/*
Copyright 2017 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 spdy

import (
	"fmt"
	"net/http"
	"net/url"

	"k8s.io/apimachinery/pkg/util/httpstream"
	"k8s.io/apimachinery/pkg/util/httpstream/spdy"
	restclient "k8s.io/client-go/rest"
)

// Upgrader validates a response from the server after a SPDY upgrade.
type Upgrader interface {
	// NewConnection validates the response and creates a new Connection.
	NewConnection(resp *http.Response) (httpstream.Connection, error)
}

// RoundTripperFor returns a round tripper and upgrader to use with SPDY.
func RoundTripperFor(config *restclient.Config) (http.RoundTripper, Upgrader, error) {
	tlsConfig, err := restclient.TLSConfigFor(config)
	if err != nil {
		return nil, nil, err
	}
	proxy := http.ProxyFromEnvironment
	if config.Proxy != nil {
		proxy = config.Proxy
	}
	upgradeRoundTripper := spdy.NewRoundTripperWithProxy(tlsConfig, true, false, proxy)
	wrapper, err := restclient.HTTPWrappersForConfig(config, upgradeRoundTripper)
	if err != nil {
		return nil, nil, err
	}
	return wrapper, upgradeRoundTripper, nil
}

// dialer implements the httpstream.Dialer interface.
type dialer struct {
	client   *http.Client
	upgrader Upgrader
	method   string
	url      *url.URL
}

var _ httpstream.Dialer = &dialer{}

// NewDialer will create a dialer that connects to the provided URL and upgrades the connection to SPDY.
func NewDialer(upgrader Upgrader, client *http.Client, method string, url *url.URL) httpstream.Dialer {
	return &dialer{
		client:   client,
		upgrader: upgrader,
		method:   method,
		url:      url,
	}
}

func (d *dialer) Dial(protocols ...string) (httpstream.Connection, string, error) {
	req, err := http.NewRequest(d.method, d.url.String(), nil)
	if err != nil {
		return nil, "", fmt.Errorf("error creating request: %v", err)
	}
	return Negotiate(d.upgrader, d.client, req, protocols...)
}

// Negotiate opens a connection to a remote server and attempts to negotiate
// a SPDY connection. Upon success, it returns the connection and the protocol selected by
// the server. The client transport must use the upgradeRoundTripper - see RoundTripperFor.
func Negotiate(upgrader Upgrader, client *http.Client, req *http.Request, protocols ...string) (httpstream.Connection, string, error) {
	for i := range protocols {
		req.Header.Add(httpstream.HeaderProtocolVersion, protocols[i])
	}
	resp, err := client.Do(req)
	if err != nil {
		return nil, "", fmt.Errorf("error sending request: %v", err)
	}
	defer resp.Body.Close()
	conn, err := upgrader.NewConnection(resp)
	if err != nil {
		return nil, "", err
	}
	return conn, resp.Header.Get(httpstream.HeaderProtocolVersion), nil
}
