interface IRequestMessage<T> {

req: string;

command: string;

args: T;

}

interface IReplyMessage {

seq: string;

err: any;

res: any;

}

declare var acquireVsCodeApi: any;

export const vscode = acquireVsCodeApi();

export class MessageHandler {

private _commandHandler: ((message: any) => void) | null;

private lastSentReq: number;

private pendingReplies: any;

constructor(commandHandler: any) {

this._commandHandler = commandHandler;

this.lastSentReq = 0;

this.pendingReplies = Object.create(null);

window.addEventListener('message', this.handleMessage.bind(this));

}

public registerCommandHandler(commandHandler: (message: any) => void) {

this._commandHandler = commandHandler;

}

public async postMessage(message: any): Promise<any> {

let req = String(++this.lastSentReq);

return new Promise<any>((resolve, reject) => {

this.pendingReplies[req] = {

resolve: resolve,

reject: reject

};

message = Object.assign(message, {

req: req

});

vscode.postMessage(message as IRequestMessage<any>);

});

}

// handle message should resolve promises

private handleMessage(event: any) {

const message: IReplyMessage = event.data; // The json data that the extension sent

if (message.seq) {

// this is a reply

let pendingReply = this.pendingReplies[message.seq];

if (pendingReply) {

if (message.err) {

pendingReply.reject(message.err);

} else {

pendingReply.resolve(message.res);

}

return;

}

}

if (this._commandHandler) {

this._commandHandler(message.res);

}

}

}

export function getMessageHandler(handler: ((message: any) => void) | null) {

return new MessageHandler(handler);

}