// Copyright (c) 2023, Marvin Borner <dev@marvinborner.de>
// SPDX-License-Identifier: MIT

#ifndef CALM_TERM_H
#define CALM_TERM_H

#include <lib/pqueue.h>
#include <lib/hash.h>
#include <lib/hashmap.h>

typedef enum { INV, ABS, APP, VAR } term_type_t;

struct term {
	term_type_t type;

	hash_t hash;
	struct hashmap *parents;
	size_t refs;
	size_t depth;

	pqueue_pri_t priority;
	size_t position;

	union {
		struct {
			struct term *term;
		} abs;
		struct {
			struct term *lhs;
			struct term *rhs;
		} app;
		struct {
			size_t index;
		} var;
	} u;
};

struct term *term_new(term_type_t type, hash_t hash, size_t depth);
void term_destroy_head(struct term *term, char including_parents);
char term_is_beta_redex(struct term *term);
void term_rehash_parents(struct term *term);
struct term *term_rehash(struct term *term, int including_parents);
struct term *term_rehash_abs(struct term *head, struct term *term,
			     int including_parents);
struct term *term_rehash_app(struct term *head, struct term *lhs,
			     struct term *rhs, int including_parents);
struct term *term_rehash_var(struct term *head, size_t index,
			     int including_parents);
void term_refer_head(struct term *term, size_t depth);
void term_refer(struct term *term, size_t depth);
char term_deref_head(struct term *term, char destroy_parents);
char term_deref(struct term *term, char destroy_parents);

size_t term_print(struct term *term);

#endif