"use strict";

const Promise = require("bluebird");
const postcss = require("postcss");
const defaultValue = require("default-value");
const objectFromEntries = require("object.fromentries");

const icssParser = require("./postcss-icss-parser");

module.exports = function createFilePostprocessor(options) {
	let allExports = new Map(); // url -> (remoteKey -> mangledName)

	return function processFile(item) {
		return Promise.try(() => {
			// TODO: Reuse instance, figure out how to pass the file metadata to the callback for an individual `process` call
			let postcssInstance = postcss([
				icssParser({
					keyReplacer: ({ url, remoteKey }) => {
						let resolvedSourcePath = item.deps[url];
		
						if (resolvedSourcePath == null) {
							throw new Error(`Referenced file '${sourceFile}' not resolved. This should never happen; please file a bug!`);
						}
		
						let sourceFile = allExports.get(resolvedSourcePath);
		
						if (sourceFile == null) {
							throw new Error(`Referenced file '${sourceFile}' not processed. This should never happen; please file a bug!`);
						}
		
						let mangledName = sourceFile.get(remoteKey);
		
						if (mangledName == null) {
							// TODO: Error type
							throw new Error(`No export named '${remoteKey}' found in file ${url}`);
						}
		
						/* The replacement is to deal with the difference in multiple-class notation between CSS and HTML; in CSS they are dot-delimited, but in HTML (which the ICSS spec targets) they are space-delimited. We need the CSS notation here. */
						return mangledName.replace(/ /g, ".");
					}
				}),
				... defaultValue(options.after, [])
			]);

			return postcssInstance.process(item.source, {
				from: item.file,
				... options
			});
		}).then((result) => {
			let exportMessages = result.messages.filter((message) => {
				return (message.pluginName === "postcss-icss-parser" && message.type === "icss-export");
			});

			let exportEntries = exportMessages.map((message) => {
				return [ message.item.name, message.item.value ];
			});

			let exportMap = new Map(exportEntries);
			let exportObject = objectFromEntries(exportEntries);
			
			allExports.set(item.file, exportMap);

			return { result, icssExports: exportObject };
		});
	};
};