openethereum/js/src/abi/spec/event/event.js

// Copyright 2015, 2016 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

import Decoder from '../../decoder/decoder';
import DecodedLog from './decodedLog';
import DecodedLogParam from './decodedLogParam';
import EventParam from './eventParam';
import { asAddress } from '../../util/sliceAs';
import { eventSignature } from '../../util/signature';

export default class Event {
  constructor (abi) {
    this._name = abi.name;
    this._inputs = EventParam.toEventParams(abi.inputs || []);
    this._anonymous = !!abi.anonymous;

    const { id, signature } = eventSignature(this._name, this.inputParamTypes());
    this._id = id;
    this._signature = signature;
  }

  get name () {
    return this._name;
  }

  get id () {
    return this._id;
  }

  get inputs () {
    return this._inputs;
  }

  get anonymous () {
    return this._anonymous;
  }

  get signature () {
    return this._signature;
  }

  inputParamTypes () {
    return this._inputs.map((input) => input.kind);
  }

  inputParamNames () {
    return this._inputs.map((input) => input.name);
  }

  indexedParams (indexed) {
    return this._inputs.filter((input) => input.indexed === indexed);
  }

  decodeLog (topics, data) {
    const topicParams = this.indexedParams(true);
    const dataParams = this.indexedParams(false);

    let address;
    let toSkip;

    if (!this.anonymous) {
      address = asAddress(topics[0]);
      toSkip = 1;
    } else {
      toSkip = 0;
    }

    const topicTypes = topicParams.map((param) => param.kind);
    const flatTopics = topics
      .filter((topic, idx) => idx >= toSkip)
      .map((topic) => {
        return (topic.substr(0, 2) === '0x')
          ? topic.substr(2)
          : topic;
      }).join('');
    const topicTokens = Decoder.decode(topicTypes, flatTopics);

    if (topicTokens.length !== (topics.length - toSkip)) {
      throw new Error('Invalid topic data');
    }

    const dataTypes = dataParams.map((param) => param.kind);
    const dataTokens = Decoder.decode(dataTypes, data);

    const namedTokens = {};

    topicParams.forEach((param, idx) => {
      namedTokens[param.name] = topicTokens[idx];
    });
    dataParams.forEach((param, idx) => {
      namedTokens[param.name] = dataTokens[idx];
    });

    const inputParamTypes = this.inputParamTypes();
    const decodedParams = this.inputParamNames()
      .map((name, idx) => new DecodedLogParam(name, inputParamTypes[idx], namedTokens[name]));

    return new DecodedLog(decodedParams, address);
  }
}