/**
 * mds — A micro-display server
 * Copyright © 2014, 2015, 2016, 2017  Mattias Andrée (maandree@kth.se)
 * 
 * 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/>.
 */
#include "linked-list.h"

#include "macros.h"

#include <string.h>
#include <errno.h>


/**
 * The default initial capacity
 */
#ifndef LINKED_LIST_DEFAULT_INITIAL_CAPACITY
# define LINKED_LIST_DEFAULT_INITIAL_CAPACITY 128
#endif


/**
 * Computes the nearest, but higher, power of two,
 * but only if the current value is not a power of two
 * 
 * @param   value  The value to be rounded up to a power of two
 * @return         The nearest, but not smaller, power of two
 */
static size_t __attribute__((const))
to_power_of_two(size_t value)
{
	value -= 1;
	value |= value >> 1;
	value |= value >> 2;
	value |= value >> 4;
	value |= value >> 8;
	value |= value >> 16;
#if SIZE_MAX == UINT64_MAX
	value |= value >> 32;
#endif
	return value + 1;
}


/**
 * Create a linked list
 * 
 * @param   this      Memory slot in which to store the new linked list
 * @param   capacity  The minimum initial capacity of the linked list, 0 for default
 * @return            Non-zero on error, `errno` will have been set accordingly
 */
int
linked_list_create(linked_list_t *restrict this, size_t capacity)
{
	/* Use default capacity of zero is specified. */
	if (!capacity)
		capacity = LINKED_LIST_DEFAULT_INITIAL_CAPACITY;

	/* Initialise the linked list. */
	this->capacity   = capacity = to_power_of_two(capacity);
	this->edge       = 0;
	this->end        = 1;
	this->reuse_head = 0;
	this->reusable   = NULL;
	this->values     = NULL;
	this->next       = NULL;
	this->previous   = NULL;
	fail_if (xmalloc(this->reusable, capacity, ssize_t));
	fail_if (xmalloc(this->values,   capacity,  size_t));
	fail_if (xmalloc(this->next,     capacity, ssize_t));
	fail_if (xmalloc(this->previous, capacity, ssize_t));
	this->values[this->edge]   = 0;
	this->next[this->edge]     = this->edge;
	this->previous[this->edge] = this->edge;

	return 0;
fail:
	return -1;
}


/**
 * Release all resources in a linked list, should
 * be done even if `linked_list_create` fails
 * 
 * @param  this  The linked list
 */
void
linked_list_destroy(linked_list_t *restrict this)
{
	free(this->reusable), this->reusable = NULL;
	free(this->values),   this->values   = NULL;
	free(this->next),     this->next     = NULL;
	free(this->previous), this->previous = NULL;
}


/**
 * Clone a linked list
 * 
 * @param   this  The linked list to clone
 * @param   out   Memory slot in which to store the new linked list
 * @return        Non-zero on error, `errno` will have been set accordingly
 */
int
linked_list_clone(const linked_list_t *restrict this, linked_list_t *restrict out)
{
	fail_if (xmemdup(out->values,   this->values,   this->capacity, size_t));
	fail_if (xmemdup(out->next,     this->next,     this->capacity, ssize_t));
	fail_if (xmemdup(out->previous, this->previous, this->capacity, ssize_t));
	fail_if (xmemdup(out->reusable, this->reusable, this->capacity, ssize_t));

	out->capacity   = this->capacity;
	out->end        = this->end;
	out->reuse_head = this->reuse_head;
	out->edge       = this->edge;

	return 0;

fail:
	return -1;
}


/**
 * Pack the list so that there are no reusable
 * positions, and reduce the capacity to the
 * smallest capacity that can be used. Note that
 * values (nodes) returned by the list's methods
 * will become invalid. Additionally (to reduce
 * the complexity) the list will be defragment
 * so that the nodes' indices are continuous.
 * This method has linear time complexity and
 * linear memory complexity.
 * 
 * @param   this  The list
 * @return        Non-zero on error, `errno` will have been set accordingly
 */
int
linked_list_pack(linked_list_t *restrict this)
{
	ssize_t *restrict new_next = NULL;
	ssize_t *restrict new_previous = NULL;
	ssize_t *restrict new_reusable = NULL;
	size_t size = this->end - this->reuse_head;
	size_t cap = to_power_of_two(size);
	ssize_t head = 0;
	size_t i = 0;
	ssize_t node;
	size_t *restrict vals;
	int saved_errno;

	fail_if (xmalloc(vals, cap, size_t));
	while ((size_t)head != this->end && this->next[head] == LINKED_LIST_UNUSED)
		head++;
	if ((size_t)head != this->end) {
		for (node = head; (node != head) || (i == 0); i++) {
			vals[i] = this->values[node];
			node = this->next[node];
		}
	}

	if (cap != this->capacity) {
		fail_if (xmalloc(new_next,     cap, ssize_t));
		fail_if (xmalloc(new_previous, cap, ssize_t));
		fail_if (xmalloc(new_reusable, cap, ssize_t));

		free(this->next);
		free(this->previous);
		free(this->reusable);

		this->next     = new_next;
		this->previous = new_previous;
		this->reusable = new_reusable;
	}

	for (i = 0; i < size; i++)
		this->next[i] = (ssize_t)(i + 1);
	this->next[size - 1] = 0;

	for (i = 1; i < size; i++)
		this->previous[i] = (ssize_t)(i - 1);
	this->previous[0] = (ssize_t)(size - 1);

	this->values = vals;
	this->end = size;
	this->reuse_head = 0;

	return 0;

fail:
	saved_errno = errno;
	free(vals);
	free(new_next);
	free(new_previous);
	return errno = saved_errno, -1;
}


/**
 * Gets the next free position, and grow the
 * arrays if necessary. This methods has constant
 * amortised time complexity.
 * 
 * @param   this  The list
 * @return        The next free position,
 *                `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly
 */
static ssize_t __attribute__((nonnull))
linked_list_get_next(linked_list_t *restrict this)
{
	size_t *tmp_values;
	ssize_t *tmp;

	if (this->reuse_head > 0)
		return this->reusable[--(this->reuse_head)];
	if (this->end == this->capacity) {
		if ((ssize_t)(this->end) < 0)
			fail_if ((errno = ENOMEM));

		this->capacity <<= 1;

		fail_if (yrealloc(tmp_values, this->values,   this->capacity, size_t));
		fail_if (yrealloc(tmp,        this->next,     this->capacity, ssize_t));
		fail_if (yrealloc(tmp,        this->previous, this->capacity, ssize_t));
		fail_if (yrealloc(tmp,        this->reusable, this->capacity, ssize_t));
	}
	return (ssize_t)(this->end++);
fail:
	return LINKED_LIST_UNUSED;
}


/**
 * Mark a position as unused
 * 
 * @param   this  The list
 * @param   node  The position
 * @return        The position
 */
static ssize_t __attribute__((nonnull))
linked_list_unuse(linked_list_t *restrict this, ssize_t node)
{
	if (node < 0)
		return node;
	this->reusable[this->reuse_head++] = node;
	this->next[node] = LINKED_LIST_UNUSED;
	this->previous[node] = LINKED_LIST_UNUSED;
	return node;
}


/**
 * Insert a value after a specified, reference, node
 * 
 * @param   this         The list
 * @param   value        The value to insert
 * @param   predecessor  The reference node
 * @return               The node that has been created and inserted,
 *                       `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly
 */
ssize_t
linked_list_insert_after(linked_list_t *this, size_t value, ssize_t predecessor)
{
	ssize_t node = linked_list_get_next(this);
	fail_if (node == LINKED_LIST_UNUSED);
	this->values[node] = value;
	this->next[node] = this->next[predecessor];
	this->next[predecessor] = node;
	this->previous[node] = predecessor;
	this->previous[this->next[node]] = node;
	return node;
fail:
	return LINKED_LIST_UNUSED;
}


/**
 * Remove the node after a specified, reference, node
 * 
 * @param   this         The list
 * @param   predecessor  The reference node
 * @return               The node that has been removed
 */
ssize_t
linked_list_remove_after(linked_list_t *restrict this, ssize_t predecessor)
{
	ssize_t node = this->next[predecessor];
	this->next[predecessor] = this->next[node];
	this->previous[this->next[node]] = predecessor;
	return linked_list_unuse(this, node);
}


/**
 * Insert a value before a specified, reference, node
 * 
 * @param   this       The list
 * @param   value      The value to insert
 * @param   successor  The reference node
 * @return             The node that has been created and inserted,
 *                     `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly
 */
ssize_t
linked_list_insert_before(linked_list_t *restrict this, size_t value, ssize_t successor)
{
	ssize_t node = linked_list_get_next(this);
	fail_if (node == LINKED_LIST_UNUSED);
	this->values[node] = value;
	this->previous[node] = this->previous[successor];
	this->previous[successor] = node;
	this->next[node] = successor;
	this->next[this->previous[node]] = node;
	return node;
fail:
	return LINKED_LIST_UNUSED;
}


/**
 * Remove the node before a specified, reference, node
 * 
 * @param   this       The list
 * @param   successor  The reference node
 * @return             The node that has been removed
 */
ssize_t
linked_list_remove_before(linked_list_t *restrict this, ssize_t successor)
{
	ssize_t node = this->previous[successor];
	this->previous[successor] = this->previous[node];
	this->next[this->previous[node]] = successor;
	return linked_list_unuse(this, node);
}


/**
 * Remove the node from the list
 * 
 * @param  this  The list
 * @param  node  The node to remove
 */
void
linked_list_remove(linked_list_t *restrict this, ssize_t node)
{
	this->next[this->previous[node]] = this->next[node];
	this->previous[this->next[node]] = this->previous[node];
	linked_list_unuse(this, node);
}


/**
 * Calculate the buffer size need to marshal a linked list
 * 
 * @param   this  The list
 * @return        The number of bytes to allocate to the output buffer
 */
size_t
linked_list_marshal_size(const linked_list_t *restrict this)
{
	return sizeof(size_t) * (4 + this->reuse_head + 3 * this->end) + sizeof(int);
}


/**
 * Marshals a linked list
 * 
 * @param  this  The list
 * @param  data  Output buffer for the marshalled data
 */
void
linked_list_marshal(const linked_list_t *restrict this, char *restrict data)
{
	buf_set(data, int, 0, LINKED_LIST_T_VERSION);
	buf_next(data, int, 1);

	buf_set(data, size_t, 0, this->capacity);
	buf_set(data, size_t, 1, this->end);
	buf_set(data, size_t, 2, this->reuse_head);
	buf_set(data, ssize_t, 3, this->edge);
	buf_next(data, size_t, 4);

	memcpy(data, this->reusable, this->reuse_head * sizeof(ssize_t));
	buf_next(data, ssize_t, this->reuse_head);

	memcpy(data, this->values, this->end * sizeof(size_t));
	buf_next(data, size_t, this->end);

	memcpy(data, this->next, this->end * sizeof(ssize_t));
	buf_next(data, ssize_t, this->end);

	memcpy(data, this->previous, this->end * sizeof(ssize_t));
}


/**
 * Unmarshals a linked list
 * 
 * @param   this  Memory slot in which to store the new linked list
 * @param   data  In buffer with the marshalled data
 * @return        Non-zero on error, `errno` will be set accordingly.
 *                Destroy the list on error.
 */
int
linked_list_unmarshal(linked_list_t *restrict this, char *restrict data)
{
	/* buf_get(data, int, 0, LINKED_LIST_T_VERSION); */
	buf_next(data, int, 1);

	this->reusable = NULL;
	this->values   = NULL;
	this->next     = NULL;
	this->previous = NULL;

	buf_get(data, size_t, 0, this->capacity);
	buf_get(data, size_t, 1, this->end);
	buf_get(data, size_t, 2, this->reuse_head);
	buf_get(data, ssize_t, 3, this->edge);
	buf_next(data, size_t, 4);

	fail_if (xmalloc(this->reusable, this->capacity, size_t));
	fail_if (xmalloc(this->values,   this->capacity, size_t));
	fail_if (xmalloc(this->next,     this->capacity, size_t));
	fail_if (xmalloc(this->previous, this->capacity, size_t));

	memcpy(this->reusable, data, this->reuse_head * sizeof(ssize_t));
	buf_next(data, ssize_t, this->reuse_head);

	memcpy(this->values, data, this->end * sizeof(size_t));
	buf_next(data, size_t, this->end);

	memcpy(this->next, data, this->end * sizeof(ssize_t));
	buf_next(data, ssize_t, this->end);

	memcpy(this->previous, data, this->end * sizeof(ssize_t));

	return 0;
fail:
	return -1;
}


/**
 * Print the content of the list
 * 
 * @param  this    The list
 * @param  output  Output file
 */
void
linked_list_dump(linked_list_t *restrict this, FILE *restrict output)
{
	ssize_t i;
	size_t j;
	fprintf(output, "======= LINKED LIST DUMP =======\n");
	fprintf(output, "Capacity:    %zu\n", this->capacity);
	fprintf(output, "End:         %zu\n", this->end);
	fprintf(output, "Reuse head:  %zu\n", this->reuse_head);
	fprintf(output, "Edge:        %zi\n", this->edge);
	fprintf(output, "--------------------------------\n");
	fprintf(output, "Node table (Next, Prev, Value):\n");
	i = this->edge;
	fprintf(output, "    %zi: %zi, %zi, %zu\n", i, this->next[i], this->previous[i], this->values[i]);
	foreach_linked_list_node((*this), i)
		fprintf(output, "    %zi: %zi, %zi, %zu\n", i, this->next[i], this->previous[i], this->values[i]);
	i = this->edge;
	fprintf(output, "    %zi: %zi, %zi, %zu\n", i, this->next[i], this->previous[i], this->values[i]);
	fprintf(output, "--------------------------------\n");
	fprintf(output, "Raw node table:\n");
	for (j = 0; j < this->end; j++)
		fprintf(output, "    %zu: %zi, %zi, %zu\n", i, this->next[i], this->previous[i], this->values[i]);
	fprintf(output, "--------------------------------\n");
	fprintf(output, "Reuse stack:\n");
	for (j = 0; j < this->reuse_head; j++)
		fprintf(output, "    %zu: %zi\n", j, this->reusable[j]);
	fprintf(output, "================================\n");
}