/**
 * Support utilities for rendering html pages and emails
 * It is based on [pug](https://pugjs.org) - previously jade - and retains
 * a similar api to jade.renderFile() but leverages pre-compiled functions for
 * performance.
 */
'use strict';

const _ = require('lodash');
const pug = require('pug');
const Handlebars = require('handlebars/runtime');
const path = require('path');

module.exports = {
    initTemplates: initTemplates,
    render: render
};

/**
 * Location for the root templates directory
 */
const PUG_TEMPLATE_DIR = path.join(global.pathPrefix, '..', 'pug');
const HANDLEBARS_TEMPLATE_DIR = path.join(global.pathPrefix, '..', 'email_templates');

/**
 * List of templates that we have available for use
 */
const PUG_TEMPLATES = [
    /* HTML templates for Register7.  Remove as part of T1469 */
    'templates/10005_reg_deleted.pug',
    'templates/54_email_not_found.pug',
    'templates/56_mobile_number_not_found.pug',
    'templates/57_association_error.pug',
    'templates/58_fully_registered.pug',
    'templates/undef_database_offline.pug',

    /* Admin notifications */
    'adminNotifier/identity_check.pug',
    'adminNotifier/credits_low.pug'
];

const HANDLEBARS_TEMPLATES = [
    /* Emails */
    'account-locked',
    'account-recovery',
    'bridge-welcome',
    'device-added',
    'device-locked',
    'device-new-hardware',
    'device-re-registration',
    'email-changed-old',
    'email-changed-new',
    'email-reverted-from',
    'email-reverted-to',
    'invoice-new',
    'invoice-cancelled',
    'invoice-queried',
    'invoice-updated',
    'marketing-generic',
    'password-changed',
    'password-changed-web',
    'pin-reset',
    'thoughtful-enterprises-marketing'
];

/**
 * Object to store the rendered template functions for later use
 */
var renderedTemplates = {};

/**
 * Pre-loads and compiles the pug templates into render functions.
 */
function initTemplates() {
    //
    // Init the pug templates
    //
    for (let i = 0; i < PUG_TEMPLATES.length; ++i) {
        /* Find the full path to the template */
        let templatePath = path.join(PUG_TEMPLATE_DIR, PUG_TEMPLATES[i]);

        /* compile the render function */
        let renderFunc = pug.compileFile(templatePath);

        /* store it in the cache */
        renderedTemplates[PUG_TEMPLATES[i]] = renderFunc;
    }

    //
    // Init the handlebars templates
    //
    for (let i = 0; i < HANDLEBARS_TEMPLATES.length; ++i) {
        /* Find the full path to the template */
        let templatePath = path.join(HANDLEBARS_TEMPLATE_DIR, HANDLEBARS_TEMPLATES[i]);

        /**
         * Require the template. This returns the template render function
         */
        let renderFunc = require(templatePath);

        /* store it in the cache */
        renderedTemplates[HANDLEBARS_TEMPLATES[i]] = renderFunc;
    }
}

/**
 * Renders the given template using the provided data.  Uses the cached render
 * functions that are generated by initTemplates()
 *
 * @param {String} templateName     - the name of the template, e.g. `account-locked`
 * @param {Object} data             - the data to render into the template
 *
 * @throws {Error}                  - throws an Error if the template hasn't been loaded
 * @returns {String}                - the rendered HTML
 */
function render(templateName, data) {
    var renderFunc = renderedTemplates[templateName];
    if (!_.isFunction(renderFunc)) {
        throw new Error('Template [' + templateName + '] doesn\'t exist.');
    }

    return renderFunc(data);
}