// Copyright (c) 2024 Tulir Asokan
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package hicli

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/rs/zerolog"
	"github.com/yuin/goldmark"
	"go.mau.fi/util/jsontime"
	"go.mau.fi/util/ptr"
	"maunium.net/go/mautrix"
	"maunium.net/go/mautrix/crypto"
	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/format"
	"maunium.net/go/mautrix/format/mdext"
	"maunium.net/go/mautrix/id"

	"go.mau.fi/gomuks/pkg/hicli/database"
	"go.mau.fi/gomuks/pkg/rainbow"
)

var (
	rainbowWithHTML = goldmark.New(format.Extensions, goldmark.WithExtensions(mdext.Math, mdext.CustomEmoji), format.HTMLOptions, goldmark.WithExtensions(rainbow.Extension))
	defaultNoHTML   = goldmark.New(format.Extensions, goldmark.WithExtensions(mdext.Math, mdext.CustomEmoji, mdext.EscapeHTML), format.HTMLOptions)
)

var htmlToMarkdownForInput = ptr.Clone(format.MarkdownHTMLParser)

func init() {
	htmlToMarkdownForInput.PillConverter = func(displayname, mxid, eventID string, ctx format.Context) string {
		switch {
		case len(mxid) == 0, mxid[0] == '@':
			return fmt.Sprintf("[%s](%s)", displayname, id.UserID(mxid).URI().MatrixToURL())
		case len(eventID) > 0:
			return fmt.Sprintf("[%s](%s)", displayname, id.RoomID(mxid).EventURI(id.EventID(eventID)).MatrixToURL())
		case mxid[0] == '!' && displayname == mxid:
			return fmt.Sprintf("[%s](%s)", displayname, id.RoomID(mxid).URI().MatrixToURL())
		case mxid[0] == '#':
			return fmt.Sprintf("[%s](%s)", displayname, id.RoomAlias(mxid).URI().MatrixToURL())
		default:
			return htmlToMarkdownForInput.LinkConverter(displayname, "https://matrix.to/#/"+mxid, ctx)
		}
	}
	htmlToMarkdownForInput.ImageConverter = func(src, alt, title, width, height string, isEmoji bool) string {
		if isEmoji {
			return fmt.Sprintf(`![%s](%s %q)`, alt, src, "Emoji: "+title)
		} else if title != "" {
			return fmt.Sprintf(`![%s](%s %q)`, alt, src, title)
		} else {
			return fmt.Sprintf(`![%s](%s)`, alt, src)
		}
	}
}

func (h *HiClient) SendMessage(
	ctx context.Context,
	roomID id.RoomID,
	base *event.MessageEventContent,
	extra map[string]any,
	text string,
	relatesTo *event.RelatesTo,
	mentions *event.Mentions,
) (*database.Event, error) {
	if text == "/discardsession" {
		err := h.CryptoStore.RemoveOutboundGroupSession(ctx, roomID)
		if err != nil {
			return nil, err
		}
		return nil, fmt.Errorf("outbound megolm session successfully discarded")
	}
	var unencrypted bool
	if strings.HasPrefix(text, "/unencrypted ") {
		text = strings.TrimPrefix(text, "/unencrypted ")
		unencrypted = true
	}
	if strings.HasPrefix(text, "/raw ") {
		parts := strings.SplitN(text, " ", 3)
		if len(parts) < 2 || len(parts[1]) == 0 {
			return nil, fmt.Errorf("invalid /raw command")
		}
		var content json.RawMessage
		if len(parts) == 3 {
			content = json.RawMessage(parts[2])
		} else {
			content = json.RawMessage("{}")
		}
		if !json.Valid(content) {
			return nil, fmt.Errorf("invalid JSON in /raw command")
		}
		return h.send(ctx, roomID, event.Type{Type: parts[1]}, content, "", unencrypted)
	} else if strings.HasPrefix(text, "/rawstate ") {
		parts := strings.SplitN(text, " ", 4)
		if len(parts) < 4 || len(parts[1]) == 0 {
			return nil, fmt.Errorf("invalid /rawstate command")
		}
		content := json.RawMessage(parts[3])
		if !json.Valid(content) {
			return nil, fmt.Errorf("invalid JSON in /rawstate command")
		}
		_, err := h.SetState(ctx, roomID, event.Type{Type: parts[1], Class: event.StateEventType}, parts[2], content)
		return nil, err
	}
	var content event.MessageEventContent
	msgType := event.MsgText
	origText := text
	if strings.HasPrefix(text, "/me ") {
		msgType = event.MsgEmote
		text = strings.TrimPrefix(text, "/me ")
	} else if strings.HasPrefix(text, "/notice ") {
		msgType = event.MsgNotice
		text = strings.TrimPrefix(text, "/notice ")
	}
	if strings.HasPrefix(text, "/rainbow ") {
		text = strings.TrimPrefix(text, "/rainbow ")
		content = format.RenderMarkdownCustom(text, rainbowWithHTML)
		content.FormattedBody = rainbow.ApplyColor(content.FormattedBody)
	} else if strings.HasPrefix(text, "/plain ") {
		text = strings.TrimPrefix(text, "/plain ")
		content = format.TextToContent(text)
	} else if strings.HasPrefix(text, "/html ") {
		text = strings.TrimPrefix(text, "/html ")
		text = strings.Replace(text, "\n", "<br>", -1)
		content = format.HTMLToContent(text)
	} else if text != "" {
		content = format.RenderMarkdownCustom(text, defaultNoHTML)
	}
	content.MsgType = msgType
	if base != nil {
		if text != "" {
			base.Body = content.Body
			base.Format = content.Format
			base.FormattedBody = content.FormattedBody
		}
		content = *base
	}
	if content.Mentions == nil {
		content.Mentions = &event.Mentions{}
	}
	if mentions != nil {
		content.Mentions.Room = mentions.Room
		for _, userID := range mentions.UserIDs {
			if userID != h.Account.UserID {
				content.Mentions.Add(userID)
			}
		}
	}
	if relatesTo != nil {
		if relatesTo.Type == event.RelReplace {
			contentCopy := content
			content = event.MessageEventContent{
				Body:       "",
				MsgType:    contentCopy.MsgType,
				URL:        contentCopy.URL,
				NewContent: &contentCopy,
				RelatesTo:  relatesTo,
			}
			if contentCopy.File != nil {
				content.URL = contentCopy.File.URL
			}
		} else {
			content.RelatesTo = relatesTo
		}
	}
	evtType := event.EventMessage
	if content.MsgType == "m.sticker" {
		content.MsgType = ""
		evtType = event.EventSticker
	}
	return h.send(ctx, roomID, evtType, &event.Content{Parsed: content, Raw: extra}, origText, unencrypted)
}

func (h *HiClient) MarkRead(ctx context.Context, roomID id.RoomID, eventID id.EventID, receiptType event.ReceiptType) error {
	room, err := h.DB.Room.Get(ctx, roomID)
	if err != nil {
		return fmt.Errorf("failed to get room metadata: %w", err)
	} else if room == nil {
		return fmt.Errorf("unknown room")
	}
	content := &mautrix.ReqSetReadMarkers{
		FullyRead: eventID,
	}
	if receiptType == event.ReceiptTypeRead {
		content.Read = eventID
	} else if receiptType == event.ReceiptTypeReadPrivate {
		content.ReadPrivate = eventID
	} else {
		return fmt.Errorf("invalid receipt type: %v", receiptType)
	}
	err = h.Client.SetReadMarkers(ctx, roomID, content)
	if err != nil {
		return fmt.Errorf("failed to mark event as read: %w", err)
	}
	if ptr.Val(room.MarkedUnread) {
		err = h.Client.SetRoomAccountData(ctx, roomID, event.AccountDataMarkedUnread.Type, &event.MarkedUnreadEventContent{Unread: false})
		if err != nil {
			return fmt.Errorf("failed to mark room as read: %w", err)
		}
	}
	return nil
}

func (h *HiClient) SetTyping(ctx context.Context, roomID id.RoomID, timeout time.Duration) error {
	_, err := h.Client.UserTyping(ctx, roomID, timeout > 0, timeout)
	return err
}

func (h *HiClient) SetState(
	ctx context.Context,
	roomID id.RoomID,
	evtType event.Type,
	stateKey string,
	content any,
) (id.EventID, error) {
	room, err := h.DB.Room.Get(ctx, roomID)
	if err != nil {
		return "", fmt.Errorf("failed to get room metadata: %w", err)
	} else if room == nil {
		return "", fmt.Errorf("unknown room")
	}
	resp, err := h.Client.SendStateEvent(ctx, room.ID, evtType, stateKey, content)
	if err != nil {
		return "", err
	}
	return resp.EventID, nil
}

func (h *HiClient) Send(
	ctx context.Context,
	roomID id.RoomID,
	evtType event.Type,
	content any,
) (*database.Event, error) {
	return h.send(ctx, roomID, evtType, content, "", false)
}

func (h *HiClient) Resend(ctx context.Context, txnID string) (*database.Event, error) {
	dbEvt, err := h.DB.Event.GetByTransactionID(ctx, txnID)
	if err != nil {
		return nil, fmt.Errorf("failed to get event by transaction ID: %w", err)
	} else if dbEvt == nil {
		return nil, fmt.Errorf("unknown transaction ID")
	} else if dbEvt.ID != "" && !strings.HasPrefix(dbEvt.ID.String(), "~") {
		return nil, fmt.Errorf("event was already sent successfully")
	}
	room, err := h.DB.Room.Get(ctx, dbEvt.RoomID)
	if err != nil {
		return nil, fmt.Errorf("failed to get room metadata: %w", err)
	} else if room == nil {
		return nil, fmt.Errorf("unknown room")
	}
	dbEvt.SendError = ""
	go h.actuallySend(context.WithoutCancel(ctx), room, dbEvt, event.Type{Type: dbEvt.Type, Class: event.MessageEventType})
	return dbEvt, nil
}

func (h *HiClient) send(
	ctx context.Context,
	roomID id.RoomID,
	evtType event.Type,
	content any,
	overrideEditSource string,
	disableEncryption bool,
) (*database.Event, error) {
	room, err := h.DB.Room.Get(ctx, roomID)
	if err != nil {
		return nil, fmt.Errorf("failed to get room metadata: %w", err)
	} else if room == nil {
		return nil, fmt.Errorf("unknown room")
	}
	txnID := "hicli-" + h.Client.TxnID()
	dbEvt := &database.Event{
		RoomID:          room.ID,
		ID:              id.EventID(fmt.Sprintf("~%s", txnID)),
		Sender:          h.Account.UserID,
		Timestamp:       jsontime.UnixMilliNow(),
		Unsigned:        []byte("{}"),
		TransactionID:   txnID,
		DecryptionError: "",
		SendError:       "not sent",
		Reactions:       map[string]int{},
		LastEditRowID:   ptr.Ptr(database.EventRowID(0)),
	}
	if room.EncryptionEvent != nil && evtType != event.EventReaction && !disableEncryption {
		dbEvt.Type = event.EventEncrypted.Type
		dbEvt.DecryptedType = evtType.Type
		dbEvt.Decrypted, err = json.Marshal(content)
		if err != nil {
			return nil, fmt.Errorf("failed to marshal event content: %w", err)
		}
		dbEvt.Content = json.RawMessage("{}")
		dbEvt.RelatesTo, dbEvt.RelationType = database.GetRelatesToFromBytes(dbEvt.Decrypted)
	} else {
		dbEvt.Type = evtType.Type
		dbEvt.Content, err = json.Marshal(content)
		if err != nil {
			return nil, fmt.Errorf("failed to marshal event content: %w", err)
		}
		dbEvt.RelatesTo, dbEvt.RelationType = database.GetRelatesToFromBytes(dbEvt.Content)
	}
	var inlineImages []id.ContentURI
	mautrixEvt := dbEvt.AsRawMautrix()
	dbEvt.LocalContent, inlineImages = h.calculateLocalContent(ctx, dbEvt, mautrixEvt)
	if overrideEditSource != "" && dbEvt.LocalContent != nil {
		dbEvt.LocalContent.EditSource = overrideEditSource
	}
	_, err = h.DB.Event.Insert(ctx, dbEvt)
	if err != nil {
		return nil, fmt.Errorf("failed to insert event into database: %w", err)
	}
	h.cacheMedia(ctx, mautrixEvt, dbEvt.RowID)
	for _, uri := range inlineImages {
		h.addMediaCache(ctx, dbEvt.RowID, uri.CUString(), nil, nil, "")
	}
	ctx = context.WithoutCancel(ctx)
	go func() {
		err := h.SetTyping(ctx, room.ID, 0)
		if err != nil {
			zerolog.Ctx(ctx).Err(err).Msg("Failed to stop typing while sending message")
		}
	}()
	go h.actuallySend(ctx, room, dbEvt, evtType)
	return dbEvt, nil
}

func (h *HiClient) actuallySend(ctx context.Context, room *database.Room, dbEvt *database.Event, evtType event.Type) {
	var err error
	defer func() {
		if dbEvt.SendError != "" {
			err2 := h.DB.Event.UpdateSendError(ctx, dbEvt.RowID, dbEvt.SendError)
			if err2 != nil {
				zerolog.Ctx(ctx).Err(err2).AnErr("send_error", err).
					Msg("Failed to update send error in database after sending failed")
			}
		}
		h.EventHandler(&SendComplete{
			Event: dbEvt,
			Error: err,
		})
	}()
	if dbEvt.Decrypted != nil && len(dbEvt.Content) <= 2 {
		var encryptedContent *event.EncryptedEventContent
		encryptedContent, err = h.Encrypt(ctx, room, evtType, dbEvt.Decrypted)
		if err != nil {
			dbEvt.SendError = fmt.Sprintf("failed to encrypt: %v", err)
			zerolog.Ctx(ctx).Err(err).Msg("Failed to encrypt event")
			return
		}
		evtType = event.EventEncrypted
		dbEvt.MegolmSessionID = encryptedContent.SessionID
		dbEvt.Content, err = json.Marshal(encryptedContent)
		if err != nil {
			dbEvt.SendError = fmt.Sprintf("failed to marshal encrypted content: %v", err)
			zerolog.Ctx(ctx).Err(err).Msg("Failed to marshal encrypted content")
			return
		}
		err = h.DB.Event.UpdateEncryptedContent(ctx, dbEvt)
		if err != nil {
			dbEvt.SendError = fmt.Sprintf("failed to save event after encryption: %v", err)
			zerolog.Ctx(ctx).Err(err).Msg("Failed to save event after encryption")
			return
		}
	}
	var resp *mautrix.RespSendEvent
	resp, err = h.Client.SendMessageEvent(ctx, room.ID, evtType, dbEvt.Content, mautrix.ReqSendEvent{
		Timestamp:     dbEvt.Timestamp.UnixMilli(),
		TransactionID: dbEvt.TransactionID,
		DontEncrypt:   true,
	})
	if err != nil {
		dbEvt.SendError = err.Error()
		err = fmt.Errorf("failed to send event: %w", err)
		return
	}
	dbEvt.ID = resp.EventID
	err = h.DB.Event.UpdateID(ctx, dbEvt.RowID, dbEvt.ID)
	if err != nil {
		err = fmt.Errorf("failed to update event ID in database: %w", err)
	}
}

func (h *HiClient) Encrypt(ctx context.Context, room *database.Room, evtType event.Type, content any) (encrypted *event.EncryptedEventContent, err error) {
	h.encryptLock.Lock()
	defer h.encryptLock.Unlock()
	encrypted, err = h.Crypto.EncryptMegolmEvent(ctx, room.ID, evtType, content)
	if errors.Is(err, crypto.SessionExpired) || errors.Is(err, crypto.NoGroupSession) || errors.Is(err, crypto.SessionNotShared) {
		if err = h.shareGroupSession(ctx, room); err != nil {
			err = fmt.Errorf("failed to share group session: %w", err)
		} else if encrypted, err = h.Crypto.EncryptMegolmEvent(ctx, room.ID, evtType, content); err != nil {
			err = fmt.Errorf("failed to encrypt event after re-sharing group session: %w", err)
		}
	}
	return
}

func (h *HiClient) EnsureGroupSessionShared(ctx context.Context, roomID id.RoomID) error {
	h.encryptLock.Lock()
	defer h.encryptLock.Unlock()
	if session, err := h.CryptoStore.GetOutboundGroupSession(ctx, roomID); err != nil {
		return fmt.Errorf("failed to get previous outbound group session: %w", err)
	} else if session != nil && session.Shared && !session.Expired() {
		return nil
	} else if roomMeta, err := h.DB.Room.Get(ctx, roomID); err != nil {
		return fmt.Errorf("failed to get room metadata: %w", err)
	} else if roomMeta == nil {
		return fmt.Errorf("unknown room")
	} else {
		return h.shareGroupSession(ctx, roomMeta)
	}
}

func (h *HiClient) loadMembers(ctx context.Context, room *database.Room) error {
	if room.HasMemberList {
		return nil
	}
	resp, err := h.Client.Members(ctx, room.ID)
	if err != nil {
		return fmt.Errorf("failed to get room member list: %w", err)
	}
	err = h.DB.DoTxn(ctx, nil, func(ctx context.Context) error {
		entries := make([]*database.CurrentStateEntry, len(resp.Chunk))
		for i, evt := range resp.Chunk {
			dbEvt, err := h.processEvent(ctx, evt, nil, nil, true)
			if err != nil {
				return err
			}
			entries[i] = &database.CurrentStateEntry{
				EventType:  evt.Type,
				StateKey:   *evt.StateKey,
				EventRowID: dbEvt.RowID,
				Membership: event.Membership(evt.Content.Raw["membership"].(string)),
			}
		}
		err := h.DB.CurrentState.AddMany(ctx, room.ID, false, entries)
		if err != nil {
			return err
		}
		return h.DB.Room.Upsert(ctx, &database.Room{
			ID:            room.ID,
			HasMemberList: true,
		})
	})
	if err != nil {
		return fmt.Errorf("failed to process room member list: %w", err)
	}
	return nil
}

func (h *HiClient) shareGroupSession(ctx context.Context, room *database.Room) error {
	err := h.loadMembers(ctx, room)
	if err != nil {
		return err
	}
	shareToInvited := h.shouldShareKeysToInvitedUsers(ctx, room.ID)
	var users []id.UserID
	if shareToInvited {
		users, err = h.ClientStore.GetRoomJoinedOrInvitedMembers(ctx, room.ID)
	} else {
		users, err = h.ClientStore.GetRoomJoinedMembers(ctx, room.ID)
	}
	if err != nil {
		return fmt.Errorf("failed to get room member list: %w", err)
	} else if err = h.Crypto.ShareGroupSession(ctx, room.ID, users); err != nil {
		return fmt.Errorf("failed to share group session: %w", err)
	}
	return nil
}

func (h *HiClient) shouldShareKeysToInvitedUsers(ctx context.Context, roomID id.RoomID) bool {
	historyVisibility, err := h.DB.CurrentState.Get(ctx, roomID, event.StateHistoryVisibility, "")
	if err != nil {
		zerolog.Ctx(ctx).Err(err).Msg("Failed to get history visibility event")
		return false
	}
	mautrixEvt := historyVisibility.AsRawMautrix()
	err = mautrixEvt.Content.ParseRaw(mautrixEvt.Type)
	if err != nil && !errors.Is(err, event.ErrContentAlreadyParsed) {
		zerolog.Ctx(ctx).Err(err).Msg("Failed to parse history visibility event")
		return false
	}
	hv, ok := mautrixEvt.Content.Parsed.(*event.HistoryVisibilityEventContent)
	if !ok {
		zerolog.Ctx(ctx).Warn().Msg("Unexpected parsed content type for history visibility event")
		return false
	}
	return hv.HistoryVisibility == event.HistoryVisibilityInvited ||
		hv.HistoryVisibility == event.HistoryVisibilityShared ||
		hv.HistoryVisibility == event.HistoryVisibilityWorldReadable
}