/* Copyright (c) 2024, Peter McGoron
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1) Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2) Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <assert.h>
#include <string.h>
#include "uns.h"
#include "uns_hashtable.h"

enum {
	HTBL_LEN_PTR,
	HTBL_USED_PTR,
	HTBL_HDR_LEN
};

static size_t get_size_t(struct uns_gc *gc, struct uns_ctr *root, size_t i)
{
	size_t r;

	void *p = gc->record_get_ptr(root->p, i);
	memcpy(&r, p, sizeof(r));

	return r;
}

static void set_size_t(struct uns_gc *gc, struct uns_ctr *root, size_t i, size_t val)
{
	void *p = gc->record_get_ptr(root->p, i);
	memcpy(p, &val, sizeof(val));
}

static void *index(struct uns_gc *gc, struct uns_ctr *htbl, size_t i)
{
	return gc->record_get_ptr(htbl->p, i + HTBL_HDR_LEN);
}

void uns_hashtable_alloc_into(struct uns_gc *gc, struct uns_ctr *r, size_t size)
{
	unsigned char *p;
	size_t i;
	r->p = gc->alloc_record(gc, size + HTBL_HDR_LEN);

	p = gc->alloc(gc, sizeof(size_t));
	gc->record_set_ptr(r->p, HTBL_LEN_PTR, p);
	set_size_t(gc, r, HTBL_LEN_PTR, size);

	p = gc->alloc(gc, sizeof(size_t));
	gc->record_set_ptr(r->p, HTBL_USED_PTR, p);
	set_size_t(gc, r, HTBL_USED_PTR, 0);

	/* Set entries to zero. */
	for (i = HTBL_HDR_LEN; i <= size; i++)
		gc->record_set_ptr(r->p, i, NULL);
}

size_t uns_hashtable_len(struct uns_gc *gc, struct uns_ctr *htbl)
{
	return get_size_t(gc, htbl, HTBL_LEN_PTR);
}

size_t uns_hashtable_used(struct uns_gc *gc, struct uns_ctr *htbl)
{
	return get_size_t(gc, htbl, HTBL_USED_PTR);
}

enum {
	LENGTH,
	STRING,
	VALUE,
	NEXT,
	HTBL_ENTRY_LEN
};

static void alloc_holder(struct uns_gc *gc, struct uns_ctr *r, struct uns_ctr *string,
                         struct uns_ctr *value, size_t len)
{
	unsigned char *alloc_ptr;
	r->p = gc->alloc_record(gc, HTBL_ENTRY_LEN);

	alloc_ptr = gc->alloc(gc, sizeof(size_t));
	memcpy(alloc_ptr, &len, sizeof(size_t));

	gc->record_set_ptr(r->p, LENGTH, alloc_ptr);
	gc->record_set_ptr(r->p, STRING, string->p);
	gc->record_set_ptr(r->p, VALUE, value->p);
	gc->record_set_ptr(r->p, NEXT, NULL);
}

static unsigned long fnv(unsigned char *p, size_t len)
{
	unsigned long hash = 0x811c9dc5;
	size_t i;

	for (i = 0; i < len; i++) {
		hash ^= p[i];
		hash *= 16777619;
	}

	return hash;
}

static int search_container(struct uns_gc *gc, struct uns_ctr *cur_ctr,
                            unsigned char *str, size_t len)
{
	unsigned char *ctr_str = gc->record_get_ptr(cur_ctr->p, STRING);
	size_t ctr_str_len = get_size_t(gc, cur_ctr, LENGTH);
	void *next;

	if (ctr_str_len != len || memcmp(ctr_str, str, len) != 0) {
		/* strings do not match */
		next = gc->record_get_ptr(cur_ctr->p, NEXT);
		if (!next)
			return 0;
		cur_ctr->p = next;
		return search_container(gc, cur_ctr, str, len);
	} else {
		return 1;
	}
}

static int search_for_container(struct uns_gc *gc, struct uns_ctr *htbl,
                                struct uns_ctr *container,
                                unsigned char *str, size_t len, size_t *hash_out)
{
	size_t htbl_len = uns_hashtable_len(gc, htbl);
	size_t hash = fnv(str, len) % htbl_len;
	if (hash_out)
		*hash_out = hash;

	container->p = index(gc, htbl, hash);
	if (!container->p)
		return 0;
	return search_container(gc, container, str, len);
}

/* This could be made better with internal pointers, but that is not
 * portable.
 */
void uns_hashtable_del(struct uns_gc *gc, struct uns_ctr *htbl,
                       unsigned char *str, size_t len,
                       struct uns_ctr *old_value)
{
	size_t hash = fnv(str, len) % uns_hashtable_len(gc, htbl);
	struct uns_ctr rec = {0};
	struct uns_ctr prevptr = {0};

	old_value->p = NULL;
	rec.p = index(gc, htbl, hash);
	if (!rec.p) {
		return;
	}

	/* Special case: first pointer */
	if (len == get_size_t(gc, &rec, LENGTH) &&
	    memcmp(str, gc->record_get_ptr(rec.p, STRING), len) == 0) {
		old_value->p = gc->record_get_ptr(rec.p, VALUE);
		gc->record_set_ptr(htbl->p, HTBL_HDR_LEN + hash,
		                   gc->record_get_ptr(rec.p, NEXT));
	}

	prevptr = rec;
	for (rec.p = gc->record_get_ptr(rec.p, NEXT); rec.p;
	     rec.p = gc->record_get_ptr(rec.p, NEXT)) {
		if (len == get_size_t(gc, &rec, LENGTH)
		    && memcmp(str, gc->record_get_ptr(rec.p, VALUE), len) == 0) {
			old_value->p = gc->record_get_ptr(rec.p, VALUE);
			gc->record_set_ptr(prevptr.p, NEXT,
			                   gc->record_get_ptr(rec.p, NEXT));
			return;
		}
	}
}

void uns_hashtable_search(struct uns_gc *gc, struct uns_ctr *htbl,
                          unsigned char *str, size_t string_len,
                          struct uns_ctr *found)
{
	int r;

	r = search_for_container(gc, htbl, found, str, string_len, NULL);
	if (r)
		found->p = gc->record_get_ptr(found->p, VALUE);
	else
		found->p = NULL;
}

void uns_hashtable_add(struct uns_gc *gc, struct uns_ctr *htbl,
                       struct uns_ctr *string, size_t string_len,
                       struct uns_ctr *value, struct uns_ctr *old_value)
{
	struct uns_ctr container = {0};
	struct uns_ctr next_container = {0};
	size_t hash;

	if (uns_hashtable_used(gc, htbl) >= uns_hashtable_len(gc, htbl)*7/10)
		uns_hashtable_resize(gc, htbl, uns_hashtable_len(gc, htbl)*2);

	if (search_for_container(gc, htbl, &container, (unsigned char *)string->p, string_len, &hash)) {
		old_value->p = gc->record_get_ptr(container.p, VALUE);
		gc->record_set_ptr(container.p, VALUE, value->p);
		return;
	}

	set_size_t(gc, htbl, HTBL_USED_PTR,
	           uns_hashtable_used(gc, htbl) + 1);
	old_value->p = NULL;
	uns_root_add(gc, &container);
	uns_root_add(gc, &next_container);

	alloc_holder(gc, &next_container, string, value, string_len);

	if (container.p) {
		gc->record_set_ptr(container.p, NEXT, next_container.p);
	} else {
		gc->record_set_ptr(htbl->p, hash + HTBL_HDR_LEN, next_container.p);
	}

	uns_root_remove(gc, &next_container);
	uns_root_remove(gc, &container);
}

/* TODO: add delete */

static void add_for_ent(struct uns_gc *gc, struct uns_ctr *htbl, void *ctrp)
{
	struct uns_ctr ctr = {0};
	struct uns_ctr str = {0};
	size_t str_len;
	struct uns_ctr value = {0};
	struct uns_ctr old_value_should_never_happen = {0};

	if (!ctrp)
		return;

	ctr.p = ctrp;
	uns_root_add(gc, &ctr);
	uns_root_add(gc, &str);
	uns_root_add(gc, &value);
	uns_root_add(gc, &old_value_should_never_happen);

	str.p = gc->record_get_ptr(ctr.p, STRING);
	value.p = gc->record_get_ptr(ctr.p, VALUE);
	str_len = get_size_t(gc, &ctr, LENGTH);

	uns_hashtable_add(gc, htbl, &str, str_len, &value,
	                  &old_value_should_never_happen);
	assert(!old_value_should_never_happen.p);

	uns_root_remove(gc, &old_value_should_never_happen);
	uns_root_remove(gc, &value);
	uns_root_remove(gc, &str);
	uns_root_remove(gc, &ctr);

	ctrp = gc->record_get_ptr(ctr.p, NEXT);
	add_for_ent(gc, htbl, ctrp);
}

void uns_hashtable_resize(struct uns_gc *gc, struct uns_ctr *htbl, size_t newsize)
{
	struct uns_ctr newtbl = {0};
	size_t i;
	size_t oldlen = uns_hashtable_len(gc, htbl);

	uns_root_add(gc, &newtbl);

	uns_hashtable_alloc_into(gc, &newtbl, newsize);
	set_size_t(gc, &newtbl, HTBL_USED_PTR,
	           uns_hashtable_used(gc, &newtbl));

	for (i = 0; i < oldlen; i++)
		add_for_ent(gc, &newtbl, index(gc, htbl, i));

	htbl->p = newtbl.p;
	uns_root_remove(gc, &newtbl);
}