#include "prim.h"

#include "env.h"

#include <assert.h>

#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))

typedef struct {
	const char *name;
	prim_proc_t prim_proc;
} prim_table_entry_t;

static void add(am_t *am)
{
	assert(AM_ARGL(am));

	int64_t total = 0;
	for (expr_t *list = AM_ARGL(am); !list->is_atom; list = list->pair.cdr) {
		assert(list->pair.car->is_atom);
		assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
		total += list->pair.car->atom.integer;
	}
	AM_VAL(am) = expr_integer(am, total);
}

static void mul(am_t *am)
{
	assert(AM_ARGL(am));

	int64_t total = 1;
	for (expr_t *list = AM_ARGL(am); !list->is_atom; list = list->pair.cdr) {
		assert(list->pair.car->is_atom);
		assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
		total *= list->pair.car->atom.integer;
	}
	AM_VAL(am) = expr_integer(am, total);
}

static void sub(am_t *am)
{
	assert(AM_ARGL(am));
	assert(!AM_ARGL(am)->is_atom);
	assert(AM_ARGL(am)->pair.car->is_atom);
	assert(AM_ARGL(am)->pair.car->atom.type == ATOM_TYPE_INTEGER);

	int64_t total = AM_ARGL(am)->pair.car->atom.integer;
	if (!AM_ARGL(am)->is_atom && AM_ARGL(am)->pair.cdr->is_atom) {
		total *= -1;
	} else {
		for (expr_t *list = AM_ARGL(am)->pair.cdr; !list->is_atom;
		     list = list->pair.cdr) {
			assert(list->pair.car->is_atom);
			assert(list->pair.car->atom.type == ATOM_TYPE_INTEGER);
			total -= list->pair.car->atom.integer;
		}
	}
	AM_VAL(am) = expr_integer(am, total);
}

static const prim_table_entry_t prim_table[] = {
	{ "+", add },
	{ "*", mul },
	{ "-", sub },
};

void prim_load(am_t *am)
{
	for (unsigned i = 0; i < NELEMS(prim_table); ++i) {
		AM_EXPR(am) = expr_str_symbol(am, prim_table[i].name);
		AM_VAL(am) = expr_prim_proc(am, prim_table[i].prim_proc);
		env_set(am);
	}
}