err = bus.Dispatch(&userQuery)

	// create account if missing
	if err == m.ErrUserNotFound {
		if !connect.IsSignupAllowed() {
			redirectWithError(ctx, ErrSignUpNotAllowed)
			return
		}
		limitReached, err := middleware.QuotaReached(ctx, "user")
		if err != nil {
			ctx.Handle(500, "Failed to get user quota", err)
			return
		}
		if limitReached {
			redirectWithError(ctx, ErrUsersQuotaReached)
			return
		}
		cmd := m.CreateUserCommand{
			Login:          userInfo.Login,
			Email:          userInfo.Email,
			Name:           userInfo.Name,
			Company:        userInfo.Company,
			DefaultOrgRole: userInfo.Role,
		}

		if err = bus.Dispatch(&cmd); err != nil {
			ctx.Handle(500, "Failed to create account", err)
			return
		}

		userQuery.Result = &cmd.Result
	} else if err != nil {
		ctx.Handle(500, "Unexpected error", err)
	}

	// login
	loginUserWithUser(userQuery.Result, ctx)

	metrics.M_Api_Login_OAuth.Inc()

	if redirectTo, _ := url.QueryUnescape(ctx.GetCookie("redirect_to")); len(redirectTo) > 0 {
		ctx.SetCookie("redirect_to", "", -1, setting.AppSubUrl+"/")
		ctx.Redirect(redirectTo)
		return
	}

	ctx.Redirect(setting.AppSubUrl + "/")
}

func redirectWithError(ctx *middleware.Context, err error, v ...interface{}) {
	ctx.Logger.Error(err.Error(), v...)
	ctx.Session.Set("loginError", err.Error())
	ctx.Redirect(setting.AppSubUrl + "/login")
}
