/*
 * hashtable.c
 *
 *  Created on: 24.10.2017
 *      Author: julian
 */

#include "strhash.h"
#include "hashtable.h"

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

#include <errno.h>
#include <assert.h>

int key_compare(entry_key_t one, entry_key_t two) {
	return strcmp(one, two) == 0;
}

entry_hash_t key_hash(entry_key_t key) {
	return strhash_str(key) + 1; // make hash always nonzero
}

void hashtable_init(struct hashtable * table) {
	memset(table, 0, sizeof(table));
}

hashtable_iterator_t hashtable_end(struct hashtable * table) {
	return table->data + table->len;
}


hashtable_iterator_t hashtable_next(struct hashtable * table, hashtable_iterator_t current) {
	if (table == NULL) {
		return NULL;
	}

	if (current == NULL) {
		current = table->data;
	} else {
		// we want the NEXT pointer :)
		current++;
	}

	while(current != hashtable_end(table)) {
		if (current->hash != 0)
			break;

		current++;
	}

	return current;
}

hashtable_iterator_t hashtable_get_hash(struct hashtable * table, entry_hash_t hash) {
	if (!table->len) {
		return hashtable_end(table);
	}

	size_t index = hash % table->len;

	if (table->data[index].hash == 0) {
		return hashtable_end(table);
	}

	return table->data + index;
}

hashtable_iterator_t hashtable_get(struct hashtable * table, entry_key_t key) {
	entry_hash_t hash = key_hash(key);
	return hashtable_get_hash(table, hash);
}

void hashtable_clear(struct hashtable * table) {
	if (table->dealloc_data) {
		hashtable_iterator_t it = hashtable_next(table, NULL);
		for(;it != hashtable_end(table); it = hashtable_next(table, it)){
			table->dealloc_data(it->data);
		}
	}

	free(table->data);
	table->data = NULL;
	table->count = table->len = 0;
}

int hashtable_resize(struct hashtable * table, size_t newsize) {
	if (table == NULL) {
		return 0;
	}

	if (newsize == 0) {
		// will fail, correct to 1
		newsize = 1;
	}

	struct hashtable temp = *table;
	table->data = calloc(newsize, sizeof(struct entry));

	if (table->data == NULL) {
		table->data = temp.data;

		errno = ENOMEM;
		return -1;
	}

	// try to reinsert old data
	table->len = newsize;

	for (size_t i = 0; i < temp.len; i++) {
		if (temp.data[i].hash && hashtable_add(table, temp.data[i]) == -1) {
			// abort mission, restore old table
			free(table->data);
			*table = temp;

			return -2;
		}
	}

	// delete old table
	free(temp.data);

	return 0;
}

int hashtable_add(struct hashtable * table, struct entry entry) {
	if (table == NULL) {
		return 0;
	}

	if (table->len == 0) {
		// initial alloc
		int err = hashtable_resize(table, 1);

		if (err < 0) {
			return err;
		}
		return hashtable_add(table, entry);
	}


	// try to insert into table
	size_t index = entry.hash % table->len;

	if (table->data->hash && !key_compare(table->data[index].key, entry.key)) {
		// key collision
		// make table bigger
		if (hashtable_resize(table, table->len*2) != 0) {
			return -1;
		}

		return hashtable_add(table, entry);
	}

	// insert new entry
	table->data[index] = entry;
	table->count++;
	return 0;
}

struct entry hashtable_make_entry(entry_key_t key, void * data) {
	return (struct entry){ .data = data,
		.key = key,
		.hash = key_hash(key),
	};
}

int hashtable_remove(struct hashtable * table, hashtable_iterator_t it) {
	if (!it || it->hash == 0) {
		return 0;
	}

	if (table->dealloc_data) {
		table->dealloc_data(it->data);
	}

	it->data = NULL;
	it->hash = 0;
	table->count--;
	return 1;
}