/* slist.c
 *
 * Copyright 2025 Francois Techene
 *
 * 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/>.
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

#include "slist.h"

#include <stdlib.h>


SListItem*
SListItem_new(void* data)
{
	SListItem* self = (SListItem*)NewPtr(sizeof(SListItem));
	self->data 	= data;
	self->next 	= NULL;

	return self;
}

void
SListItem_delete(SListItem** item)
{
	if (*item) {
		DisposPtr(*item);
		*item = NULL;
	}
}

SList*
SList_new()
{
	SList* self = (SList*)NewPtr(sizeof(SList));

	self->first = slist_first;
	self->last 	= slist_last;
	self->next 	= slist_next;

	self->head 	= NULL;
	self->count	= 0;

	return self;
}

void
SList_delete(SList** list)
{
	slist_empty(*list);

	if (*list) {
		DisposPtr(*list);
		*list = NULL;
	}
}

void*
slist_first(SList* self)
{
	return self->head;
}

void*
slist_last(SList* self)
{
	return NULL;
}

void*
slist_next(SList* self, SListItem* item)
{
	return item->next;
}

void
slist_append(SList* self, void* data)
{
	SListItem* elem 		= self->head;
	SListItem* new_elem		= SListItem_new(data);

	if (!elem) {
		self->head = new_elem;
		self->count++;
		return;
	}

	while (elem->next) {
		elem = elem->next;
	}
	elem->next = new_elem;

	self->count++;
}

void
slist_insert_at(SList* self, void* data, int index)
{
    int count               = 0;
    SListItem* prev_elem 	= NULL;
    SListItem* elem 		= self->head;
	SListItem* new_elem		= SListItem_new(data);

	while (elem && count < index) {
        prev_elem   = elem;
		elem        = elem->next;
        count++;
	}

    new_elem->next  = elem;

    if (!prev_elem) {
        self->head = new_elem;
    }
    else {
        prev_elem->next = new_elem;
    }

	self->count++;
}

void
slist_insert_after(SList* self, void* data, void* value)
{
    SListItem* elem 		= self->head;
	SListItem* new_elem		= SListItem_new(data);

	if (!self->head) {
		self->head = new_elem;
		self->count++;
		return;
	}

	while (elem->next && elem->data != value) {
		elem = elem->next;
	}

    new_elem->next  = elem->next;
    elem->next      = new_elem;

	self->count++;
}


void slist_empty(SList* self)
{
	while (self->head) {
		slist_remove_at(self, 0);
	}
	self->head 	= NULL;
	self->count = 0;
}

void
slist_remove_at(SList* self, int index)
{
	int count               = 0;
    SListItem* prev_elem 	= NULL;
    SListItem* elem 		= self->head;

	if (!elem) {
		return; // List is empty;
	}

	while (elem && count < index) {
        prev_elem   = elem;
		elem        = elem->next;
        count++;
	}
	
	if (!elem) {
		return; // No element at that index position.
	}

    if (!prev_elem) {
        self->head = elem->next;
    }
    else {
        prev_elem->next = elem->next;
    }

	SListItem_delete(&elem);
	elem = NULL;

	self->count--;
}

void
slist_remove_last(SList* self)
{
	SListItem* prev_elem 	= NULL;
	SListItem* elem 		= self->head;

	if (!elem) {
		return; // List is empty
	}

	while (elem->next) {
		prev_elem = elem;
		elem = elem->next;
	}

	// prev_elem->next is freed and set to NULL by the
	// delete method.
	//
	SListItem_delete(&(prev_elem->next));
	prev_elem->next = NULL;

	self->count--;
}

// Remove the first occurence of the item having the same value
// as 'value'.
//
void
slist_remove_value(SList* self, void* value)
{
	SListItem* 	prev_elem 	= NULL;
	SListItem* 	elem 		= self->head;


	while (elem != NULL) {
		if (elem->data == value) {

			if (!prev_elem) {
				self->head = elem->next;
			}
			else {
				prev_elem->next = elem->next;
			}

			// elem is freed and set to NULL by the
			// delete method.
			//
			SListItem_delete(&elem);
			elem = NULL;

			self->count--;
		}
		else {
			prev_elem 	= elem;
			elem 		= elem->next;
		}
	}
}