steal-tools/lib/bundle/make_bundle.js

// # lib/bundle/make_bundle.js
// Makes a __bundle__ graph from a dependency graph.
// A bundle graph contains objects that look like:
//
//     {
//       size: 231231,
//       nodes: [node1, node2, ...],
//       bundles: [bundleName1, bundleName2]	
//     }
//

var prettySize = function(bytes){
	if(bytes >= 9900) {
		return Math.round(bytes / 100) / 10 +"kb";
	}
	if(bytes > 200) {
		return Math.round(bytes / 10) / 100+"kb";
	}
	return bytes+"b";
};

var _ = require("lodash"),
	nodeSize = require("../node/size"),
	winston = require('winston');
var getMostBundled = function(sharedGraph){
	if (!sharedGraph.length ) {
		return null;
	}
	// get the highest shared number
	var mostShared = sharedGraph.pop(),
		mostSize = 0,
		most;
		
	// go through each app combo, get the one that has
	// the bigest size
	for ( var apps in mostShared ) {
		if ( mostShared[apps].size > mostSize ) {
			most = mostShared[apps];
			mostSize = most.size;
		}
	}
	
	winston.debug('  bundle for '+most.bundles+" "+prettySize(mostSize)+":");
	
	// order the files by when they should be included
	most.nodes = most.nodes.sort(function( f1, f2 ) {
		return f1.order - f2.order;
	});
	
	most.nodes.forEach(function(node){
		winston.debug('  + '+node.load.name);
	});
	return most;
};


module.exports = function(graph){
	
	// Records if a module has already been bundled
	var bundled = {};
	
	/**
	 * A sharedGraph looks like:
	 * 
	 *     {
	 * 	     BUNDLE_SHARED_BY_COUNT: {
	 * 	       JOINED_BUNDLE_NAMES: BUNDLE
	 *       }
	 *     }
	 * 
	 *     {
	 *       2 : {
	 * 	        "app_a,app_b" : {
	 * 	          size: 123,
	 *            nodes: [node1, node2],
	 *            bundles: ["app_a","app_b"]
	 *          }  
	 *       },
	 *       3: {
	 * 	        ...
	 *       }
	 *     }
	 */
	var makeSharedGraph = function(){
		var sharedGraph = [];
		for(var name in graph) {
			// ignore files that have already been bundled
			if(bundled[name]) {
				continue;
			}
			var node = graph[name];
			// Adds the shared set for the number of apps 2: {}
			var sharedSet = setProp(sharedGraph, node.bundles.length, {});
			
			// a name for the combo
			var bundlesName = node.bundles.sort().join(),
				// a pack is data for a specific appNames combo
				sharing = setProp(sharedSet, bundlesName, function(){
					return {
						size: 0,
						nodes: [],
						bundles: node.bundles
					};
				});
				
			sharing.nodes.push(node);
			sharing.size += nodeSize(node);
		}
		return sharedGraph;
	};
	
	
	var bundles = [],
		bundle;
		
	while( ( bundle = getMostBundled( makeSharedGraph() ) ) ) {
		
		//mark files as packaged
		bundle.nodes.forEach(function(n){
			bundled[n.load.name] = true;
		});
		
		bundles.push(bundle);
	}
	return bundles;
};


var setProp = function(root, prop, raw, cb){
	if(!root[prop]){
		root[prop] = ( typeof raw === 'object' ?
			_.assign({},raw) :
			raw() );
	}

	if(cb) {
		cb( root[prop] );
	}
	return root[prop];
};