/server/combine.js

var util     = require('util'),
    events   = require('events'),
    fs       = require('fs'),
    path     = require('path'),
    _        = require('underscore'),
    Backbone = require('backbone'),
    logger   = require('./logging').logger;

// Location of reapers
var REAPER_DIR = path.join(__dirname, 'reapers');

/**
 * Combine for collecting reaper data
 */
function Combine(config) {
    events.EventEmitter.call(this);
    // List of Reapers
    this.reapers = [];

    // Collected actions from reapers
    this.actions = new ActionsCollection();
    this.actions.on('add', function(action, collection, index) {
        this.emit('action', action);
    }.bind(this));

    // Try to load configured reapers
    if (config.reapers) {
        config.reapers.forEach(function(spec) {
            var reaper = createReaper(spec);
            this.addReaper(reaper);
        }, this);
    }
}
util.inherits(Combine, events.EventEmitter);

/**
 * Harvest Actions from a data set, provided by a reaper
 */
Combine.prototype.harvest = function(data, reaper) {
    // Add a custom ID for recognizing the action and
    // prevent ID collisions from other systems.
    data.pid = data.id + '@' + reaper.source;

    // Add a prefixed type to the action
    data.ptype = reaper.source + '#' + data.type;

    // Add timestamp of the action date for convenience
    if ('string' === typeof(data.date)) {
        data.date = moment(data.date).toDate();
    }
    data.timestamp = data.date.getTime();

    // Add the action model
    this.actions.add(new ActionModel(data));
};

/**
 * Add a reaper. This will keep watch for `data` events on the
 * reaper and pass this information to the `harvest` method.
 */
Combine.prototype.addReaper = function(reaper) {
    // Watch for reaper data
    reaper.on('data', this.harvest.bind(this));

    // Keep a reference to the reaper
    this.reapers.push(reaper);

    return this;
};

/**
 * Start harvesting
 */
Combine.prototype.start = function() {
    this.reapers.forEach(function(reaper) {
        reaper.start();
    });
};

// # getActionCount
// ================
// @TODO Add filter method to count subsets
Combine.prototype.getActionCount = function(filter) {
    return this.actions.length;
};

// # getActionSet
// ============
// Get a subset of the Combine actions.
Combine.prototype.getActionSet = function(number, startAt) {
    startAt = startAt - 1 || 0;
    if (0 > startAt) {
        startAt = 0;
    }

    // Get the actions
    var actions = this.actions.toArray();

    // If a number is specified return a subset
    if (_.isNumber(number)) {
        actions = actions.slice(startAt, number);
    }

    return actions;
};

/**
 * Create a reaper instance based on a small specification
 */
function createReaper(spec) {
    // @TODO Check if reaper file exists
    // @TODO Crash gracefully

    // Load the reaper from disk
    var Reaper = require(path.join(REAPER_DIR, spec.module));

    // Return a new instance
    return new Reaper(spec.config);
}

// # ActionModel
// =============
// Model for data received from a reaper
var ActionModel = Backbone.Model.extend();

// # ActionsCollection
// ===================
// Collection for storing Action Models
var ActionsCollection = Backbone.Collection.extend({
    model: ActionModel,
    comparator: function(a, b) {
        var aTime = a.get('date'),
            bTime = b.get('date');

        if (aTime > bTime) {      return -1; }
        else if (aTime < bTime) { return 1;  }
        else {                    return 0;  }
    },
    // Override the default add method to add duplicate id check
    add: function(models, options) {
        if (!_.isArray(models)) {
            models = [models];
        }

        // Filter duplicate models
        models = models.filter(function(model) {
            return (0 === this.where({ id: model.get('id') }).length);
        }.bind(this));

        // Pass through to the prototype add method
        Backbone.Collection.prototype.add.call(this, models, options);
    }
});

// our awesome export products
exports = module.exports = {
    "Combine": Combine,
    "reaper":  {},
    "create":  function(options) {
        return new Combine(options);
    }
};