/*
Copyright 2015 The Kubernetes 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 authreq

import (
	"fmt"
	"net/url"
	"strings"

	"k8s.io/ingress/core/pkg/ingress/annotations/parser"
	"k8s.io/kubernetes/pkg/apis/extensions"
)

const (
	// external URL that provides the authentication
	authURL    = "ingress.kubernetes.io/auth-url"
	authMethod = "ingress.kubernetes.io/auth-method"
	authBody   = "ingress.kubernetes.io/auth-send-body"
)

// External returns external authentication configuration for an Ingress rule
type External struct {
	URL      string
	Method   string
	SendBody bool
}

var (
	methods = []string{"GET", "HEAD", "POST", "PUT", "PATCH", "DELETE", "CONNECT", "OPTIONS", "TRACE"}
)

func validMethod(method string) bool {
	if len(method) == 0 {
		return false
	}

	for _, m := range methods {
		if method == m {
			return true
		}
	}
	return false
}

// ParseAnnotations parses the annotations contained in the ingress
// rule used to use an external URL as source for authentication
func ParseAnnotations(ing *extensions.Ingress) (External, error) {
	if ing.GetAnnotations() == nil {
		return External{}, parser.ErrMissingAnnotations
	}

	str, err := parser.GetStringAnnotation(authURL, ing)
	if err != nil {
		return External{}, err
	}
	if str == "" {
		return External{}, fmt.Errorf("an empty string is not a valid URL")
	}

	ur, err := url.Parse(str)
	if err != nil {
		return External{}, err
	}
	if ur.Scheme == "" {
		return External{}, fmt.Errorf("url scheme is empty")
	}
	if ur.Host == "" {
		return External{}, fmt.Errorf("url host is empty")
	}

	if strings.Contains(ur.Host, "..") {
		return External{}, fmt.Errorf("invalid url host")
	}

	m, _ := parser.GetStringAnnotation(authMethod, ing)
	if len(m) != 0 && !validMethod(m) {
		return External{}, fmt.Errorf("invalid HTTP method")
	}

	sb, _ := parser.GetBoolAnnotation(authBody, ing)

	return External{
		URL:      str,
		Method:   m,
		SendBody: sb,
	}, nil
}