/* Copyright (c) 2023 Contrast Security, Inc.  See
 * https://www.contrastsecurity.com/enduser-terms-0317a for more details. */

#include "cs__assess_string.h"
#include "../cs__common/cs__common.h"
#include <ruby.h>

/*
 * The -@ method source:
 *
 *                static VALUE
 * str_uminus(VALUE str)
 * {
 *     if (!BARE_STRING_P(str) && !rb_obj_frozen_p(str)) {
 *         str = rb_str_dup(str);
 *     }
 *     return rb_fstring(str);
 * }
 */

/*
 * This patch won't do the Prepend. We would call to the String instance'
 * uminus directly and skip other propagation from prepended modules.
 * We could come back to this one and rethink it's prepend patching.
 */

static VALUE contrast_assess_string_freeze(const int argc, VALUE *argv,
                                           const VALUE obj) {
    if (!OBJ_FROZEN(obj)) {
        rb_funcall(properties_hash, rb_sym_pre_freeze, 1, obj);
    }
    return rb_funcall(obj, rb_sym_assess_string_freeze, 0);
}

static VALUE contrast_assess_string_uminus(const int argc, VALUE *argv,
                                           const VALUE obj) {
    if (!OBJ_FROZEN(obj)) {
        /* We're doing something intentionally different here. Ruby, for -@,
         * attempts to de-duplicate the String and use an "interned" copy of
         * the String. We cannot allow that to happen for a couple reasons:
         * - prior to Ruby 2.7, this would cause us to track ALL instances of
         *   that interned copy.
         * - 2.7 and later, this action is actually missed because of a change
         *   to the str_uminus method in Ruby, which dups the String in a way
         *   that we cannot see.
         * B/c we cannot track this in 2.7, rather than having a version check
         * and two approaches, we'll instead directly call the #freeze method,
         * so the end result is that this String itself is frozen and never
         * deduplicated.
         */
        return contrast_assess_string_freeze(argc, argv, obj);
    }
    /* in all other cases, preserve monkey patching and c call */
    return rb_funcall(obj, rb_sym_assess_string_uminus, 0);
}

void Init_cs__assess_string(void) {
    rb_sym_dup = rb_intern("dup");
    rb_sym_freeze = rb_intern("freeze");
    rb_sym_pre_freeze = rb_intern("pre_freeze");
    /* Contrast::Agent::Assess::Tracker::PROPERTIES_HASH */
    VALUE tracker = rb_define_class_under(assess, "Tracker", rb_cObject);
    properties_hash = rb_const_get(tracker, rb_intern("PROPERTIES_HASH"));

    /* We only do alias for this one */
    rb_sym_assess_string_uminus =
        contrast_register_patch("String", "-@", &contrast_assess_string_uminus);
    rb_sym_assess_string_freeze = contrast_register_patch(
        "String", "freeze", &contrast_assess_string_freeze);
}