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/*
 * SonarQube Java
 * Copyright (C) 2012-2016 SonarSource SA
 * mailto:contact AT sonarsource DOT com
 *
 * 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 3 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.java.se.symbolicvalues;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import org.sonar.java.se.ExplodedGraphWalker;
import org.sonar.java.se.ProgramState;
import org.sonar.java.se.constraint.BooleanConstraint;
import org.sonar.java.se.constraint.Constraint;
import org.sonar.java.se.constraint.ObjectConstraint;
import org.sonar.java.se.constraint.TypedConstraint;

import javax.annotation.CheckForNull;

import java.util.ArrayList;
import java.util.List;

public class SymbolicValue {

  public static final SymbolicValue NULL_LITERAL = new SymbolicValue(0) {
    @Override
    public String toString() {
      return super.toString() + "_NULL";
    }
  };

  public static final SymbolicValue TRUE_LITERAL = new SymbolicValue(1) {
    @Override
    public String toString() {
      return super.toString() + "_TRUE";
    }
  };

  public static final SymbolicValue FALSE_LITERAL = new SymbolicValue(2) {
    @Override
    public String toString() {
      return super.toString() + "_FALSE";
    }
  };

  public static final List PROTECTED_SYMBOLIC_VALUES = ImmutableList.of(
    NULL_LITERAL,
    TRUE_LITERAL,
    FALSE_LITERAL
  );

  public static boolean isDisposable(SymbolicValue symbolicValue) {
    if (symbolicValue instanceof NotSymbolicValue) {
      NotSymbolicValue notSV = (NotSymbolicValue) symbolicValue;
      return !(notSV.operand instanceof RelationalSymbolicValue);
    }
    return !PROTECTED_SYMBOLIC_VALUES.contains(symbolicValue) && !(symbolicValue instanceof RelationalSymbolicValue);
  }

  private final int id;

  public SymbolicValue(int id) {
    this.id = id;
  }

  public int id() {
    return id;
  }

  public boolean references(SymbolicValue other) {
    return false;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    SymbolicValue that = (SymbolicValue) o;
    return id == that.id;
  }

  @Override
  public int hashCode() {
    return id;
  }

  @Override
  public String toString() {
    return "SV_" + id;
  }

  public void computedFrom(List symbolicValues) {
    // no op in general case
  }

  public List setConstraint(ProgramState programState, ObjectConstraint nullConstraint) {
    Object data = programState.getConstraint(this);
    if (data instanceof ObjectConstraint) {
      ObjectConstraint nc = (ObjectConstraint) data;
      if (nc.isNull() ^ nullConstraint.isNull()) {
        // setting null where value is known to be non null or the contrary
        return ImmutableList.of();
      }
    }
    if (data == null || !data.equals(nullConstraint)) {
      return ImmutableList.of(programState.addConstraint(this, nullConstraint));
    }
    return ImmutableList.of(programState);
  }

  public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
    Object data = programState.getConstraint(this);
    // update program state only for a different constraint
    if (data instanceof BooleanConstraint) {
      BooleanConstraint bc = (BooleanConstraint) data;
      if (!bc.equals(booleanConstraint)) {
        // setting null where value is known to be non null or the contrary
        return ImmutableList.of();
      }
    }
    if ((data == null || !data.equals(booleanConstraint)) && programState.canReach(this)) {
      // store constraint only if symbolic value can be reached by a symbol.
      return ImmutableList.of(programState.addConstraint(this, booleanConstraint));
    }
    return ImmutableList.of(programState);
  }

  public ProgramState setSingleConstraint(ProgramState programState, ObjectConstraint nullConstraint) {
    final List states = setConstraint(programState, nullConstraint);
    if (states.size() != 1) {
      throw new IllegalStateException("Only a single program state is expected at this location");
    }
    return states.get(0);
  }

  public SymbolicValue wrappedValue() {
    return this;
  }

  public abstract static class UnarySymbolicValue extends SymbolicValue {
    protected SymbolicValue operand;

    public UnarySymbolicValue(int id) {
      super(id);
    }

    @Override
    public boolean references(SymbolicValue other) {
      return operand.equals(other) || operand.references(other);
    }

    @Override
    public void computedFrom(List symbolicValues) {
      Preconditions.checkArgument(symbolicValues.size() == 1);
      this.operand = symbolicValues.get(0);
    }

  }

  public static class NotSymbolicValue extends UnarySymbolicValue {

    public NotSymbolicValue(int id) {
      super(id);
    }

    @Override
    public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
      return operand.setConstraint(programState, booleanConstraint.inverse());
    }

    @Override
    public String toString() {
      return "!" + operand;
    }
  }

  public static class InstanceOfSymbolicValue extends UnarySymbolicValue {
    public InstanceOfSymbolicValue(int id) {
      super(id);
    }

    @Override
    public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
      if (booleanConstraint.isTrue()) {
        Constraint constraint = programState.getConstraint(operand);
        if (constraint !=null && constraint.isNull()) {
          // irrealizable constraint : instance of true if operand is null
          return ImmutableList.of();
        }
        // if instanceof is true then we know for sure that expression is not null.
        List ps = operand.setConstraint(programState, ObjectConstraint.NOT_NULL);
        if (ps.size() == 1 && ps.get(0).equals(programState)) {
          // FIXME we already know that operand is NOT NULL, so we add a different constraint to distinguish program state. Typed Constraint
          // should store the deduced type.
          return ImmutableList.of(programState.addConstraint(this, new TypedConstraint()));
        }
        return ps;
      }
      return ImmutableList.of(programState);
    }
  }

  public abstract static class BooleanExpressionSymbolicValue extends BinarySymbolicValue {

    protected BooleanExpressionSymbolicValue(int id) {
      super(id);
    }

    @Override
    public BooleanConstraint shouldNotInverse() {
      return BooleanConstraint.TRUE;
    }

    protected static void addStates(List states, List newStates) {
      if (states.size() > ExplodedGraphWalker.MAX_NESTED_BOOLEAN_STATES || newStates.size() > ExplodedGraphWalker.MAX_NESTED_BOOLEAN_STATES) {
        throw new ExplodedGraphWalker.TooManyNestedBooleanStatesException();
      }
      states.addAll(newStates);
    }
  }

  public static class AndSymbolicValue extends BooleanExpressionSymbolicValue {

    public AndSymbolicValue(int id) {
      super(id);
    }

    @Override
    public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
      final List states = new ArrayList<>();
      if (booleanConstraint.isFalse()) {
        List falseFirstOp = leftOp.setConstraint(programState, BooleanConstraint.FALSE);
        for (ProgramState ps : falseFirstOp) {
          addStates(states, rightOp.setConstraint(ps, BooleanConstraint.TRUE));
          addStates(states, rightOp.setConstraint(ps, BooleanConstraint.FALSE));
        }
      }
      List trueFirstOp = leftOp.setConstraint(programState, BooleanConstraint.TRUE);
      for (ProgramState ps : trueFirstOp) {
        addStates(states, rightOp.setConstraint(ps, booleanConstraint));
      }
      return states;
    }

    @Override
    public String toString() {
      return leftOp + " & " + rightOp;
    }
  }

  public static class OrSymbolicValue extends BooleanExpressionSymbolicValue {

    public OrSymbolicValue(int id) {
      super(id);
    }

    @Override
    public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
      List states = new ArrayList<>();
      if (booleanConstraint.isTrue()) {
        List trueFirstOp = leftOp.setConstraint(programState, BooleanConstraint.TRUE);
        for (ProgramState ps : trueFirstOp) {
          addStates(states, rightOp.setConstraint(ps, BooleanConstraint.TRUE));
          addStates(states, rightOp.setConstraint(ps, BooleanConstraint.FALSE));
        }
      }
      List falseFirstOp = leftOp.setConstraint(programState, BooleanConstraint.FALSE);
      for (ProgramState ps : falseFirstOp) {
        addStates(states, rightOp.setConstraint(ps, booleanConstraint));
      }
      return states;
    }

    @Override
    public String toString() {
      return leftOp + " | " + rightOp;
    }
  }

  public static class XorSymbolicValue extends BooleanExpressionSymbolicValue {

    public XorSymbolicValue(int id) {
      super(id);
    }

    @Override
    public List setConstraint(ProgramState programState, BooleanConstraint booleanConstraint) {
      List states = new ArrayList<>();
      List trueFirstOp = leftOp.setConstraint(programState, BooleanConstraint.TRUE);
      for (ProgramState ps : trueFirstOp) {
        addStates(states, rightOp.setConstraint(ps, booleanConstraint.inverse()));
      }
      List falseFirstOp = leftOp.setConstraint(programState, BooleanConstraint.FALSE);
      for (ProgramState ps : falseFirstOp) {
        addStates(states, rightOp.setConstraint(ps, booleanConstraint));
      }
      return states;
    }

    @Override
    public String toString() {
      return leftOp + " ^ " + rightOp;
    }
  }

  @CheckForNull
  public BinaryRelation binaryRelation() {
    return null;
  }
}