// Detect if multiple versions of the same yarn dependency are pulled in

module.exports = class WebpackDuplicateModulesPlugin {
	apply(compiler) {
		let modulePaths = {};

	    compiler.plugin('compilation', function(compilation, params) {
	        compilation.plugin('after-optimize-chunk-assets', function(chunks) {
	        	for(let chunk of chunks) {
	        		for(let file of chunk.modules) {
	        			let module = file.resource && file.resource.match(/^.*\/node_modules\/([^/]+)\//);
				        if(module) {
	        				if(!modulePaths[module[1]])
	        					modulePaths[module[1]] = new Set();

	        				modulePaths[module[1]].add(module[0]);
				        }
			        }
		        }
	        });
	    });

	    compiler.plugin('done', function() {
	    	for(let module in modulePaths) {
	    		if(modulePaths[module].size > 1) {
	    			console.warn(`Warning: Multiple paths for module ${module}: ${Array.from(modulePaths[module])}`);
			    }
		    }
	    });
	}
};