// mmc -- Mattermost client
// Copyright (C) 2023 Sergey Matveev <stargrave@stargrave.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"archive/tar"
	"bytes"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"io/fs"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"path"
	"sort"
	"strings"
	"syscall"
	"time"

	"github.com/davecgh/go-spew/spew"
	"github.com/mattermost/mattermost-server/v6/model"
	"go.stargrave.org/mmc"
)

const CmdFile = "/FILE "

var (
	Newwin    = flag.String("newwin", "cmd/newwin", "Path to newwin command")
	DebugFifo = flag.String("debug", "", "Path to debug FIFO to be created")
	DebugFd   *os.File
	UmaskCur  int
)

func rewriteIfChanged(fn string, data string) {
	if their, err := os.ReadFile(fn); err != nil ||
		bytes.Compare([]byte(data), their) != 0 {
		if err = os.WriteFile(fn, []byte(data), 0o666); err != nil {
			log.Fatalln(err)
		}
	}
}

func main() {
	entrypoint := flag.String("entrypoint", mmc.GetEntrypoint(), "Entrypoint")
	notifyCmd := flag.String("notify", "cmd/notify", "Path to notification handler")
	heartbeatCh := flag.String("heartbeat-ch", "town-square", "Channel for heartbeating")
	userStatusFifo := flag.String("user-status", "", "Path to FIFO for user statuses")
	flag.Parse()
	log.SetFlags(log.Lshortfile)
	log.SetOutput(os.Stdout)
	UmaskCur = syscall.Umask(0)
	syscall.Umask(UmaskCur)

	var err error
	if *DebugFifo != "" {
		DebugFd, err = os.OpenFile(
			*DebugFifo, os.O_WRONLY|os.O_APPEND, os.FileMode(0666),
		)
		if err != nil {
			log.Fatalln(err)
		}
		defer DebugFd.Close()
	}

	login, password := mmc.FindInNetrc(*entrypoint)
	if login == "" || password == "" {
		log.Fatalln("no credentials found for:", *entrypoint)
	}
	c := model.NewAPIv4Client("https://" + *entrypoint)
	c.Login(login, password)
	me, resp, err := c.GetMe("")
	if err != nil {
		if DebugFd != nil {
			spew.Fdump(DebugFd, resp)
		}
		log.Fatalln(err)
	}
	if DebugFd != nil {
		spew.Fdump(DebugFd, me)
	}
	log.Println("logged in")

	time.Sleep(mmc.SleepTime)
	teams, resp, err := c.GetTeamsForUser(me.Id, "")
	if err != nil {
		if DebugFd != nil {
			spew.Fdump(DebugFd, resp)
		}
		log.Fatalln(err)
	}
	if DebugFd != nil {
		spew.Fdump(DebugFd, teams)
	}
	Team := teams[0]

	var updateQueue []string
	LastSent := time.Now()

	Users, err := mmc.GetUsers(c, DebugFd)
	if err != nil {
		log.Fatalln(err)
	}

	UsersDC := make(map[string]*model.Channel, len(Users))
	userIds := make([]string, 0, len(Users))
	for _, u := range Users {
		userIds = append(userIds, u.Id)
		pth := path.Join("users", strings.ReplaceAll(u.Username, ".", "_"))
		os.MkdirAll(pth, 0777)
		rewriteIfChanged(
			path.Join(pth, "name"),
			fmt.Sprintf("%s %s\n", u.FirstName, u.LastName),
		)
		rewriteIfChanged(path.Join(pth, "email"), u.Email+"\n")
		rewriteIfChanged(path.Join(pth, "id"), u.Id+"\n")
		if _, err := os.Stat(path.Join(pth, mmc.OutRec)); err != nil &&
			errors.Is(err, fs.ErrNotExist) {
			if _, err = os.OpenFile(
				path.Join(pth, mmc.OutRec), os.O_WRONLY|os.O_CREATE, 0o666,
			); err != nil {
				log.Fatalln(err)
			}
		}

		if fi, err := os.Stat(path.Join(pth, mmc.OutRec)); err == nil && fi.Size() > 0 {
			time.Sleep(mmc.SleepTime)
			dc, resp, err := c.CreateDirectChannel(me.Id, u.Id)
			if err != nil {
				if DebugFd != nil {
					spew.Fdump(DebugFd, resp)
				}
				log.Println("CreateDirectChannel:", err)
				continue
			}
			if DebugFd != nil {
				spew.Fdump(DebugFd, dc)
			}
			UsersDC[u.Id] = dc
			updateQueue = append(updateQueue, pth, dc.Id)
		}

		statusPth := path.Join(pth, "status")
		os.Remove(statusPth)
		if err := syscall.Mkfifo(statusPth, 0666); err != nil {
			log.Fatalln(err)
		}
		go func(u *model.User) {
			for {
				time.Sleep(mmc.SleepTime)
				fd, err := os.OpenFile(
					statusPth, os.O_WRONLY|os.O_APPEND, os.FileMode(0666),
				)
				if err != nil {
					log.Println("OpenFile:", statusPth, err)
					continue
				}
				status, resp, err := c.GetUserStatus(u.Id, "")
				if err != nil {
					if DebugFd != nil {
						spew.Fdump(DebugFd, resp)
					}
					log.Println("GetUserStatus:", err)
					fd.Close()
					continue
				}
				if DebugFd != nil {
					spew.Fdump(DebugFd, status)
				}
				fmt.Fprintf(fd, "%s\n", status.Status)
				fd.Close()
			}
		}(u)

		pth = path.Join(pth, "in")
		os.Remove(pth)
		if err := syscall.Mkfifo(pth, 0666); err != nil {
			log.Fatalln(err)
		}
		go func(u *model.User) {
			var dc *model.Channel
			for {
				fd, err := os.OpenFile(pth, os.O_RDONLY, os.FileMode(0666))
				if err != nil {
					continue
				}
				data, err := io.ReadAll(fd)
				fd.Close()
				if err != nil {
					continue
				}
				dc = UsersDC[u.Id]
				if dc == nil {
					dc, resp, err = c.CreateDirectChannel(me.Id, u.Id)
					if err != nil {
						if DebugFd != nil {
							spew.Fdump(DebugFd, resp)
						}
						log.Println("CreateDirectChannel:", err)
						continue
					}
					UsersDC[u.Id] = dc
					if DebugFd != nil {
						spew.Fdump(DebugFd, dc)
					}
				}
				if _, err = makePost(c, dc.Id, string(data)); err != nil {
					log.Println("makePost:", err)
				}
				LastSent = time.Now()
			}
		}(u)
	}

	UserStatus := make(map[string]string)
	updateUserStatus := func() {
		statuses, resp, err := c.GetUsersStatusesByIds(userIds)
		if err != nil {
			if DebugFd != nil {
				spew.Fdump(DebugFd, resp)
			}
			log.Fatalln(err)
		}
		if DebugFd != nil {
			spew.Fdump(DebugFd, teams)
		}
		for _, s := range statuses {
			UserStatus[Users[s.UserId].Username] = s.Status
		}
	}
	if *userStatusFifo != "" {
		updateUserStatus()
		go func() {
			for {
				time.Sleep(mmc.SleepTime)
				fd, err := os.OpenFile(
					*userStatusFifo, os.O_WRONLY|os.O_APPEND, os.FileMode(0666),
				)
				if err != nil {
					log.Println("OpenFile:", *userStatusFifo, err)
					continue
				}
				statuses := make(map[string][]string)
				for name, status := range UserStatus {
					statuses[status] = append(statuses[status], name)
				}
				for status := range statuses {
					if status == "offline" {
						continue
					}
					sort.Strings(statuses[status])
					fmt.Fprintln(fd, status+":", strings.Join(statuses[status], " "))
				}
				fd.Close()
			}
		}()
	}

	Chans := make(map[string]*model.Channel)
	time.Sleep(mmc.SleepTime)
	page, resp, err := c.GetChannelsForTeamForUser(Team.Id, me.Id, false, "")
	if err != nil {
		if DebugFd != nil {
			spew.Fdump(DebugFd, resp)
		}
		log.Fatalln(err)
	}
	if DebugFd != nil {
		spew.Fdump(DebugFd, page)
	}
	for _, ch := range page {
		if ch.Type == "D" {
			continue
		}
		Chans[ch.Name] = ch
		pth := path.Join("chans", strings.ReplaceAll(ch.Name, ".", "_"))
		updateQueue = append(updateQueue, pth, ch.Id)
		os.MkdirAll(pth, 0777)
		rewriteIfChanged(path.Join(pth, "id"), ch.Id+"\n")
		rewriteIfChanged(path.Join(pth, "info"), fmt.Sprintf(
			"%s\n%s\n%s\n",
			ch.DisplayName,
			ch.Header,
			ch.Purpose,
		))
		if _, err := os.Stat(path.Join(pth, mmc.OutRec)); err != nil &&
			errors.Is(err, fs.ErrNotExist) {
			if _, err = os.OpenFile(
				path.Join(pth, mmc.OutRec), os.O_WRONLY|os.O_CREATE, 0o666,
			); err != nil {
				log.Fatalln(err)
			}
		}

		usersPth := path.Join(pth, "users")
		os.Remove(usersPth)
		if err := syscall.Mkfifo(usersPth, 0666); err != nil {
			log.Fatalln(err)
		}
		go func(ch *model.Channel) {
			for {
				time.Sleep(mmc.SleepTime)
				fd, err := os.OpenFile(
					usersPth, os.O_WRONLY|os.O_APPEND, os.FileMode(0666),
				)
				if err != nil {
					log.Println("OpenFile:", usersPth, err)
					continue
				}
				for n := 0; ; n++ {
					users, resp, err := c.GetUsersInChannel(ch.Id, n, mmc.PerPage, "")
					if err != nil {
						if DebugFd != nil {
							spew.Fdump(DebugFd, resp)
						}
						log.Println("GetUsersInChannel:", err)
						fd.Close()
						continue
					}
					if DebugFd != nil {
						spew.Fdump(DebugFd, users)
					}
					for _, u := range users {
						fmt.Fprintf(fd, "%s\n", u.Username)
					}
					if len(users) < mmc.PerPage {
						break
					}
				}
				fd.Close()
			}
		}(ch)

		pth = path.Join(pth, "in")
		os.Remove(pth)
		if err := syscall.Mkfifo(pth, 0666); err != nil {
			log.Fatalln(err)
		}
		go func(ch *model.Channel) {
			for {
				fd, err := os.OpenFile(pth, os.O_RDONLY, os.FileMode(0666))
				if err != nil {
					continue
				}
				data, err := io.ReadAll(fd)
				fd.Close()
				if err != nil {
					continue
				}
				if _, err = makePost(c, ch.Id, string(data)); err != nil {
					log.Println("makePost:", err)
				}
				LastSent = time.Now()
			}
		}(ch)
	}

	log.Println("syncing", len(updateQueue)/2, "rooms")
	for len(updateQueue) > 0 {
		err := updatePosts(c, Users, updateQueue[0], updateQueue[1])
		if err != nil {
			log.Println("updatePosts:", err)
		}
		updateQueue = updateQueue[2:]
	}
	log.Println("sync done")
	if *notifyCmd != "" {
		exec.Command(*notifyCmd, "sync done").Run()
	}

	go func() {
		os.MkdirAll("file", 0777)
		pthGet := path.Join("file", "get")
		os.Remove(pthGet)
		if err := syscall.Mkfifo(pthGet, 0666); err != nil {
			log.Fatalln(err)
		}
		pthOut := path.Join("file", "out")
		os.Remove(pthOut)
		if err := syscall.Mkfifo(pthOut, 0666); err != nil {
			log.Fatalln(err)
		}
		for {
			time.Sleep(mmc.SleepTime)
			fd, err := os.OpenFile(pthGet, os.O_RDONLY, os.FileMode(0666))
			if err != nil {
				continue
			}
			data, err := io.ReadAll(fd)
			fd.Close()
			if err != nil {
				continue
			}
			fileId := strings.TrimRight(string(data), " \n")
			if len(fileId) == 0 {
				continue
			}
			fi, resp, err := c.GetFileInfo(fileId)
			if DebugFd != nil {
				spew.Fdump(DebugFd, fi, resp)
			}
			if err != nil {
				log.Println(err)
				continue
			}
			if fi == nil {
				fmt.Println(resp)
				continue
			}
			data, resp, err = c.GetFile(fileId)
			if err != nil {
				if DebugFd != nil {
					spew.Fdump(DebugFd, resp)
				}
				log.Println(err)
				continue
			}
			fd, err = os.OpenFile(
				pthOut, os.O_WRONLY|os.O_APPEND, os.FileMode(0666),
			)
			if err != nil {
				log.Println(err)
				continue
			}
			w := tar.NewWriter(fd)
			if err = w.WriteHeader(&tar.Header{
				Format:   tar.FormatPAX,
				Typeflag: tar.TypeReg,
				Name:     fi.Name,
				Size:     int64(len(data)),
				Mode:     0o666,
				ModTime:  time.Unix(fi.CreateAt/1000, 0),
				PAXRecords: map[string]string{
					"MM.FileId":   fi.Id,
					"MM.MIMEType": fi.MimeType,
				},
			}); err != nil {
				log.Println(err)
				fd.Close()
				continue
			}
			if _, err = io.Copy(w, bytes.NewReader(data)); err != nil {
				log.Println(err)
				fd.Close()
				continue
			}
			err = w.Close()
			fd.Close()
			if err != nil {
				log.Println(err)
			}
		}
	}()

	needsShutdown := make(chan os.Signal)
	wc, err := model.NewWebSocketClient4("wss://"+*entrypoint, c.AuthToken)
	if err != nil {
		log.Fatalln(err)
	}
	go func() {
		wc.Listen()
		t := time.NewTicker(time.Minute)
		for {
			select {
			case <-t.C:
				updateUserStatus()
				if time.Now().Before(LastSent.Add(time.Minute)) {
					continue
				}
				wc.SendMessage("ping", nil)
				if *heartbeatCh != "" {
					if _, _, err = c.ViewChannel(
						me.Id,
						&model.ChannelView{ChannelId: Chans[*heartbeatCh].Id},
					); err != nil {
						log.Println("ChannelView:", err)
					}
				}
			case <-wc.PingTimeoutChannel:
				log.Println("PING timeout")
				needsShutdown <- syscall.SIGTERM
			case e := <-wc.EventChannel:
				if e == nil || !e.IsValid() {
					continue
				}
				data := e.GetData()
				if DebugFd != nil {
					spew.Fdump(DebugFd, e.EventType(), data)
				}
				var user *model.User
				if userId, ok := data["user_id"]; ok && userId.(string) != "" {
					user = Users[userId.(string)]
					if user == nil {
						log.Println("unknown user for event:", e)
						continue
					}
				}
				switch eventType := e.EventType(); eventType {
				case model.WebsocketEventTyping:
					if *notifyCmd != "" {
						exec.Command(*notifyCmd, "typing: "+user.Username).Run()
					}
				case model.WebsocketEventPostEdited,
					model.WebsocketEventPostDeleted,
					model.WebsocketEventPosted:
					chName := data["channel_name"].(string)
					var post model.Post
					if err = json.NewDecoder(
						strings.NewReader(data["post"].(string)),
					).Decode(&post); err != nil {
						log.Fatalln(err)
					}
					var recipient string
					switch model.ChannelType(data["channel_type"].(string)) {
					case model.ChannelTypeDirect:
						userId := strings.TrimPrefix(chName, me.Id+"__")
						userId = strings.TrimSuffix(userId, "__"+me.Id)
						user := Users[userId]
						if user == nil {
							log.Println("unknown user:", post)
							continue
						}
						recipient = path.Join("users", user.Username)
					case model.ChannelTypeOpen:
						fallthrough
					case model.ChannelTypePrivate:
						fallthrough
					case model.ChannelTypeGroup:
						recipient = path.Join("chans", chName)
					}
					if err = writePosts(
						recipient, Users, []mmc.Post{{P: &post, E: eventType}},
					); err != nil {
						log.Fatalln(err)
					}
				case model.WebsocketEventStatusChange:
					status := data["status"].(string)
					UserStatus[user.Username] = status
					if *notifyCmd != "" {
						exec.Command(*notifyCmd, fmt.Sprintf(
							"status: %s -> %s", user.Username, status,
						)).Run()
					}
				case model.WebsocketEventHello:
				case model.WebsocketEventChannelViewed:
				default:
					log.Println(e)
				}
			case resp := <-wc.ResponseChannel:
				if resp == nil || !resp.IsValid() {
					continue
				}
				if DebugFd != nil {
					spew.Fdump(DebugFd, resp)
				}
				if text, ok := resp.Data["text"].(string); ok && text == "pong" {
					LastSent = time.Now()
				}
			}
		}
	}()

	signal.Notify(needsShutdown, syscall.SIGTERM, syscall.SIGINT)
	<-needsShutdown
	c.Logout()
	log.Println("finished")
}