import { EventEmitter } from "events";

import { ChildProcess } from "child_process";

export interface IpcMessage {

readonly event: string;

readonly args: any[]; // tslint:disable-line no-any

}

export class StdioIpcHandler extends EventEmitter {

private isListening: boolean = false;

public constructor(

private readonly childProcess?: ChildProcess,

) {

super();

}

// tslint:disable-next-line no-any

public on(event: string, cb: (...args: any[]) => void): this {

this.listen();

return super.on(event, cb);

}

// tslint:disable-next-line no-any

public once(event: string, cb: (...args: any[]) => void): this {

this.listen();

return super.once(event, cb);

}

// tslint:disable-next-line no-any

public addListener(event: string, cb: (...args: any[]) => void): this {

this.listen();

return super.addListener(event, cb);

}

// tslint:disable-next-line no-any

public send(event: string, ...args: any[]): void {

const msg: IpcMessage = {

event,

args,

};

const d = JSON.stringify(msg);

if (this.childProcess) {

this.childProcess.stdin.write(d + "\n");

} else {

process.stdout.write(d);

}

}

private listen(): void {

if (this.isListening) {

return;

}

// tslint:disable-next-line no-any

const onData = (data: any): void => {

try {

const d = JSON.parse(data.toString()) as IpcMessage;

this.emit(d.event, ...d.args);

} catch (ex) {

if (!this.childProcess) {

process.stderr.write(`Failed to parse incoming data: ${ex.message}`);

}

}

};

if (this.childProcess) {

this.childProcess.stdout.resume();

this.childProcess.stdout.on("data", onData);

} else {

process.stdin.resume();

process.stdin.on("data", onData);

}

}

}