// mautrix-whatsapp - A Matrix-WhatsApp puppeting bridge.
// Copyright (C) 2022 Tulir Asokan
//
// 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, or
// (at your option) any later version.
//
// 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 <https://www.gnu.org/licenses/>.

package main

import (
	"context"
	"errors"
	"fmt"
	"sync"

	"go.mau.fi/whatsmeow"
	log "maunium.net/go/maulogger/v2"
	"maunium.net/go/mautrix"
	"maunium.net/go/mautrix/bridge"
	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/id"
)

var (
	errUserNotConnected            = errors.New("you are not connected to WhatsApp")
	errDifferentUser               = errors.New("user is not the recipient of this private chat portal")
	errUserNotLoggedIn             = errors.New("user is not logged in and chat has no relay bot")
	errMNoticeDisabled             = errors.New("bridging m.notice messages is disabled")
	errUnexpectedParsedContentType = errors.New("unexpected parsed content type")
	errInvalidGeoURI               = errors.New("invalid `geo:` URI in message")
	errUnknownMsgType              = errors.New("unknown msgtype")
	errMediaDownloadFailed         = errors.New("failed to download media")
	errMediaDecryptFailed          = errors.New("failed to decrypt media")
	errMediaConvertFailed          = errors.New("failed to convert media")
	errMediaWhatsAppUploadFailed   = errors.New("failed to upload media to WhatsApp")
	errTargetNotFound              = errors.New("target event not found")
	errReactionDatabaseNotFound    = errors.New("reaction database entry not found")
	errReactionTargetNotFound      = errors.New("reaction target message not found")
	errTargetIsFake                = errors.New("target is a fake event")
	errTargetSentBySomeoneElse     = errors.New("target is a fake event")

	errBroadcastReactionNotSupported = errors.New("reacting to status messages is not currently supported")
	errBroadcastSendDisabled         = errors.New("sending status messages is disabled")

	errMessageDisconnected      = &whatsmeow.DisconnectedError{Action: "message send"}
	errMessageRetryDisconnected = &whatsmeow.DisconnectedError{Action: "message send (retry)"}

	errMessageTakingLong     = errors.New("bridging the message is taking longer than usual")
	errTimeoutBeforeHandling = errors.New("message timed out before handling was started")
)

func errorToStatusReason(err error) (reason event.MessageStatusReason, isCertain, canRetry, sendNotice bool) {
	switch {
	case errors.Is(err, whatsmeow.ErrBroadcastListUnsupported),
		errors.Is(err, errUnexpectedParsedContentType),
		errors.Is(err, errUnknownMsgType),
		errors.Is(err, errInvalidGeoURI),
		errors.Is(err, whatsmeow.ErrUnknownServer),
		errors.Is(err, whatsmeow.ErrRecipientADJID),
		errors.Is(err, errBroadcastReactionNotSupported),
		errors.Is(err, errBroadcastSendDisabled):
		return event.MessageStatusUnsupported, true, false, true
	case errors.Is(err, errTimeoutBeforeHandling):
		return event.MessageStatusTooOld, true, true, true
	case errors.Is(err, context.DeadlineExceeded), errors.Is(err, errMessageTakingLong):
		return event.MessageStatusTooOld, false, true, true
	case errors.Is(err, errTargetNotFound),
		errors.Is(err, errTargetIsFake),
		errors.Is(err, errReactionDatabaseNotFound),
		errors.Is(err, errReactionTargetNotFound),
		errors.Is(err, errTargetSentBySomeoneElse):
		return event.MessageStatusGenericError, true, false, false
	case errors.Is(err, whatsmeow.ErrNotConnected),
		errors.Is(err, errUserNotConnected):
		return event.MessageStatusGenericError, true, true, true
	case errors.Is(err, errUserNotLoggedIn),
		errors.Is(err, errDifferentUser):
		return event.MessageStatusGenericError, true, true, false
	case errors.Is(err, errMessageDisconnected),
		errors.Is(err, errMessageRetryDisconnected):
		return event.MessageStatusGenericError, false, true, true
	default:
		return event.MessageStatusGenericError, false, true, true
	}
}

func (portal *Portal) sendErrorMessage(err error, confirmed bool, editID id.EventID) id.EventID {
	if !portal.bridge.Config.Bridge.MessageErrorNotices {
		return ""
	}
	certainty := "may not have been"
	if confirmed {
		certainty = "was not"
	}
	msg := fmt.Sprintf("\u26a0 Your message %s bridged: %v", certainty, err)
	if errors.Is(err, errMessageTakingLong) {
		msg = "\u26a0 Bridging your message is taking longer than usual"
	}
	content := &event.MessageEventContent{
		MsgType: event.MsgNotice,
		Body:    msg,
	}
	if editID != "" {
		content.SetEdit(editID)
	}
	resp, err := portal.sendMainIntentMessage(content)
	if err != nil {
		portal.log.Warnfln("Failed to send bridging error message:", err)
		return ""
	}
	return resp.EventID
}

func (portal *Portal) sendStatusEvent(evtID, lastRetry id.EventID, err error) {
	if !portal.bridge.Config.Bridge.MessageStatusEvents {
		return
	}
	if lastRetry == evtID {
		lastRetry = ""
	}
	intent := portal.bridge.Bot
	if !portal.Encrypted {
		// Bridge bot isn't present in unencrypted DMs
		intent = portal.MainIntent()
	}
	content := event.BeeperMessageStatusEventContent{
		Network: portal.getBridgeInfoStateKey(),
		RelatesTo: event.RelatesTo{
			Type:    event.RelReference,
			EventID: evtID,
		},
		Success:   err == nil,
		LastRetry: lastRetry,
	}
	if !content.Success {
		reason, isCertain, canRetry, _ := errorToStatusReason(err)
		content.Reason = reason
		content.IsCertain = &isCertain
		content.CanRetry = &canRetry
		content.Error = err.Error()
	}
	_, err = intent.SendMessageEvent(portal.MXID, event.BeeperMessageStatus, &content)
	if err != nil {
		portal.log.Warnln("Failed to send message status event:", err)
	}
}

func (portal *Portal) sendDeliveryReceipt(eventID id.EventID) {
	if portal.bridge.Config.Bridge.DeliveryReceipts {
		err := portal.bridge.Bot.MarkRead(portal.MXID, eventID)
		if err != nil {
			portal.log.Debugfln("Failed to send delivery receipt for %s: %v", eventID, err)
		}
	}
}

func (portal *Portal) sendMessageMetrics(evt *event.Event, err error, part string, ms *metricSender) {
	var msgType string
	switch evt.Type {
	case event.EventMessage:
		msgType = "message"
	case event.EventReaction:
		msgType = "reaction"
	case event.EventRedaction:
		msgType = "redaction"
	default:
		msgType = "unknown event"
	}
	evtDescription := evt.ID.String()
	if evt.Type == event.EventRedaction {
		evtDescription += fmt.Sprintf(" of %s", evt.Redacts)
	}
	origEvtID := evt.ID
	if retryMeta := evt.Content.AsMessage().MessageSendRetry; retryMeta != nil {
		origEvtID = retryMeta.OriginalEventID
	}
	if err != nil {
		level := log.LevelError
		if part == "Ignoring" {
			level = log.LevelDebug
		}
		portal.log.Logfln(level, "%s %s %s from %s: %v", part, msgType, evtDescription, evt.Sender, err)
		reason, isCertain, _, sendNotice := errorToStatusReason(err)
		status := bridge.ReasonToCheckpointStatus(reason)
		if errors.Is(err, errMessageTakingLong) {
			status = bridge.MsgStatusWillRetry
		}
		portal.bridge.SendMessageCheckpoint(evt, bridge.MsgStepRemote, err, status, ms.getRetryNum())
		if sendNotice {
			ms.setNoticeID(portal.sendErrorMessage(err, isCertain, ms.getNoticeID()))
		}
		portal.sendStatusEvent(origEvtID, evt.ID, err)
	} else {
		portal.log.Debugfln("Handled Matrix %s %s", msgType, evtDescription)
		portal.sendDeliveryReceipt(evt.ID)
		portal.bridge.SendMessageSuccessCheckpoint(evt, bridge.MsgStepRemote, ms.getRetryNum())
		portal.sendStatusEvent(origEvtID, evt.ID, nil)
		if prevNotice := ms.popNoticeID(); prevNotice != "" {
			_, _ = portal.MainIntent().RedactEvent(portal.MXID, prevNotice, mautrix.ReqRedact{
				Reason: "error resolved",
			})
		}
	}
}

type metricSender struct {
	portal         *Portal
	previousNotice id.EventID
	lock           sync.Mutex
	completed      bool
	retryNum       int
}

func (ms *metricSender) getRetryNum() int {
	if ms != nil {
		return ms.retryNum
	}
	return 0
}

func (ms *metricSender) getNoticeID() id.EventID {
	if ms == nil {
		return ""
	}
	return ms.previousNotice
}

func (ms *metricSender) popNoticeID() id.EventID {
	if ms == nil {
		return ""
	}
	evtID := ms.previousNotice
	ms.previousNotice = ""
	return evtID
}

func (ms *metricSender) setNoticeID(evtID id.EventID) {
	if ms != nil && ms.previousNotice == "" {
		ms.previousNotice = evtID
	}
}

func (ms *metricSender) sendMessageMetrics(evt *event.Event, err error, part string, completed bool) {
	ms.lock.Lock()
	defer ms.lock.Unlock()
	if !completed && ms.completed {
		return
	}
	ms.portal.sendMessageMetrics(evt, err, part, ms)
	ms.retryNum++
	ms.completed = completed
}