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/*******************************************************************************
 * Copyright (c) 2005, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui;

import org.eclipse.core.expressions.EvaluationResult;
import org.eclipse.core.expressions.Expression;
import org.eclipse.core.expressions.ExpressionInfo;
import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.swt.widgets.Shell;

/**
 * <p>
 * An expression encapsulating all of the information from legacy handler
 * submissions.
 * </p>
 * 
 * @since 3.1
 */
public final class LegacyHandlerSubmissionExpression extends Expression {

  /**
   * The seed for the hash code for all schemes.
   */
  private static final int HASH_INITIAL = LegacyHandlerSubmissionExpression.class
      .getName().hashCode();

  /**
   * The identifier for the part that must be active for this expression to
   * evaluate to <code>true</code>. If this value is <code>null</code>,
   * then any part may be active.
   */
  private final String activePartId;

  /**
   * The shell that must be active for this expression to evaluate to
   * <code>true</code>. If this value is <code>null</code>, then any
   * shell may be active.
   */
  private final Shell activeShell;

  /**
   * The site that must be active for this expression to evaluate to
   * <code>true</code>. If this value is <code>null</code>, then any
   * site may be active.
   */
  private final IWorkbenchPartSite activeSite;

  /**
   * Constructs a new instance of
   * <code>LegacyHandlerSubmissionExpression</code>
   * 
   * @param activePartId
   *            The part identifier to match with the active part;
   *            <code>null</code> if it will match any active part.
   * @param activeShell
   *            The shell to match with the active shell; <code>null</code>
   *            if it will match any active shell.
   * @param activeSite
   *            The site to match with the active site; <code>null</code> if
   *            it will match any active site.
   */
  public LegacyHandlerSubmissionExpression(final String activePartId,
      final Shell activeShell, final IWorkbenchPartSite activeSite) {

    this.activePartId = activePartId;
    this.activeShell = activeShell;
    this.activeSite = activeSite;
  }

  /**
   * Collect expression info for a legacy handler submission.  Namely 
   * the active part id and name, active shell name, active workbench
   * window shell name and the active site name.
   * 
   * @since 3.2
   */
  public final void collectExpressionInfo(final ExpressionInfo info) {
    if (activePartId != null) {
      info.addVariableNameAccess(ISources.ACTIVE_PART_ID_NAME);
    }
    if (activeShell != null) {
      info.addVariableNameAccess(ISources.ACTIVE_SHELL_NAME);
      info
          .addVariableNameAccess(ISources.ACTIVE_WORKBENCH_WINDOW_SHELL_NAME);
    }
    if (activeSite != null) {
      info.addVariableNameAccess(ISources.ACTIVE_SITE_NAME);
    }
  }

  protected final int computeHashCode() {
    int hashCode = HASH_INITIAL * HASH_FACTOR + hashCode(activePartId);
    hashCode = hashCode * HASH_FACTOR + hashCode(activeShell);
    hashCode = hashCode * HASH_FACTOR + hashCode(activeSite);
    return hashCode;
  }

  public final boolean equals(final Object object) {
    if (object instanceof LegacyHandlerSubmissionExpression) {
      final LegacyHandlerSubmissionExpression that = (LegacyHandlerSubmissionExpression) object;
      return equals(this.activePartId, that.activePartId)
          && equals(this.activeShell, that.activeShell)
          && equals(this.activeSite, that.activeSite);
    }

    return false;
  }

  /**
   * Evaluates this expression. This tests the three conditions against the
   * current state of the application (as defined by <code>context</code>).
   * If a condition is <code>null</code>, then it matches any possible
   * value (i.e., it is not tested at all).
   * 
   * @param context
   *            The context providing the current workbench state; must not be
   *            <code>null</code>.
   * @return <code>EvaluationResult.TRUE</code> if the conditions all
   *         matches; <code>EvaluationResult.FALSE</code> otherwise.
   */
  public final EvaluationResult evaluate(final IEvaluationContext context) {
    if (activePartId != null) {
      final Object value = context
          .getVariable(ISources.ACTIVE_PART_ID_NAME);
      if (!activePartId.equals(value)) {
        return EvaluationResult.FALSE;
      }
    }

    if (activeShell != null) {
      Object value = context.getVariable(ISources.ACTIVE_SHELL_NAME);
      if (!activeShell.equals(value)) {
        value = context
            .getVariable(ISources.ACTIVE_WORKBENCH_WINDOW_SHELL_NAME);
        if (!activeShell.equals(value)) {
          return EvaluationResult.FALSE;
        }
      }
    }

    if (activeSite != null) {
      final Object value = context.getVariable(ISources.ACTIVE_SITE_NAME);
      if (!activeSite.equals(value)) {
        return EvaluationResult.FALSE;
      }
    }

    return EvaluationResult.TRUE;
  }

  public final String toString() {
    final StringBuffer buffer = new StringBuffer();
    buffer.append("LegacyHandlerSubmission("); //$NON-NLS-1$
    buffer.append(activeShell);
    buffer.append(',');
    buffer.append(activePartId);
    buffer.append(',');
    buffer.append(activeSite);
    buffer.append(')');
    return buffer.toString();
  }
}
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