use.js

var     assert  = require("assert")
    ,   path    = require("path")
    ,   fs      = require("fs")


var use = exports;

var MODULE_FILE_EXTENSION = '.js';

/*
 * Project setup
 */
use.setup =
    function( source /* path or array of paths */ )
    {
        use.modules(source);
        global.use = use.use;
        global.use.lib = use;
    }

/*
 *  Import either a module or Class.
 *
 * It follows the following naming convention:
 *      modules have lowercase names
 *      Classes's name are capitalized
 */
use.use =
    function(name)
    {
        assert( name && name.length>0 , 'invalid name');

        var isClassName = name[0].toUpperCase() == name[0];
        
        return isClassName ? _useClass(name) : _useModule(name);
    };


/*
 * konstants util
 */
use.k =
    function(module, constantName)
    {
        assert(module.constants != undefined, 'module has no constants (' + module.filename + ')');
        var result = module.constants[constantName];
        assert(result != undefined, 'Constant `' + constantName + '` is undefined');
        return result;
    };


var _modules;

use.modules =
    function(source /* path or array of paths */)
    {
        if (!_modules) {
            if (source == undefined) {
                throw new Error('use.setup was not called');
            }

            if (typeof source == 'string')
                source = [ source ];

            // console.log('source: ' + source);
            // console.log('Loading modules to use...');

           _modules = _loadModules(source);
        }
        
        return _modules;
    }

// Private
function ___PRIVATE___(){}

use._module = _useModule;

function _useModule(name)
{
    var modules = use.modules();

    var modulePath = modules[name];

    if (modulePath)
    {
        var moduleId = modulePath.substring(0, modulePath.length - MODULE_FILE_EXTENSION.length);
        return require(moduleId);
    }
    else
        throw new Error('Cannot find module: `'+ name +'`');
};

use._class = _useClass;

function _useClass(name)
{
    var module = _useModule(name);
    var classInModule = module[name];

    if (classInModule == undefined)
    {
        if ( Object.keys(module).length == 0 )
        {
            var circularErrString = 'Module: `' + name + '` appears to be empty - Is there circular dependency?';
            console.error(circularErrString);
            console.error('Circular dependency are not supported by the `use` directive');
            throw new Error(circularErrString);
        }
        else
        {
            console.error('Error finding main class in module: `' + name + '`');
            console.error('Module:');
            console.error(module);                
            throw new Error(name + '.' + name + ' is undefined');
        }
    }
    else if (typeof classInModule == 'function')
        return classInModule;
    else
        throw new Error(name + '.' + name + ' is not a function');       
}


/* aux ==================================================== */

function _loadModules(srcArray)
{
    var result = {};

    for (i in srcArray)
    {
        var src_i = srcArray[i];

        _loadModulesForDir(src_i);
    }

    return result;

    /* aux ==== */

    function _loadModulesForDir(dirPath)
    {

        var files = fs.readdirSync(dirPath);

        for (var i in files)
        {
            var file_i = files[i];
            var filepath_i = path.normalize(dirPath + '/' + file_i);

            if (path.extname(file_i) == MODULE_FILE_EXTENSION)
            {
                var moduleName = path.basename(file_i, MODULE_FILE_EXTENSION);

                _addModule(moduleName, filepath_i);
            }
            else
            {
                var subdirectory;

                try {
                    subdirectory = _loadModulesForDir(filepath_i); // assume is a directory
                }
                catch(e) {
                    if (e.code != 'ENOTDIR')
                        throw e;
                }

                // Merge modules
                for (var module in subdirectory) {
                    _addModule(module, subdirectory[module]);
                }
            }
            
            /* aux ==== */

            function _addModule(name, filepath)
            {
                if (result.hasOwnProperty(name))
                {
                    throw new Error('Duplicate module: ' + filepath + ' and '+ result[name].path );
                }
                else
                {
                    result[name] = filepath;
                }
            }
        }
    }
}