#pragma once

#include "iter.qh"

const int IL_MAX = 128;

ERASEABLE
void IL_INIT(entity this);
ERASEABLE
void IL_DTOR(entity this);
ERASEABLE
void IL_ENDFRAME();

/**
 * limitations:
 *   NULL cannot be present
 *   elements can only be present once
 *   a maximum of `IL_MAX` lists can exist at one time
 *   freed entities must be removed from the list
 */
CLASS(IntrusiveList, Object)
	ATTRIB(IntrusiveList, il_head, entity);
	ATTRIB(IntrusiveList, il_tail, entity);
	ATTRIB(IntrusiveList, il_nextfld, .entity, nil);
	ATTRIB(IntrusiveList, il_prevfld, .entity, nil);
	INIT(IntrusiveList) { IL_INIT(this); }
	DESTRUCTOR(IntrusiveList) { IL_DTOR(this); }
ENDCLASS(IntrusiveList)

// bitflags
.vector il_lists;
// bitflags
.vector il_listmask;

#define IL_NEW() NEW(IntrusiveList)

#define IL_EMPTY(this) (this.il_head == NULL)

#define IL_FIRST(this) (this.il_head)
#define IL_LAST(this) (this.il_tail)
#define IL_PEEK(this) (this.il_tail)

ERASEABLE
bool IL_CONTAINS(IntrusiveList this, entity it)
{
	assert(this, return false);
	return it.(this.il_nextfld) || this.il_head == it || this.il_tail == it;
}

/**
 * Push to tail
 */
ERASEABLE
entity IL_PUSH(IntrusiveList this, entity it)
{
	assert(this, return NULL);
	assert(it, return NULL);
	.entity il_next = this.il_nextfld;
	.entity il_prev = this.il_prevfld;
	assert(!IL_CONTAINS(this, it), return NULL);

	entity tail = it.(il_prev) = this.il_tail;
	tail ? (tail.(il_next) = it) : this.il_head = it;
	this.il_tail = it;
	it.il_lists |= this.il_listmask;
	return it;
}

/**
 * Push to head
 */
ERASEABLE
entity IL_UNSHIFT(IntrusiveList this, entity it)
{
	assert(this, return NULL);
	assert(it, return NULL);
	.entity il_next = this.il_nextfld;
	.entity il_prev = this.il_prevfld;
	assert(!IL_CONTAINS(this, it), return NULL);

	entity head = it.(il_next) = this.il_head;
	head ? (head.(il_prev) = it) : this.il_tail = it;
	this.il_head = it;
	it.il_lists |= this.il_listmask;
	return it;
}

/**
 * Pop from tail
 */
ERASEABLE
entity IL_POP(IntrusiveList this)
{
	assert(this, return NULL);
	.entity il_next = this.il_nextfld;
	.entity il_prev = this.il_prevfld;

	if (!this.il_tail) return NULL;
	entity it = this.il_tail;
	entity prev = it.(il_prev);
	if (prev) (this.il_tail = prev).(il_next) = NULL;
	else this.il_head = this.il_tail = NULL;
	return it;
}

/**
 * Pop from head
 */
ERASEABLE
entity IL_SHIFT(IntrusiveList this)
{
	assert(this, return NULL);
	.entity il_next = this.il_nextfld;
	.entity il_prev = this.il_prevfld;

	if (!this.il_head) return NULL;
	entity it = this.il_head;
	entity next = it.(il_next);
	if (next) (this.il_head = next).(il_prev) = NULL;
	else this.il_head = this.il_tail = NULL;
	return it;
}

/**
 * Remove any element, anywhere in the list
 */
ERASEABLE
void IL_REMOVE(IntrusiveList this, entity it)
{
	assert(this, return);
	.entity il_next = this.il_nextfld;
	.entity il_prev = this.il_prevfld;
	//assert(!IL_CONTAINS(this, it), return);
	entity next = it.(il_next);
	entity prev = it.(il_prev);
	entity ohead = this.il_head;
	entity otail = this.il_tail;
	next ? next.(il_prev) = prev : this.il_tail = prev;
	prev ? prev.(il_next) = next : this.il_head = next;
	LOG_DEBUGF("remove %i (%i :: %i), head: %i -> %i, tail: %i -> %i", it, it.(il_prev), it.(il_next), ohead, this.il_head, otail, this.il_tail);
	it.(il_next) = it.(il_prev) = NULL;
}

/**
 * Remove all elements
 */
#define IL_CLEAR(this) \
	MACRO_BEGIN \
		IntrusiveList __il = this; \
		assert(__il); \
		.entity il_prev = __il.il_prevfld; \
		IL_EACH(__il, true, it.(il_next) = it.(il_prev) = NULL); \
		__il.il_head = __il.il_tail = NULL; \
	MACRO_END

/**
 * Delete the list
 */
#define IL_DELETE(this) \
	MACRO_BEGIN \
		delete(this); \
		this = NULL; \
	MACRO_END

#define IL_EACH(this, cond, body) \
	MACRO_BEGIN \
		IntrusiveList _il = this; \
		assert(_il); \
		.entity il_next = _il.il_nextfld; \
		noref int i = 0; \
		for (entity _next, _it = _il.il_head; _it; (_it = _next, ++i)) \
		{ \
			const noref entity it = _it; \
			_next = it.(il_next); \
			if (cond) { LAMBDA(body) } \
		} \
	MACRO_END

.int il_id;
IntrusiveList il_links[IL_MAX];
.entity il_links_flds[IL_MAX * 2];
int il_links_ptr;

#define IL_FLOOR(n) ((n) | 0)
#define IL_CEIL(n)  IL_FLOOR((n) + 0.5)

#define IL_LISTS_PER_BIT IL_CEIL(IL_MAX / (3 * 24))

ERASEABLE
void IL_INIT(IntrusiveList this)
{
	.entity nextfld, prevfld;
	for (int i = il_links_ptr; i < il_links_ptr + IL_MAX; ++i) {
		int idx = i;
		if (idx >= IL_MAX) idx -= IL_MAX;
		int id = idx;
		idx *= 2;
		if (!il_links[idx]) {
			il_links[idx] = this;
			nextfld = il_links_flds[idx + 0];
			prevfld = il_links_flds[idx + 1];
			this.il_id = id;
			int bit = IL_FLOOR(id / IL_LISTS_PER_BIT);
			if (bit < (1 * 24)) this.il_listmask = '1 0 0' * (1 << (bit - (0 * 24)));
			else if (bit < (2 * 24)) this.il_listmask = '0 1 0' * (1 << (bit - (1 * 24)));
			else if (bit < (3 * 24)) this.il_listmask = '0 0 1' * (1 << (bit - (2 * 24)));
			else assert(false);
			il_links_ptr = id + 1;
			if (il_links_ptr >= IL_MAX) il_links_ptr -= IL_MAX;
			this.il_nextfld = nextfld;
			this.il_prevfld = prevfld;
			return;
		}
	}
	LOG_WARN("IntrusiveList overflow");
}

ERASEABLE
void IL_DTOR(IntrusiveList this)
{
	IL_CLEAR(this);
	il_links[this.il_id] = NULL;
}

ERASEABLE
void IL_ENDFRAME()
{
#if 0
	// incompatible with CSQC, remove() clears entities
	for (int i = 0; i < IL_MAX; ++i) {
		IntrusiveList list = il_links[i];
		if (list) {
			.entity nextfld = list.il_nextfld;
			for (entity next, it = list.il_head; it; it = next) {
				next = it.(nextfld);
				if (wasfreed(it)) {
					IL_REMOVE(list, it);
				}
			}
		}
	}
#endif
}

ERASEABLE
void ONREMOVE(entity this)
{
	if (this.il_lists) {
		for (int i = 0; i < IL_MAX; ++i) {
			IntrusiveList list = il_links[i];
			if (this.il_lists & list.il_listmask && IL_CONTAINS(list, this)) {
				IL_REMOVE(list, this);
			}
		}
	}
}