/*
Copyright 2020 KubeSphere Authors

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 registries

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strings"
)

func (t authToken) String() (string, error) {
	if t.Token != "" {
		return t.Token, nil
	}
	if t.AccessToken != "" {
		return t.AccessToken, nil
	}
	return "", errors.New("auth token cannot be empty")
}

func (a *authService) Request(username, password string) (*http.Request, error) {
	q := a.Realm.Query()
	q.Set("service", a.Service)
	for _, s := range a.Scope {
		q.Set("scope", s)
	}
	//	q.Set("scope", "repository:r.j3ss.co/htop:push,pull")
	a.Realm.RawQuery = q.Encode()

	req, err := http.NewRequest("GET", a.Realm.String(), nil)

	if username != "" || password != "" {
		req.SetBasicAuth(username, password)
	}

	return req, err
}

func isTokenDemand(resp *http.Response) (*authService, error) {
	if resp == nil {
		return nil, nil
	}
	if resp.StatusCode != http.StatusUnauthorized {
		return nil, nil
	}
	return parseAuthHeader(resp.Header)
}

// Token returns the required token for the specific resource url. If the registry requires basic authentication, this
// function returns ErrBasicAuth.
func (r *Registry) Token(url string) (str string, err error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return "", err
	}

	resp, err := r.Client.Do(req)
	if err != nil {
		return "", err
	}

	defer resp.Body.Close()

	if resp.StatusCode == http.StatusForbidden && gcrMatcher.MatchString(url) {
		// GCR is not sending HTTP 401 on missing credentials but a HTTP 403 without
		// any further information about why the request failed. Sending the credentials
		// from the Docker config fixes this.
		return "", ErrBasicAuth
	}

	authService, err := isTokenDemand(resp)
	if err != nil {
		return "", err
	}

	if authService == nil {
		return "", nil
	}

	authReq, err := authService.Request(r.Username, r.Password)
	if err != nil {
		return "", err
	}

	resp, err = r.Client.Do(authReq)
	if err != nil {
		return "", err
	}

	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("getting image failed with secret")
	}

	var authToken authToken
	if err := json.NewDecoder(resp.Body).Decode(&authToken); err != nil {
		return "", err
	}

	token, err := authToken.String()
	return token, err
}

func parseAuthHeader(header http.Header) (*authService, error) {
	ch, err := parseChallenge(header.Get("www-authenticate"))
	if err != nil {
		return nil, err
	}

	return ch, nil
}

func parseChallenge(challengeHeader string) (*authService, error) {
	if basicRegex.MatchString(challengeHeader) {
		return nil, ErrBasicAuth
	}

	match := bearerRegex.FindAllStringSubmatch(challengeHeader, -1)
	if d := len(match); d != 1 {
		return nil, fmt.Errorf("malformed auth challenge header: '%s', %d", challengeHeader, d)
	}
	parts := strings.SplitN(strings.TrimSpace(match[0][1]), ",", 3)

	var realm, service string
	var scope []string
	for _, s := range parts {
		p := strings.SplitN(s, "=", 2)
		if len(p) != 2 {
			return nil, fmt.Errorf("malformed auth challenge header: '%s'", challengeHeader)
		}
		key := p[0]
		value := strings.TrimSuffix(strings.TrimPrefix(p[1], `"`), `"`)
		switch key {
		case "realm":
			realm = value
		case "service":
			service = value
		case "scope":
			scope = strings.Fields(value)
		default:
			return nil, fmt.Errorf("unknown field in challenge header %s: %v", key, challengeHeader)
		}
	}
	parsedRealm, err := url.Parse(realm)
	if err != nil {
		return nil, err
	}

	a := &authService{
		Realm:   parsedRealm,
		Service: service,
		Scope:   scope,
	}

	return a, nil
}