/* Copyright (C) 2024 Peter McGoron
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser General Public
 * License along with this program. If not, see
 * <https://www.gnu.org/licenses/>.
*/

/* TODO: add support for freestanding */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#include "uns.h"

/** Internal GC state.
 *
 * The exact structure is hidden from implementations. The function API
 * is stable(r).
 */
struct uns_gc {
	/** Context pointer used by specific collector implementations. */
	void *ctx;

	/** Head of the roots linked list. */
	struct uns_ctr *roots;

	/** Function called when OOM occurs. If not specified, the library
	  * will print to standard error and exit.
	  */
	void (*oom)(struct uns_gc *);

	/** Implementations of allocator functions. */

	void (*deinit)(Uns_GC);
	int (*collect)(Uns_GC);

	void *(*alloc)(Uns_GC, size_t, enum uns_bytes_type);
	void *(*alloc_rec)(Uns_GC, size_t, enum uns_record_type);
	void (*free)(Uns_GC, Uns_ptr);

	/** Generic implementation of record access. Values in a record may
	  * have unused bits filled in so raw reads may not work correctly.
	  * Values may also not be aligned correctly. The `get` and `set`
	  * functions will handle all of this so the caller gets what is
	  * expected.
	  */

	void (*set)(Uns_ptr, size_t, enum uns_fld_type, void *);
	void *(*get)(Uns_ptr, size_t, enum uns_fld_type *);
};
const size_t uns_gc_size = sizeof(struct uns_gc);

void uns_gc_zero(Uns_GC gc)
{
	gc->ctx = NULL;
	gc->roots = NULL;
	gc->oom = NULL;
	gc->deinit = NULL;
	gc->collect = NULL;
	gc->alloc = NULL;
	gc->alloc_rec = NULL;
	gc->free = NULL;
	gc->set = NULL;
	gc->get = NULL;
}

/** Wrapper to define a setter for the generic state struct. */
#define SETTER(name, arg) \
void uns_set_##name(Uns_GC gc, arg) {gc->name = name;}

SETTER(deinit, void(*deinit)(Uns_GC))
SETTER(oom, void(*oom)(Uns_GC))
SETTER(collect, int(*collect)(Uns_GC))
SETTER(alloc, void*(*alloc)(Uns_GC, size_t, enum uns_bytes_type))
SETTER(alloc_rec, void*(*alloc_rec)(Uns_GC, size_t, enum uns_record_type))
SETTER(free, void(*free)(Uns_GC, Uns_ptr))
SETTER(set, void(*set)(Uns_ptr, size_t, enum uns_fld_type, void*))
SETTER(get, void*(*get)(Uns_ptr, size_t, enum uns_fld_type *))
#undef SETTER

void uns_deinit(Uns_GC gc)
{
	if (gc->deinit)
		gc->deinit(gc);
	uns_gc_zero(gc);
}

int uns_collect(Uns_GC gc)
{
	if (gc->collect)
		return gc->collect(gc);
	abort();
}

void *uns_alloc(Uns_GC gc, size_t bytes, enum uns_bytes_type typ)
{
	if (gc->alloc)
		return gc->alloc(gc, bytes, typ);
	abort();
}

void *uns_alloc_rec(Uns_GC gc, size_t bytes, enum uns_record_type typ)
{
	if (gc->alloc_rec)
		return gc->alloc_rec(gc, bytes, typ);
	abort();
}

void uns_free(Uns_GC gc, Uns_ptr p)
{
	if (gc->free)
		gc->free(gc, p);
}

void *uns_get(Uns_GC gc, Uns_ptr rec, size_t ind, enum uns_fld_type *typ)
{
	if (gc->get)
		return gc->get(rec, ind, typ);
	else
		abort();
}

void uns_set(Uns_GC gc, Uns_ptr rec, size_t ind, enum uns_fld_type typ, void *val)
{
	if (gc->set)
		gc->set(rec, ind, typ, val);
	else
		abort();
}

void uns_on_oom(Uns_GC gc)
{
	if (gc->oom) {
		gc->oom(gc);
	} else {
		fprintf(stderr, "oom\n");
		abort();
	}
}

void uns_root_add(Uns_GC gc, struct uns_ctr *root)
{
	root->prev = NULL;
	root->next = gc->roots;

	if (gc->roots)
		gc->roots->prev = root;
	gc->roots = root;
}

void uns_root_remove(Uns_GC gc, struct uns_ctr *root)
{
	if (root->prev) {
		root->prev->next = root->next;
	}
	if (root->next) {
		root->next->prev = root->prev;
	}

	if (gc->roots == root) {
		assert(!root->prev);
		gc->roots = root->next;
	}

	root->prev = root->next = NULL;
}

struct uns_ctr *uns_roots(Uns_GC gc)
{
	return gc->roots;
}