// Copyright 2015 Google 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 ipauth provides a martian.Modifier that sets auth based on IP.
package ipauth

import (
	"net"
	"net/http"

	"github.com/google/martian"
	"github.com/google/martian/auth"
)

var noop = martian.Noop("ipauth.Modifier")

// Modifier is the IP authentication modifier.
type Modifier struct {
	reqmod martian.RequestModifier
	resmod martian.ResponseModifier
}

// NewModifier returns a new IP authentication modifier.
func NewModifier() *Modifier {
	return &Modifier{
		reqmod: noop,
		resmod: noop,
	}
}

// SetRequestModifier sets the request modifier.
func (m *Modifier) SetRequestModifier(reqmod martian.RequestModifier) {
	if reqmod == nil {
		reqmod = noop
	}

	m.reqmod = reqmod
}

// SetResponseModifier sets the response modifier.
func (m *Modifier) SetResponseModifier(resmod martian.ResponseModifier) {
	if resmod == nil {
		resmod = noop
	}

	m.resmod = resmod
}

// ModifyRequest sets the auth ID in the context from the request iff it has
// not already been set and runs reqmod.ModifyRequest. If the underlying
// modifier has indicated via auth error that no valid auth credentials
// have been found we set ctx.SkipRoundTrip.
func (m *Modifier) ModifyRequest(req *http.Request) error {
	ctx := martian.NewContext(req)
	actx := auth.FromContext(ctx)

	ip, _, err := net.SplitHostPort(req.RemoteAddr)
	if err != nil {
		ip = req.RemoteAddr
	}

	actx.SetID(ip)

	err = m.reqmod.ModifyRequest(req)

	if actx.Error() != nil {
		ctx.SkipRoundTrip()
	}

	return err
}

// ModifyResponse runs resmod.ModifyResponse.
//
// If an error is returned from resmod.ModifyResponse it is returned.
func (m *Modifier) ModifyResponse(res *http.Response) error {
	ctx := martian.NewContext(res.Request)
	actx := auth.FromContext(ctx)

	err := m.resmod.ModifyResponse(res)

	if actx.Error() != nil {
		res.StatusCode = 403
		res.Status = http.StatusText(403)
	}

	return err
}