/*
 * Copyright (C)2005-2019 Haxe Foundation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

package haxe.ds;

import java.NativeArray;
import java.lang.ref.WeakReference;
import java.lang.ref.ReferenceQueue;

@:coreApi class WeakMap<K:{}, V> implements haxe.Constraints.IMap<K, V> {
	extern private static inline var HASH_UPPER = 0.77;
	extern private static inline var FLAG_EMPTY = 0;
	extern private static inline var FLAG_DEL = 1;

	/**
	 * This is the most important structure here and the reason why it's so fast.
	 * It's an array of all the hashes contained in the table. These hashes cannot be 0 nor 1,
	 * which stand for "empty" and "deleted" states.
	 *
	 * The lookup algorithm will keep looking until a 0 or the key wanted is found;
	 * The insertion algorithm will do the same but will also break when FLAG_DEL is found;
	 */
	private var hashes:NativeArray<HashType>;

	private var entries:NativeArray<Entry<K, V>>;

	// weak map specific
	private var queue:ReferenceQueue<K>;

	private var nBuckets:Int;
	private var _size:Int;
	private var nOccupied:Int;
	private var upperBound:Int;

	#if !no_map_cache
	private var cachedEntry:Entry<K, V>;
	private var cachedIndex:Int;
	#end

	#if DEBUG_HASHTBL
	private var totalProbes:Int;
	private var probeTimes:Int;
	private var sameHash:Int;
	private var maxProbe:Int;
	#end

	public function new():Void {
		#if !no_map_cache
		cachedIndex = -1;
		#end
		queue = new ReferenceQueue();
	}

	@:analyzer(ignore)
	private function cleanupRefs():Void {
		var x:Dynamic = null, nOccupied = nOccupied;
		while ((x = queue.poll()) != null) {
			// even if not found on hashtable (already removed), release value
			var x:Entry<K, V> = cast x;
			x.value = null;

			// lookup index
			if (nOccupied != 0) {
				var mask = nBuckets - 1, hash = x.hash, nProbes = 0;
				var i = hash & mask;
				var last = i, flag;
				while (!isEmpty(flag = hashes[i]) && (isDel(flag) || flag != hash || entries[i] != x)) {
					i = (i + ++nProbes) & mask;
				}

				if (entries[i] == x) {
					#if !no_map_cache
					if (cachedIndex == i) {
						cachedIndex = -1;
						cachedEntry = null;
					}
					#end
					entries[i] = null;
					hashes[i] = FLAG_DEL;
					--_size;
				}
			}
		}
	}

	public function set(key:K, value:V):Void {
		cleanupRefs();
		var x:Int, k:Int;
		if (nOccupied >= upperBound) {
			if (nBuckets > (_size << 1))
				resize(nBuckets - 1); // clear "deleted" elements
			else
				resize(nBuckets + 2);
		}

		k = hash(key);
		var hashes = hashes, entries = entries;
		{
			var mask = (nBuckets == 0) ? 0 : nBuckets - 1;
			var site = x = nBuckets;
			var i = k & mask, nProbes = 0;

			var delKey = -1;
			// for speed up
			if (isEmpty(hashes[i])) {
				x = i;
			} else {
				// var inc = getInc(k, mask);
				var last = i, flag;
				while (!(isEmpty(flag = hashes[i]) || (flag == k && entries[i].keyEquals(key)))) {
					if (delKey == -1 && isDel(flag))
						delKey = i;
					i = (i + ++nProbes) & mask;
					#if DEBUG_HASHTBL
					probeTimes++;
					if (i == last)
						throw "assert";
					#end
				}

				if (isEmpty(flag) && delKey != -1)
					x = delKey;
				else
					x = i;
			}

			#if DEBUG_HASHTBL
			if (nProbes > maxProbe)
				maxProbe = nProbes;
			totalProbes++;
			#end
		}

		var flag = hashes[x], entry = new Entry(key, value, k, queue);
		if (isEmpty(flag)) {
			entries[x] = entry;
			hashes[x] = k;
			_size++;
			nOccupied++;
		} else if (isDel(flag)) {
			entries[x] = entry;
			hashes[x] = k;
			_size++;
		} else {
			assert(entries[x].keyEquals(key));
			entries[x] = entry;
		}

		#if !no_map_cache
		cachedIndex = x;
		cachedEntry = entry;
		#end
	}

	private final function lookup(key:K):Int {
		if (nBuckets != 0) {
			var hashes = hashes, entries = entries;

			var mask = nBuckets - 1, hash = hash(key), k = hash, nProbes = 0;
			var i = k & mask;
			var last = i, flag;
			// var inc = getInc(k, mask);
			while (!isEmpty(flag = hashes[i]) && (isDel(flag) || flag != k || !entries[i].keyEquals(key))) {
				i = (i + ++nProbes) & mask;
				#if DEBUG_HASHTBL
				probeTimes++;
				if (i == last)
					throw "assert";
				#end
			}

			#if DEBUG_HASHTBL
			if (nProbes > maxProbe)
				maxProbe = nProbes;
			totalProbes++;
			#end
			return isEither(flag) ? -1 : i;
		}

		return -1;
	}

	@:private final function resize(newNBuckets:Int):Void {
		// This function uses 0.25*n_bucktes bytes of working space instead of [sizeof(key_t+val_t)+.25]*n_buckets.
		var newHash = null;
		var j = 1;
		{
			newNBuckets = roundUp(newNBuckets);
			if (newNBuckets < 4)
				newNBuckets = 4;
			if (_size >= (newNBuckets * HASH_UPPER + 0.5))
				/* requested _size is too small */ {
				j = 0;
			} else { /* hash table _size to be changed (shrink or expand); rehash */
				var nfSize = newNBuckets;
				newHash = new NativeArray(nfSize);
				if (nBuckets < newNBuckets) // expand
				{
					var e = new NativeArray(newNBuckets);
					if (entries != null)
						arrayCopy(entries, 0, e, 0, nBuckets);
					entries = e;
				} // otherwise shrink
			}
		}

		if (j != 0) { // rehashing is required
			// resetting cache
			#if !no_map_cache
			cachedEntry = null;
			cachedIndex = -1;
			#end

			j = -1;
			var nBuckets = nBuckets, entries = entries, hashes = hashes;

			var newMask = newNBuckets - 1;
			while (++j < nBuckets) {
				var k;
				if (!isEither(k = hashes[j])) {
					var entry = entries[j];

					entries[j] = null;
					hashes[j] = FLAG_DEL;
					while (true)
						/* kick-out process; sort of like in Cuckoo hashing */ {
						var nProbes = 0;
						var i = k & newMask;

						while (!isEmpty(newHash[i]))
							i = (i + ++nProbes) & newMask;

						newHash[i] = k;

						if (i < nBuckets && !isEither(k = hashes[i]))
							/* kick out the existing element */ {
							{
								var tmp = entries[i];
								entries[i] = entry;
								entry = tmp;
							}

							hashes[i] = FLAG_DEL; /* mark it as deleted in the old hash table */
						} else { /* write the element and jump out of the loop */
							entries[i] = entry;
							break;
						}
					}
				}
			}

			if (nBuckets > newNBuckets)
				/* shrink the hash table */ {
				{
					var e = new NativeArray(newNBuckets);
					arrayCopy(entries, 0, e, 0, newNBuckets);
					this.entries = e;
				}
			}

			this.hashes = newHash;
			this.nBuckets = newNBuckets;
			this.nOccupied = _size;
			this.upperBound = Std.int(newNBuckets * HASH_UPPER + .5);
		}
	}

	public function get(key:K):Null<V> {
		cleanupRefs();
		var idx = -1;
		#if !no_map_cache
		if (cachedEntry != null && cachedEntry.keyEquals(key) && ((idx = cachedIndex) != -1)) {
			return cachedEntry.value;
		}
		#end

		idx = lookup(key);
		if (idx != -1) {
			var entry = entries[idx];
			#if !no_map_cache
			cachedEntry = entry;
			cachedIndex = idx;
			#end

			return entry.value;
		}

		return null;
	}

	private function getDefault(key:K, def:V):V {
		cleanupRefs();
		var idx = -1;
		#if !no_map_cache
		if (cachedEntry != null && cachedEntry.keyEquals(key) && ((idx = cachedIndex) != -1)) {
			return cachedEntry.value;
		}
		#end

		idx = lookup(key);
		if (idx != -1) {
			var entry = entries[idx];
			#if !no_map_cache
			cachedEntry = entry;
			cachedIndex = idx;
			#end

			return entry.value;
		}

		return def;
	}

	public function exists(key:K):Bool {
		cleanupRefs();
		var idx = -1;
		#if !no_map_cache
		if (cachedEntry != null && cachedEntry.keyEquals(key) && ((idx = cachedIndex) != -1)) {
			return true;
		}
		#end

		idx = lookup(key);
		if (idx != -1) {
			var entry = entries[idx];
			#if !no_map_cache
			cachedEntry = entry;
			cachedIndex = idx;
			#end

			return true;
		}

		return false;
	}

	public function remove(key:K):Bool {
		cleanupRefs();
		var idx = -1;
		#if !no_map_cache
		if (!(cachedEntry != null && cachedEntry.keyEquals(key) && ((idx = cachedIndex) != -1)))
		#end
		{
			idx = lookup(key);
		}

		if (idx == -1) {
			return false;
		} else {
			#if !no_map_cache
			if (cachedEntry != null && cachedEntry.keyEquals(key)) {
				cachedIndex = -1;
				cachedEntry = null;
			}
			#end

			hashes[idx] = FLAG_DEL;
			entries[idx] = null;
			--_size;

			return true;
		}
	}

	public inline function keys():Iterator<K> {
		cleanupRefs();
		return new WeakMapKeyIterator(this);
	}

	public inline function iterator():Iterator<V> {
		cleanupRefs();
		return new WeakMapValueIterator(this);
	}

	public inline function keyValueIterator():KeyValueIterator<K, V> {
		return new haxe.iterators.MapKeyValueIterator(this);
	}

	public function copy():WeakMap<K, V> {
		var copied = new WeakMap();
		for (key in keys())
			copied.set(key, get(key));
		return copied;
	}

	public function toString():String {
		var s = new StringBuf();
		s.add("[");
		var it = keys();
		for (i in it) {
			s.add(Std.string(i));
			s.add(" => ");
			s.add(Std.string(get(i)));
			if (it.hasNext())
				s.add(", ");
		}
		s.add("]");
		return s.toString();
	}

	public function clear():Void {
		hashes = null;
		entries = null;
		queue = new ReferenceQueue();
		nBuckets = 0;
		_size = 0;
		nOccupied = 0;
		upperBound = 0;
		#if !no_map_cache
		cachedEntry = null;
		cachedIndex = -1;
		#end
		#if DEBUG_HASHTBL
		totalProbes = 0;
		probeTimes = 0;
		sameHash = 0;
		maxProbe = 0;
		#end
	}
	
	public inline function size():Int {
		return _size;
	}

	extern private static inline function roundUp(x:Int):Int {
		--x;
		x |= (x) >>> 1;
		x |= (x) >>> 2;
		x |= (x) >>> 4;
		x |= (x) >>> 8;
		x |= (x) >>> 16;
		return ++x;
	}

	extern private static inline function getInc(k:Int, mask:Int):Int // return 1 for linear probing
		return (((k) >> 3 ^ (k) << 3) | 1) & (mask);

	extern private static inline function isEither(v:HashType):Bool
		return (v & 0xFFFFFFFE) == 0;

	extern private static inline function isEmpty(v:HashType):Bool
		return v == FLAG_EMPTY;

	extern private static inline function isDel(v:HashType):Bool
		return v == FLAG_DEL;

	// guarantee: Whatever this function is, it will never return 0 nor 1
	extern private static inline function hash(s:Dynamic):HashType {
		var k:Int = untyped s.hashCode();
		// k *= 357913941;
		// k ^= k << 24;
		// k += ~357913941;
		// k ^= k >> 31;
		// k ^= k << 31;

		k = (k + 0x7ed55d16) + (k << 12);
		k = (k ^ 0xc761c23c) ^ (k >> 19);
		k = (k + 0x165667b1) + (k << 5);
		k = (k + 0xd3a2646c) ^ (k << 9);
		k = (k + 0xfd7046c5) + (k << 3);
		k = (k ^ 0xb55a4f09) ^ (k >> 16);

		var ret = k;
		if (isEither(ret)) {
			if (ret == 0)
				ret = 2;
			else
				ret = 0xFFFFFFFF;
		}

		return ret;
	}

	extern private static inline function arrayCopy(sourceArray:Dynamic, sourceIndex:Int, destinationArray:Dynamic, destinationIndex:Int, length:Int):Void
		java.lang.System.arraycopy(sourceArray, sourceIndex, destinationArray, destinationIndex, length);

	extern private static inline function assert(x:Bool):Void {
		#if DEBUG_HASHTBL
		if (!x)
			throw "assert failed";
		#end
	}
}

private class Entry<K, V> extends WeakReference<K> {
	public var value:V;
	public var hash(default, null):Int;

	public function new(key:K, value:V, hash:Int, queue:ReferenceQueue<K>) {
		super(key, queue);
		this.value = value;
		this.hash = hash;
	}

	final inline public function keyEquals(k:K):Bool {
		return k != null && untyped k.equals(get());
	}
}

@:access(haxe.ds.WeakMap)
private final class WeakMapKeyIterator<T:{}, V> {
	var m:WeakMap<T, V>;
	var i:Int;
	var len:Int;
	var lastKey:T;

	public function new(m:WeakMap<T, V>) {
		this.i = 0;
		this.m = m;
		this.len = m.nBuckets;
	}

	public function hasNext():Bool {
		for (j in i...len) {
			if (!WeakMap.isEither(m.hashes[j])) {
				var entry = m.entries[j], last = entry.get();
				if (last != null) {
					#if !no_map_cache
					m.cachedIndex = i;
					m.cachedEntry = entry;
					#end
					lastKey = last; // keep a strong reference to the key while iterating, so it doesn't get collected
					i = j;
					return true;
				}
			}
		}
		lastKey = null;
		return false;
	}

	public function next():T {
		i = i + 1;
		return lastKey;
	}
}

@:access(haxe.ds.WeakMap)
private final class WeakMapValueIterator<K:{}, T> {
	var m:WeakMap<K, T>;
	var i:Int;
	var len:Int;

	public function new(m:WeakMap<K, T>) {
		this.i = 0;
		this.m = m;
		this.len = m.nBuckets;
	}

	public function hasNext():Bool {
		for (j in i...len) {
			if (!WeakMap.isEither(m.hashes[j]) && m.entries[j].get() != null) {
				i = j;
				return true;
			}
		}
		return false;
	}

	public inline function next():T {
		var ret = m.entries[i];
		i = i + 1;
		return ret.value;
	}
}

private typedef HashType = Int;
