package soot.jimple.toolkits.annotation.logic;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2004 Jennifer Lhotak
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import soot.Body;
import soot.BodyTransformer;
import soot.G;
import soot.Local;
import soot.Singletons;
import soot.Value;
import soot.ValueBox;
import soot.jimple.Constant;
import soot.jimple.DefinitionStmt;
import soot.jimple.Expr;
import soot.jimple.GotoStmt;
import soot.jimple.InvokeExpr;
import soot.jimple.InvokeStmt;
import soot.jimple.NaiveSideEffectTester;
import soot.jimple.NewExpr;
import soot.jimple.Stmt;
import soot.tagkit.ColorTag;
import soot.tagkit.LoopInvariantTag;
import soot.toolkits.graph.UnitGraph;
import soot.toolkits.scalar.SmartLocalDefs;
import soot.toolkits.scalar.SmartLocalDefsPool;

public class LoopInvariantFinder extends BodyTransformer {
  private static final Logger logger = LoggerFactory.getLogger(LoopInvariantFinder.class);

  private ArrayList constants;

  public LoopInvariantFinder(Singletons.Global g) {
  }

  public static LoopInvariantFinder v() {
    return G.v().soot_jimple_toolkits_annotation_logic_LoopInvariantFinder();
  }

  /**
   * this one uses the side effect tester
   */
  protected void internalTransform(Body b, String phaseName, Map options) {

    SmartLocalDefs sld = SmartLocalDefsPool.v().getSmartLocalDefsFor(b);
    UnitGraph g = sld.getGraph();
    NaiveSideEffectTester nset = new NaiveSideEffectTester();

    Collection<Loop> loops = new LoopFinder().getLoops(b);
    constants = new ArrayList();

    // no loop invariants if no loops
    if (loops.isEmpty()) {
      return;
    }

    Iterator<Loop> lIt = loops.iterator();
    while (lIt.hasNext()) {
      Loop loop = lIt.next();
      Stmt header = loop.getHead();
      Collection<Stmt> loopStmts = loop.getLoopStatements();
      Iterator<Stmt> bIt = loopStmts.iterator();
      while (bIt.hasNext()) {
        Stmt tStmt = bIt.next();
        // System.out.println("will test stmt: "+tStmt+" for loop header: "+header);
        // System.out.println("will test with loop stmts: "+loopStmts);
        handleLoopBodyStmt(tStmt, nset, loopStmts);
      }
    }
  }

  private void handleLoopBodyStmt(Stmt s, NaiveSideEffectTester nset, Collection<Stmt> loopStmts) {
    // need to do some checks for arrays - when there is an multi-dim array
    // --> for defs there is a get of one of the dims that claims to be
    // loop invariant

    // handle constants
    if (s instanceof DefinitionStmt) {
      DefinitionStmt ds = (DefinitionStmt) s;
      if (ds.getLeftOp() instanceof Local && ds.getRightOp() instanceof Constant) {
        if (!constants.contains(ds.getLeftOp())) {
          constants.add(ds.getLeftOp());
        } else {
          constants.remove(ds.getLeftOp());
        }
      }
    }

    // ignore goto stmts
    // ignore invoke stmts
    if ((s instanceof GotoStmt) || (s instanceof InvokeStmt)) {
      return;
    }

    logger.debug("s : " + s + " use boxes: " + s.getUseBoxes() + " def boxes: " + s.getDefBoxes());
    // just use boxes here
    Iterator useBoxesIt = s.getUseBoxes().iterator();
    boolean result = true;
    uses: while (useBoxesIt.hasNext()) {
      ValueBox vb = (ValueBox) useBoxesIt.next();
      Value v = vb.getValue();
      // System.out.println("next vb: "+v+" is a: "+vb.getClass());
      // System.out.println("next vb: "+v+" class is a: "+v.getClass());
      // new's are not invariant
      if (v instanceof NewExpr) {
        result = false;
        logger.debug("break uses: due to new expr");
        break uses;
      }
      // invokes are not invariant
      if (v instanceof InvokeExpr) {
        result = false;
        logger.debug("break uses: due to invoke expr");
        break uses;
      }
      // side effect tester doesn't handle expr
      if (v instanceof Expr) {
        continue;
      }

      logger.debug("test: " + v + " of kind: " + v.getClass());
      Iterator loopStmtsIt = loopStmts.iterator();
      while (loopStmtsIt.hasNext()) {
        Stmt next = (Stmt) loopStmtsIt.next();
        if (nset.unitCanWriteTo(next, v)) {
          if (!isConstant(next)) {
            logger.debug("result = false unit can be written to by: " + next);
            result = false;
            break uses;
          }
        }
      }

    }

    Iterator defBoxesIt = s.getDefBoxes().iterator();
    defs: while (defBoxesIt.hasNext()) {
      ValueBox vb = (ValueBox) defBoxesIt.next();
      Value v = vb.getValue();
      // new's are not invariant
      if (v instanceof NewExpr) {
        result = false;
        logger.debug("break defs due to new");
        break defs;
      }
      // invokes are not invariant
      if (v instanceof InvokeExpr) {
        result = false;
        logger.debug("break defs due to invoke");
        break defs;
      }
      // side effect tester doesn't handle expr
      if (v instanceof Expr) {
        continue;
      }

      logger.debug("test: " + v + " of kind: " + v.getClass());

      Iterator loopStmtsIt = loopStmts.iterator();
      while (loopStmtsIt.hasNext()) {
        Stmt next = (Stmt) loopStmtsIt.next();
        if (next.equals(s)) {
          continue;
        }
        if (nset.unitCanWriteTo(next, v)) {
          if (!isConstant(next)) {
            logger.debug("result false: unit can be written to by: " + next);
            result = false;
            break defs;
          }
        }
      }

    }
    logger.debug("stmt: " + s + " result: " + result);
    if (result) {
      s.addTag(new LoopInvariantTag("is loop invariant"));
      s.addTag(new ColorTag(ColorTag.RED, "Loop Invariant Analysis"));
    } else {
      // if loops are nested it might be invariant in one of them
      // so remove tag
      // if (s.hasTag(LoopInvariantTag.NAME)) {
      // s.removeTag(LoopInvariantTag.NAME);
      // }
    }
  }

  private boolean isConstant(Stmt s) {
    if (s instanceof DefinitionStmt) {
      DefinitionStmt ds = (DefinitionStmt) s;
      if (constants.contains(ds.getLeftOp())) {
        return true;
      }
    }
    return false;
  }
}
