#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stdarg.h>

#include <rc.h>

#include "vector.h"

#define RC_CHK 0xabadcafe


struct rc {
	uint32_t check;
	_Atomic size_t refs;
	_Atomic size_t weak_refs;

	vec_t* _rc_restrict weaks; //vec type `rc_weak_t*`

	uint8_t ptr[];
};

struct rc_weak {
	_Atomic rc_bool is_valid;
	const struct rc* _rc_attr((may_alias)) _ptr;
}; 

_rc_attr((noreturn)) void panic(const char* string, ...)
{
	va_list args;
	va_start(args, string);
	fprintf(stderr, "(librc) Fatal error: ");
	vfprintf(stderr, string, args);
	va_end(args);
	fprintf(stderr, "\n");
	abort();
}

_rc_attr((noinline, noreturn, cold)) static void _fail_invptr() 
{
	panic("Invalid RC pointer");
}

 _rc_attr((noinline, noreturn, cold)) static void _fail_malloc(size_t sz)
{
	panic("malloc() failed to allocate %d bytes (%d + sizeof(struct rc))", sz+sizeof(struct rc), sz);
}
_rc_attr((artificial, const, always_inline)) inline static const struct rc* ptr_crev(const void* ptr)
{
	if (!ptr) _fail_invptr();
	return (const struct rc*)(((const uint8_t*)ptr) - sizeof(struct rc));
}

_rc_attr((artificial, const, always_inline)) inline static rc_t ptr_rev(void* ptr)
{
	if (!ptr) _fail_invptr();
	return (rc_t)(((uint8_t*)ptr) - sizeof(struct rc));
}


_rc_attr((artificial, const, always_inline)) inline static rc_t ptr_ucrev(const void* ptr)
{
	if (!ptr) _fail_invptr();
	return (rc_t)(((uintptr_t)ptr) - sizeof(struct rc));
}

_rc_attr((nonnull)) inline static void rc_checkptr(const struct rc* rc)
{
	if (rc->check != RC_CHK) _fail_invptr();
}

 _rc_attr((malloc, alloc_size(1), returns_nonnull)) void* restrict rc_malloc(size_t sz)
{
	register rc_t rc = malloc(sz + sizeof(struct rc));

	if (!rc) _fail_malloc(sz);

	rc->check = RC_CHK;
	rc->refs = 1;
	rc->weak_refs =0;
	rc->weaks = vec_new();

	return (void*) rc->ptr;	
}

 _rc_gmut_fn void rc_free(rc_ptr_t ptr)
{
	register rc_t rc = ptr_rev(ptr);
	rc_checkptr(rc);
	if (!--rc->refs) {
		for(size_t i=0;i<rc->weaks->len;i++) {
			vec_tnptr(rc_weak_t, rc->weaks->buffer[i])->is_valid = RC_FALSE;
		}
		free(rc->weaks);
		free(rc);
	}
}

_rc_mut_fn _rc_attr((returns_nonnull)) rc_ptr_t rc_clone(rc_const_ptr_t ptr)
{
	register rc_t rc = ptr_ucrev(ptr);
	rc_checkptr(rc);
	++rc->refs;
	return rc->ptr;
}

_rc_fn size_t rc_refs(rc_const_ptr_t ptr)
{
	register const struct rc* rc = ptr_crev(ptr);
	rc_checkptr(rc);
	return rc->refs;
}

_rc_fn rc_bool rc_is_valid(rc_const_ptr_t ptr)
{
	register const struct rc* rc = ptr_crev(ptr);
	return rc->check == RC_CHK 
		&& rc->refs>0;
}

_rc_alloc_fn _rc_gmut_fn rc_weak_t* _rc_restrict rc_downgrade(rc_const_ptr_t ptr)
{
	register rc_t rc = ptr_ucrev(ptr);
	rc_weak_t* weak = calloc(sizeof(rc_weak_t), 1);
	
	//TODO: push `weak` to rc->weaks

	weak->_ptr = rc;
	weak->is_valid = RC_TRUE;


	rc->weak_refs++;
	return weak;
}

_rc_gmut_fn void rc_weak_free(rc_weak_t* _rc_restrict ptr)
{
	if (ptr->is_valid) {
		struct rc* _rc_attr((may_alias)) rc = (struct rc* _rc_attr((may_alias)))ptr->_ptr;
		rc_checkptr(rc);

		//TODO: remove `weak` from `rc->weaks`
		rc->weak_refs--;
	}
	free(ptr);
}

_rc_mut_fn rc_ptr_t rc_weak_upgrade(const rc_weak_t * _rc_restrict weak)
{
	if (weak->is_valid) {
		struct rc* _rc_attr((may_alias)) rc = (struct rc* _rc_attr((may_alias)))weak->_ptr;
		
		if (rc->check == RC_CHK && rc->refs>0) {
			rc->refs++;
			return rc->ptr;
		}
	}
	return NULL;
}