// Copyright 2020 Joshua J Baker. All rights reserved.
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.

#include <stdint.h>
#include <stddef.h>
#include "hashmap.h"

static void *(*_malloc)(size_t) = NULL;
static void *(*_realloc)(void *, size_t) = NULL;
static void (*_free)(const void *) = NULL;

// hashmap_set_allocator allows for configuring a custom allocator for
// all hashmap library operations. This function, if needed, should be called
// only once at startup and a prior to calling hashmap_new().
void hashmap_set_allocator([[maybe_unused]] void *(*malloc)(size_t), [[maybe_unused]] void (*free)(const void*)) 
{
	_malloc = kmalloc;
	_free = kfree;
}

struct bucket {
	uint64_t hash:48;
	uint64_t dib:16;
};

// hashmap is an open addressed hash map using robinhood hashing.
struct hashmap {
	void *(*malloc)(size_t);
	void *(*realloc)(void *, size_t);
	void (*free)(const void *);
	bool oom;
	size_t elsize;
	size_t cap;
	uint64_t seed0;
	uint64_t seed1;
	uint64_t (*hash)(const void *item, uint64_t seed0, uint64_t seed1);
	int (*compare)(const void *a, const void *b, void *udata);
	void (*elfree)(const void *item);
	void *udata;
	size_t bucketsz;
	size_t nbuckets;
	size_t count;
	size_t mask;
	size_t growat;
	size_t shrinkat;
	void *buckets;
	void *spare;
	void *edata;
};

static struct bucket *bucket_at(struct hashmap *map, size_t index) {
	return (struct bucket*)(((char*)map->buckets)+(map->bucketsz*index));
}

static void *bucket_item(struct bucket *entry) {
	return ((char*)entry)+sizeof(struct bucket);
}

static uint64_t get_hash(struct hashmap *map, const void *key) {
	return map->hash(key, map->seed0, map->seed1) << 16 >> 16;
}

// hashmap_new_with_allocator returns a new hash map using a custom allocator.
// See hashmap_new for more information information
struct hashmap *hashmap_new_with_allocator(
							void *(*_malloc)(size_t), 
							void *(*_realloc)(void*, size_t), 
							void (*_free)(const void*),
							size_t elsize, size_t cap, 
							uint64_t seed0, uint64_t seed1,
							uint64_t (*hash)(const void *item, 
											 uint64_t seed0, uint64_t seed1),
							int (*compare)(const void *a, const void *b, 
										   void *udata),
							void (*elfree)(const void *item),
							void *udata)
{
	_malloc = _malloc ? _malloc : kmalloc;
	_realloc = _realloc ? _realloc : krealloc;
	_free = _free ? _free : kfree;
	size_t ncap = 16;
	if (cap < ncap) {
		cap = ncap;
	} else {
		while (ncap < cap) {
			ncap *= 2;
		}
		cap = ncap;
	}
	size_t bucketsz = sizeof(struct bucket) + elsize;
	while (bucketsz & (sizeof(uintptr_t)-1)) {
		bucketsz++;
	}
	// hashmap + spare + edata
	size_t size = sizeof(struct hashmap)+bucketsz*2;
	struct hashmap *map = _malloc(size);
	if (!map) {
		return NULL;
	}
	memset(map, 0, sizeof(struct hashmap));
	map->elsize = elsize;
	map->bucketsz = bucketsz;
	map->seed0 = seed0;
	map->seed1 = seed1;
	map->hash = hash;
	map->compare = compare;
	map->elfree = elfree;
	map->udata = udata;
	map->spare = ((char*)map)+sizeof(struct hashmap);
	map->edata = (char*)map->spare+bucketsz;
	map->cap = cap;
	map->nbuckets = cap;
	map->mask = map->nbuckets-1;
	map->buckets = _malloc(map->bucketsz*map->nbuckets);
	if (!map->buckets) {
		_free(map);
		return NULL;
	}
	memset(map->buckets, 0, map->bucketsz*map->nbuckets);
	map->growat = map->nbuckets*0.75;
	map->shrinkat = map->nbuckets*0.10;
    	map->malloc = _malloc;
	map->realloc = _realloc;
	map->free = _free;
	return map;  
}


// hashmap_new returns a new hash map. 
// Param `elsize` is the size of each element in the tree. Every element that
// is inserted, deleted, or retrieved will be this size.
// Param `cap` is the default lower capacity of the hashmap. Setting this to
// zero will default to 16.
// Params `seed0` and `seed1` are optional seed values that are passed to the 
// following `hash` function. These can be any value you wish but it's often 
// best to use randomly generated values.
// Param `hash` is a function that generates a hash value for an item. It's
// important that you provide a good hash function, otherwise it will perform
// poorly or be vulnerable to Denial-of-service attacks. This implementation
// comes with two helper functions `hashmap_sip()` and `hashmap_murmur()`.
// Param `compare` is a function that compares items in the tree. See the 
// qsort stdlib function for an example of how this function works.
// The hashmap must be freed with hashmap_free(). 
// Param `elfree` is a function that frees a specific item. This should be NULL
// unless you're storing some kind of reference data in the hash.
struct hashmap *hashmap_new(size_t elsize, size_t cap, 
							uint64_t seed0, uint64_t seed1,
							uint64_t (*hash)(const void *item, 
											 uint64_t seed0, uint64_t seed1),
							int (*compare)(const void *a, const void *b, 
										   void *udata),
							void (*elfree)(const void *item),
							void *udata)
{
	return hashmap_new_with_allocator(
		(_malloc?_malloc:kmalloc),
		(_realloc?_realloc:krealloc),
		(_free?_free:kfree),
		elsize, cap, seed0, seed1, hash, compare, elfree, udata
	);
}

static void free_elements(struct hashmap *map) {
	if (map->elfree) {
		for (size_t i = 0; i < map->nbuckets; i++) {
			struct bucket *bucket = bucket_at(map, i);
			if (bucket->dib) map->elfree(bucket_item(bucket));
		}
	}
}


// hashmap_clear quickly clears the map. 
// Every item is called with the element-freeing function given in hashmap_new,
// if present, to free any data referenced in the elements of the hashmap.
// When the update_cap is provided, the map's capacity will be updated to match
// the currently number of allocated buckets. This is an optimization to ensure
// that this operation does not perform any allocations.
void hashmap_clear(struct hashmap *map, bool update_cap) {
	map->count = 0;
	free_elements(map);
	if (update_cap) {
		map->cap = map->nbuckets;
	} else if (map->nbuckets != map->cap) {
		void *new_buckets = map->malloc(map->bucketsz*map->cap);
		if (new_buckets) {
			map->free(map->buckets);
			map->buckets = new_buckets;
		}
		map->nbuckets = map->cap;
	}
	memset(map->buckets, 0, map->bucketsz*map->nbuckets);
	map->mask = map->nbuckets-1;
	map->growat = map->nbuckets*0.75;
	map->shrinkat = map->nbuckets*0.10;
}


static bool resize(struct hashmap *map, size_t new_cap) {
	struct hashmap *map2 = hashmap_new_with_allocator(map->malloc, map->realloc, map->free,
			map->elsize, new_cap, map->seed0, 
			map->seed1, map->hash, map->compare,
			map->elfree, map->udata);
	if (!map2) {
		return false;
	}
	for (size_t i = 0; i < map->nbuckets; i++) {
		struct bucket *entry = bucket_at(map, i);
		if (!entry->dib) {
			continue;
		}
		entry->dib = 1;
		size_t j = entry->hash & map2->mask;
		for (;;) {
			struct bucket *bucket = bucket_at(map2, j);
			if (bucket->dib == 0) {
				memcpy(bucket, entry, map->bucketsz);
				break;
			}
			if (bucket->dib < entry->dib) {
				memcpy(map2->spare, bucket, map->bucketsz);
				memcpy(bucket, entry, map->bucketsz);
				memcpy(entry, map2->spare, map->bucketsz);
			}
			j = (j + 1) & map2->mask;
			entry->dib += 1;
		}
	}
	map->free(map->buckets);
	map->buckets = map2->buckets;
	map->nbuckets = map2->nbuckets;
	map->mask = map2->mask;
	map->growat = map2->growat;
	map->shrinkat = map2->shrinkat;
	map->free(map2);
	return true;
}

// hashmap_set inserts or replaces an item in the hash map. If an item is
// replaced then it is returned otherwise NULL is returned. This operation
// may allocate memory. If the system is unable to allocate additional
// memory then NULL is returned and hashmap_oom() returns true.
void *hashmap_set(struct hashmap *map, const void *item) {
	if (!item) {
		return NULL;
	}
	map->oom = false;
	if (map->count == map->growat) {
		if (!resize(map, map->nbuckets*2)) {
			map->oom = true;
			return NULL;
		}
	}

	
	struct bucket *entry = map->edata;
	entry->hash = get_hash(map, item);
	entry->dib = 1;
	memcpy(bucket_item(entry), item, map->elsize);
	size_t i = entry->hash & map->mask;
	for (;;) {
		struct bucket *bucket = bucket_at(map, i);
		if (bucket->dib == 0) {
			memcpy(bucket, entry, map->bucketsz);
			map->count++;
			return NULL;
		}
		if (entry->hash == bucket->hash && 
			map->compare(bucket_item(entry), bucket_item(bucket), map->udata) == 0)
		{
			memcpy(map->spare, bucket_item(bucket), map->elsize);
			memcpy(bucket_item(bucket), bucket_item(entry), map->elsize);
			return map->spare;
		}
		if (bucket->dib < entry->dib) {
			memcpy(map->spare, bucket, map->bucketsz);
			memcpy(bucket, entry, map->bucketsz);
			memcpy(entry, map->spare, map->bucketsz);
		}		
		i = (i + 1) & map->mask;
		entry->dib += 1;
	}
}

// hashmap_get returns the item based on the provided key. If the item is not
// found then NULL is returned.
void *hashmap_get(struct hashmap *map, const void *key) {
	if (!key) {
		return NULL;
	}
	uint64_t hash = get_hash(map, key);
	size_t i = hash & map->mask;
	for (;;) {
		struct bucket *bucket = bucket_at(map, i);
		if (!bucket->dib) {
			return NULL;
		}
		if (bucket->hash == hash && 
			map->compare(key, bucket_item(bucket), map->udata) == 0)
		{
			return bucket_item(bucket);
		}
		i = (i + 1) & map->mask;
	}
}

// hashmap_probe returns the item in the bucket at position or NULL if an item
// is not set for that bucket. The position is 'moduloed' by the number of 
// buckets in the hashmap.
void *hashmap_probe(struct hashmap *map, uint64_t position) {
	size_t i = position & map->mask;
	struct bucket *bucket = bucket_at(map, i);
	if (!bucket->dib) {
		return NULL;
	}
	return bucket_item(bucket);
}


// hashmap_delete removes an item from the hash map and returns it. If the
// item is not found then NULL is returned.
void *hashmap_delete(struct hashmap *map, void *key) {
	if (!key) {
		return NULL;
	}
	map->oom = false;
	uint64_t hash = get_hash(map, key);
	size_t i = hash & map->mask;
	for (;;) {
		struct bucket *bucket = bucket_at(map, i);
		if (!bucket->dib) {
			return NULL;
		}
		if (bucket->hash == hash && 
			map->compare(key, bucket_item(bucket), map->udata) == 0)
		{
			memcpy(map->spare, bucket_item(bucket), map->elsize);
			bucket->dib = 0;
			for (;;) {
				struct bucket *prev = bucket;
				i = (i + 1) & map->mask;
				bucket = bucket_at(map, i);
				if (bucket->dib <= 1) {
					prev->dib = 0;
					break;
				}
				memcpy(prev, bucket, map->bucketsz);
				prev->dib--;
			}
			map->count--;
			if (map->nbuckets > map->cap && map->count <= map->shrinkat) {
				// Ignore the return value. It's ok for the resize operation to
				// fail to allocate enough memory because a shrink operation
				// does not change the integrity of the data.
				resize(map, map->nbuckets/2);
			}
			return map->spare;
		}
		i = (i + 1) & map->mask;
	}
}

// hashmap_count returns the number of items in the hash map.
size_t hashmap_count(struct hashmap *map) {
	return map->count;
}

// hashmap_free frees the hash map
// Every item is called with the element-freeing function given in hashmap_new,
// if present, to free any data referenced in the elements of the hashmap.
void hashmap_free(struct hashmap *map) {
	if (!map) return;
	free_elements(map);
	map->free(map->buckets);
	map->free(map);
}

// hashmap_oom returns true if the last hashmap_set() call failed due to the 
// system being out of memory.
bool hashmap_oom(struct hashmap *map) {
	return map->oom;
}

// hashmap_scan iterates over all items in the hash map
// Param `iter` can return false to stop iteration early.
// Returns false if the iteration has been stopped early.
bool hashmap_scan(struct hashmap *map, 
				  bool (*iter)(const void *item, void *udata), void *udata)
{
	for (size_t i = 0; i < map->nbuckets; i++) {
		struct bucket *bucket = bucket_at(map, i);
		if (bucket->dib) {
			if (!iter(bucket_item(bucket), udata)) {
				return false;
			}
		}
	}
	return true;
}


// hashmap_iter iterates one key at a time yielding a reference to an
// entry at each iteration. Useful to write simple loops and avoid writing
// dedicated callbacks and udata structures, as in hashmap_scan.
//
// map is a hash map handle. i is a pointer to a size_t cursor that
// should be initialized to 0 at the beginning of the loop. item is a void
// pointer pointer that is populated with the retrieved item. Note that this
// is NOT a copy of the item stored in the hash map and can be directly
// modified.
//
// Note that if hashmap_delete() is called on the hashmap being iterated,
// the buckets are rearranged and the iterator must be reset to 0, otherwise
// unexpected results may be returned after deletion.
//
// This function has not been tested for thread safety.
//
// The function returns true if an item was retrieved; false if the end of the
// iteration has been reached.
bool hashmap_iter(struct hashmap *map, size_t *i, void **item)
{
	struct bucket *bucket;

	do {
		if (*i >= map->nbuckets) return false;

		bucket = bucket_at(map, *i);
		(*i)++;
	} while (!bucket->dib);

	*item = bucket_item(bucket);

	return true;
}


//-----------------------------------------------------------------------------
// SipHash reference C implementation
//
// Copyright (c) 2012-2016 Jean-Philippe Aumasson
// <jeanphilippe.aumasson@gmail.com>
// Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
//
// To the extent possible under law, the author(s) have dedicated all copyright
// and related and neighboring rights to this software to the public domain
// worldwide. This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication along
// with this software. If not, see
// <http://creativecommons.org/publicdomain/zero/1.0/>.
//
// default: SipHash-2-4
//-----------------------------------------------------------------------------
static uint64_t SIP64(const uint8_t *in, const size_t inlen, 
					  uint64_t seed0, uint64_t seed1) 
{
#define U8TO64_LE(p) \
	{  (((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8) | \
		((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24) | \
		((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40) | \
		((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56)) }
#define U64TO8_LE(p, v) \
	{ U32TO8_LE((p), (uint32_t)((v))); \
	  U32TO8_LE((p) + 4, (uint32_t)((v) >> 32)); }
#define U32TO8_LE(p, v) \
	{ (p)[0] = (uint8_t)((v)); \
	  (p)[1] = (uint8_t)((v) >> 8); \
	  (p)[2] = (uint8_t)((v) >> 16); \
	  (p)[3] = (uint8_t)((v) >> 24); }
#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
#define SIPROUND \
	{ v0 += v1; v1 = ROTL(v1, 13); \
	  v1 ^= v0; v0 = ROTL(v0, 32); \
	  v2 += v3; v3 = ROTL(v3, 16); \
	  v3 ^= v2; \
	  v0 += v3; v3 = ROTL(v3, 21); \
	  v3 ^= v0; \
	  v2 += v1; v1 = ROTL(v1, 17); \
	  v1 ^= v2; v2 = ROTL(v2, 32); }
	uint64_t k0 = U8TO64_LE((uint8_t*)&seed0);
	uint64_t k1 = U8TO64_LE((uint8_t*)&seed1);
	uint64_t v3 = UINT64_C(0x7465646279746573) ^ k1;
	uint64_t v2 = UINT64_C(0x6c7967656e657261) ^ k0;
	uint64_t v1 = UINT64_C(0x646f72616e646f6d) ^ k1;
	uint64_t v0 = UINT64_C(0x736f6d6570736575) ^ k0;
	const uint8_t *end = in + inlen - (inlen % sizeof(uint64_t));
	for (; in != end; in += 8) {
		uint64_t m = U8TO64_LE(in);
		v3 ^= m;
		SIPROUND; SIPROUND;
		v0 ^= m;
	}
	const int left = inlen & 7;
	uint64_t b = ((uint64_t)inlen) << 56;
	switch (left) {
	case 7: b |= ((uint64_t)in[6]) << 48; __attribute__((fallthrough));
	case 6: b |= ((uint64_t)in[5]) << 40; __attribute__((fallthrough));
	case 5: b |= ((uint64_t)in[4]) << 32; __attribute__((fallthrough));
	case 4: b |= ((uint64_t)in[3]) << 24; __attribute__((fallthrough));
	case 3: b |= ((uint64_t)in[2]) << 16; __attribute__((fallthrough));
	case 2: b |= ((uint64_t)in[1]) << 8; __attribute__((fallthrough));
	case 1: b |= ((uint64_t)in[0]); break;
	case 0: break;
	}
	v3 ^= b;
	SIPROUND; SIPROUND;
	v0 ^= b;
	v2 ^= 0xff;
	SIPROUND; SIPROUND; SIPROUND; SIPROUND;
	b = v0 ^ v1 ^ v2 ^ v3;
	uint64_t out = 0;
	U64TO8_LE((uint8_t*)&out, b);
	return out;
}

//-----------------------------------------------------------------------------
// MurmurHash3 was written by Austin Appleby, and is placed in the public
// domain. The author hereby disclaims copyright to this source code.
//
// Murmur3_86_128
//-----------------------------------------------------------------------------
static void MM86128(const void *key, const int len, uint32_t seed, void *out) {
#define	ROTL32(x, r) ((x << r) | (x >> (32 - r)))
#define FMIX32(h) h^=h>>16; h*=0x85ebca6b; h^=h>>13; h*=0xc2b2ae35; h^=h>>16;
	const uint8_t * data = (const uint8_t*)key;
	const int nblocks = len / 16;
	uint32_t h1 = seed;
	uint32_t h2 = seed;
	uint32_t h3 = seed;
	uint32_t h4 = seed;
	uint32_t c1 = 0x239b961b; 
	uint32_t c2 = 0xab0e9789;
	uint32_t c3 = 0x38b34ae5; 
	uint32_t c4 = 0xa1e38b93;
	const uint32_t * blocks = (const uint32_t *)(data + nblocks*16);
	for (int i = -nblocks; i; i++) {
		uint32_t k1 = blocks[i*4+0];
		uint32_t k2 = blocks[i*4+1];
		uint32_t k3 = blocks[i*4+2];
		uint32_t k4 = blocks[i*4+3];
		k1 *= c1; k1  = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
		h1 = ROTL32(h1,19); h1 += h2; h1 = h1*5+0x561ccd1b;
		k2 *= c2; k2  = ROTL32(k2,16); k2 *= c3; h2 ^= k2;
		h2 = ROTL32(h2,17); h2 += h3; h2 = h2*5+0x0bcaa747;
		k3 *= c3; k3  = ROTL32(k3,17); k3 *= c4; h3 ^= k3;
		h3 = ROTL32(h3,15); h3 += h4; h3 = h3*5+0x96cd1c35;
		k4 *= c4; k4  = ROTL32(k4,18); k4 *= c1; h4 ^= k4;
		h4 = ROTL32(h4,13); h4 += h1; h4 = h4*5+0x32ac3b17;
	}
	const uint8_t * tail = (const uint8_t*)(data + nblocks*16);
	uint32_t k1 = 0;
	uint32_t k2 = 0;
	uint32_t k3 = 0;
	uint32_t k4 = 0;
	switch(len & 15) {
	case 15: k4 ^= tail[14] << 16; __attribute__((fallthrough));
	case 14: k4 ^= tail[13] << 8; __attribute__((fallthrough));
	case 13: k4 ^= tail[12] << 0;
		k4 *= c4; k4  = ROTL32(k4,18); k4 *= c1; h4 ^= k4; __attribute__((fallthrough));
	case 12: k3 ^= tail[11] << 24; __attribute__((fallthrough));
	case 11: k3 ^= tail[10] << 16; __attribute__((fallthrough));
	case 10: k3 ^= tail[ 9] << 8; __attribute__((fallthrough));
	case  9: k3 ^= tail[ 8] << 0;
		k3 *= c3; k3  = ROTL32(k3,17); k3 *= c4; h3 ^= k3; __attribute__((fallthrough));
	case  8: k2 ^= tail[ 7] << 24; __attribute__((fallthrough));
	case  7: k2 ^= tail[ 6] << 16; __attribute__((fallthrough));
	case  6: k2 ^= tail[ 5] << 8; __attribute__((fallthrough));
	case  5: k2 ^= tail[ 4] << 0;
		k2 *= c2; k2  = ROTL32(k2,16); k2 *= c3; h2 ^= k2; __attribute__((fallthrough));
	case  4: k1 ^= tail[ 3] << 24; __attribute__((fallthrough));
	case  3: k1 ^= tail[ 2] << 16; __attribute__((fallthrough));
	case  2: k1 ^= tail[ 1] << 8; __attribute__((fallthrough));
	case  1: k1 ^= tail[ 0] << 0;
		k1 *= c1; k1  = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
	};
	h1 ^= len; h2 ^= len; h3 ^= len; h4 ^= len;
	h1 += h2; h1 += h3; h1 += h4;
	h2 += h1; h3 += h1; h4 += h1;
	FMIX32(h1); FMIX32(h2); FMIX32(h3); FMIX32(h4);
	h1 += h2; h1 += h3; h1 += h4;
	h2 += h1; h3 += h1; h4 += h1;
	((uint32_t*)out)[0] = h1;
	((uint32_t*)out)[1] = h2;
	((uint32_t*)out)[2] = h3;
	((uint32_t*)out)[3] = h4;
}

// hashmap_sip returns a hash value for `data` using SipHash-2-4.
uint64_t hashmap_sip(const void *data, size_t len, 
					 uint64_t seed0, uint64_t seed1)
{
	return SIP64((uint8_t*)data, len, seed0, seed1);
}

// hashmap_murmur returns a hash value for `data` using Murmur3_86_128.
uint64_t hashmap_murmur(const void *data, size_t len, 
						uint64_t seed0, [[maybe_unused]] uint64_t seed1)
{
	char out[16];
	MM86128(data, len, seed0, &out);
	return *(uint64_t*)out;
}
