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// Copyright (c) 2023, Marvin Borner <dev@marvinborner.de>
// SPDX-License-Identifier: MIT
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <term.h>
#include <spec.h>
#include <parse.h>
#include <log.h>
static struct term *rec_blc(const char **term)
{
struct term *res = 0;
if (!**term) {
fatal("invalid parsing state!\n");
} else if (**term == '0' && *(*term + 1) == '0') {
(*term) += 2;
res = new_term(ABS);
res->u.abs.term = rec_blc(term);
} else if (**term == '0' && *(*term + 1) == '1') {
(*term) += 2;
res = new_term(APP);
res->u.app.lhs = rec_blc(term);
res->u.app.rhs = rec_blc(term);
} else if (**term == '1') {
const char *cur = *term;
while (**term == '1')
(*term)++;
res = new_term(VAR);
res->u.var.index = *term - cur - 1;
(*term)++;
} else {
(*term)++;
res = rec_blc(term);
}
return res;
}
struct term *parse_blc(const char *term)
{
return rec_blc(&term);
}
#define BIT_AT(i) (term[(i) / 8] & (1 << (7 - ((i) % 8))))
// parses bloc's bit-encoded blc
// 00M -> abstraction of M
// 010MN -> application of M and N
// 1X0 -> bruijn index, amount of 1s in X
// 011I -> 2B index to entry
static struct term *parse_bloc_bblc(const char *term, size_t *bit)
{
struct term *res = 0;
if (!BIT_AT(*bit) && !BIT_AT(*bit + 1)) {
(*bit) += 2;
res = new_term(ABS);
res->u.abs.term = parse_bloc_bblc(term, bit);
} else if (!BIT_AT(*bit) && BIT_AT(*bit + 1) && !BIT_AT(*bit + 2)) {
(*bit) += 3;
res = new_term(APP);
res->u.app.lhs = parse_bloc_bblc(term, bit);
res->u.app.rhs = parse_bloc_bblc(term, bit);
} else if (BIT_AT(*bit)) {
const size_t cur = *bit;
while (BIT_AT(*bit))
(*bit)++;
res = new_term(VAR);
res->u.var.index = *bit - cur - 1;
(*bit)++;
} else if (!BIT_AT(*bit) && BIT_AT(*bit + 1) && BIT_AT(*bit + 2)) {
(*bit) += 3;
res = new_term(REF);
short index = 0;
for (int i = 0; i < 16; i++) {
index |= (BIT_AT(*bit) >> (7 - (*bit % 8))) << i;
(*bit) += 1;
}
res->u.ref.index = index;
} else {
(*bit)++;
res = parse_bloc_bblc(term, bit);
}
return res;
}
struct bloc_parsed *parse_bloc(const void *bloc)
{
const struct bloc_header *header = bloc;
if (memcmp(header->identifier, BLOC_IDENTIFIER,
(size_t)BLOC_IDENTIFIER_LENGTH)) {
fatal("invalid BLoC identifier!\n");
return 0;
}
struct bloc_parsed *parsed = malloc(sizeof(*parsed));
parsed->length = header->length;
parsed->entries = malloc(header->length * sizeof(struct term *));
const struct bloc_entry *current = (const void *)&header->entries;
for (size_t i = 0; i < parsed->length; i++) {
size_t len = 0;
parsed->entries[i] =
parse_bloc_bblc((const char *)current, &len);
current =
(const struct bloc_entry *)(((const char *)current) +
(len / 8) + (len % 8 != 0));
}
return parsed;
}
void free_bloc(struct bloc_parsed *bloc)
{
for (size_t i = 0; i < bloc->length; i++) {
free_term(bloc->entries[i]);
}
free(bloc->entries);
free(bloc);
}
static struct term *rec_bloc(struct term *term, struct bloc_parsed *bloc)
{
switch (term->type) {
case ABS:
rec_bloc(term->u.abs.term, bloc);
break;
case APP:
rec_bloc(term->u.app.lhs, bloc);
rec_bloc(term->u.app.rhs, bloc);
break;
case VAR:
break;
case REF:
if (term->u.ref.index >= bloc->length)
fatal("invalid entry reference\n");
memcpy(term,
bloc->entries[bloc->length - term->u.ref.index - 1],
sizeof(*term));
break;
default:
fatal("invalid type %d\n", term->type);
return 0;
}
return term;
}
struct term *from_bloc(struct bloc_parsed *bloc)
{
struct term *last = bloc->entries[bloc->length - 1];
return rec_bloc(last, bloc);
}
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