/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const { STAGE_BASIC } = require("../OptimizationStages");

/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../ChunkGroup")} ChunkGroup */
/** @typedef {import("../Compiler")} Compiler */

const PLUGIN_NAME = "EnsureChunkConditionsPlugin";

class EnsureChunkConditionsPlugin {
	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
			/**
			 * Handles the hook callback for this code path.
			 * @param {Iterable<Chunk>} chunks the chunks
			 */
			const handler = (chunks) => {
				const chunkGraph = compilation.chunkGraph;
				// These sets are hoisted here to save memory
				// They are cleared at the end of every loop
				/** @type {Set<Chunk>} */
				const sourceChunks = new Set();
				/** @type {Set<ChunkGroup>} */
				const chunkGroups = new Set();
				for (const module of compilation.modules) {
					if (!module.hasChunkCondition()) continue;
					for (const chunk of chunkGraph.getModuleChunksIterable(module)) {
						if (!module.chunkCondition(chunk, compilation)) {
							sourceChunks.add(chunk);
							for (const group of chunk.groupsIterable) {
								chunkGroups.add(group);
							}
						}
					}
					if (sourceChunks.size === 0) continue;
					/** @type {Set<Chunk>} */
					const targetChunks = new Set();
					chunkGroupLoop: for (const chunkGroup of chunkGroups) {
						// Can module be placed in a chunk of this group?
						for (const chunk of chunkGroup.chunks) {
							if (module.chunkCondition(chunk, compilation)) {
								targetChunks.add(chunk);
								continue chunkGroupLoop;
							}
						}
						// We reached the entrypoint: fail
						if (chunkGroup.isInitial()) {
							throw new Error(
								`Cannot fulfil chunk condition of ${module.identifier()}`
							);
						}
						// Try placing in all parents
						for (const group of chunkGroup.parentsIterable) {
							chunkGroups.add(group);
						}
					}
					for (const sourceChunk of sourceChunks) {
						chunkGraph.disconnectChunkAndModule(sourceChunk, module);
					}
					for (const targetChunk of targetChunks) {
						chunkGraph.connectChunkAndModule(targetChunk, module);
					}
					sourceChunks.clear();
					chunkGroups.clear();
				}
			};
			compilation.hooks.optimizeChunks.tap(
				{
					name: PLUGIN_NAME,
					stage: STAGE_BASIC
				},
				handler
			);
		});
	}
}

module.exports = EnsureChunkConditionsPlugin;
