import { decodeText, encodeText } from "./byte_util";
import { Bytes } from "./rtmt";

const headerLenght = 4

export type Message = {
    channel : string,
    data : Bytes,
}
//
// channel is string, message is byte array
//
export function encode(message : Message) {
    const {channel, data} = message
    const channelLenght = channel.length
    const messageLenght = data.length
    const totalLenght = headerLenght + channelLenght + messageLenght

    const buffer = new ArrayBuffer(totalLenght);
    const view = new DataView(buffer);

    view.setUint32(0, channelLenght);

    const channelBytes = encodeText(channel)

    let count = headerLenght
    channelBytes.forEach((byte : any)=>{
         view.setUint8(count, byte)
        count++
    })

    for (const byte of data) {
        view.setUint8(count, byte)
        count++
    }

    return buffer
}

// 
// return { channel :  string, message :  byte array} 
//
export function decode(bytes : Bytes) : Message {
    const view = new DataView(bytes.buffer);

    const channelLenght = view.getUint32(0)


    const channel = decodeText(
        bytes.slice(headerLenght, headerLenght + channelLenght))

    const message =  bytes.slice(headerLenght + channelLenght)

    return {
        "channel": channel,
        "data": message,
    }
}