denis-sokolov/portent

'use strict';

var frozen = require('frozen-express');
var gulp = require('gulp');
var Promise = require('promise');
var streamCombiner = require('stream-combiner');

var streamEndToPromise = function(stream){
    return new Promise(function(resolve, reject){
        stream.on('end', function(){ resolve(); });
        stream.on('error', reject);
    });
};

var rootRelativeUrlCheck = function(urls){
    var bad = urls.filter(u => u[0] === '/');
    if (bad.length)
        throw new Error(
            'Some plugins have provided root-relative URLs. ' +
            'This is incorrect, and it also suggests you may have these URLs in your modifyHtml function. ' +
            'Here are the URLs: ' +
            bad.join(', ') + '.'
        );
};

module.exports = function(server, directory, plugins){
    var app = server(directory, plugins);

    var paths = plugins.map(function(plugin){
        if (plugin.paths)
            return plugin.paths();
    }).filter(function(x){ return x; });

    return function(destinationDirectory){
        return Promise.all(paths).then(function(deepUrls){
            var urls = [].concat.apply([], deepUrls);
            rootRelativeUrlCheck(urls);
            return streamEndToPromise(streamCombiner(
                frozen(app, { urls: urls.map(u => '/' + u) }),
                gulp.dest(destinationDirectory)
            ));
        });
    };
};