/**
 * mds — A micro-display server
 * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
 * 
 * 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_TABLE_H
#define MDS_LIBMDSSERVER_HASH_TABLE_H


#include <stdlib.h>


/**
 * Hash table entry
 */
typedef struct hash_entry
{
  /**
   * A key
   */
  void* key;
  
  /**
   * The value associated with the key
   */
  void* value;
  
  /**
   * The truncated hash value of the key
   */
  long hash;
  
  /**
   * The next entry in the bucket
   */
  struct hash_entry* next;
  
} hash_entry_t;


/**
 * Value lookup table based on hash value, that do not support `NULL` keys nor `NULL` values
 */
typedef struct hash_table
{
  /**
   * The table's capacity, i.e. the number of buckets
   */
  size_t capacity;
  
  /**
   * Entry buckets
   */
  hash_entry_t** buckets;
  
  /**
   * When, in the ratio of entries comparied to the capacity, to grow the table
   */
  float load_factor;
  
  /**
   * When, in the number of entries, to grow the table
   */
  size_t threshold;
  
  /**
   * The number of entries stored in the table
   */
  size_t size;
  
  /**
   * Check whether two values are equal
   * 
   * If this function pointer is `NULL`, the identity is used
   * 
   * Be aware, this variable cannot be marshalled
   * 
   * @param   value_a  The first value
   * @param   value_b  The second value
   * @return           Whether the values are equals
   */
  int (*value_comparator)(const void* value_a, const void* value_b);
  
  /**
   * Check whether two keys are equal
   * 
   * If this function pointer is `NULL`, the identity is used
   * 
   * Be aware, this variable cannot be marshalled
   * 
   * @param   key_a  The first key
   * @param   key_b  The second key
   * @return         Whether the keys are equals
   */
  int (*key_comparator)(const void* key_a, const void* key_b);
  
  /**
   * Calculate the hash of a key
   * 
   * If this function pointer is `NULL`, the identity hash is used
   * 
   * Be aware, this variable cannot be marshalled
   * 
   * @param   key  The key
   * @return       The hash of the key
   */
  long (*hasher)(const void* key);
  
} hash_table_t;



/**
 * 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);

/**
 * Create a hash table
 * 
 * @param   this:hash_table_t*       Memory slot in which to store the new hash table
 * @param   initial_capacity:size_t  The initial capacity of the table
 * @return  :int                     Non-zero on error, `errno` will have been set accordingly
 */
#define hash_table_create_tuned(this, initial_capacity)  \
  hash_table_create_fine_tuned(this, initial_capacity, 0.75)

/**
 * Create a hash table
 * 
 * @param   this:hash_table_t*  Memory slot in which to store the new hash table
 * @return  :int                Non-zero on error, `errno` will have been set accordingly
 */
#define hash_table_create(this)  \
  hash_table_create_tuned(this, 16)

/**
 * Clone a hash table
 * 
 * @param   this  The hash table to clone
 * @param   out   Memory slot in which to store the new hash table
 * @return        Non-zero on error, `errno` will have been set accordingly
 */
int hash_table_clone(const hash_table_t* restrict this, hash_table_t* restrict out);

/**
 * Release all resources in a hash table, should
 * be done even if construction fails
 * 
 * @param  this    The hash table
 * @param  values  Whether to free all stored values
 * @param  keys    Whether to free all stored keys
 */
void hash_table_destroy(hash_table_t* restrict this, int values, int keys);

/**
 * 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, void* restrict value) __attribute__((pure));

/**
 * 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, void* restrict key) __attribute__((pure));

/**
 * 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, `NULL` i the key was not used
 */
void* hash_table_get(const hash_table_t* restrict this, const void* restrict key);

/**
 * 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, `NULL` i the key was not used
 */
void* hash_table_put(hash_table_t* restrict this, void* restrict key, void* restrict value);

/**
 * 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, `NULL` i the key was not used
 */
void* hash_table_remove(hash_table_t* restrict this, const void* restrict key);

/**
 * Remove all entries in the table
 * 
 * @param  this  The hash table
 */
void hash_table_clear(hash_table_t* restrict this);

/**
 * 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) __attribute__((pure));

/**
 * 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);

/**
 * Unmarshals a hash table
 * 
 * @param   this  Memory slot in which to store the new hash table
 * @param   data  In buffer with the marshalled data
 * @return        Non-zero one error, errno will be set accordingly.
 *                Destroy the list on error.
 */
int hash_table_unmarshal(hash_table_t* restrict this, char* restrict data);


#endif