Factory + Inheritance

factory_plus_inheritance.js

'use strict';

/* At Config.JSON file
*/

// Define the functions all the DAOs must implement
DaoInterfaces: {
    ImportDaoInterface: {
        ATTRS: [func1, func2, func3, func4]
    }
}

// Define the interface
RegisteredDAOs: {
    ids.grubhub: {
        IMPORT: GrubhubImportDAO,
    }
}


class DaoInterface {
    // This class defines what the API is for the Specific DAO
    // This will come into play when we dynamically generate the Factory   
    this.FUNCS = config.ImportDaoInterface    
}

class ImportDaoInterface extends DaoInterface{
    // Define the API functions the Daos must implement:
    FUNCS = [getOrders, FuncB, funcC]
    
    /**
        This methods contract is x, y, z
    */
    getOrders(dateRange, cb) {
        throw 'Extend Me!'
    }
}



class GrubhubImportDao extends ImportDaoInterface {
    
    getOrders(dateRange, cb) {
        cb(false, [])
    }

}


function DaoFactory(id, functionality, props={}){
    // Can abstract config to be a class
    // I think it makes sense to pass the DAO here too, but either way works
    var daoKlass = config.registeredDaos[id][functionality]

    // Meta program the wrapping
    var ProxyWrapper = function(klass){
        var copyOfKlass = Object.copyPrototype(klass);
        klass.FUNCS.forEach(function(copyOfKlass.func) {
            // Rewrite the class to overwrite
            klass.prototype[func] = wrapFuncsWithStats(copyOfKlass.prototype[func])
        })
        return klass
    }


    var wrapFuncsWithStats = function(func){
        return function() {
            var cb = LAST_ARG(arguments)
            func(arguments*, function() {
                var err = FIRST_ARG(SCOPED_ARGS)
                if (err) err Sentry(err); return cb(err);
                
                // Stats histogram/increment
                Stats.incr(err || success)
                Stats.hist(timer)

                cb(err, REST_OF_ARGS(SCOPED_ARGS))
            })
        }
    }


    return new ProxyWrapper(daoKlass)(props)
}



// test...
ImportDaoFactory('GrubhubImport').getOrders('last 3 hours', function(err,orders){
    console.log('orders=',orders)
})