#ifndef CMAYBE_H
#define CMAYBE_H

#define MAYBE_TYPE(name, type) struct cmaybe_maybe_##name {type value; char is_value;}
#define MAYBE(name) struct cmaybe_maybe_##name

#define ENABLE_RETURN(name) MAYBE(name) cmaybe_return_value
#define RETURN_VALUE(x) do {\
	cmaybe_return_value.is_value = 1;\
	cmaybe_return_value.value = x;\
	return cmaybe_return_value;\
} while(0)
#define RETURN_NOTHING() do {\
	cmaybe_return_value.is_value = 0;\
	return cmaybe_return_value;\
} while(0)

#define IS_VALUE(x) if ((x).is_value)
#define IS_NOT_VALUE(x) if (!(x).is_value)
#define VALUE(x) (x).value

struct cmaybe_free_list {
	struct cmaybe_free_list *next;
	void *ptr;
	void (*freer)(void*);
};
#define ENABLE_TRY() \
	struct cmaybe_free_list *cmaybe_allocations = NULL, *cmaybe_free_list_node;\
	void *cmaybe_allocation;\
	jmp_buf cmaybe_try_fail_jmp_buf;\
	if (setjmp(cmaybe_try_fail_jmp_buf)) do {\
		TRY_FAIL_HANDLE();\
		RETURN_NOTHING();\
	} while(0)
#define TRY_TYPE(name) MAYBE(name) cmaybe_try_tmp_##name
#define TRY(name, maybe_value) (\
	cmaybe_try_tmp_##name = maybe_value,\
	(cmaybe_try_tmp_##name.is_value ? 0 :\
		longjmp(cmaybe_try_fail_jmp_buf, 1)\
	),\
	cmaybe_try_tmp_##name.value\
)

#define TRY_HOF_HANDLE(freer_func, pointer) (\
	cmaybe_allocation = pointer,\
	cmaybe_free_list_node = malloc(sizeof(struct cmaybe_free_list)),\
	(cmaybe_free_list_node == NULL ? (\
		free(cmaybe_allocation),\
		longjmp(cmaybe_try_fail_jmp_buf, 1)\
	) : (\
		cmaybe_free_list_node->next = cmaybe_allocations,\
		cmaybe_free_list_node->ptr = cmaybe_allocation,\
		cmaybe_free_list_node->freer = freer_func,\
		cmaybe_allocations = cmaybe_free_list_node\
	)),\
	cmaybe_allocation\
)
#define FREE_ON_TRY_FAIL(pointer) TRY_HOF_HANDLE(free, pointer)

// free() is passed as an argument to avoid errors in case the program uses
// no TRY functionality and doesn't include stdlib.h
static void cmaybe_remove_free_list(struct cmaybe_free_list **head, void *ptr, void (*free)(void*)) {
	struct cmaybe_free_list **current = head;
	while (*current != NULL) {
		if (current[0]->ptr == ptr) {
			struct cmaybe_free_list *deleted = *current;
			*current = deleted->next;
			free(deleted);
			break;
		}
		current = &current[0]->next;
	}
}

#define TRY_HOF_REMOVE(allocation) cmaybe_remove_free_list(&cmaybe_allocations, allocation, free)
#define TRY_FAIL_HANDLE() \
	while (cmaybe_allocations != NULL) {\
		struct cmaybe_free_list *current = cmaybe_allocations;\
		void (*freer)(void*) = current->freer;\
		freer(current->ptr);\
		cmaybe_allocations = current->next;\
		free(current);\
	}

static void cmaybe_replace_free_list(struct cmaybe_free_list **head, void *from, void *to) {
	struct cmaybe_free_list **current = head;
	while (*current != NULL) {
		if (current[0]->ptr == from) {
			current[0]->ptr = to;
			break;
		}
		current = &current[0]->next;
	}
}
#define TRY_HOF_REPLACE(old_ptr, new_ptr) cmaybe_replace_free_list(&cmaybe_allocations, old_ptr, new_ptr)

#endif