// ******************************************************************************
// Copyright 2024 TypeFox GmbH
// This program and the accompanying materials are made available under the
// terms of the MIT License, which is available in the project root.
// ******************************************************************************

import { Deferred, DisposableCollection, ProtocolBroadcastConnection } from 'open-collaboration-protocol';
import * as Y from 'yjs';
import * as monaco from 'monaco-editor';
import * as awarenessProtocol from 'y-protocols/awareness';
import * as types from 'open-collaboration-protocol';
import { LOCAL_ORIGIN, OpenCollaborationYjsProvider, YTextChange, YTextChangeDelta } from 'open-collaboration-yjs';
import { createMutex } from 'lib0/mutex';
import { debounce } from 'lodash';
import { MonacoCollabCallbacks } from './monaco-api.js';
import { DisposablePeer } from './collaboration-peer.js';

export type UsersChangeEvent = () => void;
export type FileNameChangeEvent = (fileName: string) => void;

export interface Disposable {
    dispose(): void;
}

export interface CollaborationInstanceOptions {
    connection: ProtocolBroadcastConnection;
    host: boolean;
    callbacks: MonacoCollabCallbacks;
    editor?: monaco.editor.IStandaloneCodeEditor;
    roomClaim: types.CreateRoomResponse | types.JoinRoomResponse;
}

export class CollaborationInstance implements Disposable {
    protected readonly yjs: Y.Doc = new Y.Doc();
    protected readonly yjsAwareness: awarenessProtocol.Awareness;
    protected readonly yjsProvider: OpenCollaborationYjsProvider;
    protected readonly yjsMutex = createMutex();

    protected readonly identity = new Deferred<types.Peer>();
    protected readonly documentDisposables = new Map<string, DisposableCollection>();
    protected readonly peers = new Map<string, DisposablePeer>();
    protected readonly throttles = new Map<string, () => void>();
    protected readonly decorations = new Map<DisposablePeer, monaco.editor.IEditorDecorationsCollection>();
    protected readonly usersChangedCallbacks: UsersChangeEvent[] = [];
    protected readonly fileNameChangeCallbacks: FileNameChangeEvent[] = [];

    protected currentPath?: string;
    protected stopPropagation = false;
    protected _following?: string;
    protected _fileName: string;
    protected previousFileName?: string;
    protected _workspaceName: string;

    protected connection: ProtocolBroadcastConnection;

    get following(): string | undefined {
        return this._following;
    }

    get connectedUsers(): DisposablePeer[] {
        return Array.from(this.peers.values());
    }

    get ownUserData(): Promise<types.Peer> {
        return this.identity.promise;
    }

    get isHost(): boolean {
        return this.options.host;
    }

    get host(): types.Peer | undefined {
        return 'host' in this.options.roomClaim ? this.options.roomClaim.host : undefined;
    }

    get roomId(): string {
        return this.options.roomClaim.roomId;
    }

    get fileName(): string {
        return this._fileName;
    }

    get workspaceName(): string {
        return this._workspaceName;
    }

    set workspaceName(_workspaceName: string) {
        this._workspaceName = _workspaceName;
    }

    /**
     * access token for the room. allow to join or reconnect as host
     */
    get roomToken(): string {
        return this.options.roomClaim.roomToken;
    }

    onUsersChanged(callback: UsersChangeEvent) {
        this.usersChangedCallbacks.push(callback);
    }

    onFileNameChange(callback: FileNameChangeEvent) {
        this.fileNameChangeCallbacks.push(callback);
    }

    constructor(protected options: CollaborationInstanceOptions) {
        this.connection = options.connection;
        this.yjsAwareness = new awarenessProtocol.Awareness(this.yjs);
        this.yjsProvider = new OpenCollaborationYjsProvider(this.options.connection, this.yjs, this.yjsAwareness, {
            resyncTimer: 10_000
        });
        this.yjsProvider.connect();

        this._fileName = 'myFile.txt';
        this._workspaceName = this.roomId;

        this.setupConnectionHandlers();
        this.setupFileSystemHandlers();
        this.options.editor && this.registerEditorEvents();
    }

    private setupConnectionHandlers(): void {
        this.connection.peer.onJoinRequest(async (_, user) => {
            const result = await this.options.callbacks.onUserRequestsAccess(user);
            return result ? {
                workspace: {
                    name: this.workspaceName,
                    folders: [this.workspaceName]
                }
            } : undefined;
        });

        this.connection.room.onJoin(async (_, peer) => {
            this.peers.set(peer.id, new DisposablePeer(this.yjsAwareness, peer));
            const initData: types.InitData = {
                protocol: '0.0.1',
                host: await this.identity.promise,
                guests: Array.from(this.peers.values()).map(e => e.peer),
                capabilities: {},
                permissions: { readonly: false },
                workspace: {
                    name: this.workspaceName,
                    folders: [this.workspaceName]
                }
            };
            this.connection.peer.init(peer.id, initData);
            this.notifyUsersChanged();
        });

        this.connection.room.onLeave(async (_, peer) => {
            const disposable = this.peers.get(peer.id);
            if (disposable) {
                this.peers.delete(peer.id);
                this.notifyUsersChanged();
            }
            this.rerenderPresence();
        });

        this.connection.peer.onInfo((_, peer) => {
            this.yjsAwareness.setLocalStateField('peer', peer.id);
            this.identity.resolve(peer);
        });

        this.connection.peer.onInit(async (_, initData) => {
            await this.initialize(initData);
        });
    }

    private setupFileSystemHandlers(): void {
        this.connection.fs.onReadFile(this.handleReadFile.bind(this));
        this.connection.fs.onStat(this.handleStat.bind(this));
        this.connection.fs.onReaddir(this.handleReaddir.bind(this));
        this.connection.fs.onChange(this.handleFileChange.bind(this));
    }

    private async handleReadFile(_: unknown, path: string): Promise<{ content: Uint8Array }> {
        if (path === this._fileName && this.options.editor) {
            const text = this.options.editor.getModel()?.getValue();
            const encoder = new TextEncoder();
            const content = encoder.encode(text);
            return { content };
        }
        throw new Error('Could not read file');
    }

    private async handleStat(_: unknown, path: string): Promise<{ type: types.FileType; mtime: number; ctime: number; size: number }> {
        return {
            type: path === this.workspaceName ? types.FileType.Directory : types.FileType.File,
            mtime: 0,
            ctime: 0,
            size: 0
        };
    }

    private async handleReaddir(_: unknown, path: string): Promise<Record<string, types.FileType>> {
        const uri = this.getResourceUri(path);
        if (uri) {
            return {
                [this._fileName]: types.FileType.File
            };
        }
        throw new Error('Could not read directory');
    }

    private handleFileChange(_: unknown, change: types.FileChangeEvent): void {
        const deleteChange = change.changes.find(c => c.type === types.FileChangeEventType.Delete);
        const createChange = change.changes.find(c => c.type === types.FileChangeEventType.Create);
        if (deleteChange && createChange) {
            this._fileName = createChange.path;
            const model = this.options.editor?.getModel();
            if (model) {
                this.registerTextDocument(model);
            }
        }
    }

    private notifyUsersChanged(): void {
        this.usersChangedCallbacks.forEach(callback => callback());
    }

    private notifyFileNameChanged(fileName: string): void {
        this.fileNameChangeCallbacks.forEach(callback => callback(fileName));
    }

    setEditor(editor: monaco.editor.IStandaloneCodeEditor): void {
        this.options.editor = editor;
        this.registerEditorEvents();
    }

    async setFileName(fileName: string): Promise<void> {
        const oldFileName = this._fileName;
        this._fileName = fileName;
        const model = this.options.editor?.getModel();
        if (model) {
            await this.registerTextDocument(model);
            this.connection.fs.change({
                changes: [
                    {
                        type: types.FileChangeEventType.Create,
                        path: fileName
                    },
                    {
                        type: types.FileChangeEventType.Delete,
                        path: oldFileName
                    }
                ]
            });
        }
    }

    dispose() {
        this.peers.clear();
        this.documentDisposables.forEach(e => e.dispose());
        this.documentDisposables.clear();
    }

    leaveRoom() {
        this.options.connection.room.leave();
    }

    getCurrentConnection(): ProtocolBroadcastConnection {
        return this.options.connection;
    }

    protected pushDocumentDisposable(path: string, disposable: Disposable) {
        let disposables = this.documentDisposables.get(path);
        if (!disposables) {
            disposables = new DisposableCollection();
            this.documentDisposables.set(path, disposables);
        }
        disposables.push(disposable);
    }

    protected registerEditorEvents(): void {
        if (!this.options.editor) {
            return;
        }
        const text = this.options.editor.getModel();
        if (text) {
            this.registerTextDocument(text);
        }

        this.options.editor.onDidChangeModelContent(event => {
            if (text && !this.stopPropagation) {
                this.updateTextDocument(event, text);
            }
        });

        this.options.editor.onDidChangeCursorSelection(() => {
            if (this.options.editor && !this.stopPropagation) {
                this.updateTextSelection(this.options.editor);
            }
        });

        const awarenessDebounce = debounce(() => {
            this.rerenderPresence();
        }, 2000);

        this.yjsAwareness.on('change', async (_: unknown, origin: string) => {
            if (origin !== LOCAL_ORIGIN) {
                this.updateFollow();
                this.rerenderPresence();
                awarenessDebounce();
            }
        });
    }

    followUser(id?: string) {
        this._following = id;
        if (id) {
            this.updateFollow();
        }
    }

    protected updateFollow(): void {
        if (this._following) {
            let userState: types.ClientAwareness | undefined = undefined;
            const states = this.yjsAwareness.getStates() as Map<number, types.ClientAwareness>;
            for (const state of states.values()) {
                const peer = this.peers.get(state.peer);
                if (peer?.peer.id === this._following) {
                    userState = state;
                }
            }
            if (userState) {
                if (types.ClientTextSelection.is(userState.selection)) {
                    this.followSelection(userState.selection);
                }
            }
        }
    }

    protected async followSelection(selection: types.ClientTextSelection): Promise<void> {
        if (!this.options.editor) {
            return;
        }
        const uri = this.getResourceUri(selection.path);
        const text = this.yjs.getText(selection.path);

        const prevPath = this.currentPath;
        this.currentPath = selection.path;
        if (prevPath !== selection.path) {
            this.stopPropagation = true;
            this.options.editor.setValue(text.toString());
            this.stopPropagation = false;
        }

        const filename = this.getHostPath(selection.path);
        if (this._fileName !== filename) {
            this._fileName = filename;
            this.previousFileName = filename;
            this.notifyFileNameChanged(this._fileName);
        }

        this.registerTextObserver(selection.path, this.options.editor.getModel()!, text);
        if (uri && selection.visibleRanges && selection.visibleRanges.length > 0) {
            const visibleRange = selection.visibleRanges[0];
            const range = new monaco.Range(visibleRange.start.line, visibleRange.start.character, visibleRange.end.line, visibleRange.end.character);
            this.options.editor && this.options.editor.revealRange(range);
        }
    }

    protected updateTextSelection(editor: monaco.editor.IStandaloneCodeEditor): void {
        const document = editor.getModel();
        const selections = editor.getSelections();
        if (!document || !selections) {
            return;
        }
        const path = this.currentPath;
        if (path) {
            const ytext = this.yjs.getText(path);
            const textSelections: types.RelativeTextSelection[] = [];
            for (const selection of selections) {
                const start = document.getOffsetAt(selection.getStartPosition());
                const end = document.getOffsetAt(selection.getEndPosition());
                const direction = selection.getDirection() === monaco.SelectionDirection.RTL
                    ? types.SelectionDirection.RightToLeft
                    : types.SelectionDirection.LeftToRight;
                const editorSelection: types.RelativeTextSelection = {
                    start: Y.createRelativePositionFromTypeIndex(ytext, start),
                    end: Y.createRelativePositionFromTypeIndex(ytext, end),
                    direction
                };
                textSelections.push(editorSelection);
            }
            const textSelection: types.ClientTextSelection = {
                path,
                textSelections,
                visibleRanges: editor.getVisibleRanges().map(range => ({
                    start: {
                        line: range.startLineNumber,
                        character: range.startColumn
                    },
                    end: {
                        line: range.endLineNumber,
                        character: range.endColumn
                    }
                }))
            };
            this.setSharedSelection(textSelection);
        }
    }

    protected async registerTextDocument(document: monaco.editor.ITextModel): Promise<void> {
        const uri = this.getResourceUri(`${this._workspaceName}/${this._fileName}`);
        const path = this.getProtocolPath(uri);
        if (!this.currentPath || this.currentPath !== path) {
            this.currentPath = path;
        }
        if (path) {
            const text = document.getValue();
            const yjsText = this.yjs.getText(path);
            let ytextContent = '';
            if (this.isHost) {
                this.yjs.transact(() => {
                    yjsText.delete(0, yjsText.length);
                    yjsText.insert(0, text);
                });
                ytextContent = yjsText.toString();
            } else {
                ytextContent = await this.readFile();
                if (this._fileName !== this.previousFileName) {
                    this.previousFileName = this._fileName;
                    this.notifyFileNameChanged(this._fileName);
                }
            }
            if (text !== ytextContent) {
                this.yjsMutex(() => {
                    document.setValue(ytextContent);
                });
            }
            this.registerTextObserver(path, document, yjsText);
        }
    }

    protected registerTextObserver(path: string, document: monaco.editor.ITextModel, yjsText: Y.Text): void {
        const textObserver = this.documentDisposables.get(path);
        if (textObserver) {
            textObserver.dispose();
        }

        const resyncThrottle = this.getOrCreateThrottle(path, document);
        const observer = (textEvent: Y.YTextEvent) => {
            this.yjsMutex(async () => {
                if (this.options.editor) {
                    const changes = YTextChangeDelta.toChanges(textEvent.delta);
                    const edits = this.createEditsFromTextEvent(changes, document);
                    this.updateDocument(document, edits);
                    resyncThrottle();
                }
            });
        };
        yjsText.observe(observer);
        this.pushDocumentDisposable(path, { dispose: () => yjsText.unobserve(observer) });
    }

    protected updateDocument(document: monaco.editor.ITextModel, edits: monaco.editor.IIdentifiedSingleEditOperation[]): void {
        document.pushStackElement();
        document.pushEditOperations(null, edits, () => null);
        document.pushStackElement();
    }

    private createEditsFromTextEvent(changes: YTextChange[], document: monaco.editor.ITextModel): monaco.editor.IIdentifiedSingleEditOperation[] {
        const edits: monaco.editor.IIdentifiedSingleEditOperation[] = [];
        changes.forEach(change => {
            const start = document.getPositionAt(change.start);
            const end = document.getPositionAt(change.end);
            edits.push({
                range: new monaco.Range(start.lineNumber, start.column, end.lineNumber, end.column),
                text: change.text
            });
        });
        return edits;
    }

    protected updateTextDocument(event: monaco.editor.IModelContentChangedEvent, document: monaco.editor.ITextModel): void {
        const path = this.currentPath;
        if (path) {
            this.yjsMutex(() => {
                const ytext = this.yjs.getText(path);
                this.yjs.transact(() => {
                    for (const change of event.changes) {
                        ytext.delete(change.rangeOffset, change.rangeLength);
                        ytext.insert(change.rangeOffset, change.text);
                    }
                });
                this.getOrCreateThrottle(path, document)();
            });
        }
    }

    protected getOrCreateThrottle(path: string, document: monaco.editor.ITextModel): () => void {
        let value = this.throttles.get(path);
        if (!value) {
            value = debounce(() => {
                this.yjsMutex(() => {
                    const yjsText = this.yjs.getText(path);
                    const newContent = yjsText.toString();
                    if (newContent !== document.getValue()) {
                        this.updateDocumentContent(document, newContent);
                    }
                });
            }, 100, {
                leading: false,
                trailing: true
            });
            this.throttles.set(path, value);
        }
        return value;
    }

    private updateDocumentContent(document: monaco.editor.ITextModel, newContent: string): void {
        this.yjsMutex(() => {
            if (this.options.editor) {
                const edits: monaco.editor.IIdentifiedSingleEditOperation[] = [{
                    range: document.getFullModelRange(),
                    text: newContent
                }];
                this.updateDocument(document, edits);
            }
        });
    }

    protected rerenderPresence() {
        const states = this.yjsAwareness.getStates() as Map<number, types.ClientAwareness>;
        for (const [clientID, state] of states.entries()) {
            if (clientID === this.yjs.clientID) {
                // Ignore own awareness state
                continue;
            }
            const peerId = state.peer;
            const peer = this.peers.get(peerId);
            if (!state.selection || !peer) {
                continue;
            }
            if (!types.ClientTextSelection.is(state.selection)) {
                continue;
            }
            const { path, textSelections } = state.selection;
            const selection = textSelections[0];
            if (!selection) {
                continue;
            }
            const uri = this.getResourceUri(path);
            if (uri && this.options.editor) {
                const model = this.options.editor.getModel();
                const forward = selection.direction === 1;
                let startIndex = Y.createAbsolutePositionFromRelativePosition(selection.start, this.yjs);
                let endIndex = Y.createAbsolutePositionFromRelativePosition(selection.end, this.yjs);
                if (model && startIndex && endIndex) {
                    if (startIndex.index > endIndex.index) {
                        [startIndex, endIndex] = [endIndex, startIndex];
                    }
                    const start = model.getPositionAt(startIndex.index);
                    const end = model.getPositionAt(endIndex.index);
                    const inverted = (forward && end.lineNumber === 1) || (!forward && start.lineNumber === 1);
                    const range: monaco.IRange = {
                        startLineNumber: start.lineNumber,
                        startColumn: start.column,
                        endLineNumber: end.lineNumber,
                        endColumn: end.column
                    };
                    const contentClassNames: string[] = [peer.decoration.cursorClassName];
                    if (inverted) {
                        contentClassNames.push(peer.decoration.cursorInvertedClassName);
                    }
                    this.setDecorations(peer, [{
                        range,
                        options: {
                            className: peer.decoration.selectionClassName,
                            beforeContentClassName: !forward ? contentClassNames.join(' ') : undefined,
                            afterContentClassName: forward ? contentClassNames.join(' ') : undefined,
                            stickiness: monaco.editor.TrackedRangeStickiness.NeverGrowsWhenTypingAtEdges
                        }
                    }]);
                }
            }
        }
    }

    protected setDecorations(peer: DisposablePeer, decorations: monaco.editor.IModelDeltaDecoration[]): void {
        if (this.decorations.has(peer)) {
            this.decorations.get(peer)?.set(decorations);
        } else if (this.options.editor) {
            this.decorations.set(peer, this.options.editor.createDecorationsCollection(decorations));
        }
    }

    protected setSharedSelection(selection?: types.ClientSelection): void {
        this.yjsAwareness.setLocalStateField('selection', selection);
    }

    protected updateSelectionPath(newPath: string): void {
        const currentState = this.yjsAwareness.getLocalState() as types.ClientAwareness;
        if (currentState?.selection && types.ClientTextSelection.is(currentState.selection)) {
            const newSelection: types.ClientTextSelection = {
                ...currentState.selection,
                path: newPath
            };
            this.setSharedSelection(newSelection);
        }
    }

    protected createSelectionFromRelative(selection: types.RelativeTextSelection, model: monaco.editor.ITextModel): monaco.Selection | undefined {
        const start = Y.createAbsolutePositionFromRelativePosition(selection.start, this.yjs);
        const end = Y.createAbsolutePositionFromRelativePosition(selection.end, this.yjs);
        if (start && end) {
            let anchor = model.getPositionAt(start.index);
            let head = model.getPositionAt(end.index);
            if (selection.direction === types.SelectionDirection.RightToLeft) {
                [anchor, head] = [head, anchor];
            }
            return new monaco.Selection(anchor.lineNumber, anchor.column, head.lineNumber, head.column);
        }
        return undefined;
    }

    protected getHostPath(path: string): string {
        // When creating a URI as a guest, we always prepend it with the name of the workspace
        // This just removes the workspace name from the path to get the path expected by the protocol
        const subpath = path.substring(1).split('/');
        return subpath.slice(1).join('/');
    }

    async initialize(data: types.InitData): Promise<void> {
        for (const peer of [data.host, ...data.guests]) {
            this.peers.set(peer.id, new DisposablePeer(this.yjsAwareness, peer));
        }
        this.notifyUsersChanged();
    }

    getProtocolPath(uri?: monaco.Uri): string | undefined {
        if (!uri) {
            return undefined;
        }
        return uri.path.startsWith('/') ? uri.path.substring(1) : uri.path;
    }

    getResourceUri(path?: string): monaco.Uri | undefined {
        return new monaco.Uri().with({ path });
    }

    async readFile(): Promise<string> {
        if (!this.currentPath) {
            return '';
        }
        const path = this.getHostPath(this.currentPath);

        if (this.yjs.share.has(path)) {
            const stringValue = this.yjs.getText(path);
            return stringValue.toString();
        } else {
            const file = await this.connection.fs.readFile(this.host?.id, path);
            const decoder = new TextDecoder();
            return decoder.decode(file.content);
        }
    }
}