/*
 * Copyright 2010-2012 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.
 */

package org.jetbrains.jet.lang.cfg.pseudocode;

import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.jet.lang.cfg.Label;
import org.jetbrains.jet.lang.cfg.LoopInfo;
import org.jetbrains.jet.lang.psi.JetElement;
import org.jetbrains.jet.lang.psi.JetExpression;

import java.util.*;

/**
* @author abreslav
* @author svtk
*/
public class PseudocodeImpl implements IPseudocode {

    public class PseudocodeLabel implements Label {
        private final String name;
        private Integer targetInstructionIndex;


        private PseudocodeLabel(String name) {
            this.name = name;
        }

        @Override
        public String getName() {
            return name;
        }

        @Override
        public String toString() {
            return name;
        }

        public Integer getTargetInstructionIndex() {
            return targetInstructionIndex;
        }

        public void setTargetInstructionIndex(int targetInstructionIndex) {
            this.targetInstructionIndex = targetInstructionIndex;
        }

        @Nullable
        private List<Instruction> resolve() {
            assert targetInstructionIndex != null;
            return mutableInstructionList.subList(getTargetInstructionIndex(), mutableInstructionList.size());
        }

        public Instruction resolveToInstruction() {
            assert targetInstructionIndex != null;
            return mutableInstructionList.get(targetInstructionIndex);
        }

    }

    private final List<Instruction> mutableInstructionList = new ArrayList<Instruction>();
    private final List<Instruction> instructions = new ArrayList<Instruction>();
    private List<Instruction> deadInstructions;

    final Map<JetElement, Instruction> representativeInstructions = new HashMap<JetElement, Instruction>();
    final Map<JetExpression, LoopInfo> loopInfo = Maps.newHashMap();
    
    private final List<PseudocodeLabel> labels = new ArrayList<PseudocodeLabel>();
    private final List<PseudocodeLabel> allowedDeadLabels = new ArrayList<PseudocodeLabel>();
    private final List<PseudocodeLabel> stopAllowDeadLabels = new ArrayList<PseudocodeLabel>();

    private final JetElement correspondingElement;
    private SubroutineExitInstruction exitInstruction;
    private SubroutineSinkInstruction sinkInstruction;
    private SubroutineExitInstruction errorInstruction;
    private boolean postPrecessed = false;

    public PseudocodeImpl(JetElement correspondingElement) {
        this.correspondingElement = correspondingElement;
    }

    @NotNull
    @Override
    public JetElement getCorrespondingElement() {
        return correspondingElement;
    }

    @NotNull
    @Override
    public Set<IPseudocode> getLocalDeclarations() {
        Set<IPseudocode> localDeclarations = Sets.newLinkedHashSet();
        //todo look recursively inside local declarations
        for (Instruction instruction : instructions) {
            if (instruction instanceof LocalDeclarationInstruction) {
                localDeclarations.add(((LocalDeclarationInstruction) instruction).getBody());
            }
        }
        return localDeclarations;
    }

    public PseudocodeLabel createLabel(String name) {
        PseudocodeLabel label = new PseudocodeLabel(name);
        labels.add(label);
        return label;
    }
    
    public void allowDead(Label label) {
        allowedDeadLabels.add((PseudocodeLabel) label);
    }
    
    public void stopAllowDead(Label label) {
        stopAllowDeadLabels.add((PseudocodeLabel) label);
    }

    @Override
    @NotNull
    public List<Instruction> getInstructions() {
        return instructions;
    }

    @Deprecated //for tests only
    @NotNull
    public List<Instruction> getMutableInstructionList() {
        return mutableInstructionList;
    }

    @Override
    @NotNull
    public List<Instruction> getDeadInstructions() {
        if (deadInstructions != null) {
            return deadInstructions;
        }
        deadInstructions = Lists.newArrayList();
        Collection<Instruction> allowedDeadInstructions = collectAllowedDeadInstructions();

        for (Instruction instruction : mutableInstructionList) {
            if (((InstructionImpl)instruction).isDead()) {
                if (!allowedDeadInstructions.contains(instruction)) {
                    deadInstructions.add(instruction);
                }
            }
        }
        return deadInstructions;
    }

    @Deprecated //for tests only
    @NotNull
    public List<PseudocodeLabel> getLabels() {
        return labels;
    }

    public void addExitInstruction(SubroutineExitInstruction exitInstruction) {
        addInstruction(exitInstruction);
        assert this.exitInstruction == null;
        this.exitInstruction = exitInstruction;
    }
    
    public void addSinkInstruction(SubroutineSinkInstruction sinkInstruction) {
        addInstruction(sinkInstruction);
        assert this.sinkInstruction == null;
        this.sinkInstruction = sinkInstruction;
    }

    public void addErrorInstruction(SubroutineExitInstruction errorInstruction) {
        addInstruction(errorInstruction);
        assert this.errorInstruction == null;
        this.errorInstruction = errorInstruction;
    }

    public void addInstruction(Instruction instruction) {
        mutableInstructionList.add(instruction);
        instruction.setOwner(this);

        if (instruction instanceof JetElementInstruction) {
            JetElementInstruction elementInstruction = (JetElementInstruction) instruction;
            representativeInstructions.put(elementInstruction.getElement(), instruction);
        }
    }

    public void recordLoopInfo(JetExpression expression, LoopInfo blockInfo) {
        loopInfo.put(expression, blockInfo);
    }

    @Override
    @NotNull
    public SubroutineExitInstruction getExitInstruction() {
        return exitInstruction;
    }

    @Override
    @NotNull
    public SubroutineSinkInstruction getSinkInstruction() {
        return sinkInstruction;
    }

    @Override
    @NotNull
    public SubroutineEnterInstruction getEnterInstruction() {
        return (SubroutineEnterInstruction) mutableInstructionList.get(0);
    }

    public void bindLabel(Label label) {
        ((PseudocodeLabel) label).setTargetInstructionIndex(mutableInstructionList.size());
    }

    public void postProcess() {
        if (postPrecessed) return;
        postPrecessed = true;
        errorInstruction.setSink(getSinkInstruction());
        exitInstruction.setSink(getSinkInstruction());
        for (int i = 0, instructionsSize = mutableInstructionList.size(); i < instructionsSize; i++) {
            processInstruction(mutableInstructionList.get(i), i);
        }
        Set<Instruction> reachableInstructions = collectReachableInstructions();
        for (Instruction instruction : mutableInstructionList) {
            if (reachableInstructions.contains(instruction)) {
                instructions.add(instruction);
            }
        }
        markDeadInstructions();
    }

    private void processInstruction(Instruction instruction, final int currentPosition) {
        instruction.accept(new InstructionVisitor() {
            @Override
            public void visitInstructionWithNext(InstructionWithNext instruction) {
                instruction.setNext(getNextPosition(currentPosition));
            }

            @Override
            public void visitJump(AbstractJumpInstruction instruction) {
                instruction.setResolvedTarget(getJumpTarget(instruction.getTargetLabel()));
            }

            @Override
            public void visitNondeterministicJump(NondeterministicJumpInstruction instruction) {
                instruction.setNext(getNextPosition(currentPosition));
                List<Label> targetLabels = instruction.getTargetLabels();
                for (Label targetLabel : targetLabels) {
                    instruction.setResolvedTarget(targetLabel, getJumpTarget(targetLabel));
                }
            }

            @Override
            public void visitConditionalJump(ConditionalJumpInstruction instruction) {
                Instruction nextInstruction = getNextPosition(currentPosition);
                Instruction jumpTarget = getJumpTarget(instruction.getTargetLabel());
                if (instruction.onTrue()) {
                    instruction.setNextOnFalse(nextInstruction);
                    instruction.setNextOnTrue(jumpTarget);
                }
                else {
                    instruction.setNextOnFalse(jumpTarget);
                    instruction.setNextOnTrue(nextInstruction);
                }
                visitJump(instruction);
            }

            @Override
            public void visitLocalDeclarationInstruction(LocalDeclarationInstruction instruction) {
                ((PseudocodeImpl)instruction.getBody()).postProcess();
                instruction.setNext(getSinkInstruction());
            }

            @Override
            public void visitSubroutineExit(SubroutineExitInstruction instruction) {
                // Nothing
            }

            @Override
            public void visitSubroutineSink(SubroutineSinkInstruction instruction) {
                // Nothing
            }

            @Override
            public void visitInstruction(Instruction instruction) {
                throw new UnsupportedOperationException(instruction.toString());
            }
        });
    }

    private Set<Instruction> collectReachableInstructions() {
        Set<Instruction> visited = Sets.newHashSet();
        traverseNextInstructions(getEnterInstruction(), visited);
        if (!visited.contains(getExitInstruction())) {
            visited.add(getExitInstruction());
        }
        if (!visited.contains(errorInstruction)) {
            visited.add(errorInstruction);
        }
        if (!visited.contains(getSinkInstruction())) {
            visited.add(getSinkInstruction());
        }
        return visited;
    }
    
    private void traverseNextInstructions(@NotNull Instruction instruction, @NotNull Set<Instruction> visited) {
        if (visited.contains(instruction)) return;
        visited.add(instruction);
        for (Instruction nextInstruction : instruction.getNextInstructions()) {
            if (nextInstruction == null) continue; //todo it might be null on incomplete code
            traverseNextInstructions(nextInstruction, visited);
        }
    }

    private void markDeadInstructions() {
        Set<Instruction> instructionSet = Sets.newHashSet(instructions);
        for (Instruction instruction : mutableInstructionList) {
            if (!instructionSet.contains(instruction)) {
                ((InstructionImpl)instruction).die();
                for (Instruction nextInstruction : instruction.getNextInstructions()) {
                    nextInstruction.getPreviousInstructions().remove(instruction);
                }
            }
        }
    }

    @NotNull
    private Set<Instruction> prepareAllowedDeadInstructions() {
        Set<Instruction> allowedDeadStartInstructions = Sets.newHashSet();
        for (PseudocodeLabel allowedDeadLabel : allowedDeadLabels) {
            Instruction allowedDeadInstruction = getJumpTarget(allowedDeadLabel);
            if (((InstructionImpl)allowedDeadInstruction).isDead()) {
                allowedDeadStartInstructions.add(allowedDeadInstruction);
            }
        }
        return allowedDeadStartInstructions;
    }
    
    @NotNull
    private Set<Instruction> prepareStopAllowedDeadInstructions() {
        Set<Instruction> stopAllowedDeadInstructions = Sets.newHashSet();
        for (PseudocodeLabel stopAllowedDeadLabel : stopAllowDeadLabels) {
            Instruction stopAllowDeadInsruction = getJumpTarget(stopAllowedDeadLabel);
            if (((InstructionImpl)stopAllowDeadInsruction).isDead()) {
                stopAllowedDeadInstructions.add(stopAllowDeadInsruction);
            }
        }
        return stopAllowedDeadInstructions;
    }

    @NotNull
    private Collection<Instruction> collectAllowedDeadInstructions() {
        Set<Instruction> allowedDeadStartInstructions = prepareAllowedDeadInstructions();
        Set<Instruction> stopAllowDeadInstructions = prepareStopAllowedDeadInstructions();
        Set<Instruction> allowedDeadInstructions = Sets.newHashSet();

        for (Instruction allowedDeadStartInstruction : allowedDeadStartInstructions) {
            collectAllowedDeadInstructions(allowedDeadStartInstruction, allowedDeadInstructions, stopAllowDeadInstructions);
        }
        return allowedDeadInstructions;
    }
    
    private void collectAllowedDeadInstructions(Instruction allowedDeadInstruction, Set<Instruction> instructionSet, Set<Instruction> stopAllowDeadInstructions) {
        if (instructionSet.contains(allowedDeadInstruction) || stopAllowDeadInstructions.contains(allowedDeadInstruction)) return;
        if (((InstructionImpl)allowedDeadInstruction).isDead()) {
            instructionSet.add(allowedDeadInstruction);
            for (Instruction instruction : allowedDeadInstruction.getNextInstructions()) {
                collectAllowedDeadInstructions(instruction, instructionSet, stopAllowDeadInstructions);
            }
        }
    }

    @NotNull
    private Instruction getJumpTarget(@NotNull Label targetLabel) {
        return ((PseudocodeLabel)targetLabel).resolveToInstruction();
    }

    @NotNull
    private Instruction getNextPosition(int currentPosition) {
        int targetPosition = currentPosition + 1;
        assert targetPosition < mutableInstructionList.size() : currentPosition;
        return mutableInstructionList.get(targetPosition);
    }
}