/**
 * hashtable.c - A basic hashtable implementation
 * 
 */

#include <string.h>
#include <stdlib.h>

#include "llist.h"
#include "hashtable.h"

#define SIZE 128

typedef struct
{
    void* key;
    void* data;
}
HTEntry;

/**
 * Simple hash function used
 */
int hash(char* key, int ht_size)
{
    int h = 0;

    // basic modulo hash
    for (size_t i = 0; i < strlen(key); i++)
    {
        h = (31 * h + key[i]) % ht_size;
    }    

    return h;
}

/**
 * Compare function for searching a bucket
 */
int compare(void* data, void* arg)
{
    char* key = arg;
    HTEntry* entry = data;
    return strcmp(entry->key, key);
}

/**
 * Delete HT entry from bucket
 */
int delete_entry(void* data, void* arg)
{
    (void) arg;
    HTEntry* entry = data;
    free(entry);
    return 0;
}

/**
 * Create a new hashtable
 */
HT* ht_create(void)
{
    HT* ht = malloc(sizeof(HT));

    ht->size = SIZE;
    ht->entries = 0;
    ht->store = malloc(ht->size * sizeof(LL*));

    for (int i = 0; i < ht->size; i++)
    {
        ht->store[i] = ll_create();
    }

    return ht;
}

/**
 * Add a new key value pair to a hashtable
 */
int ht_put(HT* ht, char* key, void* data)
{
    int addr = hash(key, ht->size);

    LL* bucket = ht->store[addr];

    HTEntry* entry = malloc(sizeof(HTEntry));
    entry->key = strdup(key);
    entry->data = data;

    ll_push(bucket, entry);

    ht->entries++;

    return 0;
}

/**
 * Get a value from a hashtable with a key
 */
void* ht_get(HT* ht, char* key)
{
    int addr = hash(key, ht->size);

    LL* bucket = ht->store[addr];

    HTEntry* entry = ll_search(bucket, compare, (void*) key);

    if (entry == NULL)
    {
        return NULL;
    }

    return entry->data;
}

/**
 * Delete a key value pair from a hashtable
 */
void* ht_delete(HT* ht, char* key)
{
    int addr = hash(key, ht->size);

    LL* bucket = ht->store[addr];

    HTEntry* entry = ll_delete(bucket, compare, key);

    if (entry == NULL)
    {
        return NULL;
    }

    ht->entries--;

    return entry->data;
}


/**
 * Destroy/free an entire hashtable
 */
int ht_free(HT* ht)
{
    for (int i = 0; i < ht->size; i++)
    {
        LL* bucket = ht->store[i];
        ll_loop(bucket, delete_entry, NULL);
        ll_free(bucket);
    }

    free(ht);

    return 0;
}