/*
   Copyright (c) 2016 VMware, Inc. All Rights Reserved.
   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 (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"strings"
	"sync"
	"time"

	token_util "github.com/vmware/harbor/service/token"
	"github.com/vmware/harbor/utils/log"
	"github.com/vmware/harbor/utils/registry"
	registry_error "github.com/vmware/harbor/utils/registry/error"
)

const (
	latency int = 10 //second, the network latency when token is received
)

type scope struct {
	Type    string
	Name    string
	Actions []string
}

func (s *scope) string() string {
	return fmt.Sprintf("%s:%s:%s", s.Type, s.Name, strings.Join(s.Actions, ","))
}

type tokenGenerator func(realm, service string, scopes []string) (token string, expiresIn int, issuedAt *time.Time, err error)

// Implements interface Authorizer
type tokenAuthorizer struct {
	scope     *scope
	tg        tokenGenerator
	cache     string     // cached token
	expiresAt *time.Time // The UTC standard time at when the token will expire
	sync.Mutex
}

// Scheme returns the scheme that the handler can handle
func (t *tokenAuthorizer) Scheme() string {
	return "bearer"
}

// AuthorizeRequest will add authorization header which contains a token before the request is sent
func (t *tokenAuthorizer) Authorize(req *http.Request, params map[string]string) error {
	var scopes []*scope
	var token string

	hasFrom := false
	from := req.URL.Query().Get("from")
	if len(from) != 0 {
		s := &scope{
			Type:    "repository",
			Name:    from,
			Actions: []string{"pull"},
		}
		scopes = append(scopes, s)
		// do not cache the token if "from" appears
		hasFrom = true
	}

	if t.scope != nil {
		scopes = append(scopes, t.scope)
	}

	expired := true

	cachedToken, cachedExpiredAt := t.getCachedToken()

	if len(cachedToken) != 0 && cachedExpiredAt != nil {
		expired = cachedExpiredAt.Before(time.Now().UTC())
	}

	if expired || hasFrom {
		scopeStrs := []string{}
		for _, scope := range scopes {
			scopeStrs = append(scopeStrs, scope.string())
		}
		to, expiresIn, _, err := t.tg(params["realm"], params["service"], scopeStrs)
		if err != nil {
			return err
		}
		token = to

		if !hasFrom {
			t.updateCachedToken(to, expiresIn)
		}
	} else {
		token = cachedToken
	}

	req.Header.Add(http.CanonicalHeaderKey("Authorization"), fmt.Sprintf("Bearer %s", token))

	return nil
}

func (t *tokenAuthorizer) getCachedToken() (string, *time.Time) {
	t.Lock()
	defer t.Unlock()
	return t.cache, t.expiresAt
}

func (t *tokenAuthorizer) updateCachedToken(token string, expiresIn int) {
	t.Lock()
	defer t.Unlock()
	t.cache = token
	n := (time.Duration)(expiresIn - latency)
	e := time.Now().Add(n * time.Second).UTC()
	t.expiresAt = &e
}

// Implements interface Authorizer
type standardTokenAuthorizer struct {
	tokenAuthorizer
	client     *http.Client
	credential Credential
}

// NewStandardTokenAuthorizer returns a standard token authorizer. The authorizer will request a token
// from token server and add it to the origin request
func NewStandardTokenAuthorizer(credential Credential, insecure bool, scopeType, scopeName string, scopeActions ...string) Authorizer {
	authorizer := &standardTokenAuthorizer{
		client: &http.Client{
			Transport: registry.GetHTTPTransport(insecure),
			Timeout:   30 * time.Second,
		},
		credential: credential,
	}

	if len(scopeType) != 0 || len(scopeName) != 0 {
		authorizer.scope = &scope{
			Type:    scopeType,
			Name:    scopeName,
			Actions: scopeActions,
		}
	}

	authorizer.tg = authorizer.generateToken

	return authorizer
}

func (s *standardTokenAuthorizer) generateToken(realm, service string, scopes []string) (token string, expiresIn int, issuedAt *time.Time, err error) {
	realm = tokenURL(realm)

	u, err := url.Parse(realm)
	if err != nil {
		return
	}
	q := u.Query()
	q.Add("service", service)
	for _, scope := range scopes {
		q.Add("scope", scope)
	}
	u.RawQuery = q.Encode()
	r, err := http.NewRequest("GET", u.String(), nil)
	if err != nil {
		return
	}

	if s.credential != nil {
		s.credential.AddAuthorization(r)
	}

	resp, err := s.client.Do(r)
	if err != nil {
		return
	}

	defer resp.Body.Close()
	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return
	}
	if resp.StatusCode != http.StatusOK {
		err = &registry_error.Error{
			StatusCode: resp.StatusCode,
			Detail:     string(b),
		}
		return
	}

	tk := struct {
		Token     string `json:"token"`
		ExpiresIn int    `json:"expires_in"`
		IssuedAt  string `json:"issued_at"`
	}{}
	if err = json.Unmarshal(b, &tk); err != nil {
		return
	}

	token = tk.Token

	expiresIn = tk.ExpiresIn

	if len(tk.IssuedAt) != 0 {
		t, err := time.Parse(time.RFC3339, tk.IssuedAt)
		if err != nil {
			log.Errorf("error occurred while parsing issued_at: %v", err)
			err = nil
		} else {
			issuedAt = &t
		}
	}

	return
}

// when the registry client is used inside Harbor, the token request
// can be posted to token service directly rather than going through nginx.
// this solution can resolve two problems:
// 1. performance issue
// 2. the realm field returned by registry is an IP which can not reachable
// inside Harbor
func tokenURL(realm string) string {
	extEndpoint := os.Getenv("EXT_ENDPOINT")
	tokenURL := os.Getenv("TOKEN_URL")
	if len(extEndpoint) != 0 && len(tokenURL) != 0 &&
		strings.Contains(realm, extEndpoint) {
		realm = strings.TrimRight(tokenURL, "/") + "/service/token"
	}
	return realm
}

// Implements interface Handler
type usernameTokenAuthorizer struct {
	tokenAuthorizer
	username string
}

// NewUsernameTokenAuthorizer returns a authorizer which will generate a token according to
// the user's privileges
func NewUsernameTokenAuthorizer(username string, scopeType, scopeName string, scopeActions ...string) Authorizer {
	authorizer := &usernameTokenAuthorizer{
		username: username,
	}

	authorizer.scope = &scope{
		Type:    scopeType,
		Name:    scopeName,
		Actions: scopeActions,
	}

	authorizer.tg = authorizer.generateToken

	return authorizer
}

func (u *usernameTokenAuthorizer) generateToken(realm, service string, scopes []string) (token string, expiresIn int, issuedAt *time.Time, err error) {
	token, expiresIn, issuedAt, err = token_util.GenTokenForUI(u.username, service, scopes)
	return
}