# all files / packages/web3-core-subscriptions/src/ subscription.js

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     /*
        This file is part of web3.js.

        web3.js is free software: you can redistribute it and/or modify
        it under the terms of the GNU Lesser General Public License as published by
        the Free Software Foundation, either version 3 of the License, or
        (at your option) any later version.

        web3.js 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 Lesser General Public License for more details.

        You should have received a copy of the GNU Lesser General Public License
        along with web3.js.  If not, see <http://www.gnu.org/licenses/>.
    */
    /**
     * @file subscription.js
     * @author Fabian Vogelsteller <fabian@ethereum.org>
     * @date 2017
     */

    "use strict";

    var _ = require('underscore');
    var errors = require('web3-core-helpers').errors;
    var EventEmitter = require('eventemitter3');

    function Subscription(options) {
        EventEmitter.call(this);

        this.id = null;
        this.callback = null;
        this.arguments = null;
        this._reconnectIntervalId = null;

        this.options = {
            subscription: options.subscription,
            type: options.type,
            requestManager: options.requestManager
        };
    }

    // INHERIT
    Subscription.prototype = Object.create(EventEmitter.prototype);
    Subscription.prototype.constructor = Subscription;

    /**
     * Should be used to extract callback from array of arguments. Modifies input param
     *
     * @method extractCallback
     * @param {Array} arguments
     * @return {Function|Null} callback, if exists
     */

    Subscription.prototype._extractCallback = function (args) {
        Eif (_.isFunction(args[args.length - 1])) {
            return args.pop(); // modify the args array!
        }
    };

    /**
     * Should be called to check if the number of arguments is correct
     *
     * @method validateArgs
     * @param {Array} arguments
     * @throws {Error} if it is not
     */

    Subscription.prototype._validateArgs = function (args) {
        var subscription = this.options.subscription;

        Iif(!subscription)
            subscription = {};

        if(!subscription.params)
            subscription.params = 0;

        Iif (args.length !== subscription.params) {
            throw errors.InvalidNumberOfParams(args.length, subscription.params + 1, args[0]);
        }
    };

    /**
     * Should be called to format input args of method
     *
     * @method formatInput
     * @param {Array}
     * @return {Array}
     */

    Subscription.prototype._formatInput = function (args) {
        var subscription = this.options.subscription;

        Iif (!subscription) {
            return args;
        }

        if (!subscription.inputFormatter) {
            return args;
        }

        var formattedArgs = subscription.inputFormatter.map(function (formatter, index) {
            return formatter ? formatter(args[index]) : args[index];
        });

        return formattedArgs;
    };

    /**
     * Should be called to format output(result) of method
     *
     * @method formatOutput
     * @param {Object}
     * @return {Object}
     */

    Subscription.prototype._formatOutput = function (result) {
        var subscription = this.options.subscription;

        return (subscription && subscription.outputFormatter && result) ? subscription.outputFormatter(result) : result;
    };

    /**
     * Should create payload from given input args
     *
     * @method toPayload
     * @param {Array} args
     * @return {Object}
     */
    Subscription.prototype._toPayload = function (args) {
        var params = [];
        this.callback = this._extractCallback(args);

        Eif (!this.subscriptionMethod) {
            this.subscriptionMethod = args.shift();

            // replace subscription with given name
            if (this.options.subscription.subscriptionName) {
                this.subscriptionMethod = this.options.subscription.subscriptionName;
            }
        }

        Eif (!this.arguments) {
            this.arguments = this._formatInput(args);
            this._validateArgs(this.arguments);
            args = []; // make empty after validation

        }

        // re-add subscriptionName
        params.push(this.subscriptionMethod);
        params = params.concat(this.arguments);

        Iif (args.length) {
            throw new Error('Only a callback is allowed as parameter on an already instantiated subscription.');
        }

        return {
            method: this.options.type + '_subscribe',
            params: params
        };
    };

    /**
     * Unsubscribes and clears callbacks
     *
     * @method unsubscribe
     * @return {Object}
     */
    Subscription.prototype.unsubscribe = function(callback) {
        this.options.requestManager.removeSubscription(this.id, callback);
        this.id = null;
        this.removeAllListeners();
        clearInterval(this._reconnectIntervalId);
    };

    /**
     * Subscribes and watches for changes
     *
     * @method subscribe
     * @param {String} subscription the subscription
     * @param {Object} options the options object with address topics and fromBlock
     * @return {Object}
     */
    Subscription.prototype.subscribe = function() {
        var _this = this;
        var args = Array.prototype.slice.call(arguments);
        var payload = this._toPayload(args);

        Iif(!payload) {
            return this;
        }

        // throw error, if provider doesnt support subscriptions
        Iif(!this.options.requestManager.provider.on) {
            var err = new Error('The current provider doesn\'t support subscriptions'+ this.options.requestManager.provider.constructor.name);
            this.callback(err, null, this);
            this.emit('error', err);
            return this;
        }

        // if id is there unsubscribe first
        Iif (this.id) {
            this.unsubscribe();
        }

        // store the params in the options object
        this.options.params = payload.params[1];

        // get past logs, if fromBlock is available
        if(payload.params[0] === 'logs' && _.isObject(payload.params[1]) && payload.params[1].hasOwnProperty('fromBlock') && isFinite(payload.params[1].fromBlock)) {
            // send the subscription request
            this.options.requestManager.send({
                method: 'eth_getLogs',
                params: [payload.params[1]]
            }, function (err, logs) {
                Eif(!err) {
                    logs.forEach(function(log){
                        var output = _this._formatOutput(log);
                        _this.callback(null, output, _this);
                        _this.emit('data', output);
                    });

                    // TODO subscribe here? after the past logs?

                } else {
                    _this.callback(err, null, _this);
                    _this.emit('error', err);
                }
            });
        }

        // create subscription
        // TODO move to separate function? so that past logs can go first?

        if(typeof payload.params[1] === 'object')
            delete payload.params[1].fromBlock;

        this.options.requestManager.send(payload, function (err, result) {
            if(!err && result) {
                _this.id = result;

                // call callback on notifications
                _this.options.requestManager.addSubscription(_this.id, payload.params[0] , _this.options.type, function(err, result) {

                    // TODO remove once its fixed in geth
                    Iif(_.isArray(result))
                        result = result[0];

                    var output = _this._formatOutput(result);

                    Eif (!err) {

                        if(_.isFunction(_this.options.subscription.subscriptionHandler)) {
                            return _this.options.subscription.subscriptionHandler.call(_this, output);
                        } else {
                            _this.emit('data', output);
                        }

                    } else {
                        // unsubscribe, but keep listeners
                        _this.options.requestManager.removeSubscription(_this.id);

                        // re-subscribe, if connection fails
                        if(_this.options.requestManager.provider.once) {
                            _this._reconnectIntervalId = setInterval(function () {
                                // TODO check if that makes sense!
                                _this.options.requestManager.provider.reconnect();
                            }, 500);

                            _this.options.requestManager.provider.once('connect', function () {
                                clearInterval(_this._reconnectIntervalId);
                                _this.subscribe(_this.callback);
                            });
                        }
                        _this.emit('error', err);
                    }

                    // call the callback, last so that unsubscribe there won't affect the emit above
                    Eif (_.isFunction(_this.callback)) {
                        _this.callback(err, output, _this);
                    }
                });
            } else Eif (_.isFunction(_this.callback)) {
                _this.callback(err, null, _this);
                _this.emit('error', err);
            }
        });

        // return an object to cancel the subscription
        return this;
    };

    module.exports = Subscription;