// 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.symbian.tools.tmw.debug.internal.model;

import org.chromium.debug.core.model.DebugElementImpl;
import org.chromium.debug.core.model.EvaluateContext;
import org.chromium.debug.core.model.Variable;
import org.chromium.sdk.JsEvaluateContext;
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;
import org.symbian.tools.tmw.debug.internal.Activator;

/**
 * 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() {
            if (exception == null) {
                return EMPTY_STRINGS;
            } else {
                return 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;
        }

        final EvaluateContext evaluateContext = (EvaluateContext) contextImpl.getAdapter(EvaluateContext.class);
        if (evaluateContext == null) {
            listener.watchEvaluationFinished(new BadWatchExpressionResult(new DebugException(new Status(Status.ERROR,
                    Activator.PLUGIN_ID, "Bad debug context")), //$NON-NLS-1$
                    expression));
            return;
        }

        evaluateContext.getJsEvaluateContext().evaluateAsync(expression, new JsEvaluateContext.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 ? "Error evaluating expression" : message, null)), expression));
                return;
            }
        }, null);
    }

    private static Status createErrorStatus(String message, Exception e) {
        return new Status(Status.ERROR, Activator.PLUGIN_ID, message, e);
    }

}