var ConcatSource = require('webpack/lib/ConcatSource');
var loaderUtils = require('loader-utils');

module.exports = CombineChunksPlugin;

// opts.filename = 'vendor.[contenthash].js'

function CombineChunksPlugin(opts) {
	if (opts) {
		this.filename = opts.filename ? opts.filename : 'vendor.bundle.js';
		this.prelude = opts.prelude;
	}
}

CombineChunksPlugin.prototype.apply = function(compiler) {
	var filename = this.filename;
	var prelude = this.prelude;

	compiler.plugin('compilation', function(compilation) {

		// put chunks in correct order
		// prelude first - which will contain common chunk and webpackJsonp defn
		compilation.plugin('optimize-chunk-order', function(chunks) {
			chunks.sort(function(a, b) {
				if (a.name === prelude) return -1;
				if (b.name === prelude) return 1;
				return 0;
			});
		});

		// add our asset into compilation
		compilation.plugin('optimize-chunk-assets', function(chunks, callback) {
			var vendorSource = new ConcatSource('');
			chunks.forEach(function(chunk) {
				chunk.files.forEach(function(file) {
					vendorSource.add(compilation.assets[file]);
					vendorSource.add('\n');
				});
			});
			filename = filename.replace(/\[(?:(\w+):)?contenthash(?::([a-z]+\d*))?(?::(\d+))?\]/ig, function() {
				return loaderUtils.getHashDigest(vendorSource.source(), arguments[1], arguments[2], parseInt(arguments[3], 10));
			});
			compilation.assets[filename] = vendorSource;
			callback();
		});
	});

	// now we can clean up other chunks that we don't require after the compilation is over
	// note that we don't iterate over compilation.assets
	// we do this just before emit giving chance for other plugins
	// to add its last file as the compilation results to preserve state
	compiler.plugin('after-compile', function(compilation, callback) {
		compilation.chunks.forEach(function(chunk) {
			chunk.files.forEach(function(file) {
				delete compilation.assets[file];
			});
		});
		callback();
	});
};