trezor-link/lib/lowlevel/protobuf/message_decoder.js.flow

Trezor Link for browser

/* @flow */

"use strict";

// Helper module for converting Trezor's raw input to
// ProtoBuf's message and from there to regular JSON to trezor.js

import * as ProtoBuf from "protobufjs-old-fixed-webpack";
const ByteBuffer = ProtoBuf.ByteBuffer;
const Long = ProtoBuf.Long;

import {Messages} from "./messages.js";

export class MessageDecoder {
  // Builders, generated by reading config
  messages: Messages;
  // message type number
  type: number;
  // raw data to push to Trezor
  data: ArrayBuffer;

  constructor(messages: Messages, type: number, data: ArrayBuffer) {
    this.type = type;
    this.data = data;
    this.messages = messages;
  }

  // Returns an info about this message,
  // which includes the constructor object and a name
  _messageInfo() : MessageInfo {
    const r = this.messages.messagesByType[this.type];
    if (r == null) {
      throw new Error(`Method type not found - ${this.type}`);
    }
    return new MessageInfo(r.constructor, r.name);
  }

  // Returns the name of the message
  messageName() : string {
    return this._messageInfo().name;
  }

  // Returns the actual decoded message, as a ProtoBuf.js object
  _decodedMessage() : ProtoBuf.Builder.Message {
    const constructor = this._messageInfo().messageConstructor;
    return constructor.decode(this.data);
  }

  // Returns the message decoded to JSON, that could be handed back
  // to trezor.js
  decodedJSON() : Object {
    const decoded = this._decodedMessage();
    const converted = messageToJSON(decoded);

    return JSON.parse(JSON.stringify(converted));
  }
}

class MessageInfo {
  messageConstructor: ProtoBuf.Builder.Message;
  name: string;
  constructor(messageConstructor: ProtoBuf.Builder.Message, name: string) {
    this.messageConstructor = messageConstructor;
    this.name = name;
  }
}

// Converts any ProtoBuf message to JSON in Trezor.js-friendly format
function messageToJSON(message: ProtoBuf.Builder.Message) : Object {
  const res = {};
  const meta = message.$type;

  for (const key in message) {
    const value = message[key];
    if (typeof value === `function`) {
      // ignoring
    } else if (value instanceof ByteBuffer) {
      const hex = value.toHex();
      res[key] = hex;
    } else if (value instanceof Long) {
      const num = value.toNumber();
      res[key] = num;
    } else if (Array.isArray(value)) {
      const decodedArr = value.map((i) => {
        if (typeof i === `object`) {
          return messageToJSON(i);
        } else {
          return i;
        }
      });
      res[key] = decodedArr;
    } else if (value instanceof ProtoBuf.Builder.Message) {
      res[key] = messageToJSON(value);
    } else if (meta._fieldsByName[key].type.name === `enum`) {
      if (value == null) {
        res[key] = null;
      } else {
        const enumValues = meta._fieldsByName[key].resolvedType.getChildren();
        res[key] = enumValues.find(e => e.id === value).name;
      }
    } else {
      res[key] = value;
    }
  }
  return res;
}