/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "txPatternOptimizer.h"
#include "txXSLTPatterns.h"

void txPatternOptimizer::optimize(txPattern* aInPattern,
                                  txPattern** aOutPattern) {
  *aOutPattern = nullptr;

  // First optimize sub expressions
  uint32_t i = 0;
  Expr* subExpr;
  while ((subExpr = aInPattern->getSubExprAt(i))) {
    Expr* newExpr = nullptr;
    mXPathOptimizer.optimize(subExpr, &newExpr);
    if (newExpr) {
      delete subExpr;
      aInPattern->setSubExprAt(i, newExpr);
    }

    ++i;
  }

  // Then optimize sub patterns
  txPattern* subPattern;
  i = 0;
  while ((subPattern = aInPattern->getSubPatternAt(i))) {
    txPattern* newPattern = nullptr;
    optimize(subPattern, &newPattern);
    if (newPattern) {
      delete subPattern;
      aInPattern->setSubPatternAt(i, newPattern);
    }

    ++i;
  }

  // Finally see if current pattern can be optimized
  switch (aInPattern->getType()) {
    case txPattern::STEP_PATTERN:
      optimizeStep(aInPattern, aOutPattern);
      return;

    default:
      break;
  }
}

void txPatternOptimizer::optimizeStep(txPattern* aInPattern,
                                      txPattern** aOutPattern) {
  txStepPattern* step = static_cast<txStepPattern*>(aInPattern);

  // Test for predicates that can be combined into the nodetest
  Expr* pred;
  while ((pred = step->getSubExprAt(0)) &&
         !pred->canReturnType(Expr::NUMBER_RESULT) &&
         !pred->isSensitiveTo(Expr::NODESET_CONTEXT)) {
    txNodeTest* predTest = new txPredicatedNodeTest(step->getNodeTest(), pred);
    step->dropFirst();
    step->setNodeTest(predTest);
  }
}