/*
 * Copyright 2000-2015 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Created by IntelliJ IDEA.
 * User: max
 * Date: Jan 28, 2002
 * Time: 10:16:39 PM
 * To change template for new class use
 * Code Style | Class Templates options (Tools | IDE Options).
 */
package com.intellij.codeInspection.dataFlow;

import com.intellij.codeInspection.dataFlow.instructions.*;
import com.intellij.codeInspection.dataFlow.value.DfaValueFactory;
import com.intellij.codeInspection.dataFlow.value.DfaVariableValue;
import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.progress.ProgressManager;
import com.intellij.openapi.util.Key;
import com.intellij.openapi.util.Pair;
import com.intellij.openapi.util.registry.Registry;
import com.intellij.psi.*;
import com.intellij.psi.templateLanguages.OuterLanguageElement;
import com.intellij.psi.util.PsiTreeUtil;
import com.intellij.psi.util.PsiUtil;
import com.intellij.util.Processor;
import com.intellij.util.containers.ContainerUtil;
import com.intellij.util.containers.MultiMap;
import gnu.trove.THashSet;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.*;

public class DataFlowRunner {
  private static final Logger LOG = Logger.getInstance("#com.intellij.codeInspection.dataFlow.DataFlowRunner");
  private static final Key<Integer> TOO_EXPENSIVE_HASH = Key.create("TOO_EXPENSIVE_HASH");

  private Instruction[] myInstructions;
  private final MultiMap<PsiElement, DfaMemoryState> myNestedClosures = new MultiMap<PsiElement, DfaMemoryState>();
  @NotNull
  private final DfaValueFactory myValueFactory;

  // Maximum allowed attempts to process instruction. Fail as too complex to process if certain instruction
  // is executed more than this limit times.
  static final int MAX_STATES_PER_BRANCH = 300;

  protected DataFlowRunner() {
    this(false, true);
  }

  protected DataFlowRunner(boolean unknownMembersAreNullable, boolean honorFieldInitializers) {
    myValueFactory = new DfaValueFactory(honorFieldInitializers, unknownMembersAreNullable);
  }

  @NotNull
  public DfaValueFactory getFactory() {
    return myValueFactory;
  }

  @Nullable
  private Collection<DfaMemoryState> createInitialStates(@NotNull PsiElement psiBlock, @NotNull InstructionVisitor visitor) {
    PsiElement container = PsiTreeUtil.getParentOfType(psiBlock, PsiClass.class, PsiLambdaExpression.class);
    if (container != null && (!(container instanceof PsiClass) || PsiUtil.isLocalOrAnonymousClass((PsiClass)container))) {
      final PsiElement parent = container.getParent();
      final PsiCodeBlock block = DfaPsiUtil.getTopmostBlockInSameClass(parent);
      if (block != null) {
        final RunnerResult result = analyzeMethod(block, visitor);
        if (result == RunnerResult.OK) {
          final Collection<DfaMemoryState> closureStates = myNestedClosures.get(DfaPsiUtil.getTopmostBlockInSameClass(psiBlock));
          if (!closureStates.isEmpty()) {
            return closureStates;
          }
        }
        return null;
      }
    }

    return Collections.singletonList(createMemoryState());
  }

  @NotNull
  public final RunnerResult analyzeMethod(@NotNull PsiElement psiBlock, @NotNull InstructionVisitor visitor) {
    Collection<DfaMemoryState> initialStates = createInitialStates(psiBlock, visitor);
    return initialStates == null ? RunnerResult.NOT_APPLICABLE : analyzeMethod(psiBlock, visitor, false, initialStates);
  }

  @NotNull
  final RunnerResult analyzeMethod(@NotNull PsiElement psiBlock,
                                   @NotNull InstructionVisitor visitor,
                                   boolean ignoreAssertions,
                                   @NotNull Collection<DfaMemoryState> initialStates) {
    if (PsiTreeUtil.findChildOfType(psiBlock, OuterLanguageElement.class) != null) return RunnerResult.NOT_APPLICABLE;

    try {
      final ControlFlow flow = new ControlFlowAnalyzer(myValueFactory, psiBlock, ignoreAssertions).buildControlFlow();
      if (flow == null) return RunnerResult.NOT_APPLICABLE;
      int[] loopNumber = LoopAnalyzer.calcInLoop(flow);

      int endOffset = flow.getInstructionCount();
      myInstructions = flow.getInstructions();
      myNestedClosures.clear();
      
      Set<Instruction> joinInstructions = ContainerUtil.newHashSet();
      for (int index = 0; index < myInstructions.length; index++) {
        Instruction instruction = myInstructions[index];
        if (instruction instanceof GotoInstruction) {
          joinInstructions.add(myInstructions[((GotoInstruction)instruction).getOffset()]);
        } else if (instruction instanceof ConditionalGotoInstruction) {
          joinInstructions.add(myInstructions[((ConditionalGotoInstruction)instruction).getOffset()]);
        } else if (instruction instanceof MethodCallInstruction && !((MethodCallInstruction)instruction).getContracts().isEmpty()) {
          joinInstructions.add(myInstructions[index + 1]);
        }
      }

      if (LOG.isDebugEnabled()) {
        LOG.debug("Analyzing code block: " + psiBlock.getText());
        for (int i = 0; i < myInstructions.length; i++) {
          LOG.debug(i + ": " + myInstructions[i]);
        }
      }
      //for (int i = 0; i < myInstructions.length; i++) System.out.println(i + ": " + myInstructions[i].toString());
      
      Integer tooExpensiveHash = psiBlock.getUserData(TOO_EXPENSIVE_HASH);
      if (tooExpensiveHash != null && tooExpensiveHash == psiBlock.getText().hashCode()) {
        LOG.debug("Too complex because hasn't changed since being too complex already");
        return RunnerResult.TOO_COMPLEX;
      }

      final StateQueue queue = new StateQueue();
      for (final DfaMemoryState initialState : initialStates) {
        queue.offer(new DfaInstructionState(myInstructions[0], initialState));
      }

      MultiMap<BranchingInstruction, DfaMemoryState> processedStates = MultiMap.createSet();
      MultiMap<BranchingInstruction, DfaMemoryState> incomingStates = MultiMap.createSet();

      long msLimit = shouldCheckTimeLimit() ? Registry.intValue("ide.dfa.time.limit.online") : Registry.intValue("ide.dfa.time.limit.offline");
      WorkingTimeMeasurer measurer = new WorkingTimeMeasurer(msLimit * 1000 * 1000);
      int count = 0;
      while (!queue.isEmpty()) {
        List<DfaInstructionState> states = queue.getNextInstructionStates(joinInstructions);
        for (DfaInstructionState instructionState : states) {
          if (count++ % 1024 == 0 && measurer.isTimeOver()) {
            LOG.debug("Too complex because the analysis took too long");
            psiBlock.putUserData(TOO_EXPENSIVE_HASH, psiBlock.getText().hashCode());
            return RunnerResult.TOO_COMPLEX;
          }
          ProgressManager.checkCanceled();

          if (LOG.isDebugEnabled()) {
            LOG.debug(instructionState.toString());
          }
          //System.out.println(instructionState.toString());

          Instruction instruction = instructionState.getInstruction();

          if (instruction instanceof BranchingInstruction) {
            BranchingInstruction branching = (BranchingInstruction)instruction;
            Collection<DfaMemoryState> processed = processedStates.get(branching);
            if (processed.contains(instructionState.getMemoryState())) {
              continue;
            }
            if (processed.size() > MAX_STATES_PER_BRANCH) {
              LOG.debug("Too complex because too many different possible states");
              return RunnerResult.TOO_COMPLEX; // Too complex :(
            }
            if (loopNumber[branching.getIndex()] != 0) {
              processedStates.putValue(branching, instructionState.getMemoryState().createCopy());
            }
          }

          DfaInstructionState[] after = acceptInstruction(visitor, instructionState);
          for (DfaInstructionState state : after) {
            Instruction nextInstruction = state.getInstruction();
            if (nextInstruction.getIndex() >= endOffset) {
              continue;
            }
            handleStepOutOfLoop(instruction, nextInstruction, loopNumber, processedStates, incomingStates, states, after, queue);
            if (nextInstruction instanceof BranchingInstruction) {
              BranchingInstruction branching = (BranchingInstruction)nextInstruction;
              if (processedStates.get(branching).contains(state.getMemoryState()) || 
                  incomingStates.get(branching).contains(state.getMemoryState())) {
                continue;
              }
              if (loopNumber[branching.getIndex()] != 0) {
                incomingStates.putValue(branching, state.getMemoryState().createCopy());
              }
            }
            queue.offer(state);
          }
        }
      }

      psiBlock.putUserData(TOO_EXPENSIVE_HASH, null);
      LOG.debug("Analysis ok");
      return RunnerResult.OK;
    }
    catch (ArrayIndexOutOfBoundsException e) {
      LOG.error(psiBlock.getText(), e);
      return RunnerResult.ABORTED;
    }
    catch (EmptyStackException e) {
      LOG.error(psiBlock.getText(), e);
      return RunnerResult.ABORTED;
    }
  }

  private void handleStepOutOfLoop(@NotNull final Instruction prevInstruction,
                                   @NotNull Instruction nextInstruction,
                                   @NotNull final int[] loopNumber,
                                   @NotNull MultiMap<BranchingInstruction, DfaMemoryState> processedStates,
                                   @NotNull MultiMap<BranchingInstruction, DfaMemoryState> incomingStates,
                                   @NotNull List<DfaInstructionState> inFlightStates,
                                   @NotNull DfaInstructionState[] afterStates,
                                   @NotNull StateQueue queue) {
    if (loopNumber[prevInstruction.getIndex()] == 0 || inSameLoop(prevInstruction, nextInstruction, loopNumber)) {
      return;
    }
    // stepped out of loop. destroy all memory states from the loop, we don't need them anymore

    // but do not touch yet states being handled right now
    for (DfaInstructionState state : inFlightStates) {
      Instruction instruction = state.getInstruction();
      if (inSameLoop(prevInstruction, instruction, loopNumber)) {
        return;
      }
    }
    for (DfaInstructionState state : afterStates) {
      Instruction instruction = state.getInstruction();
      if (inSameLoop(prevInstruction, instruction, loopNumber)) {
        return;
      }
    }
    // and still in queue
    if (!queue.processAll(new Processor<DfaInstructionState>() {
      @Override
      public boolean process(DfaInstructionState state) {
        Instruction instruction = state.getInstruction();
        return !inSameLoop(prevInstruction, instruction, loopNumber);
      }
    })) return;

    // now remove obsolete memory states
    final Set<BranchingInstruction> mayRemoveStatesFor = new THashSet<BranchingInstruction>();
    for (Instruction instruction : myInstructions) {
      if (inSameLoop(prevInstruction, instruction, loopNumber) && instruction instanceof BranchingInstruction) {
        mayRemoveStatesFor.add((BranchingInstruction)instruction);
      }
    }

    for (Instruction instruction : mayRemoveStatesFor) {
      processedStates.remove((BranchingInstruction)instruction);
      incomingStates.remove((BranchingInstruction)instruction);
    }
  }

  private static boolean inSameLoop(@NotNull Instruction prevInstruction, @NotNull Instruction nextInstruction, @NotNull int[] loopNumber) {
    return loopNumber[nextInstruction.getIndex()] == loopNumber[prevInstruction.getIndex()];
  }

  protected boolean shouldCheckTimeLimit() {
    return !ApplicationManager.getApplication().isUnitTestMode();
  }

  @NotNull
  protected DfaInstructionState[] acceptInstruction(@NotNull InstructionVisitor visitor, @NotNull DfaInstructionState instructionState) {
    Instruction instruction = instructionState.getInstruction();
    PsiElement closure = DfaUtil.getClosureInside(instruction);
    if (closure instanceof PsiClass) {
      registerNestedClosures(instructionState, (PsiClass)closure);
    } else if (closure instanceof PsiLambdaExpression) {
      registerNestedClosures(instructionState, (PsiLambdaExpression)closure);
    }

    return instruction.accept(this, instructionState.getMemoryState(), visitor);
  }

  private void registerNestedClosures(@NotNull DfaInstructionState instructionState, @NotNull PsiClass nestedClass) {
    DfaMemoryState state = instructionState.getMemoryState();
    for (PsiMethod method : nestedClass.getMethods()) {
      PsiCodeBlock body = method.getBody();
      if (body != null) {
        myNestedClosures.putValue(body, createClosureState(state));
      }
    }
    for (PsiClassInitializer initializer : nestedClass.getInitializers()) {
      myNestedClosures.putValue(initializer.getBody(), createClosureState(state));
    }
    for (PsiField field : nestedClass.getFields()) {
      myNestedClosures.putValue(field, createClosureState(state));
    }
  }
  
  private void registerNestedClosures(@NotNull DfaInstructionState instructionState, @NotNull PsiLambdaExpression expr) {
    DfaMemoryState state = instructionState.getMemoryState();
    PsiElement body = expr.getBody();
    if (body != null) {
      myNestedClosures.putValue(body, createClosureState(state));
    }
  }

  @NotNull
  protected DfaMemoryState createMemoryState() {
    return new DfaMemoryStateImpl(myValueFactory);
  }

  @NotNull
  public Instruction[] getInstructions() {
    return myInstructions;
  }

  @NotNull
  public Instruction getInstruction(int index) {
    return myInstructions[index];
  }

  @NotNull
  MultiMap<PsiElement, DfaMemoryState> getNestedClosures() {
    return new MultiMap<PsiElement, DfaMemoryState>(myNestedClosures);
  }

  @NotNull
  public Pair<Set<Instruction>,Set<Instruction>> getConstConditionalExpressions() {
    Set<Instruction> trueSet = new HashSet<Instruction>();
    Set<Instruction> falseSet = new HashSet<Instruction>();

    for (Instruction instruction : myInstructions) {
      if (instruction instanceof BranchingInstruction) {
        BranchingInstruction branchingInstruction = (BranchingInstruction)instruction;
        if (branchingInstruction.getPsiAnchor() != null && branchingInstruction.isConditionConst()) {
          if (!branchingInstruction.isTrueReachable()) {
            falseSet.add(branchingInstruction);
          }

          if (!branchingInstruction.isFalseReachable()) {
            trueSet.add(branchingInstruction);
          }
        }
      }
    }

    for (Instruction instruction : myInstructions) {
      if (instruction instanceof BranchingInstruction) {
        BranchingInstruction branchingInstruction = (BranchingInstruction)instruction;
        if (branchingInstruction.isTrueReachable()) {
          falseSet.remove(branchingInstruction);
        }
        if (branchingInstruction.isFalseReachable()) {
          trueSet.remove(branchingInstruction);
        }
      }
    }

    return Pair.create(trueSet, falseSet);
  }

  @NotNull
  private static DfaMemoryStateImpl createClosureState(@NotNull DfaMemoryState memState) {
    DfaMemoryStateImpl copy = (DfaMemoryStateImpl)memState.createCopy();
    copy.flushFields();
    Set<DfaVariableValue> vars = new HashSet<DfaVariableValue>(copy.getVariableStates().keySet());
    for (DfaVariableValue value : vars) {
      copy.flushDependencies(value);
    }
    copy.emptyStack();
    return copy;
  }
}