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

"use strict";

const { validate } = require("schema-utils");
const schema = require("../../schemas/plugins/optimize/AggressiveSplittingPlugin.json");
const { STAGE_ADVANCED } = require("../OptimizationStages");
const { intersect } = require("../util/SetHelpers");
const {
	compareModulesByIdentifier,
	compareChunks
} = require("../util/comparators");
const identifierUtils = require("../util/identifier");

/** @typedef {import("../../declarations/plugins/optimize/AggressiveSplittingPlugin").AggressiveSplittingPluginOptions} AggressiveSplittingPluginOptions */
/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../ChunkGraph")} ChunkGraph */
/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../Module")} Module */

const moveModuleBetween = (chunkGraph, oldChunk, newChunk) => {
	return module => {
		chunkGraph.disconnectChunkAndModule(oldChunk, module);
		chunkGraph.connectChunkAndModule(newChunk, module);
	};
};

/**
 * @param {ChunkGraph} chunkGraph the chunk graph
 * @param {Chunk} chunk the chunk
 * @returns {function(Module): boolean} filter for entry module
 */
const isNotAEntryModule = (chunkGraph, chunk) => {
	return module => {
		return !chunkGraph.isEntryModuleInChunk(module, chunk);
	};
};

/** @type {WeakSet<Chunk>} */
const recordedChunks = new WeakSet();

class AggressiveSplittingPlugin {
	/**
	 * @param {AggressiveSplittingPluginOptions=} options options object
	 */
	constructor(options = {}) {
		validate(schema, options, {
			name: "Aggressive Splitting Plugin",
			baseDataPath: "options"
		});

		this.options = options;
		if (typeof this.options.minSize !== "number") {
			this.options.minSize = 30 * 1024;
		}
		if (typeof this.options.maxSize !== "number") {
			this.options.maxSize = 50 * 1024;
		}
		if (typeof this.options.chunkOverhead !== "number") {
			this.options.chunkOverhead = 0;
		}
		if (typeof this.options.entryChunkMultiplicator !== "number") {
			this.options.entryChunkMultiplicator = 1;
		}
	}

	/**
	 * @param {Chunk} chunk the chunk to test
	 * @returns {boolean} true if the chunk was recorded
	 */
	static wasChunkRecorded(chunk) {
		return recordedChunks.has(chunk);
	}

	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.thisCompilation.tap(
			"AggressiveSplittingPlugin",
			compilation => {
				let needAdditionalSeal = false;
				let newSplits;
				let fromAggressiveSplittingSet;
				let chunkSplitDataMap;
				compilation.hooks.optimize.tap("AggressiveSplittingPlugin", () => {
					newSplits = [];
					fromAggressiveSplittingSet = new Set();
					chunkSplitDataMap = new Map();
				});
				compilation.hooks.optimizeChunks.tap(
					{
						name: "AggressiveSplittingPlugin",
						stage: STAGE_ADVANCED
					},
					chunks => {
						const chunkGraph = compilation.chunkGraph;
						// Precompute stuff
						const nameToModuleMap = new Map();
						const moduleToNameMap = new Map();
						const makePathsRelative = identifierUtils.makePathsRelative.bindContextCache(
							compiler.context,
							compiler.root
						);
						for (const m of compilation.modules) {
							const name = makePathsRelative(m.identifier());
							nameToModuleMap.set(name, m);
							moduleToNameMap.set(m, name);
						}

						// Check used chunk ids
						const usedIds = new Set();
						for (const chunk of chunks) {
							usedIds.add(chunk.id);
						}

						const recordedSplits =
							(compilation.records && compilation.records.aggressiveSplits) ||
							[];
						const usedSplits = newSplits
							? recordedSplits.concat(newSplits)
							: recordedSplits;

						const minSize = this.options.minSize;
						const maxSize = this.options.maxSize;

						const applySplit = splitData => {
							// Cannot split if id is already taken
							if (splitData.id !== undefined && usedIds.has(splitData.id)) {
								return false;
							}

							// Get module objects from names
							const selectedModules = splitData.modules.map(name =>
								nameToModuleMap.get(name)
							);

							// Does the modules exist at all?
							if (!selectedModules.every(Boolean)) return false;

							// Check if size matches (faster than waiting for hash)
							let size = 0;
							for (const m of selectedModules) size += m.size();
							if (size !== splitData.size) return false;

							// get chunks with all modules
							const selectedChunks = intersect(
								selectedModules.map(
									m => new Set(chunkGraph.getModuleChunksIterable(m))
								)
							);

							// No relevant chunks found
							if (selectedChunks.size === 0) return false;

							// The found chunk is already the split or similar
							if (
								selectedChunks.size === 1 &&
								chunkGraph.getNumberOfChunkModules(
									Array.from(selectedChunks)[0]
								) === selectedModules.length
							) {
								const chunk = Array.from(selectedChunks)[0];
								if (fromAggressiveSplittingSet.has(chunk)) return false;
								fromAggressiveSplittingSet.add(chunk);
								chunkSplitDataMap.set(chunk, splitData);
								return true;
							}

							// split the chunk into two parts
							const newChunk = compilation.addChunk();
							newChunk.chunkReason = "aggressive splitted";
							for (const chunk of selectedChunks) {
								selectedModules.forEach(
									moveModuleBetween(chunkGraph, chunk, newChunk)
								);
								chunk.split(newChunk);
								chunk.name = null;
							}
							fromAggressiveSplittingSet.add(newChunk);
							chunkSplitDataMap.set(newChunk, splitData);

							if (splitData.id !== null && splitData.id !== undefined) {
								newChunk.id = splitData.id;
								newChunk.ids = [splitData.id];
							}
							return true;
						};

						// try to restore to recorded splitting
						let changed = false;
						for (let j = 0; j < usedSplits.length; j++) {
							const splitData = usedSplits[j];
							if (applySplit(splitData)) changed = true;
						}

						// for any chunk which isn't splitted yet, split it and create a new entry
						// start with the biggest chunk
						const cmpFn = compareChunks(chunkGraph);
						const sortedChunks = Array.from(chunks).sort((a, b) => {
							const diff1 =
								chunkGraph.getChunkModulesSize(b) -
								chunkGraph.getChunkModulesSize(a);
							if (diff1) return diff1;
							const diff2 =
								chunkGraph.getNumberOfChunkModules(a) -
								chunkGraph.getNumberOfChunkModules(b);
							if (diff2) return diff2;
							return cmpFn(a, b);
						});
						for (const chunk of sortedChunks) {
							if (fromAggressiveSplittingSet.has(chunk)) continue;
							const size = chunkGraph.getChunkModulesSize(chunk);
							if (
								size > maxSize &&
								chunkGraph.getNumberOfChunkModules(chunk) > 1
							) {
								const modules = chunkGraph
									.getOrderedChunkModules(chunk, compareModulesByIdentifier)
									.filter(isNotAEntryModule(chunkGraph, chunk));
								const selectedModules = [];
								let selectedModulesSize = 0;
								for (let k = 0; k < modules.length; k++) {
									const module = modules[k];
									const newSize = selectedModulesSize + module.size();
									if (newSize > maxSize && selectedModulesSize >= minSize) {
										break;
									}
									selectedModulesSize = newSize;
									selectedModules.push(module);
								}
								if (selectedModules.length === 0) continue;
								const splitData = {
									modules: selectedModules
										.map(m => moduleToNameMap.get(m))
										.sort(),
									size: selectedModulesSize
								};

								if (applySplit(splitData)) {
									newSplits = (newSplits || []).concat(splitData);
									changed = true;
								}
							}
						}
						if (changed) return true;
					}
				);
				compilation.hooks.recordHash.tap(
					"AggressiveSplittingPlugin",
					records => {
						// 4. save made splittings to records
						const allSplits = new Set();
						const invalidSplits = new Set();

						// Check if some splittings are invalid
						// We remove invalid splittings and try again
						for (const chunk of compilation.chunks) {
							const splitData = chunkSplitDataMap.get(chunk);
							if (splitData !== undefined) {
								if (splitData.hash && chunk.hash !== splitData.hash) {
									// Split was successful, but hash doesn't equal
									// We can throw away the split since it's useless now
									invalidSplits.add(splitData);
								}
							}
						}

						if (invalidSplits.size > 0) {
							records.aggressiveSplits = records.aggressiveSplits.filter(
								splitData => !invalidSplits.has(splitData)
							);
							needAdditionalSeal = true;
						} else {
							// set hash and id values on all (new) splittings
							for (const chunk of compilation.chunks) {
								const splitData = chunkSplitDataMap.get(chunk);
								if (splitData !== undefined) {
									splitData.hash = chunk.hash;
									splitData.id = chunk.id;
									allSplits.add(splitData);
									// set flag for stats
									recordedChunks.add(chunk);
								}
							}

							// Also add all unused historical splits (after the used ones)
							// They can still be used in some future compilation
							const recordedSplits =
								compilation.records && compilation.records.aggressiveSplits;
							if (recordedSplits) {
								for (const splitData of recordedSplits) {
									if (!invalidSplits.has(splitData)) allSplits.add(splitData);
								}
							}

							// record all splits
							records.aggressiveSplits = Array.from(allSplits);

							needAdditionalSeal = false;
						}
					}
				);
				compilation.hooks.needAdditionalSeal.tap(
					"AggressiveSplittingPlugin",
					() => {
						if (needAdditionalSeal) {
							needAdditionalSeal = false;
							return true;
						}
					}
				);
			}
		);
	}
}
module.exports = AggressiveSplittingPlugin;