package chat

import (
	"bytes"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"regexp"
	"slices"
	"strings"
	"sync"
	"time"
	"unicode"

	"github.com/ayn2op/discordo/internal/cache"
	"github.com/ayn2op/discordo/internal/clipboard"
	"github.com/ayn2op/discordo/internal/config"
	"github.com/ayn2op/discordo/internal/consts"
	"github.com/ayn2op/discordo/internal/ui"
	"github.com/ayn2op/tview"
	"github.com/ayn2op/tview/help"
	"github.com/ayn2op/tview/keybind"
	"github.com/diamondburned/arikawa/v3/api"
	"github.com/diamondburned/arikawa/v3/discord"
	"github.com/diamondburned/arikawa/v3/state"
	"github.com/diamondburned/arikawa/v3/utils/json/option"
	"github.com/diamondburned/arikawa/v3/utils/sendpart"
	"github.com/diamondburned/ningen/v3"
	"github.com/diamondburned/ningen/v3/discordmd"
	"github.com/gdamore/tcell/v3"
	"github.com/ncruces/zenity"
	"github.com/sahilm/fuzzy"
	"github.com/yuin/goldmark/ast"
)

const tmpFilePattern = consts.Name + "_*.md"

var mentionRegex = regexp.MustCompile("@[a-zA-Z0-9._]+")

type messageInput struct {
	*tview.TextArea
	chat *Model

	cfg *config.Config

	edit            bool
	sendMessageData *api.SendMessageData
	cache           *cache.Cache
	mentionsList    *mentionsList
	lastSearch      time.Time
	lastHeight      int

	typingTimerMu sync.Mutex
	typingTimer   *time.Timer
}

var _ help.KeyMap = (*messageInput)(nil)

func newMessageInput(cfg *config.Config, chatView *Model) *messageInput {
	mi := &messageInput{
		TextArea:        tview.NewTextArea(),
		cfg:             cfg,
		chat:            chatView,
		sendMessageData: &api.SendMessageData{},
		cache:           cache.NewCache(),
		mentionsList:    newMentionsList(cfg),
	}
	mi.Box = ui.ConfigureBox(mi.Box, &cfg.Theme)
	mi.
		SetPlaceholder(tview.NewLine(tview.NewSegment("Select a channel to start chatting", tcell.StyleDefault.Dim(true)))).
		SetClipboard(
			func(s string) {
				if err := clipboard.Write(clipboard.FmtText, []byte(s)); err != nil {
					slog.Error("failed to write clipboard text", "err", err)
				}
			},
			func() string {
				data, err := clipboard.Read(clipboard.FmtText)
				if err != nil {
					slog.Error("failed to read clipboard text", "err", err)
					return ""
				}
				return string(data)
			},
		).
		SetDisabled(true)

	return mi
}

func (mi *messageInput) reset() {
	mi.edit = false
	mi.sendMessageData = &api.SendMessageData{}
	mi.SetTitle("")
	mi.SetFooter("")
	mi.SetText("", true)
	mi.lastHeight = minInputHeight
	mi.chat.rightFlex.ResizeItem(mi, minInputHeight, 1)
}

func (mi *messageInput) stopTypingTimer() {
	if mi.typingTimer != nil {
		mi.typingTimer.Stop()
		mi.typingTimer = nil
	}
}

func (mi *messageInput) HandleEvent(event tview.Event) tview.Command {
	handler := mi.TextArea.HandleEvent
	switch event := event.(type) {
	case *tview.KeyEvent:
		switch {
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.Paste.Keybind):
			mi.paste()
			return handler(tcell.NewEventKey(tcell.KeyCtrlV, "", tcell.ModNone))
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.Send.Keybind):
			if mi.chat.GetVisible(mentionsListLayerName) {
				mi.tabComplete()
			} else {
				mi.send()
			}
			return nil
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.OpenEditor.Keybind):
			var cmds []tview.Command
			mi.stopTabCompletion(func(next tview.Command) {
				if next != nil {
					cmds = append(cmds, next)
				}
			})
			mi.editor()
			return tview.Batch(cmds...)
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.OpenFilePicker.Keybind):
			var cmds []tview.Command
			mi.stopTabCompletion(func(next tview.Command) {
				if next != nil {
					cmds = append(cmds, next)
				}
			})
			mi.openFilePicker()
			return tview.Batch(cmds...)
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.Cancel.Keybind):
			var cmds []tview.Command
			if mi.chat.GetVisible(mentionsListLayerName) {
				mi.stopTabCompletion(func(next tview.Command) {
					if next != nil {
						cmds = append(cmds, next)
					}
				})
			} else {
				mi.reset()
				cmds = append(cmds, tview.SetFocus(mi.chat.messagesList))
			}
			return tview.Batch(cmds...)
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.TabComplete.Keybind):
			go mi.chat.app.QueueUpdateDraw(func() { mi.tabComplete() })
			return nil
		case keybind.Matches(event, mi.cfg.Keybinds.MessageInput.Undo.Keybind):
			return handler(tcell.NewEventKey(tcell.KeyCtrlZ, "", tcell.ModNone))
		}

		if mi.cfg.TypingIndicator.Send && mi.typingTimer == nil {
			mi.typingTimer = time.AfterFunc(typingDuration, func() {
				mi.typingTimerMu.Lock()
				mi.typingTimer = nil
				mi.typingTimerMu.Unlock()
			})

			if selectedChannel := mi.chat.SelectedChannel(); selectedChannel != nil {
				go mi.chat.state.Typing(selectedChannel.ID)
			}
		}

		if mi.cfg.AutocompleteLimit > 0 {
			if mi.chat.GetVisible(mentionsListLayerName) {
				return mi.mentionsList.HandleEvent(event)
			}

			go mi.chat.app.QueueUpdateDraw(func() { mi.tabSuggestion() })
		}
	}
	cmd := handler(event)
	mi.updateHeight()
	return cmd
}

const (
	minInputHeight = 3
	maxInputHeight = 8
)

func (mi *messageInput) updateHeight() {
	text := mi.GetText()
	lines := strings.Count(text, "\n") + 1
	height := max(min(lines, maxInputHeight), minInputHeight)
	if height != mi.lastHeight {
		mi.lastHeight = height
		mi.chat.rightFlex.ResizeItem(mi, height, 1)
	}
}

func (mi *messageInput) paste() {
	data, err := clipboard.Read(clipboard.FmtImage)
	if err != nil {
		slog.Error("failed to read clipboard image", "err", err)
		return
	}
	if data != nil {
		name := "clipboard.png"
		mi.attach(name, bytes.NewReader(data))
	}
}

func (mi *messageInput) send() {
	selected := mi.chat.SelectedChannel()
	if selected == nil {
		return
	}

	text := strings.TrimSpace(mi.GetText())
	if text == "" && len(mi.sendMessageData.Files) == 0 {
		return
	}

	// Close attached files on return
	defer func() {
		for _, file := range mi.sendMessageData.Files {
			if closer, ok := file.Reader.(io.Closer); ok {
				closer.Close()
			}
		}
	}()

	text = mi.processText(selected, []byte(text))

	if mi.edit {
		m, err := mi.chat.messagesList.selectedMessage()
		if err != nil {
			slog.Error("failed to get selected message", "err", err)
			return
		}

		data := api.EditMessageData{Content: option.NewNullableString(text)}
		if _, err := mi.chat.state.EditMessageComplex(m.ChannelID, m.ID, data); err != nil {
			slog.Error("failed to edit message", "err", err)
		}

		mi.edit = false
	} else {
		data := mi.sendMessageData
		data.Content = text
		if _, err := mi.chat.state.SendMessageComplex(selected.ID, *data); err != nil {
			slog.Error("failed to send message in channel", "channel_id", selected.ID, "err", err)
		}
	}

	if mi.typingTimer != nil {
		mi.typingTimer.Stop()
		mi.typingTimer = nil
	}
	mi.reset()
	mi.chat.messagesList.clearSelection()
	mi.chat.messagesList.ScrollBottom()
}

func (mi *messageInput) processText(channel *discord.Channel, src []byte) string {
	// Fast path: no mentions to expand.
	if bytes.IndexByte(src, '@') == -1 {
		return string(src)
	}

	// Fast path: no back ticks (code blocks), so expand mentions directly.
	if bytes.IndexByte(src, '`') == -1 {
		return string(mi.expandMentions(channel, src))
	}

	var (
		ranges     [][2]int
		canMention = true
	)

	ast.Walk(discordmd.Parse(src), func(node ast.Node, enter bool) (ast.WalkStatus, error) {
		switch node := node.(type) {
		case *ast.CodeBlock, *ast.FencedCodeBlock:
			canMention = !enter
		case *discordmd.Inline:
			if (node.Attr & discordmd.AttrMonospace) != 0 {
				canMention = !enter
			}
		case *ast.Text:
			if canMention {
				ranges = append(ranges, [2]int{node.Segment.Start,
					node.Segment.Stop})
			}
		}
		return ast.WalkContinue, nil
	})

	for _, rng := range ranges {
		src = slices.Replace(src, rng[0], rng[1], mi.expandMentions(channel, src[rng[0]:rng[1]])...)
	}

	return string(src)
}

func (mi *messageInput) expandMentions(c *discord.Channel, src []byte) []byte {
	state := mi.chat.state
	return mentionRegex.ReplaceAllFunc(src, func(input []byte) []byte {
		output := input
		name := string(input[1:])
		if c.Type == discord.DirectMessage || c.Type == discord.GroupDM {
			for _, user := range c.DMRecipients {
				if strings.EqualFold(user.Username, name) {
					return []byte(user.ID.Mention())
				}
			}
			// self ping
			me, _ := state.Cabinet.Me()
			if me != nil && strings.EqualFold(me.Username, name) {
				return []byte(me.ID.Mention())
			}
			return output
		}
		state.MemberStore.Each(c.GuildID, func(m *discord.Member) bool {
			if strings.EqualFold(m.User.Username, name) {
				if channelHasUser(state, c.ID, m.User.ID) {
					output = []byte(m.User.ID.Mention())
				}
				return true
			}
			return false
		})
		return output
	})
}

func (mi *messageInput) tabComplete() {
	posEnd, name, r := mi.GetWordUnderCursor(func(r rune) bool {
		return unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' || r == '.'
	})
	if r != '@' {
		mi.stopTabCompletion(nil)
		return
	}
	pos := posEnd - (len(name) + 1)

	selected := mi.chat.SelectedChannel()
	if selected == nil {
		return
	}
	gID := selected.GuildID

	if mi.cfg.AutocompleteLimit == 0 {
		if !gID.IsValid() {
			users := selected.DMRecipients
			res := fuzzy.FindFrom(name, userList(users))
			if len(res) > 0 {
				mi.Replace(pos, posEnd, "@"+users[res[0].Index].Username+" ")
			}
		} else {
			mi.searchMember(gID, name)
			members, err := mi.chat.state.Cabinet.Members(gID)
			if err != nil {
				slog.Error("failed to get members from state", "guild_id", gID, "err", err)
				return
			}

			res := fuzzy.FindFrom(name, memberList(members))
			for _, r := range res {
				if channelHasUser(mi.chat.state, selected.ID, members[r.Index].User.ID) {
					mi.Replace(pos, posEnd, "@"+members[r.Index].User.Username+" ")
					return
				}
			}
		}
		return
	}
	if mi.mentionsList.itemCount() == 0 {
		return
	}
	name, ok := mi.mentionsList.selectedInsertText()
	if !ok {
		return
	}
	mi.Replace(pos, posEnd, "@"+name+" ")
	mi.stopTabCompletion(nil)
}

func (mi *messageInput) tabSuggestion() {
	_, name, r := mi.GetWordUnderCursor(func(r rune) bool {
		return unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' || r == '.'
	})
	if r != '@' {
		mi.stopTabCompletion(nil)
		return
	}
	selected := mi.chat.SelectedChannel()
	if selected == nil {
		return
	}
	gID := selected.GuildID
	cID := selected.ID
	mi.mentionsList.clear()

	var shown map[string]struct{}
	var userDone struct{}
	if name == "" {
		shown = make(map[string]struct{})
		// Don't show @me in the list of recent authors
		me, _ := mi.chat.state.Cabinet.Me()
		if me != nil {
			shown[me.Username] = userDone
		}
	}

	// DMs have recipients, not members
	if !gID.IsValid() {
		if name == "" { // show recent messages' authors
			msgs, err := mi.chat.state.Cabinet.Messages(cID)
			if err != nil {
				return
			}
			for _, m := range msgs {
				if _, ok := shown[m.Author.Username]; ok {
					continue
				}
				shown[m.Author.Username] = userDone
				mi.addMentionUser(&m.Author)
			}
		} else {
			users := selected.DMRecipients
			me, _ := mi.chat.state.Cabinet.Me()
			if me != nil {
				users = append(users, *me)
			}
			res := fuzzy.FindFrom(name, userList(users))
			for _, r := range res {
				mi.addMentionUser(&users[r.Index])
			}
		}
	} else if name == "" { // show recent messages' authors
		msgs, err := mi.chat.state.Cabinet.Messages(cID)
		if err != nil {
			return
		}
		for _, m := range msgs {
			if _, ok := shown[m.Author.Username]; ok {
				continue
			}
			shown[m.Author.Username] = userDone
			mi.chat.state.MemberState.RequestMember(gID, m.Author.ID)
			if mem, err := mi.chat.state.Cabinet.Member(gID, m.Author.ID); err == nil {
				if mi.addMentionMember(gID, mem) {
					break
				}
			}
		}
	} else {
		mi.searchMember(gID, name)
		mems, err := mi.chat.state.Cabinet.Members(gID)
		if err != nil {
			slog.Error("fetching members failed", "err", err)
			return
		}
		res := fuzzy.FindFrom(name, memberList(mems))
		if len(res) > int(mi.cfg.AutocompleteLimit) {
			res = res[:int(mi.cfg.AutocompleteLimit)]
		}
		for _, r := range res {
			if channelHasUser(mi.chat.state, cID, mems[r.Index].User.ID) &&
				mi.addMentionMember(gID, &mems[r.Index]) {
				break
			}
		}
	}

	if mi.mentionsList.itemCount() == 0 {
		mi.stopTabCompletion(nil)
		return
	}

	mi.mentionsList.rebuild()
	mi.showMentionList()
}

type memberList []discord.Member
type userList []discord.User

func (ml memberList) String(i int) string {
	return ml[i].Nick + ml[i].User.DisplayName + ml[i].User.Tag()
}

func (ml memberList) Len() int {
	return len(ml)
}

func (ul userList) String(i int) string {
	return ul[i].DisplayName + ul[i].Tag()
}

func (ul userList) Len() int {
	return len(ul)
}

// channelHasUser checks if a user has permission to view the specified channel.
func channelHasUser(state *ningen.State, channelID discord.ChannelID, userID discord.UserID) bool {
	perms, err := state.Permissions(channelID, userID)
	if err != nil {
		slog.Error("failed to get permissions", "err", err, "channel", channelID, "user", userID)
		return false
	}
	return perms.Has(discord.PermissionViewChannel)
}

func (mi *messageInput) searchMember(gID discord.GuildID, name string) {
	key := gID.String() + " " + name
	if mi.cache.Exists(key) {
		return
	}
	// If searching for "ab" returns less than SearchLimit,
	// then "abc" would not return anything new because we already searched
	// everything starting with "ab". This will still be true even if a new
	// member joins because arikawa loads new members into the state.
	if k := key[:len(key)-1]; mi.cache.Exists(k) {
		if c := mi.cache.Get(k); c < mi.chat.state.MemberState.SearchLimit {
			mi.cache.Create(key, c)
			return
		}
	}

	// Rate limit on our side because we can't distinguish between a successful search and SearchMember not doing anything because of its internal rate limit that we can't detect
	if mi.lastSearch.Add(mi.chat.state.MemberState.SearchFrequency).After(time.Now()) {
		return
	}

	mi.lastSearch = time.Now()
	mi.chat.messagesList.waitForChunkEvent()
	mi.chat.messagesList.setFetchingChunk(true, 0)
	mi.chat.state.MemberState.SearchMember(gID, name)
	mi.cache.Create(key, mi.chat.messagesList.waitForChunkEvent())
}

func (mi *messageInput) showMentionList() {
	borders := 0
	if mi.cfg.Theme.Border.Enabled {
		borders = 1
	}
	l := mi.mentionsList
	x, _, _, _ := mi.InnerRect()
	_, y, _, _ := mi.Rect()
	_, _, maxW, maxH := mi.chat.messagesList.InnerRect()
	if t := int(mi.cfg.Theme.MentionsList.MaxHeight); t != 0 {
		maxH = min(maxH, t)
	}
	count := mi.mentionsList.itemCount() + borders
	h := min(count, maxH) + borders + mi.cfg.Theme.Border.Padding[1]
	y -= h
	w := int(mi.cfg.Theme.MentionsList.MinWidth)
	if w == 0 {
		w = maxW
	} else {
		w = max(w, mi.mentionsList.maxDisplayWidth())

		w = min(w+borders*2, maxW)
		_, col, _, _ := mi.GetCursor()
		x += min(col, maxW-w)
	}

	l.SetRect(x, y, w, h)
	mi.chat.ShowLayer(mentionsListLayerName).SendToFront(mentionsListLayerName)
	mi.chat.app.SetFocus(mi)
}

func (mi *messageInput) addMentionMember(gID discord.GuildID, m *discord.Member) bool {
	if m == nil {
		return false
	}

	name := m.User.DisplayOrUsername()
	if m.Nick != "" {
		name = m.Nick
	}

	style := tcell.StyleDefault

	// This avoids a slower member color lookup path.
	color, ok := state.MemberColor(m, func(id discord.RoleID) *discord.Role {
		r, _ := mi.chat.state.Cabinet.Role(gID, id)
		return r
	})
	if ok {
		style = style.Foreground(tcell.NewHexColor(int32(color)))
	}

	presence, err := mi.chat.state.Cabinet.Presence(gID, m.User.ID)
	if err != nil {
		slog.Info("failed to get presence from state", "guild_id", gID, "user_id", m.User.ID, "err", err)
	} else if presence.Status == discord.OfflineStatus {
		style = style.Dim(true)
	}

	mi.mentionsList.append(mentionsListItem{
		insertText:  m.User.Username,
		displayText: name,
		style:       style,
	})
	return mi.mentionsList.itemCount() > int(mi.cfg.AutocompleteLimit)
}

func (mi *messageInput) addMentionUser(user *discord.User) {
	if user == nil {
		return
	}

	name := user.DisplayOrUsername()
	style := tcell.StyleDefault
	presence, err := mi.chat.state.Cabinet.Presence(discord.NullGuildID, user.ID)
	if err != nil {
		slog.Info("failed to get presence from state", "user_id", user.ID, "err", err)
	} else if presence.Status == discord.OfflineStatus {
		style = style.Dim(true)
	}

	mi.mentionsList.append(mentionsListItem{
		insertText:  user.Username,
		displayText: name,
		style:       style,
	})
}

func (mi *messageInput) removeMentionsList() {
	mi.chat.HideLayer(mentionsListLayerName)
}

func (mi *messageInput) stopTabCompletion(emit func(tview.Command)) {
	if mi.cfg.AutocompleteLimit > 0 {
		mi.mentionsList.clear()
		if emit != nil {
			emit(closeLayer(mentionsListLayerName))
			emit(tview.SetFocus(mi))
		} else {
			mi.removeMentionsList()
			mi.chat.app.SetFocus(mi)
		}
	}
}

func (mi *messageInput) editor() {
	file, err := os.CreateTemp("", tmpFilePattern)
	if err != nil {
		slog.Error("failed to create tmp file", "err", err)
		return
	}
	defer file.Close()
	defer os.Remove(file.Name())

	file.WriteString(mi.GetText())

	if mi.cfg.Editor == "" {
		slog.Warn("Attempt to open file with editor, but no editor is set")
		return
	}

	cmd := mi.cfg.CreateEditorCommand(file.Name())
	if cmd == nil {
		return
	}

	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	mi.chat.app.Suspend(func() {
		err := cmd.Run()
		if err != nil {
			slog.Error("failed to run command", "args", cmd.Args, "err", err)
			return
		}
	})

	msg, err := os.ReadFile(file.Name())
	if err != nil {
		slog.Error("failed to read tmp file", "name", file.Name(), "err", err)
		return
	}

	mi.SetText(strings.TrimSpace(string(msg)), true)
}

func (mi *messageInput) openFilePicker() {
	if mi.chat.SelectedChannel() == nil {
		return
	}

	paths, err := zenity.SelectFileMultiple()
	if err != nil {
		slog.Error("failed to open file dialog", "err", err)
		return
	}

	for _, path := range paths {
		file, err := os.Open(path)
		if err != nil {
			slog.Error("failed to open file", "path", path, "err", err)
			continue
		}

		name := filepath.Base(path)
		mi.attach(name, file)
	}
}

func (mi *messageInput) attach(name string, reader io.Reader) {
	mi.sendMessageData.Files = append(mi.sendMessageData.Files, sendpart.File{Name: name, Reader: reader})

	var names []string
	for _, file := range mi.sendMessageData.Files {
		names = append(names, file.Name)
	}
	mi.SetFooter("Attached " + humanJoin(names))
}

func (mi *messageInput) ShortHelp() []keybind.Keybind {
	if mi.chat.GetVisible(mentionsListLayerName) {
		cfg := mi.cfg.Keybinds.MentionsList
		icfg := mi.cfg.Keybinds.MessageInput
		short := []keybind.Keybind{cfg.Up.Keybind, cfg.Down.Keybind, icfg.Cancel.Keybind}
		if selected := mi.chat.SelectedChannel(); selected != nil && mi.chat.state.HasPermissions(selected.ID, discord.PermissionAttachFiles) {
			short = append(short, icfg.OpenFilePicker.Keybind)
		}
		return short
	}

	cfg := mi.cfg.Keybinds.MessageInput
	short := []keybind.Keybind{cfg.Send.Keybind, cfg.Cancel.Keybind, cfg.Paste.Keybind, cfg.OpenEditor.Keybind}
	if selected := mi.chat.SelectedChannel(); selected != nil && mi.chat.state.HasPermissions(selected.ID, discord.PermissionAttachFiles) {
		short = append(short, cfg.OpenFilePicker.Keybind)
	}
	return short
}

func (mi *messageInput) FullHelp() [][]keybind.Keybind {
	if mi.chat.GetVisible(mentionsListLayerName) {
		mcfg := mi.cfg.Keybinds.MentionsList
		icfg := mi.cfg.Keybinds.MessageInput
		return [][]keybind.Keybind{
			{mcfg.Up.Keybind, mcfg.Down.Keybind, mcfg.Top.Keybind, mcfg.Bottom.Keybind},
			{icfg.TabComplete.Keybind, icfg.Cancel.Keybind},
		}
	}

	cfg := mi.cfg.Keybinds.MessageInput
	openEditor := []keybind.Keybind{cfg.Paste.Keybind, cfg.OpenEditor.Keybind}
	if selected := mi.chat.SelectedChannel(); selected != nil && mi.chat.state.HasPermissions(selected.ID, discord.PermissionAttachFiles) {
		openEditor = append(openEditor, cfg.OpenFilePicker.Keybind)
	}

	return [][]keybind.Keybind{
		{cfg.Send.Keybind, cfg.Cancel.Keybind, cfg.TabComplete.Keybind, cfg.Undo.Keybind},
		openEditor,
	}
}