// Copyright (c) 2009 The Chromium Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

package org.chromium.debug.ui;

import org.chromium.debug.core.ChromiumDebugPlugin;

import org.chromium.debug.core.model.DebugElementImpl;

import org.chromium.debug.core.model.StackFrame;

import org.chromium.debug.core.model.Variable;

import org.chromium.sdk.CallFrame;

import org.chromium.sdk.JsVariable;

import org.eclipse.core.runtime.Status;

import org.eclipse.debug.core.DebugException;

import org.eclipse.debug.core.model.IDebugElement;

import org.eclipse.debug.core.model.IValue;

import org.eclipse.debug.core.model.IWatchExpressionDelegate;

import org.eclipse.debug.core.model.IWatchExpressionListener;

import org.eclipse.debug.core.model.IWatchExpressionResult;

/**

 * Performs the Watch expression evaluation while debugging Chromium JavaScript.

 */

public class JsWatchExpressionDelegate implements IWatchExpressionDelegate {

  private static final String[] EMPTY_STRINGS = new String[0];

  private static final class GoodWatchExpressionResult implements IWatchExpressionResult {

    private final Variable variable;

    private final String expression;

    private IValue value;

    private DebugException exception;

    private GoodWatchExpressionResult(Variable variable, String expression) {

      this.variable = variable;

      this.expression = expression;

    }

    public String[] getErrorMessages() {

      return exception == null

          ? EMPTY_STRINGS

          : new String[] { exception.getStatus().getMessage() };

    }

    public DebugException getException() {

      getValue();

      return exception;

    }

    public String getExpressionText() {

      return expression;

    }

    public synchronized IValue getValue() {

      if (value == null && exception == null) {

        try {

          value = variable.getValue();

        } catch (DebugException e) {

          this.exception = e;

        }

      }

      return value;

    }

    public boolean hasErrors() {

      getValue();

      return exception != null;

    }

  }

  private static final class BadWatchExpressionResult implements IWatchExpressionResult {

    private final DebugException exception;

    private final String expressionText;

    private BadWatchExpressionResult(DebugException exception, String expressionText) {

      this.exception = exception;

      this.expressionText = expressionText;

    }

    public String[] getErrorMessages() {

      return new String[] { exception.getStatus().getMessage() };

    }

    public DebugException getException() {

      return exception;

    }

    public String getExpressionText() {

      return expressionText;

    }

    public IValue getValue() {

      return null;

    }

    public boolean hasErrors() {

      return true;

    }

  }

  public void evaluateExpression(final String expression, final IDebugElement context,

      final IWatchExpressionListener listener) {

    final DebugElementImpl contextImpl = (DebugElementImpl) context;

    if (!contextImpl.getDebugTarget().isSuspended()) {

      // can only evaluate while suspended. Notify empty result.

      listener.watchEvaluationFinished(new IWatchExpressionResult() {

        public String[] getErrorMessages() {

          return EMPTY_STRINGS;

        }

        public DebugException getException() {

          return null;

        }

        public String getExpressionText() {

          return expression;

        }

        public IValue getValue() {

          return null;

        }

        public boolean hasErrors() {

          return false;

        }

      });

      return;

    }

    if (!(contextImpl instanceof StackFrame)) {

      listener.watchEvaluationFinished(new BadWatchExpressionResult(

          new DebugException(

              new Status(Status.ERROR, ChromiumDebugUIPlugin.PLUGIN_ID, "Bad debug context")), //$NON-NLS-1$

          expression));

      return;

    }

    StackFrame stackFrame = (StackFrame) contextImpl;

    final CallFrame frame = stackFrame.getCallFrame();

    frame.evaluateAsync(expression, new CallFrame.EvaluateCallback() {

        public void success(JsVariable variable) {

          final Variable var = new Variable(contextImpl.getDebugTarget(), variable, false);

          listener.watchEvaluationFinished(new GoodWatchExpressionResult(var, expression));

        }

        public void failure(String message) {

          listener.watchEvaluationFinished(new BadWatchExpressionResult(new DebugException(

              createErrorStatus(message == null

                  ? Messages.JsWatchExpressionDelegate_ErrorEvaluatingExpression

                  : message, null)), expression));

          return;

        }

      },

      null);

  }

  private static Status createErrorStatus(String message, Exception e) {

    return new Status(Status.ERROR, ChromiumDebugPlugin.PLUGIN_ID, message, e);

  }

}