ethers.js/providers/provider.js

'use strict';

var inherits = require('inherits');

var XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest;

var networks = require('./networks.json');

var utils = (function() {
    var convert = require('ethers-utils/convert');
    return {
        defineProperty: require('ethers-utils/properties').defineProperty,

        getAddress: require('ethers-utils/address').getAddress,
        getContractAddress: require('ethers-utils/contract-address').getContractAddress,

        bigNumberify: require('ethers-utils/bignumber').bigNumberify,
        arrayify: convert.arrayify,

        hexlify: convert.hexlify,
        isHexString: convert.isHexString,

        concat: convert.concat,
        stripZeros: convert.stripZeros,

        namehash: require('ethers-utils/namehash'),

        toUtf8String: require('ethers-utils/utf8').toUtf8String,

        RLP: require('ethers-utils/rlp'),
    }
})();

function copyObject(obj) {
    var result = {};
    for (var key in obj) { result[key] = obj[key]; }
    return result;
}

function check(format, object) {
    var result = {};
    for (var key in format) {
        try {
            var value = format[key](object[key]);
            if (value !== undefined) { result[key] = value; }
        } catch (error) {
            error.checkKey = key;
            error.checkValue = object[key];
            throw error;
        }
    }
    return result;
}

function allowNull(check, nullValue) {
    return (function(value) {
        if (value == null) { return nullValue; }
        return check(value);
    });
}

function allowFalsish(check, replaceValue) {
    return (function(value) {
        if (!value) { return replaceValue; }
        return check(value);
    });
}

function arrayOf(check) {
    return (function(array) {
        if (!Array.isArray(array)) { throw new Error('not an array'); }

        var result = [];

        array.forEach(function(value) {
            result.push(check(value));
        });

        return result;
    });
}

function checkHash(hash) {
    if (!utils.isHexString(hash) || hash.length !== 66) {
        throw new Error('invalid hash - ' + hash);
    }
    return hash;
}

function checkNumber(number) {
    return utils.bigNumberify(number).toNumber();
}

function checkBoolean(value) {
    if (typeof(value) === 'boolean') { return value; }
    if (typeof(value) === 'string') {
        if (value === 'true') { return true; }
        if (value === 'false') { return false; }
    }
    throw new Error('invaid boolean - ' + value);
}

function checkUint256(uint256) {
    if (!utils.isHexString(uint256)) {
        throw new Error('invalid uint256');
    }
    while (uint256.length < 66) {
        uint256 = '0x0' + uint256.substring(2);
    }
    return uint256;
}

function checkString(string) {
    if (typeof(string) !== 'string') { throw new Error('invalid string'); }
    return string;
}

function checkBlockTag(blockTag) {
    if (blockTag == null) { return 'latest'; }

    if (blockTag === 'earliest') { return '0x0'; }

    if (blockTag === 'latest' || blockTag === 'pending') {
        return blockTag;
    }

    if (typeof(blockTag) === 'number') {
        return utils.hexlify(blockTag);
    }

    if (utils.isHexString(blockTag)) { return blockTag; }

    throw new Error('invalid blockTag');
}

var formatBlock = {
    hash: checkHash,
    parentHash: checkHash,
    number: checkNumber,

    timestamp: checkNumber,
    nonce: allowNull(utils.hexlify),
    difficulty: allowNull(checkNumber),

    gasLimit: utils.bigNumberify,
    gasUsed: utils.bigNumberify,

    miner: utils.getAddress,
    extraData: utils.hexlify,

    //transactions: allowNull(arrayOf(checkTransaction)),
    transactions: allowNull(arrayOf(checkHash)),

    //transactionRoot: checkHash,
    //stateRoot: checkHash,
    //sha3Uncles: checkHash,

    //logsBloom: utils.hexlify,
};

function checkBlock(block) {
    if (block.author != null && block.miner == null) {
        block.miner = block.author;
    }
    return check(formatBlock, block);
}


var formatTransaction = {
   hash: checkHash,

   blockHash: allowNull(checkHash, null),
   blockNumber: allowNull(checkNumber, null),
   transactionIndex: allowNull(checkNumber, null),

   from: utils.getAddress,

   gasPrice: utils.bigNumberify,
   gasLimit: utils.bigNumberify,
   to: allowNull(utils.getAddress, null),
   value: utils.bigNumberify,
   nonce: checkNumber,
   data: utils.hexlify,

   r: allowNull(checkUint256),
   s: allowNull(checkUint256),
   v: allowNull(checkNumber),

   creates: allowNull(utils.getAddress, null),

   raw: allowNull(utils.hexlify),
};

function checkTransaction(transaction) {

    // Rename gas to gasLimit
    if (transaction.gas != null && transaction.gasLimit == null) {
        transaction.gasLimit = transaction.gas;
    }

    // Some clients (TestRPC) do strange things like return 0x0 for the
    // 0 address; correct this to be a real address
    if (transaction.to && utils.bigNumberify(transaction.to).isZero()) {
        transaction.to = '0x0000000000000000000000000000000000000000';
    }

    // Rename input to data
    if (transaction.input != null && transaction.data == null) {
        transaction.data = transaction.input;
    }

    // If to and creates are empty, populate the creates from the transaction
    if (transaction.to == null && transaction.creates == null) {
        transaction.creates = utils.getContractAddress(transaction);
    }

    if (!transaction.raw) {

        // Very loose providers (e.g. TestRPC) don't provide a signature or raw
        if (transaction.v && transaction.r && transaction.s) {
            var raw = [
                utils.stripZeros(utils.hexlify(transaction.nonce)),
                utils.stripZeros(utils.hexlify(transaction.gasPrice)),
                utils.stripZeros(utils.hexlify(transaction.gasLimit)),
                (transaction.to || "0x"),
                utils.stripZeros(utils.hexlify(transaction.value || '0x')),
                utils.hexlify(transaction.data || '0x'),
                utils.stripZeros(utils.hexlify(transaction.v || '0x')),
                utils.stripZeros(utils.hexlify(transaction.r)),
                utils.stripZeros(utils.hexlify(transaction.s)),
            ];

            transaction.raw = utils.RLP.encode(raw);
        }
    }


    var result = check(formatTransaction, transaction);

    var networkId = transaction.networkId;

    if (utils.isHexString(networkId)) {
        networkId = utils.bigNumberify(networkId).toNumber();
    }

    if (typeof(networkId) !== 'number' && result.v != null) {
        networkId = (result.v - 35) / 2;
        if (networkId < 0) { networkId = 0; }
        networkId = parseInt(networkId);
    }

    if (typeof(networkId) !== 'number') { networkId = 0; }

    result.networkId = networkId;

    // 0x0000... should actually be null
    if (result.blockHash && result.blockHash.replace(/0/g, '') === 'x') {
        result.blockHash = null;
    }

    return result;
}

var formatTransactionRequest = {
    from: allowNull(utils.getAddress),
    nonce: allowNull(checkNumber),
    gasLimit: allowNull(utils.bigNumberify),
    gasPrice: allowNull(utils.bigNumberify),
    to: allowNull(utils.getAddress),
    value: allowNull(utils.bigNumberify),
    data: allowNull(utils.hexlify),
};

function checkTransactionRequest(transaction) {
    return check(formatTransactionRequest, transaction);
}

var formatTransactionReceiptLog = {
    transactionLogIndex: allowNull(checkNumber),
    transactionIndex: checkNumber,
    blockNumber: checkNumber,
    transactionHash: checkHash,
    address: utils.getAddress,
    // @TODO: Next major release remove this
    type: allowNull(checkString),
    topics: arrayOf(checkHash),
    data: utils.hexlify,
    logIndex: checkNumber,
    blockHash: checkHash,
};

function checkTransactionReceiptLog(log) {
    return check(formatTransactionReceiptLog, log);
}

var formatTransactionReceipt = {
    contractAddress: allowNull(utils.getAddress, null),
    transactionIndex: checkNumber,
    root: allowNull(checkHash),
    gasUsed: utils.bigNumberify,
    logsBloom: utils.hexlify,
    blockHash: checkHash,
    transactionHash: checkHash,
    logs: arrayOf(checkTransactionReceiptLog),
    blockNumber: checkNumber,
    cumulativeGasUsed: utils.bigNumberify,
    status: allowNull(checkNumber)
};

function checkTransactionReceipt(transactionReceipt) {
    var status = transactionReceipt.status;
    var root = transactionReceipt.root;

    var result = check(formatTransactionReceipt, transactionReceipt);
    result.logs.forEach(function(entry, index) {
        if (entry.transactionLogIndex == null) {
            entry.transactionLogIndex = index;
        }
        // @TODO: Remove this is next major version
        if (entry.type == null) {
            entry.type = 'mined';
        }
    });
    if (transactionReceipt.status != null) {
        result.byzantium = true;
    }
    return result;
}

function checkTopics(topics) {
    if (Array.isArray(topics)) {
        topics.forEach(function(topic) {
            checkTopics(topic);
        });

    } else if (topics != null) {
        checkHash(topics);
    }

    return topics;
}

var formatFilter = {
    fromBlock: allowNull(checkBlockTag, undefined),
    toBlock: allowNull(checkBlockTag, undefined),
    address: allowNull(utils.getAddress, undefined),
    topics: allowNull(checkTopics, undefined),
};

function checkFilter(filter) {
    return check(formatFilter, filter);
}

var formatLog = {
    blockNumber: allowNull(checkNumber),
    blockHash: allowNull(checkHash),
    transactionIndex: checkNumber,

    removed: allowNull(checkBoolean),

    address: utils.getAddress,
    data: allowFalsish(utils.hexlify, '0x'),

    topics: arrayOf(checkHash),

    transactionHash: checkHash,
    logIndex: checkNumber,
}

function checkLog(log) {
    return check(formatLog, log);
}

function Provider(network) {
    if (!(this instanceof Provider)) { throw new Error('missing new'); }

    network = Provider._legacyConstructor(network, arguments.length, arguments[0], arguments[1]);

    // Check the ensAddress (if any)
    var ensAddress = null;
    if (network.ensAddress) {
        ensAddress = utils.getAddress(network.ensAddress);
    }

    // Setup our network properties
    utils.defineProperty(this, 'chainId', network.chainId);
    utils.defineProperty(this, 'ensAddress', ensAddress);
    utils.defineProperty(this, 'name', network.name);

    // @TODO: Remove in the next major release
    utils.defineProperty(this, 'testnet', (network.name !== 'homestead'));

    var events = {};
    utils.defineProperty(this, '_events', events);

    var self = this;

    var lastBlockNumber = null;

    var balances = {};

    function doPoll() {
        self.getBlockNumber().then(function(blockNumber) {

            // If the block hasn't changed, meh.
            if (blockNumber === lastBlockNumber) { return; }

            if (lastBlockNumber === null) { lastBlockNumber = blockNumber - 1; }

            // Notify all listener for each block that has passed
            for (var i = lastBlockNumber + 1; i <= blockNumber; i++) {
                self.emit('block', i);
            }

            // Sweep balances and remove addresses we no longer have events for
            var newBalances = {};

            // Find all transaction hashes we are waiting on
            Object.keys(events).forEach(function(eventName) {
                var event = parseEventString(eventName);

                if (event.type === 'transaction') {
                    self.getTransaction(event.hash).then(function(transaction) {
                        if (!transaction || !transaction.blockNumber) { return; }
                        self.emit(event.hash, transaction);
                    });

                } else if (event.type === 'address') {
                    if (balances[event.address]) {
                        newBalances[event.address] = balances[event.address];
                    }
                    self.getBalance(event.address, 'latest').then(function(balance) {
                        var lastBalance = balances[event.address];
                        if (lastBalance && balance.eq(lastBalance)) { return; }
                        balances[event.address] = balance;
                        self.emit(event.address, balance);
                    });

                } else if (event.type === 'topic') {
                    self.getLogs({
                        fromBlock: lastBlockNumber + 1,
                        toBlock: blockNumber,
                        topics: event.topic
                    }).then(function(logs) {
                        if (logs.length === 0) { return; }
                        logs.forEach(function(log) {
                            self.emit(event.topic, log);
                        });
                    });
                }
            });

            lastBlockNumber = blockNumber;

            balances = newBalances;
        });

        self.doPoll();
    }

    utils.defineProperty(this, 'resetEventsBlock', function(blockNumber) {
        lastBlockNumber = blockNumber;
        self.doPoll();
    });

    var poller = null;
    Object.defineProperty(this, 'polling', {
        get: function() { return (poller != null); },
        set: function(value) {
            setTimeout(function() {
                if (value && !poller) {
                    poller = setInterval(doPoll, 4000);

                } else if (!value && poller) {
                    clearInterval(poller);
                    poller = null;
                }
            }, 0);
        }
    });
}

function inheritable(parent) {
    return function(child) {
        inherits(child, parent);
        utils.defineProperty(child, 'inherits', inheritable(child));
    }
}

utils.defineProperty(Provider, 'inherits', inheritable(Provider));
/*
function(child) {
    inherits(child, Provider);
    child.inherits = function(grandchild) {
        inherits(grandchild, child)
    }
});
*/

utils.defineProperty(Provider, '_legacyConstructor', function(network, length, arg0, arg1) {

    // Legacy parameters Provider(testnet:boolean, chainId:Number)
    if (typeof(arg0) === 'boolean' || length === 2) {
        var testnet = !!arg0;
        var chainId = arg1;

        // true => testnet, false => mainnet
        network = networks[testnet ? 'ropsten': 'homestead'];

        // Overriding chain ID
        if (length === 2 && chainId != null) {
            network = {
                chainId: chainId,
                ensAddress: network.ensAddress,
                name: network.name
            };
        }

    } else if (typeof(network) === 'string') {
        network = networks[network];
        if (!network) { throw new Error('unknown network'); }

    } else if (network == null) {
        network = networks['homestead'];
    }

    if (typeof(network.chainId) !== 'number') { throw new Error('invalid chainId'); }

    return network;
});
// @TODO: Remove in next major version (use networks instead)
utils.defineProperty(Provider, 'chainId', {
    homestead: 1,
    morden: 2,
    ropsten: 3,
    rinkeby: 4,
    kovan: 42
});

//utils.defineProperty(Provider, 'isProvider', function(object) {
//    return (object instanceof Provider);
//});

utils.defineProperty(Provider, 'networks', networks);

utils.defineProperty(Provider, 'fetchJSON', function(url, json, processFunc) {

    return new Promise(function(resolve, reject) {
        var request = new XMLHttpRequest();

        if (json) {
            request.open('POST', url, true);
            request.setRequestHeader('Content-Type','application/json');
        } else {
            request.open('GET', url, true);
        }

        request.onreadystatechange = function() {
            if (request.readyState !== 4) { return; }

            try {
                var result = JSON.parse(request.responseText);
            } catch (error) {
                var jsonError = new Error('invalid json response');
                jsonError.orginialError = error;
                jsonError.responseText = request.responseText;
                reject(jsonError);
                return;
            }

            if (processFunc) {
                try {
                    result = processFunc(result);
                } catch (error) {
                    error.url = url;
                    error.body = json;
                    error.responseText = request.responseText;
                    reject(error);
                    return;
                }
            }

            if (request.status != 200) {
                var error = new Error('invalid response - ' + request.status);
                error.statusCode = request.statusCode;
                reject(error);
                return;
            }

            resolve(result);
        };

        request.onerror = function(error) {
            reject(error);
        }

        try {
            if (json) {
                request.send(json);
            } else {
                request.send();
            }

        } catch (error) {
            var connectionError = new Error('connection error');
            connectionError.error = error;
            reject(connectionError);
        }
    });
});


utils.defineProperty(Provider.prototype, 'waitForTransaction', function(transactionHash, timeout) {
    var self = this;
    return new Promise(function(resolve, reject) {
        var timer = null;

        function complete(transaction) {
            if (timer) { clearTimeout(timer); }
            resolve(transaction);
        }

        self.once(transactionHash, complete);

        if (typeof(timeout) === 'number' && timeout > 0) {
            timer = setTimeout(function() {
                self.removeListener(transactionHash, complete);
                reject(new Error('timeout'));
            }, timeout);
        }

    });
});


utils.defineProperty(Provider.prototype, 'getBlockNumber', function() {
    try {
        return this.perform('getBlockNumber').then(function(result) {
            var value = parseInt(result);
            if (value != result) { throw new Error('invalid response - getBlockNumber'); }
            return value;
        });
    } catch (error) {
        return Promise.reject(error);
    }
});

utils.defineProperty(Provider.prototype, 'getGasPrice', function() {
    try {
        return this.perform('getGasPrice').then(function(result) {
            return utils.bigNumberify(result);
        });
    } catch (error) {
        return Promise.reject(error);
    }
});


utils.defineProperty(Provider.prototype, 'getBalance', function(addressOrName, blockTag) {
    var self = this;
    return this.resolveName(addressOrName).then(function(address) {
        var params = { address: address, blockTag: checkBlockTag(blockTag) };
        return self.perform('getBalance', params).then(function(result) {
            return utils.bigNumberify(result);
        });
    });
});

utils.defineProperty(Provider.prototype, 'getTransactionCount', function(addressOrName, blockTag) {
    var self = this;
    return this.resolveName(addressOrName).then(function(address) {
        var params = { address: address, blockTag: checkBlockTag(blockTag) };
        return self.perform('getTransactionCount', params).then(function(result) {
            var value = parseInt(result);
            if (value != result) { throw new Error('invalid response - getTransactionCount'); }
            return value;
        });
    });
});

utils.defineProperty(Provider.prototype, 'getCode', function(addressOrName, blockTag) {
    var self = this;
    return this.resolveName(addressOrName).then(function(address) {
        var params = {address: address, blockTag: checkBlockTag(blockTag)};
        return self.perform('getCode', params).then(function(result) {
            return utils.hexlify(result);
        });
    });
});

utils.defineProperty(Provider.prototype, 'getStorageAt', function(addressOrName, position, blockTag) {
    var self = this;
    return this.resolveName(addressOrName).then(function(address) {
        var params = {
            address: address,
            blockTag: checkBlockTag(blockTag),
            position: utils.hexlify(position),
        };
        return self.perform('getStorageAt', params).then(function(result) {
            return utils.hexlify(result);
        });
    });
});

utils.defineProperty(Provider.prototype, 'sendTransaction', function(signedTransaction) {
    try {
        var params = {signedTransaction: utils.hexlify(signedTransaction)};
        return this.perform('sendTransaction', params).then(function(result) {
            result = utils.hexlify(result);
            if (result.length !== 66) { throw new Error('invalid response - sendTransaction'); }
            return result;
        });
    } catch (error) {
        return Promise.reject(error);
    }
});


utils.defineProperty(Provider.prototype, 'call', function(transaction) {
    var self = this;
    return this._resolveNames(transaction, ['to', 'from']).then(function(transaction) {
        var params = { transaction: checkTransactionRequest(transaction) };
        return self.perform('call', params).then(function(result) {
            return utils.hexlify(result);
        });
    });
});

utils.defineProperty(Provider.prototype, 'estimateGas', function(transaction) {
    var self = this;
    return this._resolveNames(transaction, ['to', 'from']).then(function(transaction) {
        var params = {transaction: checkTransactionRequest(transaction)};
        return self.perform('estimateGas', params).then(function(result) {
             return utils.bigNumberify(result);
        });
    });
});


utils.defineProperty(Provider.prototype, 'getBlock', function(blockHashOrBlockTag) {
    try {
        var blockHash = utils.hexlify(blockHashOrBlockTag);
        if (blockHash.length === 66) {
            return this.perform('getBlock', {blockHash: blockHash}).then(function(block) {
                if (block == null) { return null; }
                return checkBlock(block);
            });
        }
    } catch (error) {
        console.log('DEBUG', error);
    }

    try {
        var blockTag = checkBlockTag(blockHashOrBlockTag);
        return this.perform('getBlock', {blockTag: blockTag}).then(function(block) {
            if (block == null) { return null; }
            return checkBlock(block);
        });
    } catch (error) {
        console.log('DEBUG', error);
    }

    return Promise.reject(new Error('invalid block hash or block tag'));
});

utils.defineProperty(Provider.prototype, 'getTransaction', function(transactionHash) {
    try {
        var params = { transactionHash: checkHash(transactionHash) };
        return this.perform('getTransaction', params).then(function(result) {
            if (result != null) { result = checkTransaction(result); }
            return result;
        });
    } catch (error) {
        return Promise.reject(error);
    }
});

utils.defineProperty(Provider.prototype, 'getTransactionReceipt', function(transactionHash) {
    try {
        var params = { transactionHash: checkHash(transactionHash) };
        return this.perform('getTransactionReceipt', params).then(function(result) {
            if (result != null) { result = checkTransactionReceipt(result); }
            return result;
        });
    } catch (error) {
        return Promise.reject(error);
    }
});

utils.defineProperty(Provider.prototype, 'getLogs', function(filter) {
    var self = this;
    return this._resolveNames(filter, ['address']).then(function(filter) {
        var params = { filter: checkFilter(filter) };
        return self.perform('getLogs', params).then(function(result) {
            return arrayOf(checkLog)(result);
        });
    });
});

utils.defineProperty(Provider.prototype, 'getEtherPrice', function() {
    try {
        return this.perform('getEtherPrice', {}).then(function(result) {
            // @TODO: Check valid float
            return result;
        });
    } catch (error) {
        return Promise.reject(error);
    }
});


utils.defineProperty(Provider.prototype, '_resolveNames', function(object, keys) {
    var promises = [];

    var result = copyObject(object);

    keys.forEach(function(key) {
        if (result[key] === undefined) { return; }
        promises.push(this.resolveName(result[key]).then(function(address) {
            result[key] = address;
        }));
    }, this);

    return Promise.all(promises).then(function() { return result; });
});

utils.defineProperty(Provider.prototype, '_getResolver', function(name) {
    var nodeHash = utils.namehash(name);

    // keccak256('resolver(bytes32)')
    var data = '0x0178b8bf' + nodeHash.substring(2);
    var transaction = { to: this.ensAddress, data: data };

    // Get the resolver from the blockchain
    return this.call(transaction).then(function(data) {

        // extract the address from the data
        if (data.length != 66) { return null; }
        return utils.getAddress('0x' + data.substring(26));
    });
});

utils.defineProperty(Provider.prototype, 'resolveName', function(name) {
    // If it is already an address, nothing to resolve
    try {
        return Promise.resolve(utils.getAddress(name));
    } catch (error) { }

    var self = this;

    var nodeHash = utils.namehash(name);

    // Get the addr from the resovler
    return this._getResolver(name).then(function(resolverAddress) {

        // keccak256('addr(bytes32)')
        var data = '0x3b3b57de' + nodeHash.substring(2);
        var transaction = { to: resolverAddress, data: data };
        return self.call(transaction);

    // extract the address from the data
    }).then(function(data) {
        if (data.length != 66) { return null; }
        var address = utils.getAddress('0x' + data.substring(26));
        if (address === '0x0000000000000000000000000000000000000000') { return null; }
        return address;
    });
});

utils.defineProperty(Provider.prototype, 'lookupAddress', function(address) {
    address = utils.getAddress(address);

    var name = address.substring(2) + '.addr.reverse'
    var nodehash = utils.namehash(name);

    var self = this;

    return this._getResolver(name).then(function(resolverAddress) {
        if (!resolverAddress) { return null; }

        // keccak('name(bytes32)')
        var data = '0x691f3431' + nodehash.substring(2);
        var transaction = { to: resolverAddress, data: data };
        return self.call(transaction);

    }).then(function(data) {
        // Strip off the "0x"
        data = data.substring(2);

        // Strip off the dynamic string pointer (0x20)
        if (data.length < 64) { return null; }
        data = data.substring(64);

        if (data.length < 64) { return null; }
        var length = utils.bigNumberify('0x' + data.substring(0, 64)).toNumber();
        data = data.substring(64);

        if (2 * length > data.length) { return null; }

        var name = utils.toUtf8String('0x' + data.substring(0, 2 * length));

        // Make sure the reverse record matches the foward record
        return self.resolveName(name).then(function(addr) {
            if (addr != address) { return null; }
            return name;
        });

    });
});

utils.defineProperty(Provider.prototype, 'doPoll', function() {
});

utils.defineProperty(Provider.prototype, 'perform', function(method, params) {
    return Promise.reject(new Error('not implemented - ' + method));
});

function recurse(object, convertFunc) {
    if (Array.isArray(object)) {
        var result = [];
        object.forEach(function(object) {
            result.push(recurse(object, convertFunc));
        });
        return result;
    }
    return convertFunc(object);
}

function getEventString(object) {
    try {
        return 'address:' + utils.getAddress(object);
    } catch (error) { }

    if (object === 'block') {
        return 'block';

    } else if (utils.isHexString(object)) {
        if (object.length === 66) {
            return 'tx:' + object;
        }
    } else if (Array.isArray(object)) {
        object = recurse(object, function(object) {
            if (object == null) { object = '0x'; }
            return object;
        });

        try {
            return 'topic:' + utils.RLP.encode(object);
        } catch (error) {
            console.log(error);
        }
    }

    throw new Error('invalid event - ' + object);
}

function parseEventString(string) {
    if (string.substring(0, 3) === 'tx:') {
        return {type: 'transaction', hash: string.substring(3)};

    } else if (string === 'block') {
        return {type: 'block'};

    } else if (string.substring(0, 8) === 'address:') {
        return {type: 'address', address: string.substring(8)};

    } else if (string.substring(0, 6) === 'topic:') {
        try {
            var object = utils.RLP.decode(string.substring(6));
            object = recurse(object, function(object) {
                if (object === '0x') { object = null; }
                return object;
            });
            return {type: 'topic', topic: object};
        } catch (error) {
            console.log(error);
        }
    }

    throw new Error('invalid event string');
}

utils.defineProperty(Provider.prototype, 'on', function(eventName, listener) {
    var key = getEventString(eventName);
    if (!this._events[key]) { this._events[key] = []; }
    this._events[key].push({eventName: eventName, listener: listener, type: 'on'});
    this.polling = true;
});

utils.defineProperty(Provider.prototype, 'once', function(eventName, listener) {
    var key = getEventString(eventName);
    if (!this._events[key]) { this._events[key] = []; }
    this._events[key].push({eventName: eventName, listener: listener, type: 'once'});
    this.polling = true;
});

utils.defineProperty(Provider.prototype, 'emit', function(eventName) {
    var key = getEventString(eventName);

    var args = Array.prototype.slice.call(arguments, 1);
    var listeners = this._events[key];
    if (!listeners) { return; }

    for (var i = 0; i < listeners.length; i++) {
        var listener = listeners[i];
        if (listener.type === 'once') {
            listeners.splice(i, 1);
            i--;
        }

        try {
            listener.listener.apply(this, args);
        } catch (error) {
            console.log('Event Listener Error: ' + error.message);
        }
    }

    if (listeners.length === 0) { delete this._events[key]; }
    if (this.listenerCount() === 0) { this.polling = false; }
});

utils.defineProperty(Provider.prototype, 'listenerCount', function(eventName) {
    if (!eventName) {
        var result = 0;
        for (var key in this._events) {
            result += this._events[key].length;
        }
        return result;
    }

    var listeners = this._events[getEventString(eventName)];
    if (!listeners) { return 0; }
    return listeners.length;
});

utils.defineProperty(Provider.prototype, 'listeners', function(eventName) {
    var listeners = this._events[getEventString(eventName)];
    if (!listeners) { return 0; }
    var result = [];
    for (var i = 0; i < listeners.length; i++) {
        result.push(listeners[i].listener);
    }
    return result;
});

utils.defineProperty(Provider.prototype, 'removeAllListeners', function(eventName) {
    delete this._events[getEventString(eventName)];
    if (this.listenerCount() === 0) { this.polling = false; }
});

utils.defineProperty(Provider.prototype, 'removeListener', function(eventName, listener) {
    var listeners = this._events[getEventString(eventName)];
    if (!listeners) { return 0; }
    for (var i = 0; i < listeners.length; i++) {
        if (listeners[i].listener === listener) {
            listeners.splice(i, 1);
            return;
        }
    }
    if (this.listenerCount() === 0) { this.polling = false; }
});

module.exports = Provider;