/**
 * mds — A micro-display server
 * Copyright © 2014, 2015, 2016, 2017  Mattias Andrée (maandree@kth.se)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "hash-table.h"

#include "macros.h"

#include <stdlib.h>
#include <errno.h>


/**
 * Test if a key matches the key in a bucket
 * 
 * @param  T  The instance of the hash table
 * @param  B  The bucket
 * @param  K  The key
 * @param  H  The hash of the key
 */
#define TEST_KEY(T, B, K, H)\
	((B)->key == (K) || ((T)->key_comparator && (B)->hash == (H) && (T)->key_comparator((B)->key, (K))))


/**
 * Calculate the hash of a key
 * 
 * @param   this  The hash table
 * @param   key   The key to hash
 * @return        The hash of the key
 */
static inline size_t __attribute__((pure, nonnull))
hash(const hash_table_t *restrict this, size_t key)
{
	return this->hasher ? this->hasher(key) : key;
}


/**
 * Truncates the hash of a key to constrain it to the buckets
 * 
 * @param   this  The hash table
 * @param   key   The key to hash
 * @return        A non-negative value less the the table's capacity
 */
static inline size_t __attribute__((pure, nonnull))
truncate_hash(const hash_table_t *restrict this, size_t hash)
{
	return hash % this->capacity;
}


/**
 * Grow the table
 * 
 * @param   this  The hash table
 * @return        Non-zero on error, `errno` will be set accordingly
 */
static int __attribute__((nonnull))
rehash(hash_table_t *restrict this)
{
	hash_entry_t **old_buckets = this->buckets;
	size_t old_capacity = this->capacity;
	size_t i = old_capacity, index;
	hash_entry_t *bucket;
	hash_entry_t *destination;
	hash_entry_t *next;

	fail_if (xcalloc(this->buckets, old_capacity * 2 + 1, hash_entry_t*));
	this->capacity = old_capacity * 2 + 1;
	this->threshold = (size_t)((float)(this->capacity) * this->load_factor);

	while (i--) {
		bucket = this->buckets[i];
		while (bucket) {
			index = truncate_hash(this, bucket->hash);
			if ((destination = this->buckets[index])) {
				while ((next = destination->next))
					destination = next;
				destination->next = bucket;
			} else {
				this->buckets[index] = bucket;
			}

			next = bucket->next;
			bucket->next = NULL;
			bucket = next;
		}
	}

	free(old_buckets);
	return 0;
fail:
	return -1;
}


/**
 * Create a hash table
 * 
 * @param   this              Memory slot in which to store the new hash table
 * @param   initial_capacity  The initial capacity of the table
 * @param   load_factor       The load factor of the table, i.e. when to grow the table
 * @return                    Non-zero on error, `errno` will have been set accordingly
 */
int
hash_table_create_fine_tuned(hash_table_t *restrict this, size_t initial_capacity, float load_factor)
{
	this->buckets = NULL;

	this->capacity = initial_capacity ? initial_capacity : 1;
	fail_if (xcalloc(this->buckets, this->capacity, hash_entry_t*));
	this->load_factor = load_factor;
	this->threshold = (size_t)((float)(this->capacity) * load_factor);
	this->size = 0;
	this->value_comparator = NULL;
	this->key_comparator = NULL;
	this->hasher = NULL;

	return 0;
fail:
	return -1;
}


/**
 * Release all resources in a hash table, should
 * be done even if construction fails
 * 
 * @param  this          The hash table
 * @param  keys_freer    Function that frees a key, `NULL` if keys should not be freed
 * @param  values_freer  Function that frees a value, `NULL` if value should not be freed
 */
void
hash_table_destroy(hash_table_t *restrict this, free_func *key_freer, free_func *value_freer)
{
	size_t i = this->capacity;
	hash_entry_t *bucket, *last;

	if (this->buckets) {
		while (i) {
			bucket = this->buckets[--i];
			while (bucket) {
				if (key_freer)   key_freer(bucket->key);
				if (value_freer) value_freer(bucket->value);
				bucket = (last = bucket)->next;
				free(last);
			}
		}
		free(this->buckets);
	}
}


/**
 * Check whether a value is stored in the table
 * 
 * @param   this   The hash table
 * @param   value  The value
 * @return         Whether the value is stored in the table
 */
int
hash_table_contains_value(const hash_table_t *restrict this, size_t value)
{
	size_t i = this->capacity;
	hash_entry_t *restrict bucket;

	while (i--) {
		bucket = this->buckets[i];
		while (bucket) {
			if (bucket->value == value)
				return 1;
			if (this->value_comparator && this->value_comparator(bucket->value, value))
				return 1;
			bucket = bucket->next;
		}
	}

	return 0;
}


/**
 * Check whether a key is used in the table
 * 
 * @param   this  The hash table
 * @param   key   The key
 * @return        Whether the key is used
 */
int
hash_table_contains_key(const hash_table_t *restrict this, size_t key)
{
	size_t key_hash = hash(this, key);
	size_t index = truncate_hash(this, key_hash);
	hash_entry_t *restrict bucket = this->buckets[index];

	while (bucket) {
		if (TEST_KEY(this, bucket, key, key_hash))
			return 1;
		bucket = bucket->next;
	}

	return 0;
}


/**
 * Look up a value in the table
 * 
 * @param   this  The hash table
 * @param   key   The key associated with the value
 * @return        The value associated with the key, 0 if the key was not used
 */
size_t
hash_table_get(const hash_table_t *restrict this, size_t key)
{
	size_t key_hash = hash(this, key);
	size_t index = truncate_hash(this, key_hash);
	hash_entry_t *restrict bucket = this->buckets[index];

	while (bucket) {
		if (TEST_KEY(this, bucket, key, key_hash))
			return bucket->value;
		bucket = bucket->next;
	}

	return 0;
}


/**
 * Look up an entry in the table
 * 
 * @param   this  The hash table
 * @param   key   The key associated with the value
 * @return        The entry associated with the key, `NULL` if the key was not used
 */
hash_entry_t *
hash_table_get_entry(const hash_table_t *restrict this, size_t key)
{
	size_t key_hash = hash(this, key);
	size_t index = truncate_hash(this, key_hash);
	hash_entry_t *restrict bucket = this->buckets[index];

	while (bucket) {
		if (TEST_KEY(this, bucket, key, key_hash))
			return bucket;
		bucket = bucket->next;
	}

	return NULL;
}


/**
 * Add an entry to the table
 * 
 * @param   this   The hash table
 * @param   key    The key of the entry to add
 * @param   value  The value of the entry to add
 * @return         The previous value associated with the key, 0 if the key was not used.
 *                 0 will also be returned on error, check the `errno` variable.
 */
size_t
hash_table_put(hash_table_t *restrict this, size_t key, size_t value)
{
	size_t key_hash = hash(this, key);
	size_t index = truncate_hash(this, key_hash);
	hash_entry_t *restrict bucket = this->buckets[index];
	size_t rc;

	while (bucket) {
		if (TEST_KEY(this, bucket, key, key_hash)) {
				rc = bucket->value;
				bucket->value = value;
				return rc;
		} else {
			bucket = bucket->next;
		}
	}

	if (++(this->size) > this->threshold) {
		errno = 0;
		fail_if (rehash(this));
		index = truncate_hash(this, key_hash);
	}

	errno = 0;
	fail_if (xmalloc(bucket, 1, hash_entry_t));
	bucket->value = value;
	bucket->key = key;
	bucket->hash = key_hash;
	bucket->next = this->buckets[index];
	this->buckets[index] = bucket;

	return 0;
fail:
	return 0;
}


/**
 * Remove an entry in the table
 * 
 * @param   this  The hash table
 * @param   key   The key of the entry to remove
 * @return        The previous value associated with the key, 0 if the key was not used
 */
size_t
hash_table_remove(hash_table_t *restrict this, size_t key)
{
	size_t key_hash = hash(this, key);
	size_t index = truncate_hash(this, key_hash);
	hash_entry_t *bucket = this->buckets[index];
	hash_entry_t *last = NULL;
	size_t rc;

	while (bucket) {
		if (TEST_KEY(this, bucket, key, key_hash)) {
			if (!last)
				this->buckets[index] = bucket->next;
			else
				last->next = bucket->next;
			this->size--;
			rc = bucket->value;
			free(bucket);
			return rc;
		}
		last = bucket;
		bucket = bucket->next;
	}

	return 0;
}


/**
 * Remove all entries in the table
 * 
 * @param  this  The hash table
 */
void
hash_table_clear(hash_table_t *restrict this)
{
	hash_entry_t **buf, *bucket;
	size_t i, ptr;

	if (this->size) {
		buf = alloca((this->size + 1) * sizeof(hash_entry_t*));
		i = this->capacity;
		while (i--) {
			bucket = this->buckets[i];
			ptr = 0;
			buf[ptr++] = bucket;
			while (bucket) {
				bucket = bucket->next;
				buf[ptr++] = bucket;
			}
			while (ptr)
				free(buf[--ptr]);
			this->buckets[i] = NULL;
		}
		this->size = 0;
	}
}


/**
 * Calculate the buffer size need to marshal a hash table
 * 
 * @param   this  The hash table
 * @return        The number of bytes to allocate to the output buffer
 */
size_t
hash_table_marshal_size(const hash_table_t *restrict this)
{
	size_t n = this->capacity;
	size_t rc = 3 * sizeof(size_t) + sizeof(float) + n * sizeof(size_t);
	size_t i, m = 0;
	hash_entry_t *restrict bucket;

	for (i = 0; i < n; i++) {
		bucket = this->buckets[i];
		while (bucket) {
			bucket = bucket->next;
			m++;
		}
	}

	return rc + m * 3 * sizeof(size_t) + sizeof(int);
}


/**
 * Marshals a hash table
 * 
 * @param  this  The hash table
 * @param  data  Output buffer for the marshalled data
 */
void
hash_table_marshal(const hash_table_t *restrict this, char *restrict data)
{
	size_t i, n = this->capacity, m;
	hash_entry_t *restrict bucket;

	buf_set_next(data, int, HASH_TABLE_T_VERSION);
	buf_set_next(data, size_t, this->capacity);
	buf_set_next(data, float, this->load_factor);
	buf_set_next(data, size_t, this->threshold);
	buf_set_next(data, size_t, this->size);

	for (i = 0; i < n; i++) {
		bucket = this->buckets[i];
		m = 0;
		while (bucket) {
			buf_set(data, size_t, 1 + m * 3 + 0, bucket->key);
			buf_set(data, size_t, 1 + m * 3 + 1, bucket->value);
			buf_set(data, size_t, 1 + m * 3 + 2, bucket->hash);
			bucket = bucket->next;
			m++;
		}
		buf_set(data, size_t, 0, m);
		buf_next(data, size_t, 1 + m * 3);
	}
}


/**
 * Unmarshals a hash table
 * 
 * @param   this      Memory slot in which to store the new hash table
 * @param   data      In buffer with the marshalled data
 * @param   remapper  Function that translates values, `NULL` if not translation takes place
 * @return            Non-zero on error, `errno` will be set accordingly.
 *                    Destroy the table on error.
 */
int
hash_table_unmarshal(hash_table_t *restrict this, char *restrict data, remap_func *remapper)
{
	size_t i, n, m;
	hash_entry_t *restrict bucket;

	/* buf_get(data, int, 0, HASH_TABLE_T_VERSION); */
	buf_next(data, int, 1);

	this->value_comparator = NULL;
	this->key_comparator   = NULL;
	this->hasher           = NULL;

	buf_get_next(data, size_t, this->capacity = n);
	buf_get_next(data, float, this->load_factor);
	buf_get_next(data, size_t, this->threshold);
	buf_get_next(data, size_t, this->size);

	fail_if (xcalloc(this->buckets, this->capacity, hash_entry_t*));

	for (i = 0; i < n; i++) {
		buf_get_next(data, size_t, m);

		fail_if (xmalloc(this->buckets[i] = bucket, 1, hash_entry_t));

		while (m--) {
			if (!m)
				bucket->next = NULL;
			else
				fail_if (xmalloc(bucket->next, 1, hash_entry_t));
			buf_get_next(data, size_t, bucket->key);
			buf_get_next(data, size_t, bucket->value);
			if (remapper)
				bucket->value = remapper(bucket->value);
			buf_get_next(data, size_t, bucket->hash);
		}
	}

	return 0;
fail:
	return -1;
}