/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "tool/plinko/lib/plinko.h"

/**
 * Matches
 *
 *     (ζ (X Y) (Z))
 *
 * @return MAKE4(X,Y,Z,0) on success, or ZERO4 on mismatch
 * @note ζ means COND
 */
struct qword IsIf(int x_) {
  dword w_;
  if (x_ >= 0) return ZERO4;
  w_ = Get(x_);  // (ζ (X Y) (Z))
  int ax_ = LO(w_);
  int dx_ = HI(w_);
  if (ax_ != kCond) return ZERO4;
  if (dx_ >= 0) return ZERO4;
  w_ = Get(dx_);  // ((X Y) (Z))
  int adx_ = LO(w_);
  int ddx_ = HI(w_);
  if (adx_ >= 0) return ZERO4;
  w_ = Get(adx_);  // (X Y)
  int aadx_ = LO(w_);
  int dadx_ = HI(w_);
  if (ddx_ >= 0) return ZERO4;
  w_ = Get(ddx_);  // ((Z))
  int addx_ = LO(w_);
  int dddx_ = HI(w_);
  int X = aadx_;
  if (addx_ >= 0) return ZERO4;
  w_ = Get(addx_);  // (Z)
  int aaddx_ = LO(w_);
  int daddx_ = HI(w_);
  if (dadx_ >= 0) return ZERO4;
  w_ = Get(dadx_);  // (Y)
  int adadx_ = LO(w_);
  int ddadx_ = HI(w_);
  if (dddx_) return ZERO4;
  int Y = adadx_;
  int Z = aaddx_;
  if (ddadx_) return ZERO4;
  if (daddx_) return ZERO4;
  return MAKE4(X, Y, Z, 0);
}