// Copyright 2019 Google LLC
//
// 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
//
//     https://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 main

import (
	"flag"
	"github.com/bradfitz/go-smtpd"
	"github.com/sirupsen/logrus"
	"k8s.io/test-infra/prow/config"
	"k8s.io/test-infra/prow/kube"
	"log"
	"os"
	"prow-lkml/lkml"
	"strings"
	"time"
)

// mail server over smtp port 25
const smtpListen = ":25"

type mail struct {
	from         smtpd.MailAddress
	body         strings.Builder
	conn         smtpd.Connection
	hasRcpt      bool
	messageQueue chan<- string
}

// possibly filter connection by address
func onNewConnection(c smtpd.Connection) error {
	log.Printf("smtpd: new connection from %v", c.Addr())
	return nil
}

func (m *mail) AddRecipient(rcpt smtpd.MailAddress) error {
	m.hasRcpt = true
	log.Printf("To: email:%s", rcpt.Email())
	return nil
}

func (m *mail) BeginData() error {
	if !m.hasRcpt {
		return smtpd.SMTPError("554 5.5.1 Error: no valid recipients")
	}
	return nil
}

func (m *mail) Write(line []byte) error {
	m.body.Write(line)
	return nil
}

func (m *mail) Close() error {
	str := m.body.String()
	m.messageQueue <- str
	return nil
}

type options struct {
	configPath    string
	jobConfigPath string
	sourceRepo    string
	sourceBranch  string
	jobURI        string
}

func (o *options) validate() error {
	return nil
}

func gatherOptions() options {
	o := options{}
	flag.StringVar(&o.configPath, "config-path", "", "Path to config.yaml.")
	// TODO: support muliple mailing lists each mapped to multiple repo/branches
	// one concern is that this might put too much overhead on one container
	// might be better to split over multiple instances of the lkml pod
	flag.StringVar(&o.jobConfigPath, "job-config-path", "", "Path to prow job configs")
	flag.StringVar(&o.sourceRepo, "source-repo", "", "Repo to patch to")
	flag.StringVar(&o.sourceBranch, "source-branch", "", "Branch to patch to")
	flag.StringVar(&o.jobURI, "job-uri", "", "Mapping for presubmit job")
	flag.Parse()
	return o
}

func main() {
	o := gatherOptions()
	if err := o.validate(); err != nil {
		log.Fatal("Args to LKML component were not valid: %v", err)
	}

	// config agent for fetching current configuration
	ca := &config.Agent{}
	if err := ca.Start(o.configPath, o.jobConfigPath); err != nil {
		logrus.WithError(err).Fatal("Error starting config agent.")
	}

	// start kube client needed to trigger Jobs
	log.Printf("Namespace is %s", ca.Config().ProwJobNamespace)
	kc, err := kube.NewClientInCluster(ca.Config().ProwJobNamespace)
	if err != nil {
		logrus.WithError(err).Fatal("Error getting kube client.")
	}

	// get ClusterIP through Service Environment Variable.
	// need Service deployed before pod for this to work
	host := os.Getenv("GIT_SERVICE_HOST")
	if host == "" {
		log.Fatal("IP address for git server is invalid. Redeploy Pod after" +
			"Service is live")
	}

	// queue to pass patches from smtp to lkml controller
	var messageQueue = make(chan string, lkml.QueueSize)

	c := lkml.New(
		messageQueue,
		o.sourceRepo,
		o.sourceBranch,
		o.jobURI,
		host,
		ca,
		kc,
	)

	// closure for accessing message channel from mail
	onNewMail := func(c smtpd.Connection, from smtpd.MailAddress) (smtpd.Envelope, error) {
		log.Printf("Email From: email:%s", from.Email())
		return &mail{
			from:         from,
			conn:         c,
			messageQueue: messageQueue,
		}, nil
	}

	// start smtp server
	go func() {
		log.Printf("running smtp server on %s", smtpListen)
		s := &smtpd.Server{
			Addr:            smtpListen,
			OnNewMail:       onNewMail,
			OnNewConnection: onNewConnection,
			ReadTimeout:     time.Minute,
		}
		err := s.ListenAndServe()
		log.Printf("SMTP server died: %v", err)
		// process remaining patches and jobs before closing
		close(messageQueue)
	}()

	if err := c.Run(); err != nil {
		log.Fatal("Error from lkml controller: %v", err)
	}
}