/*
 * Copyright 2008 Google Inc.
 * 
 * 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 com.google.gwt.dev.jjs.impl;

import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JBinaryOperator;
import com.google.gwt.dev.jjs.ast.JConditional;
import com.google.gwt.dev.jjs.ast.JDeclarationStatement;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JMethodCall;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JNewArray;
import com.google.gwt.dev.jjs.ast.JParameter;
import com.google.gwt.dev.jjs.ast.JPrimitiveType;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JReturnStatement;
import com.google.gwt.dev.jjs.ast.JType;

import java.util.List;

/**
 * Synthesize explicit casts to and from the primitive long type where such a
 * cast would have been implicit. The explicit casts serve as markers for
 * {@link CastNormalizer}.
 */
public class LongCastNormalizer {

  /**
   * Synthesize casts to longs and from long to trigger conversions.
   */
  private class ImplicitCastVisitor extends JModVisitor {

    private JMethod currentMethod;
    private final JPrimitiveType longType;

    public ImplicitCastVisitor(JPrimitiveType longType) {
      this.longType = longType;
    }

    @Override
    public void endVisit(JBinaryOperation x, Context ctx) {
      JType lhsType = x.getLhs().getType();
      JType rhsType = x.getRhs().getType();
      JType resultType = x.getType();
      JBinaryOperator op = x.getOp();

      if (program.isJavaLangString(resultType)) {
        // Don't mess with concat.
        return;
      }

      if (lhsType == JPrimitiveType.BOOLEAN
          && (op == JBinaryOperator.AND || op == JBinaryOperator.OR)) {
        // Don't mess with if rewriter.
        return;
      }

      // Special case: shift operators always coerce a long RHS to int.
      if (op.isShiftOperator()) {
        if (rhsType == longType) {
          rhsType = program.getTypePrimitiveInt();
        }
      } else if (lhsType == longType || rhsType == longType) {
        // We must coerce lhs and rhs to the same type, either long or a float.

        // Assume a long type.
        JType coerceTo = longType;

        // But double / float takes precedence over long.
        JPrimitiveType floatType = program.getTypePrimitiveFloat();
        JPrimitiveType doubleType = program.getTypePrimitiveDouble();
        // See if the lhs can coerce the rhs
        if ((lhsType == floatType || lhsType == doubleType)) {
          coerceTo = lhsType;
        }
        if (op.isAssignment()) {
          // In an assignment, the lhs must coerce the rhs
          coerceTo = lhsType;
        } else if ((rhsType == floatType || rhsType == doubleType)) {
          coerceTo = rhsType;
        }
        lhsType = rhsType = coerceTo;
      }

      JExpression newLhs = checkAndReplace(x.getLhs(), lhsType);
      JExpression newRhs = checkAndReplace(x.getRhs(), rhsType);
      if (newLhs != x.getLhs() || newRhs != x.getRhs()) {
        JBinaryOperation binOp = new JBinaryOperation(x.getSourceInfo(),
            resultType, op, newLhs, newRhs);
        ctx.replaceMe(binOp);
      }
    }

    @Override
    public void endVisit(JConditional x, Context ctx) {
      JExpression newThen = checkAndReplace(x.getThenExpr(), x.getType());
      JExpression newElse = checkAndReplace(x.getElseExpr(), x.getType());
      if (newThen != x.getThenExpr() || newElse != x.getElseExpr()) {
        JConditional newCond = new JConditional(x.getSourceInfo(), x.getType(),
            x.getIfTest(), newThen, newElse);
        ctx.replaceMe(newCond);
      }
    }

    @Override
    public void endVisit(JDeclarationStatement x, Context ctx) {
      JExpression init = x.getInitializer();
      if (init != null) {
        init = checkAndReplace(init, x.getVariableRef().getType());
        if (init != x.getInitializer()) {
          JDeclarationStatement newStmt = new JDeclarationStatement(
              x.getSourceInfo(), x.getVariableRef(), init);
          ctx.replaceMe(newStmt);
        }
      }
    }

    @Override
    public void endVisit(JMethod x, Context ctx) {
      currentMethod = null;
    }

    @Override
    public void endVisit(JMethodCall x, Context ctx) {
      List<JParameter> params = x.getTarget().getParams();
      for (int i = 0; i < params.size(); ++i) {
        JParameter param = params.get(i);
        JExpression arg = x.getArgs().get(i);
        JExpression newArg = checkAndReplace(arg, param.getType());
        if (arg != newArg) {
          x.setArg(i, newArg);
          madeChanges();
        }
      }
    }

    @Override
    public void endVisit(JNewArray x, Context ctx) {
      JType elementType = x.getArrayType().getElementType();
      List<JExpression> initializers = x.initializers;
      if (initializers != null) {
        for (int i = 0; i < initializers.size(); ++i) {
          JExpression initializer = initializers.get(i);
          JExpression newInitializer = checkAndReplace(initializer, elementType);
          if (initializer != newInitializer) {
            initializers.set(i, newInitializer);
            madeChanges();
          }
        }
      }
    }

    @Override
    public void endVisit(JReturnStatement x, Context ctx) {
      JExpression expr = x.getExpr();
      if (expr != null) {
        JExpression newExpr = checkAndReplace(expr, currentMethod.getType());
        if (expr != newExpr) {
          JReturnStatement newStmt = new JReturnStatement(x.getSourceInfo(),
              newExpr);
          ctx.replaceMe(newStmt);
        }
      }
    }

    @Override
    public boolean visit(JMethod x, Context ctx) {
      currentMethod = x;
      return true;
    }

    /**
     * Returns an explicit cast if the target type is long and the input
     * expression is not a long, or if the target type is floating point and the
     * expression is a long. TODO(spoon): there is no floating point in this
     * method; update the comment
     */
    private JExpression checkAndReplace(JExpression arg, JType targetType) {
      if (targetType != longType && arg.getType() != longType) {
        return arg;
      }
      return simplifier.cast(targetType, arg);
    }
  }

  public static void exec(JProgram program) {
    new LongCastNormalizer(program).execImpl();
  }

  private final JProgram program;
  private final Simplifier simplifier;

  private LongCastNormalizer(JProgram program) {
    this.program = program;
    simplifier = new Simplifier(program);
  }

  private void execImpl() {
    ImplicitCastVisitor visitor = new ImplicitCastVisitor(
        program.getTypePrimitiveLong());
    visitor.accept(program);
  }
}