/**
 * 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/>.
 */
#ifndef MDS_LIBMDSSERVER_HASH_LIST_H
#define MDS_LIBMDSSERVER_HASH_LIST_H


#include "macros.h"

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>




/**
 * The default initial capacity
 */
#ifndef HASH_LIST_DEFAULT_INITIAL_CAPACITY
# define HASH_LIST_DEFAULT_INITIAL_CAPACITY 128
#endif

/**
 * It is encourage to run `hash_list_get` before
 * `hash_list_put` and `hash_list_remove`. This
 * way, you know exactly what is happening.
 * There is an optimisation in place to let
 * `hash_list_put` and `hash_list_remove` skip
 * the search for the item (unless it is the first
 * element) if `hash_list_get` was used directly
 * prior to `hash_list_put` or `hash_list_remove`
 * to find the element. This macro used to tell
 * the compiler that position of the element is
 * most likely already known but is not zero.
 * 
 * If you however choose to not call `hash_list_get`
 * before `hash_list_put` and `hash_list_remove`
 * you should define this macro before including
 * this header file, but with the `1` changed to
 * a `0`. If you on the other hand do not know
 * if you are going to call `hash_list_get` before
 * `hash_list_put` and `hash_list_remove` you
 * should define it to expand to the input verbatim,
 * that is, have the value `__VA_ARGS__`.
 */
#ifndef HASH_LIST_EXPECTED
# define HASH_LIST_EXPECTED(...) __builtin_expect((__VA_ARGS__), 1)
#endif


#define HASH_LIST_HASH(key) (this->hasher ? this->hasher(key) : (size_t)key)



#define HASH_LIST_T_VERSION 0


/**
 * Create a subclass of hash_list
 * 
 * @param  T        The replacement text for `hash_list`
 * @param  KEY_T    The datatype of the keys
 * @param  CKEY_T   `const` version of `KEY_T`
 * @param  VALUE_T  The datatype of the values
 */
#define CREATE_HASH_LIST_SUBCLASS(T, KEY_T, CKEY_T, VALUE_T)\
\
\
/**
 * Slot for a value in a hash list
 */\
struct T##_entry;\
\
/**
 * Slot for a value in a hash list
 */\
struct T;\
\
\
\
/**
 * The datatype of the value
 */\
typedef VALUE_T T##_value_t;\
\
/**
 * Function-type for the function responsible for freeing the key and value of an entry
 * 
 * @param  entry  The entry, will never be `NULL`, any only used entries will be passed
 */\
typedef void T##_entry_free_func(struct T##_entry *entry);\
\
/**
 * Function-type for the function responsible for hashing keys
 * 
 * @param   key  The key, will never be `NULL`
 * @return       The hash of the key
 */\
typedef size_t T##_key_hash_func(CKEY_T key);\
\
\
\
/**
 * Comparing keys
 * 
 * @param   key_a  The first key, will never be `NULL`
 * @param   key_b  The second key, will never be `NULL`
 * @return         Whether the keys are equal
 */\
__attribute__((pure, nonnull))\
static inline int T##_key_comparer(CKEY_T key_a, CKEY_T key_b);\
\
/**
 * Determine the marshal-size of an entry's key and value
 * 
 * @param   entry  The entry, will never be `NULL`, any only used entries will be passed
 * @return         The marshal-size of the entry's key and value
 */\
__attribute__((pure, nonnull))\
static inline size_t T##_submarshal_size(const struct T##_entry *entry);\
\
/**
 * Marshal an entry's key and value
 * 
 * @param   entry  The entry, will never be `NULL`, any only used entries will be passed
 * @param   data   The buffer where the entry's key and value will be stored
 * @return         The marshal-size of the entry's key and value
 */\
__attribute__((pure, nonnull))\
static inline size_t T##_submarshal(const struct T##_entry *entry, char *restrict data);\
\
/**
 * Unmarshal an entry's key and value
 * 
 * @param   entry  The entry, will never be `NULL`, any only used entries will be passed
 * @param   data   The buffer where the entry's key and value is stored
 * @return         The number of read bytes, zero on error
 */\
__attribute__((pure, nonnull))\
static inline size_t T##_subunmarshal(struct T##_entry *entry, char *restrict data);\
\
\
\
/**
 * Slot for a value in a hash list
 */\
typedef struct T##_entry\
{\
	/**
	 * The key of the entry, `NULL` if the slot is unused
	 */\
	KEY_T key;\
	\
	/**
	 * Hash of `key`, undefined but initialised if the slot is unused
	 */\
	size_t key_hash;\
	\
	/**
	 * The value of the entry
	 */\
	T##_value_t value;\
	\
} T##_entry_t;\
\
\
/**
 * The data structure of the hash list
 */\
typedef struct T\
{\
	/**
	 * The number of allocated slots
	 */\
	size_t allocated;\
	\
	/**
	 * The number of unused slot that
	 * has previously be used
	 */\
	size_t unused;\
	\
	/**
	 * The number of slots that have
	 * been used, even if no longer used
	 */\
	size_t used;\
	\
	/**
	 * This variable is used for optimisation, any
	 * time `hash_list_get` finds an element, its
	 * will be stored, and it will be the first
	 * inspected element by `hash_list_put` and
	 * `hash_list_remove`
	 */\
	size_t last;\
	\
	/**
	 * The slots
	 */\
	T##_entry_t *slots;\
	\
	/**
	 * Function used to free keys and values of entries
	 * 
	 * The freeing is not used if this function pointer is `NULL`
	 * 
	 * Be aware, this variable cannot be marshalled
	 */\
	T##_entry_free_func *freer;\
	\
	/**
	 * Function used to calculate the hash of a key
	 * 
	 * If this function pointer is `NULL`, the identity hash is used
	 * 
	 * Be aware, this variable cannot be marshalled
	 */\
	T##_key_hash_func *hasher;\
	\
} T##_t;\
\
\
\
/**
 * Create a hash list
 * 
 * @param   this      Memory slot in which to store the new hash list
 * @param   capacity  The minimum initial capacity of the hash list, 0 for default
 * @return            Non-zero on error, `errno` will have been set accordingly
 */\
static inline int __attribute__((unused, nonnull))\
T##_create(T##_t *restrict this, size_t capacity)\
{\
	if (!capacity)\
		capacity = HASH_LIST_DEFAULT_INITIAL_CAPACITY;\
	\
	this->freer = NULL;\
	this->hasher = NULL;\
	this->allocated = 0;\
	this->unused = 0;\
	this->used = 0;\
	this->last = 0;\
	\
	this->slots = malloc(capacity * sizeof(T##_t));\
	if (!this->slots)\
		return -1;\
	\
	this->allocated = capacity;\
	return 0;\
}\
\
\
/**
 * Release all resources in a hash list
 * 
 * @param  this  The hash list
 */\
static inline void __attribute__((unused, nonnull))\
T##_destroy(T##_t *restrict this)\
{\
	size_t i, n;\
	if (this->freer)\
		for (i = 0, n = this->used; i < n; i++)\
			if (this->slots[i].key)\
				this->freer(this->slots + i);\
	this->used = 0;\
	this->unused = 0;\
	this->allocated = 0;\
	this->last = 0;\
	free(this->slots);\
	this->slots = NULL;\
}\
\
\
/**
 * Clone a hash list
 * 
 * @param   this  The hash list to clone
 * @param   out   Memory slot in which to store the new hash list
 * @return        Non-zero on error, `errno` will have been set accordingly
 */\
static inline int __attribute__((unused, nonnull))\
T##_clone(const T##_t *restrict this, T##_t *restrict out)\
{\
	if (T##_create(out, this->allocated) < 0)\
		return -1;\
	out->used = this->used;\
	out->unused = this->unused;\
	out->last = this->last;\
	memcpy(out->slots, this->slots, this->used * sizeof(T##_entry_t));\
}\
\
\
/**
 * Pack the list so that there are no reusable
 * positions, and reduce the capacity to the
 * smallest capacity that can be used.
 * This method has linear time complexity and
 * constant memory complexity.
 * 
 * @param   this  The list
 * @return        Non-zero on error, `errno` will have
 *                been set accordingly. Errors are non-fatal.
 */\
static inline int __attribute__((unused, nonnull))\
T##_pack(T##_t *restrict this)\
{\
	size_t i, j, n;\
	T##_entry_t *slots = this->slots;\
	\
	if (this->unused > 0) {\
		for (i = 0, j = 0, n = this->used; i < n; i++)\
			if (slots[i].key)\
				slots[j++] = slots[i];\
		\
		this->used -= this->unused;\
		this->unused = 0;\
		this->last = 0;\
	}\
	\
	if (this->used < this->allocated) {\
		slots = realloc(slots, this->used * sizeof(T##_entry_t));\
		if (!slots)\
			return -1;\
		this->slots = slots;\
		this->allocated = this->used;\
	}\
	\
	return 0;\
}\
\
\
/**
 * Look up a value in a hash list
 * 
 * @param   this   The hash list
 * @param   key    The key associated with the value, must not be `NULL`
 * @param   value  Output parameter for the value
 * @return         Whether the key was found, error is impossible
 */\
static inline int __attribute__((unused, nonnull))\
T##_get(T##_t *restrict this, CKEY_T key, T##_value_t *restrict value)\
{\
	size_t i, n, hash = HASH_LIST_HASH(key);\
	for (i = 0, n = this->used; i < n; i++)\
		if (this->slots[i].key_hash == hash && this->slots[i].key)\
			if (T##_key_comparer(this->slots[i].key, key))\
				return *value = this->slots[this->last = i].value, 1;\
	return this->last = 0, 0;\
}\
\
\
/**
 * Remove an entry from a hash list
 * 
 * @param  this  The hash list
 * @param  key   The key of the entry to remove, must not be `NULL`
 */\
static inline void __attribute__((unused, nonnull))\
T##_remove(T##_t *restrict this, CKEY_T key)\
{\
	size_t i = this->last, n, hash = HASH_LIST_HASH(key);\
	T##_entry_t *slots = this->slots;\
	\
	/* First, try cached index. */\
	if (HASH_LIST_EXPECTED(i && slots[i].key_hash == hash && slots[i].key))\
		if (HASH_LIST_EXPECTED(T##_key_comparer(slots[i].key, key)))\
			goto do_remove;\
	/* It is discouraged to use put or remove without
	 * doing a get before it, otherwise you do not know
	 * what is happening. So we do not expect to get
	 * get to the next line. However, if do not expect to
	 * run get before put or remove, you should modify the
	 * `HASH_LIST_EXPECTED` macro. However, this is single
	 * case where will will get to the next line, when the
	 * index of the item is zero. */\
	\
	/* Then, search. */\
	for (i = 0, n = this->used; i < n; i++)\
		if (slots[i].key_hash == hash && slots[i].key)\
			if (T##_key_comparer(slots[i].key, key))\
				goto do_remove;\
	\
	return;\
do_remove:\
	if (this->freer)\
		this->freer(slots + i);\
	slots[i].key = NULL;\
	this->unused++;\
	if (this->unused >> 1 >= this->used)\
		T##_pack(this);\
	this->last = 0;\
}\
\
\
/**
 * Add an entry to a hash list
 * 
 * @param   this   The hash list
 * @param   key    The key of the entry to add, must not be `NULL`
 * @param   value  Pointer to the value of the entry to add,
 *                 `NULL` if the entry should be removed instead
 * @return         Non-zero on error, `errno` will have been set accordingly
 */\
static inline int __attribute__((unused, nonnull(1, 2)))\
T##_put(T##_t *restrict this, KEY_T key, const T##_value_t *restrict value)\
{\
	size_t i = this->last, n, empty = this->used, hash;\
	T##_entry_t* slots = this->slots;\
	\
	/* Remove entry if no value is passed. */\
	if (!value) {\
		T##_remove(this, key);\
		return 0;\
	}\
	\
	/* Hash the input key. */\
	hash = HASH_LIST_HASH(key);\
	\
	/* Try cached index. */\
	if (HASH_LIST_EXPECTED(i && slots[i].key))\
		if (HASH_LIST_EXPECTED(slots[i].key_hash == hash))\
			if (HASH_LIST_EXPECTED(T##_key_comparer(slots[i].key, key)))\
				goto put;\
	/* It is discouraged to use put or remove without
	 * doing a get before it, otherwise you do not know
	 * what is happening. So we do not expect to get
	 * get to the next line. However, if do not expect to
	 * run get before put or remove, you should modify the
	 * `HASH_LIST_EXPECTED` macro. However, this is single
	 * case where will will get to the next line, when the
	 * index of the item is zero. */\
	\
	/* Find an unused slot or the current slot. */\
	for (i = 0, n = this->used; i < n; i++) {\
		if (!slots[i].key) {\
			empty = i;\
		} else if (slots[i].key_hash == hash) {\
			if (T##_key_comparer(slots[i].key, key))\
				goto put;\
		}\
	}\
	\
	/* Grow slot allocation is required. */\
	if (empty == this->allocated) {\
		if (empty >= SIZE_MAX >> 1)\
			return errno = ENOMEM, -1;\
		slots = realloc(slots, (empty << 1) * sizeof(T##_entry_t));\
		if (!slots)\
			return -1;\
		this->slots = slots;\
		this->allocated <<= 1;\
	}\
	\
	/* Store entry. */\
	i = empty;\
	goto put_no_free;\
put:\
	if (this->freer)\
		this->freer(slots + i);\
put_no_free:\
	slots[i].key = key;\
	slots[i].key_hash = hash;\
	slots[i].value = *value;\
	return 0;\
}\
\
\
/**
 * Calculate the buffer size need to marshal a hash list
 * 
 * @param   this  The hash table
 * @return        The number of bytes to allocate to the output buffer
 */\
static inline size_t __attribute__((unused, pure, nonnull))\
T##_marshal_size(const T##_t *restrict this)\
{\
	size_t i, n = this->used;\
	size_t rc = sizeof(int) + 4 * sizeof(size_t);\
	for (i = 0; i < n; i++)\
		if (this->slots[i].key)\
			rc += T##_submarshal_size(this->slots + i);\
	return rc + n * sizeof(char) + (n - this->unused) * sizeof(size_t);\
}\
\
\
/**
 * Marshals a hash list
 * 
 * @param  this  The hash list
 * @param  data  Output buffer for the marshalled data
 */\
static inline void __attribute__((unused, nonnull))\
T##_marshal(const T##_t *restrict this, char *restrict data)\
{\
	size_t wrote, i, n = this->used;\
	\
	buf_set_next(data, int, HASH_LIST_T_VERSION);\
	buf_set_next(data, size_t, this->allocated);\
	buf_set_next(data, size_t, this->unused);\
	buf_set_next(data, size_t, this->used);\
	buf_set_next(data, size_t, this->last);\
	\
	for (i = 0; i < n; i++) {\
		if (this->slots[i].key) {\
			buf_set_next(data, char, 1);\
			buf_set_next(data, size_t, this->slots[i].key_hash);\
			wrote = T##_submarshal(this->slots + i, data);\
			data += wrote / sizeof(char);\
		} else {\
			buf_set_next(data, char, 0);\
		}\
	}\
}\
\
\
/**
 * Unmarshals a hash list
 * 
 * @param   this      Memory slot in which to store the new hash list
 * @param   data      In buffer with the marshalled data
 * @return            Non-zero on error, `errno` will be set accordingly.
 *                    Destroy the table on error.
 */\
static inline int __attribute__((unused, nonnull))\
T##_unmarshal(T##_t *restrict this, char *restrict data)\
{\
	size_t i, n, got;\
	char used;\
	\
	this->freer = NULL;\
	this->hasher = NULL;\
	\
	/* buf_get(data, int, 0, HASH_LIST_T_VERSION); */\
	buf_next(data, int, 1);\
	\
	buf_get_next(data, size_t, this->allocated);\
	buf_get_next(data, size_t, this->unused);\
	buf_get_next(data, size_t, this->used);\
	buf_get_next(data, size_t, this->last);\
	\
	this->slots = calloc(this->allocated, sizeof(T##_entry_t));\
	if (!this->slots)\
		return -1;\
	\
	for (i = 0, n = this->used; i < n; i++) {\
		buf_get_next(data, char, used);\
		if (!used)\
			continue;\
		buf_set_next(data, size_t, this->slots[i].key_hash);\
		got = T##_subunmarshal(this->slots + i, data);\
		if (!got)\
			return -1;\
		data += got / sizeof(char);\
	}\
	\
	return 0;\
}


/**
 * Wrapper for `for` keyword that iterates over entry element in a hash list
 * 
 * @param  this:hash_list_t         The hash lsit
 * @param  i:size_t                 The variable to store the buckey index in at each iteration
 * @param  entry:hash_list_enty_t*  The variable to store the entry in at each iteration
 */
#define foreach_hash_list_entry(this, i, entry)\
	for (i = 0; i < (this).used; i++)\
		if ((entry = (this).slots)->key)


#endif