package bridge

import (
	"errors"
	"fmt"
	"strings"
	"time"

	"maunium.net/go/maulogger/v2"
	"maunium.net/go/mautrix"
	"maunium.net/go/mautrix/appservice"
	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/format"
	"maunium.net/go/mautrix/id"
)

type matrixHandler struct {
	as     *appservice.AppService
	bridge *Bridge
	log    maulogger.Logger
	cmd    *commandHandler
}

func (b *Bridge) setupEvents() {
	b.eventProcessor = appservice.NewEventProcessor(b.as)

	b.matrixHandler = &matrixHandler{
		as:     b.as,
		bridge: b,
		log:    b.log.Sub("Matrix"),
		cmd:    newCommandHandler(b),
	}

	b.eventProcessor.On(event.EventMessage, b.matrixHandler.handleMessage)
	b.eventProcessor.On(event.EventEncrypted, b.matrixHandler.handleEncrypted)
	b.eventProcessor.On(event.EventReaction, b.matrixHandler.handleReaction)
	b.eventProcessor.On(event.EventRedaction, b.matrixHandler.handleRedaction)
	b.eventProcessor.On(event.StateMember, b.matrixHandler.handleMembership)
	b.eventProcessor.On(event.StateEncryption, b.matrixHandler.handleEncryption)
}

func (mh *matrixHandler) join(evt *event.Event, intent *appservice.IntentAPI) *mautrix.RespJoinedMembers {
	resp, err := intent.JoinRoomByID(evt.RoomID)
	if err != nil {
		mh.log.Debugfln("Failed to join room %s as %s with invite from %s: %v", evt.RoomID, intent.UserID, evt.Sender, err)

		return nil
	}

	members, err := intent.JoinedMembers(resp.RoomID)
	if err != nil {
		intent.LeaveRoom(resp.RoomID)

		mh.log.Debugfln("Failed to get members in room %s after accepting invite from %s as %s: %v", resp.RoomID, evt.Sender, intent.UserID, err)

		return nil
	}

	if len(members.Joined) < 2 {
		intent.LeaveRoom(resp.RoomID)

		mh.log.Debugln("Leaving empty room", resp.RoomID, "after accepting invite from", evt.Sender, "as", intent.UserID)

		return nil
	}

	return members
}

func (mh *matrixHandler) ignoreEvent(evt *event.Event) bool {
	return false
}

func (mh *matrixHandler) handleMessage(evt *event.Event) {
	if mh.ignoreEvent(evt) {
		return
	}

	user := mh.bridge.GetUserByMXID(evt.Sender)
	if user == nil {
		mh.log.Debugln("unknown user", evt.Sender)
		return
	}

	content := evt.Content.AsMessage()
	content.RemoveReplyFallback()

	if content.MsgType == event.MsgText {
		prefix := mh.bridge.Config.Bridge.CommandPrefix

		hasPrefix := strings.HasPrefix(content.Body, prefix)
		if hasPrefix {
			content.Body = strings.TrimLeft(content.Body[len(prefix):], " ")
		}

		if hasPrefix || evt.RoomID == user.ManagementRoom {
			mh.cmd.handle(evt.RoomID, user, content.Body, content.GetReplyTo())
			return
		}
	}

	portal := mh.bridge.GetPortalByMXID(evt.RoomID)
	if portal != nil {
		portal.matrixMessages <- portalMatrixMessage{user: user, evt: evt}
	}

}

func (mh *matrixHandler) joinAndCheckMembers(evt *event.Event, intent *appservice.IntentAPI) int {
	resp, err := intent.JoinRoomByID(evt.RoomID)
	if err != nil {
		mh.log.Debugfln("Failed to join room %q as %q with invite from %q: %v", evt.RoomID, intent.UserID, evt.Sender, err)

		return 0
	}

	members, err := intent.Members(resp.RoomID)
	if err != nil {
		mh.log.Debugfln("Failed to get members in room %q with invite from %q as %q: %v", resp.RoomID, evt.Sender, intent.UserID, err)

		return 0
	}

	if len(members.Chunk) < 2 {
		mh.log.Debugfln("Leaving empty room %q with invite from %q as %q", resp.RoomID, evt.Sender, intent.UserID)

		intent.LeaveRoom(resp.RoomID)

		return 0
	}

	return len(members.Chunk)
}

func (mh *matrixHandler) sendNoticeWithmarkdown(roomID id.RoomID, message string) (*mautrix.RespSendEvent, error) {
	intent := mh.as.BotIntent()
	content := format.RenderMarkdown(message, true, false)
	content.MsgType = event.MsgNotice

	return intent.SendMessageEvent(roomID, event.EventMessage, content)
}

func (mh *matrixHandler) handleBotInvite(evt *event.Event) {
	intent := mh.as.BotIntent()

	user := mh.bridge.GetUserByMXID(evt.Sender)
	if user == nil {
		return
	}

	members := mh.joinAndCheckMembers(evt, intent)
	if members == 0 {
		return
	}

	// If this is a DM and the user doesn't have a management room, make this
	// the management room.
	if members == 2 && (user.ManagementRoom == "" || evt.Content.AsMember().IsDirect) {
		user.SetManagementRoom(evt.RoomID)

		intent.SendNotice(user.ManagementRoom, "This room has been registered as your bridge management/status room")
		mh.log.Debugfln("%q registered as management room with %q", evt.RoomID, evt.Sender)
	}

	if evt.RoomID == user.ManagementRoom {
		// Wait to send the welcome message until we're sure we're not in an empty
		// room.
		mh.sendNoticeWithmarkdown(evt.RoomID, mh.bridge.Config.Bridge.ManagementRoomText.Welcome)

		if user.Connected() {
			mh.sendNoticeWithmarkdown(evt.RoomID, mh.bridge.Config.Bridge.ManagementRoomText.Connected)
		} else {
			mh.sendNoticeWithmarkdown(evt.RoomID, mh.bridge.Config.Bridge.ManagementRoomText.NotConnected)
		}

		additionalHelp := mh.bridge.Config.Bridge.ManagementRoomText.AdditionalHelp
		if additionalHelp != "" {
			mh.sendNoticeWithmarkdown(evt.RoomID, additionalHelp)
		}
	}
}

func (mh *matrixHandler) handlePuppetInvite(evt *event.Event, inviter *User, puppet *Puppet) {
	mh.log.Warnln("handling puppet invite!")
}

func (mh *matrixHandler) handleMembership(evt *event.Event) {
	// Return early if we're supposed to ignore the event.
	if mh.ignoreEvent(evt) {
		return
	}

	if mh.bridge.crypto != nil {
		mh.bridge.crypto.HandleMemberEvent(evt)
	}

	// Grab the content of the event.
	content := evt.Content.AsMember()

	// Check if this is a new conversation from a matrix user to the bot
	if content.Membership == event.MembershipInvite && id.UserID(evt.GetStateKey()) == mh.as.BotMXID() {
		mh.handleBotInvite(evt)

		return
	}

	// Load or create a new user.
	user := mh.bridge.GetUserByMXID(evt.Sender)
	if user == nil {
		return
	}

	puppet := mh.bridge.GetPuppetByMXID(id.UserID(evt.GetStateKey()))

	// Load or create a new portal.
	portal := mh.bridge.GetPortalByMXID(evt.RoomID)
	if portal == nil {
		if content.Membership == event.MembershipInvite && puppet != nil {
			mh.handlePuppetInvite(evt, user, puppet)
		}

		return
	}

	isSelf := id.UserID(evt.GetStateKey()) == evt.Sender

	if content.Membership == event.MembershipLeave {
		if evt.Unsigned.PrevContent != nil {
			_ = evt.Unsigned.PrevContent.ParseRaw(evt.Type)
			prevContent, ok := evt.Unsigned.PrevContent.Parsed.(*event.MemberEventContent)
			if ok && prevContent.Membership != "join" {
				return
			}
		}

		if isSelf {
			portal.handleMatrixLeave(user)
		} else if puppet != nil {
			portal.handleMatrixKick(user, puppet)
		}
	} else if content.Membership == event.MembershipInvite {
		portal.handleMatrixInvite(user, evt)
	}
}

func (mh *matrixHandler) handleReaction(evt *event.Event) {
	if mh.ignoreEvent(evt) {
		return
	}

	portal := mh.bridge.GetPortalByMXID(evt.RoomID)
	if portal != nil {
		portal.handleMatrixReaction(evt)
	}
}

func (mh *matrixHandler) handleRedaction(evt *event.Event) {
	if mh.ignoreEvent(evt) {
		return
	}

	portal := mh.bridge.GetPortalByMXID(evt.RoomID)
	if portal != nil {
		portal.handleMatrixRedaction(evt)
	}
}

func (mh *matrixHandler) handleEncryption(evt *event.Event) {
	if evt.Content.AsEncryption().Algorithm != id.AlgorithmMegolmV1 {
		return
	}

	portal := mh.bridge.GetPortalByMXID(evt.RoomID)
	if portal != nil && !portal.Encrypted {
		mh.log.Debugfln("%s enabled encryption in %s", evt.Sender, evt.RoomID)
		portal.Encrypted = true
		portal.Update()
	}
}

const sessionWaitTimeout = 5 * time.Second

func (mh *matrixHandler) handleEncrypted(evt *event.Event) {
	if mh.ignoreEvent(evt) || mh.bridge.crypto == nil {
		return
	}

	decrypted, err := mh.bridge.crypto.Decrypt(evt)
	decryptionRetryCount := 0
	if errors.Is(err, NoSessionFound) {
		content := evt.Content.AsEncrypted()
		mh.log.Debugfln("Couldn't find session %s trying to decrypt %s, waiting %d seconds...", content.SessionID, evt.ID, int(sessionWaitTimeout.Seconds()))
		mh.as.SendErrorMessageSendCheckpoint(evt, appservice.StepDecrypted, err, false, decryptionRetryCount)
		decryptionRetryCount++

		if mh.bridge.crypto.WaitForSession(evt.RoomID, content.SenderKey, content.SessionID, sessionWaitTimeout) {
			mh.log.Debugfln("Got session %s after waiting, trying to decrypt %s again", content.SessionID, evt.ID)
			decrypted, err = mh.bridge.crypto.Decrypt(evt)
		} else {
			mh.as.SendErrorMessageSendCheckpoint(evt, appservice.StepDecrypted, fmt.Errorf("didn't receive encryption keys"), false, decryptionRetryCount)

			go mh.waitLongerForSession(evt)

			return
		}
	}

	if err != nil {
		mh.as.SendErrorMessageSendCheckpoint(evt, appservice.StepDecrypted, err, true, decryptionRetryCount)

		mh.log.Warnfln("Failed to decrypt %s: %v", evt.ID, err)
		_, _ = mh.bridge.bot.SendNotice(evt.RoomID, fmt.Sprintf(
			"\u26a0 Your message was not bridged: %v", err))

		return
	}

	mh.as.SendMessageSendCheckpoint(decrypted, appservice.StepDecrypted, decryptionRetryCount)
	mh.bridge.eventProcessor.Dispatch(decrypted)
}

func (mh *matrixHandler) waitLongerForSession(evt *event.Event) {
	const extendedTimeout = sessionWaitTimeout * 3

	content := evt.Content.AsEncrypted()
	mh.log.Debugfln("Couldn't find session %s trying to decrypt %s, waiting %d more seconds...",
		content.SessionID, evt.ID, int(extendedTimeout.Seconds()))

	go mh.bridge.crypto.RequestSession(evt.RoomID, content.SenderKey, content.SessionID, evt.Sender, content.DeviceID)

	resp, err := mh.bridge.bot.SendNotice(evt.RoomID, fmt.Sprintf(
		"\u26a0 Your message was not bridged: the bridge hasn't received the decryption keys. "+
			"The bridge will retry for %d seconds. If this error keeps happening, try restarting your client.",
		int(extendedTimeout.Seconds())))
	if err != nil {
		mh.log.Errorfln("Failed to send decryption error to %s: %v", evt.RoomID, err)
	}

	update := event.MessageEventContent{MsgType: event.MsgNotice}

	if mh.bridge.crypto.WaitForSession(evt.RoomID, content.SenderKey, content.SessionID, extendedTimeout) {
		mh.log.Debugfln("Got session %s after waiting more, trying to decrypt %s again", content.SessionID, evt.ID)

		decrypted, err := mh.bridge.crypto.Decrypt(evt)
		if err == nil {
			mh.as.SendMessageSendCheckpoint(decrypted, appservice.StepDecrypted, 2)
			mh.bridge.eventProcessor.Dispatch(decrypted)
			_, _ = mh.bridge.bot.RedactEvent(evt.RoomID, resp.EventID)

			return
		}

		mh.log.Warnfln("Failed to decrypt %s: %v", evt.ID, err)
		mh.as.SendErrorMessageSendCheckpoint(evt, appservice.StepDecrypted, err, true, 2)
		update.Body = fmt.Sprintf("\u26a0 Your message was not bridged: %v", err)
	} else {
		mh.log.Debugfln("Didn't get %s, giving up on %s", content.SessionID, evt.ID)
		mh.as.SendErrorMessageSendCheckpoint(evt, appservice.StepDecrypted, fmt.Errorf("didn't receive encryption keys"), true, 2)
		update.Body = "\u26a0 Your message was not bridged: the bridge hasn't received the decryption keys. " +
			"If this error keeps happening, try restarting your client."
	}

	newContent := update
	update.NewContent = &newContent
	if resp != nil {
		update.RelatesTo = &event.RelatesTo{
			Type:    event.RelReplace,
			EventID: resp.EventID,
		}
	}

	_, err = mh.bridge.bot.SendMessageEvent(evt.RoomID, event.EventMessage, &update)
	if err != nil {
		mh.log.Debugfln("Failed to update decryption error notice %s: %v", resp.EventID, err)
	}
}