icssify/src/transform.js

"use strict";

const Promise = require("bluebird");
const bl = require("bl");
const through2 = require("through2");
const path = require("path");

const createFilePreprocessor = require("./postcss/preprocess");
const loaderShimPath = require("./loader-shim-path");

module.exports = function (state) {
	const isCss = require("./is-css")(state);

	return function createTransform(file, options) {
		// TODO: Reuse instance?
		let preprocessFile = createFilePreprocessor(options);
		
		if (isCss({ file: file })) {
			let buffer = new bl.BufferList();
	
			function chunkHandler(chunk, encoding, callback) {
				// NOTE: We check the `chunk` here, not the `encoding`, because in at least one instance a Buffer was passed in claiming to be a "utf8" string according to the `encoding` argument
				if (Buffer.isBuffer(chunk)) {
					buffer.append(chunk);
					callback();
				} else {
					throw new Error(`Expected Buffer, got string instead (encoding = ${encoding})`);
				}
			}
	
			function endHandler(callback) {
				return Promise.try(() => {
					return preprocessFile({ file: file, source: buffer.toString() });
				}).then((result) => {
					let imports = result.messages
						.filter((message) => {
							return (
								message.pluginName === "postcss-icss-find-imports"
								&& message.type === "import"
							);
						})
						.map((message) => message.url);
	
					imports.forEach((importUrl) => {
						this.emit("dep", importUrl);
					});
					
					// This ensures that whenever *any* CSS file is processed, the global loader file gets included as well (which is the file that eventually inserts the concatenated CSS)
					let relativeLoaderPath = path.relative(path.dirname(file), loaderShimPath);
					this.emit("dep", relativeLoaderPath);
	
					this.push(result.css);
					callback();
				}).catch((error) => {
					callback(error);
				});
			}
	
			return through2.obj(chunkHandler, endHandler);
		} else {
			return through2.obj();
		}
	};
};