flexor-apps/src/communicator/index.ts

import { Post } from '../types'

export interface MessageContent {
    [key: string]: any
    height?: number
    parent?: Post
}

export interface IncomingMessageData {
    name: string
    content: MessageContent
    publicKey: string
}

export interface OutgoingMessageData {
    name: string
    content?: MessageContent
    error?: string
    settings?: object
}

interface Listener {
    resolve: (value?: MessageContent | PromiseLike<MessageContent>) => void
    reject: (reason: any) => void
    once: boolean
}

interface ListenerCollection {
    [name: string]: Listener
}

type PostOptions = Post

export class Communicator {
    private origin = 'http://localhost:8080'
    private publicKey: string
    private listeners: ListenerCollection

    constructor(publicKey: string) {
        this.publicKey = publicKey
        this.listeners = {}

        window.addEventListener('message', (event: MessageEvent) => {
            if (event.origin !== this.origin) return

            try {
                const data = JSON.parse(event.data) as OutgoingMessageData
                this.emit(data)
            } catch (err) {
                console.error(err)
                return
            }
        }, false)
    }

    private emit(data: OutgoingMessageData) {
        const listener = this.listeners[data.name]

        if (listener) {
            if (data.content) listener.resolve(data.content)
            if (data.error) listener.reject(data.error)
            if (listener.once) delete this.listeners[data.name]
        }
    }

    private async postAndReceive(name: string, content?: MessageContent) {
        if (window.parent) {
            window.parent.postMessage(JSON.stringify({
                name,
                content,
                publicKey: this.publicKey,
            }), this.origin)

            return new Promise<MessageContent>((resolve, reject) => {
                this.listeners[name] = {
                    resolve,
                    reject,
                    once: true,
                }
            })
        }
    }

    async init() {
        return this.postAndReceive('init')
    }

    async setHeight(height: number) {
        return this.postAndReceive('setHeight', { height })
    }

    async post(options: PostOptions) {
        return this.postAndReceive('post', options)
    }
}