#include "list.h"

intptr_t list_length(LispVal *list) {
    assert(LISTP(list));
    LispVal *tortise = list;
    LispVal *hare = list;
    intptr_t length = 0;
    while (CONSP(tortise)) {
        tortise = XCDR_SAFE(tortise);
        hare = XCDR_SAFE(XCDR_SAFE(hare));
        if (!NILP(hare) && tortise == hare) {
            return -1;
        }
        ++length;
    }
    return length;
}

bool list_length_eq(LispVal *list, intptr_t size) {
    while (size && CONSP(list)) {
        list = XCDR(list);
        --size;
    }
    return size == 0 && NILP(list);
}

DEFUN(cons, "cons", (LispVal * car, LispVal *cdr), "(car cdr)",
      "Construct a new cons object from CAR and CDR.") {
    return CONS(car, cdr);
}

DEFUN(length, "length", (LispVal * list), "(list)", "") {
    // TODO type check
    // TODO list may be circular
    return MAKE_FIXNUM(list_length(list));
}

DEFUN(length_eq, "length=", (LispVal * list, LispVal *length), "(list length)",
      "Return non-nil if LIST's length is LENGTH.") {
    // TODO type check
    return list_length_eq(list, XFIXNUM(length)) ? Qt : Qnil;
}

DEFUN(nreverse, "nreverse", (LispVal * list), "(list)", "") {
    // TODO type checking
    LispVal *rev = Qnil;
    while (!NILP(list)) {
        LispVal *next = XCDR(list);
        RPLACD(list, rev);
        rev = list;
        list = next;
    }
    return rev;
}

DEFUN(listp, "listp", (LispVal * obj), "(obj)", "") {
    return LISTP(obj) ? Qt : Qnil;
}

DEFUN(list, "list", (LispVal * args), "(&rest args)", "") {
    return args;
}

DEFUN(plist_put, "plist-put", (LispVal * plist, LispVal *prop, LispVal *value),
      "(plist prop value)", "") {
    CHECK_LISTP(plist);
    DOTAILS(rest, plist) {
        if (EQ(XCAR(rest), prop)) {
            RPLACA(XCDR(rest), value);
            return plist;
        }
    }
    return CONS(prop, CONS(value, plist));
}

DEFUN(plist_get, "plist-get", (LispVal * plist, LispVal *prop, LispVal *def),
      "(plist prop &optional default)", "") {
    CHECK_LISTP(plist);
    DOTAILS(rest, plist) {
        if (EQ(XCAR(rest), prop)) {
            return SECOND(rest);
        }
    }
    return def;
}