(function () {
    "use strict";

    var fs = require('fs'),
        path = require('path'),
        _ = require('underscore'),
        handlebars = require('express-hbs').handlebars,
        nodefn = require('when/node/function'),
        GhostNavHelper;

    GhostNavHelper = function (navTemplate) {
        // Bind the context for our methods.
        _.bindAll(this, 'compileTemplate', 'renderNavItems');

        if (_.isFunction(navTemplate)) {
            this.navTemplateFunc = navTemplate;
        } else {
            this.navTemplatePath = navTemplate;
        }
    };

    GhostNavHelper.prototype.compileTemplate = function (templatePath) {
        var self = this;

        // Allow people to overwrite the navTemplatePath
        templatePath = templatePath || this.navTemplatePath;

        return nodefn.call(fs.readFile, templatePath).then(function (navTemplateContents) {
            // TODO: Can handlebars compile async?
            self.navTemplateFunc = handlebars.compile(navTemplateContents.toString());
        });
    };

    GhostNavHelper.prototype.renderNavItems = function (navItems) {
        var output;

        output = this.navTemplateFunc({links: navItems});

        return output;
    };

    // A static helper method for registering with ghost
    GhostNavHelper.registerWithGhost = function (ghost) {
        var templatePath = path.join(ghost.paths().frontendViews, 'nav.hbs'),
            ghostNavHelper = new GhostNavHelper(templatePath);

        return ghostNavHelper.compileTemplate().then(function () {
            ghost.registerThemeHelper("ghostNav", ghostNavHelper.renderNavItems);
        });
    };

    module.exports = GhostNavHelper;
}());