// Package main is the entry point for the chat-cli client.
package main

import (
	"fmt"
	"os"
	"strings"
	"sync"
	"time"

	api "git.eeqj.de/sneak/chat/cmd/chat-cli/api"
)

const (
	splitParts   = 2
	pollTimeout  = 15
	pollRetry    = 2 * time.Second
	timeFormat   = "15:04"
)

// App holds the application state.
type App struct {
	ui     *UI
	client *api.Client

	mu        sync.Mutex
	nick      string
	target    string
	connected bool
	lastQID   int64
	stopPoll  chan struct{}
}

func main() {
	app := &App{
		ui:   NewUI(),
		nick: "guest",
	}

	app.ui.OnInput(app.handleInput)
	app.ui.SetStatus(app.nick, "", "disconnected")

	app.ui.AddStatus(
		"Welcome to chat-cli — an IRC-style client",
	)
	app.ui.AddStatus(
		"Type [yellow]/connect <server-url>" +
			"[white] to begin, " +
			"or [yellow]/help[white] for commands",
	)

	err := app.ui.Run()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}
}

func (a *App) handleInput(text string) {
	if strings.HasPrefix(text, "/") {
		a.handleCommand(text)

		return
	}

	a.mu.Lock()
	target := a.target
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus(
			"[red]Not connected. Use /connect <url>",
		)

		return
	}

	if target == "" {
		a.ui.AddStatus(
			"[red]No target. " +
				"Use /join #channel or /query nick",
		)

		return
	}

	err := a.client.SendMessage(&api.Message{
		Command: "PRIVMSG",
		To:      target,
		Body:    []string{text},
	})
	if err != nil {
		a.ui.AddStatus(
			"[red]Send error: " + err.Error(),
		)

		return
	}

	ts := time.Now().Format(timeFormat)

	a.mu.Lock()
	nick := a.nick
	a.mu.Unlock()

	a.ui.AddLine(target, fmt.Sprintf(
		"[gray]%s [green]<%s>[white] %s",
		ts, nick, text,
	))
}

func (a *App) handleCommand(text string) {
	parts := strings.SplitN(text, " ", splitParts)
	cmd := strings.ToLower(parts[0])

	args := ""
	if len(parts) > 1 {
		args = parts[1]
	}

	a.dispatchCommand(cmd, args)
}

func (a *App) dispatchCommand(cmd, args string) {
	switch cmd {
	case "/connect":
		a.cmdConnect(args)
	case "/nick":
		a.cmdNick(args)
	case "/join":
		a.cmdJoin(args)
	case "/part":
		a.cmdPart(args)
	case "/msg":
		a.cmdMsg(args)
	case "/query":
		a.cmdQuery(args)
	case "/topic":
		a.cmdTopic(args)
	case "/names":
		a.cmdNames()
	case "/list":
		a.cmdList()
	case "/window", "/w":
		a.cmdWindow(args)
	case "/quit":
		a.cmdQuit()
	case "/help":
		a.cmdHelp()
	default:
		a.ui.AddStatus(
			"[red]Unknown command: " + cmd,
		)
	}
}

func (a *App) cmdConnect(serverURL string) {
	if serverURL == "" {
		a.ui.AddStatus(
			"[red]Usage: /connect <server-url>",
		)

		return
	}

	serverURL = strings.TrimRight(serverURL, "/")

	a.ui.AddStatus("Connecting to " + serverURL + "...")

	a.mu.Lock()
	nick := a.nick
	a.mu.Unlock()

	client := api.NewClient(serverURL)

	resp, err := client.CreateSession(nick)
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Connection failed: %v", err,
		))

		return
	}

	a.mu.Lock()
	a.client = client
	a.nick = resp.Nick
	a.connected = true
	a.lastQID = 0
	a.mu.Unlock()

	a.ui.AddStatus(fmt.Sprintf(
		"[green]Connected! Nick: %s, Session: %d",
		resp.Nick, resp.ID,
	))
	a.ui.SetStatus(resp.Nick, "", "connected")

	a.stopPoll = make(chan struct{})

	go a.pollLoop()
}

func (a *App) cmdNick(nick string) {
	if nick == "" {
		a.ui.AddStatus(
			"[red]Usage: /nick <name>",
		)

		return
	}

	a.mu.Lock()
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.mu.Lock()
		a.nick = nick
		a.mu.Unlock()

		a.ui.AddStatus(
			"Nick set to " + nick +
				" (will be used on connect)",
		)

		return
	}

	err := a.client.SendMessage(&api.Message{
		Command: "NICK",
		Body:    []string{nick},
	})
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Nick change failed: %v", err,
		))

		return
	}

	a.mu.Lock()
	a.nick = nick
	target := a.target
	a.mu.Unlock()

	a.ui.SetStatus(nick, target, "connected")
	a.ui.AddStatus("Nick changed to " + nick)
}

func (a *App) cmdJoin(channel string) {
	if channel == "" {
		a.ui.AddStatus(
			"[red]Usage: /join #channel",
		)

		return
	}

	if !strings.HasPrefix(channel, "#") {
		channel = "#" + channel
	}

	a.mu.Lock()
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	err := a.client.JoinChannel(channel)
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Join failed: %v", err,
		))

		return
	}

	a.mu.Lock()
	a.target = channel
	nick := a.nick
	a.mu.Unlock()

	a.ui.SwitchToBuffer(channel)
	a.ui.AddLine(channel,
		"[yellow]*** Joined "+channel,
	)
	a.ui.SetStatus(nick, channel, "connected")
}

func (a *App) cmdPart(channel string) {
	a.mu.Lock()
	if channel == "" {
		channel = a.target
	}

	connected := a.connected
	a.mu.Unlock()

	if channel == "" ||
		!strings.HasPrefix(channel, "#") {
		a.ui.AddStatus("[red]No channel to part")

		return
	}

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	err := a.client.PartChannel(channel)
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Part failed: %v", err,
		))

		return
	}

	a.ui.AddLine(channel,
		"[yellow]*** Left "+channel,
	)

	a.mu.Lock()
	if a.target == channel {
		a.target = ""
	}

	nick := a.nick
	a.mu.Unlock()

	a.ui.SwitchBuffer(0)
	a.ui.SetStatus(nick, "", "connected")
}

func (a *App) cmdMsg(args string) {
	parts := strings.SplitN(args, " ", splitParts)
	if len(parts) < splitParts {
		a.ui.AddStatus(
			"[red]Usage: /msg <nick> <text>",
		)

		return
	}

	target, text := parts[0], parts[1]

	a.mu.Lock()
	connected := a.connected
	nick := a.nick
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	err := a.client.SendMessage(&api.Message{
		Command: "PRIVMSG",
		To:      target,
		Body:    []string{text},
	})
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Send failed: %v", err,
		))

		return
	}

	ts := time.Now().Format(timeFormat)

	a.ui.AddLine(target, fmt.Sprintf(
		"[gray]%s [green]<%s>[white] %s",
		ts, nick, text,
	))
}

func (a *App) cmdQuery(nick string) {
	if nick == "" {
		a.ui.AddStatus(
			"[red]Usage: /query <nick>",
		)

		return
	}

	a.mu.Lock()
	a.target = nick
	myNick := a.nick
	a.mu.Unlock()

	a.ui.SwitchToBuffer(nick)
	a.ui.SetStatus(myNick, nick, "connected")
}

func (a *App) cmdTopic(args string) {
	a.mu.Lock()
	target := a.target
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	if !strings.HasPrefix(target, "#") {
		a.ui.AddStatus("[red]Not in a channel")

		return
	}

	if args == "" {
		err := a.client.SendMessage(&api.Message{
			Command: "TOPIC",
			To:      target,
		})
		if err != nil {
			a.ui.AddStatus(fmt.Sprintf(
				"[red]Topic query failed: %v", err,
			))
		}

		return
	}

	err := a.client.SendMessage(&api.Message{
		Command: "TOPIC",
		To:      target,
		Body:    []string{args},
	})
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Topic set failed: %v", err,
		))
	}
}

func (a *App) cmdNames() {
	a.mu.Lock()
	target := a.target
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	if !strings.HasPrefix(target, "#") {
		a.ui.AddStatus("[red]Not in a channel")

		return
	}

	members, err := a.client.GetMembers(target)
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]Names failed: %v", err,
		))

		return
	}

	a.ui.AddLine(target, fmt.Sprintf(
		"[cyan]*** Members of %s: %s",
		target, strings.Join(members, " "),
	))
}

func (a *App) cmdList() {
	a.mu.Lock()
	connected := a.connected
	a.mu.Unlock()

	if !connected {
		a.ui.AddStatus("[red]Not connected")

		return
	}

	channels, err := a.client.ListChannels()
	if err != nil {
		a.ui.AddStatus(fmt.Sprintf(
			"[red]List failed: %v", err,
		))

		return
	}

	a.ui.AddStatus("[cyan]*** Channel list:")

	for _, ch := range channels {
		a.ui.AddStatus(fmt.Sprintf(
			"  %s (%d members) %s",
			ch.Name, ch.Members, ch.Topic,
		))
	}

	a.ui.AddStatus("[cyan]*** End of channel list")
}

func (a *App) cmdWindow(args string) {
	if args == "" {
		a.ui.AddStatus(
			"[red]Usage: /window <number>",
		)

		return
	}

	var n int

	_, _ = fmt.Sscanf(args, "%d", &n)

	a.ui.SwitchBuffer(n)

	a.mu.Lock()
	nick := a.nick
	a.mu.Unlock()

	if n >= 0 && n < a.ui.BufferCount() {
		buf := a.ui.buffers[n]
		if buf.Name != "(status)" {
			a.mu.Lock()
			a.target = buf.Name
			a.mu.Unlock()

			a.ui.SetStatus(
				nick, buf.Name, "connected",
			)
		} else {
			a.ui.SetStatus(nick, "", "connected")
		}
	}
}

func (a *App) cmdQuit() {
	a.mu.Lock()

	if a.connected && a.client != nil {
		_ = a.client.SendMessage(
			&api.Message{Command: "QUIT"},
		)
	}

	if a.stopPoll != nil {
		close(a.stopPoll)
	}

	a.mu.Unlock()
	a.ui.Stop()
}

func (a *App) cmdHelp() {
	help := []string{
		"[cyan]*** chat-cli commands:",
		"  /connect <url>  — Connect to server",
		"  /nick <name>    — Change nickname",
		"  /join #channel  — Join channel",
		"  /part [#chan]    — Leave channel",
		"  /msg <nick> <text> — Send DM",
		"  /query <nick>   — Open DM window",
		"  /topic [text]   — View/set topic",
		"  /names          — List channel members",
		"  /list           — List channels",
		"  /window <n>     — Switch buffer",
		"  /quit           — Disconnect and exit",
		"  /help           — This help",
		"  Plain text sends to current target.",
	}

	for _, line := range help {
		a.ui.AddStatus(line)
	}
}

// pollLoop long-polls for messages in the background.
func (a *App) pollLoop() {
	for {
		select {
		case <-a.stopPoll:
			return
		default:
		}

		a.mu.Lock()
		client := a.client
		lastQID := a.lastQID
		a.mu.Unlock()

		if client == nil {
			return
		}

		result, err := client.PollMessages(
			lastQID, pollTimeout,
		)
		if err != nil {
			time.Sleep(pollRetry)

			continue
		}

		if result.LastID > 0 {
			a.mu.Lock()
			a.lastQID = result.LastID
			a.mu.Unlock()
		}

		for i := range result.Messages {
			a.handleServerMessage(&result.Messages[i])
		}
	}
}

func (a *App) handleServerMessage(msg *api.Message) {
	ts := a.formatTS(msg)

	a.mu.Lock()
	myNick := a.nick
	a.mu.Unlock()

	switch msg.Command {
	case "PRIVMSG":
		a.handlePrivmsgEvent(msg, ts, myNick)
	case "JOIN":
		a.handleJoinEvent(msg, ts)
	case "PART":
		a.handlePartEvent(msg, ts)
	case "QUIT":
		a.handleQuitEvent(msg, ts)
	case "NICK":
		a.handleNickEvent(msg, ts, myNick)
	case "NOTICE":
		a.handleNoticeEvent(msg, ts)
	case "TOPIC":
		a.handleTopicEvent(msg, ts)
	default:
		a.handleDefaultEvent(msg, ts)
	}
}

func (a *App) formatTS(msg *api.Message) string {
	if msg.TS != "" {
		return msg.ParseTS().UTC().Format(timeFormat)
	}

	return time.Now().Format(timeFormat)
}

func (a *App) handlePrivmsgEvent(
	msg *api.Message, ts, myNick string,
) {
	lines := msg.BodyLines()
	text := strings.Join(lines, " ")

	if msg.From == myNick {
		return
	}

	target := msg.To
	if !strings.HasPrefix(target, "#") {
		target = msg.From
	}

	a.ui.AddLine(target, fmt.Sprintf(
		"[gray]%s [green]<%s>[white] %s",
		ts, msg.From, text,
	))
}

func (a *App) handleJoinEvent(
	msg *api.Message, ts string,
) {
	if msg.To == "" {
		return
	}

	a.ui.AddLine(msg.To, fmt.Sprintf(
		"[gray]%s [yellow]*** %s has joined %s",
		ts, msg.From, msg.To,
	))
}

func (a *App) handlePartEvent(
	msg *api.Message, ts string,
) {
	if msg.To == "" {
		return
	}

	lines := msg.BodyLines()
	reason := strings.Join(lines, " ")

	if reason != "" {
		a.ui.AddLine(msg.To, fmt.Sprintf(
			"[gray]%s [yellow]*** %s has left %s (%s)",
			ts, msg.From, msg.To, reason,
		))
	} else {
		a.ui.AddLine(msg.To, fmt.Sprintf(
			"[gray]%s [yellow]*** %s has left %s",
			ts, msg.From, msg.To,
		))
	}
}

func (a *App) handleQuitEvent(
	msg *api.Message, ts string,
) {
	lines := msg.BodyLines()
	reason := strings.Join(lines, " ")

	if reason != "" {
		a.ui.AddStatus(fmt.Sprintf(
			"[gray]%s [yellow]*** %s has quit (%s)",
			ts, msg.From, reason,
		))
	} else {
		a.ui.AddStatus(fmt.Sprintf(
			"[gray]%s [yellow]*** %s has quit",
			ts, msg.From,
		))
	}
}

func (a *App) handleNickEvent(
	msg *api.Message, ts, myNick string,
) {
	lines := msg.BodyLines()

	newNick := ""
	if len(lines) > 0 {
		newNick = lines[0]
	}

	if msg.From == myNick && newNick != "" {
		a.mu.Lock()
		a.nick = newNick

		target := a.target
		a.mu.Unlock()

		a.ui.SetStatus(newNick, target, "connected")
	}

	a.ui.AddStatus(fmt.Sprintf(
		"[gray]%s [yellow]*** %s is now known as %s",
		ts, msg.From, newNick,
	))
}

func (a *App) handleNoticeEvent(
	msg *api.Message, ts string,
) {
	lines := msg.BodyLines()
	text := strings.Join(lines, " ")

	a.ui.AddStatus(fmt.Sprintf(
		"[gray]%s [magenta]--%s-- %s",
		ts, msg.From, text,
	))
}

func (a *App) handleTopicEvent(
	msg *api.Message, ts string,
) {
	if msg.To == "" {
		return
	}

	lines := msg.BodyLines()
	text := strings.Join(lines, " ")

	a.ui.AddLine(msg.To, fmt.Sprintf(
		"[gray]%s [cyan]*** %s set topic: %s",
		ts, msg.From, text,
	))
}

func (a *App) handleDefaultEvent(
	msg *api.Message, ts string,
) {
	lines := msg.BodyLines()
	text := strings.Join(lines, " ")

	if text != "" {
		a.ui.AddStatus(fmt.Sprintf(
			"[gray]%s [white][%s] %s",
			ts, msg.Command, text,
		))
	}
}