/*******************************************************************************
 * Copyright (c) 2006, 2013 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.ui.model.elements;

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

import org.eclipse.core.runtime.CoreException;
import org.eclipse.debug.core.DebugEvent;
import org.eclipse.debug.core.DebugException;
import org.eclipse.debug.core.DebugPlugin;
import org.eclipse.debug.core.IDebugEventSetListener;
import org.eclipse.debug.core.ILogicalStructureType;
import org.eclipse.debug.core.model.IDebugElement;
import org.eclipse.debug.core.model.IIndexedValue;
import org.eclipse.debug.core.model.IValue;
import org.eclipse.debug.core.model.IVariable;
import org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext;
import org.eclipse.debug.internal.ui.viewers.model.provisional.IViewerUpdate;
import org.eclipse.debug.internal.ui.views.variables.IndexedVariablePartition;
import org.eclipse.debug.internal.ui.views.variables.LogicalStructureCache;
import org.eclipse.debug.internal.ui.views.variables.VariablesView;
import org.eclipse.debug.ui.IDebugUIConstants;

/**
 * @since 3.3
 */
public class VariableContentProvider extends ElementContentProvider {

	/**
	 * Cache of logical structures to avoid computing structures for different
	 * subranges.
	 */
	private static LogicalStructureCache fgLogicalCache;

	/* (non-Javadoc)
	 * @see org.eclipse.debug.internal.ui.viewers.model.provisional.elements.ElementContentProvider#getChildCount(java.lang.Object, org.eclipse.debug.internal.ui.viewers.provisional.IPresentationContext)
	 */
	@Override
	protected int getChildCount(Object element, IPresentationContext context, IViewerUpdate monitor) throws CoreException {
		return getAllChildren(element, context).length;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.debug.internal.ui.viewers.model.provisional.elements.ElementContentProvider#getChildren(java.lang.Object, int, int, org.eclipse.debug.internal.ui.viewers.provisional.IPresentationContext)
	 */
	@Override
	protected Object[] getChildren(Object parent, int index, int length, IPresentationContext context, IViewerUpdate monitor) throws CoreException {
		return getElements(getAllChildren(parent, context), index, length);
	}

	/* (non-Javadoc)
	 * @see org.eclipse.debug.internal.ui.model.elements.ElementContentProvider#hasChildren(java.lang.Object, org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, org.eclipse.debug.internal.ui.viewers.model.provisional.IViewerUpdate)
	 */
	@Override
	protected boolean hasChildren(Object element, IPresentationContext context, IViewerUpdate monitor) throws CoreException {
		return ((IVariable)element).getValue().hasVariables();
	}

	/* (non-Javadoc)
	 * @see org.eclipse.debug.internal.ui.viewers.model.provisional.elements.ElementContentProvider#supportsContextId(java.lang.String)
	 */
	@Override
	protected boolean supportsContextId(String id) {
		 return id.equals(IDebugUIConstants.ID_EXPRESSION_VIEW) || id.equals(IDebugUIConstants.ID_VARIABLE_VIEW) || id.equals(IDebugUIConstants.ID_REGISTER_VIEW);
	}

	/**
	 * Gets all the children variables for the parent
	 * @param parent the parent IVariable
	 * @param context the context the children will be presented in
	 * @return an array of all children or an empty array if none
	 * @throws CoreException
	 */
	protected Object[] getAllChildren(Object parent, IPresentationContext context) throws CoreException {
        IVariable variable = (IVariable) parent;
        IValue value = variable.getValue();
        if (value != null) {
            return getValueChildren(variable, value, context);
        }
        return EMPTY;
	}

    /**
     * Return whether to show compute a logical structure or a raw structure
     * in the specified context
     *
     * @return whether to show compute a logical structure or a raw structure
     * in the specified context
     */
    protected boolean isShowLogicalStructure(IPresentationContext context) {
    	Boolean show = (Boolean) context.getProperty(VariablesView.PRESENTATION_SHOW_LOGICAL_STRUCTURES);
    	return show != null && show.booleanValue();
    }

    /**
     * Returns the number of entries that should be displayed in each partition
     * of an indexed collection.
     *
     * @return the number of entries that should be displayed in each partition
     *         of an indexed collection
     */
    protected int getArrayPartitionSize() {
        // TODO: should fix this with a user preference
        return 100;
    }

    /**
     * Returns any logical value for the raw value in the specified context
     *
     * @param value
     * @param context
     * @return logical value for the raw value
     */
    protected IValue getLogicalValue(IValue value, IPresentationContext context) throws CoreException {
		return getLogicalValue(value, new ArrayList<String>(), context);
    }

    /**
     * Returns children for the given value, creating array partitions if
     * required
     *
     * @param parent expression or variable containing the given value
     * @param value the value to retrieve children for
     * @param context the context in which children have been requested
     * @return children for the given value, creating array partitions if
     *         required
     * @throws CoreException
     */
    protected Object[] getValueChildren(IDebugElement parent, IValue value, IPresentationContext context) throws CoreException {
        if (value == null) {
            return EMPTY;
        }
        IValue logicalValue = getLogicalValue(value, context);
        if (logicalValue instanceof IIndexedValue) {
            IIndexedValue indexedValue = (IIndexedValue) logicalValue;
            int partitionSize = computeParitionSize(indexedValue);
            if (partitionSize > 1) {
                int offset = indexedValue.getInitialOffset();
                int length = indexedValue.getSize();
                int numPartitions = length / partitionSize;
                int remainder = length % partitionSize;
                if (remainder > 0) {
                    numPartitions++;
                }
                IVariable[] partitions = new IVariable[numPartitions];
                for (int i = 0; i < (numPartitions - 1); i++) {
                    partitions[i] = new IndexedVariablePartition(parent, indexedValue, offset, partitionSize);
                    offset = offset + partitionSize;
                }
                if (remainder == 0) {
                    remainder = partitionSize;
                }
                partitions[numPartitions - 1] = new IndexedVariablePartition(parent, indexedValue, offset, remainder);
                return partitions;
            }
        }
        if (logicalValue == null) {
            // safeguard against an structure type returning null
            logicalValue = value;
        }
        return logicalValue.getVariables();
    }

    /**
     * Returns the partition size to use for the given indexed value. The
     * partition size is computed by determining the number of levels that an
     * indexed collection must be nested in order to partition the collection
     * sub-collections of the preferred partition size.
     *
     * @param value
     *            indexed value
     * @return size of partitions the value should be subdivided into
     */
    protected int computeParitionSize(IIndexedValue value) {
        int partitionSize = 1;
        try {
            int length = value.getSize();
            int partitionDepth = 0;
            int preferredSize = getArrayPartitionSize();
            int remainder = length % preferredSize;
            length = length / preferredSize;
            while (length > 0) {
                if (remainder == 0 && length == 1) {
                    break;
                }
                partitionDepth++;
                remainder = length % preferredSize;
                length = length / preferredSize;
            }
            for (int i = 0; i < partitionDepth; i++) {
                partitionSize = partitionSize * preferredSize;
            }
        } catch (DebugException e) {
        }
        return partitionSize;
    }

    /**
     * Returns any logical value for the raw value. This method will recurse
     * over the returned value until the same structure is encountered again (to
     * avoid infinite recursion).
     *
     * @param value raw value to possibly be replaced by a logical value
     * @param previousStructureIds
     *            the list of logical structures that have already been applied
     *            to the returned value during the recursion of this method.
     *            Callers should always pass in a new, empty list.
     * @return logical value if one is calculated, otherwise the raw value is returned
     */
	protected IValue getLogicalValue(IValue value, List<String> previousStructureIds, IPresentationContext context) throws CoreException {
        if (isShowLogicalStructure(context)) {
            ILogicalStructureType[] types = DebugPlugin.getLogicalStructureTypes(value);
            if (types.length > 0) {
                ILogicalStructureType type = DebugPlugin.getDefaultStructureType(types);
                if (type != null && !previousStructureIds.contains(type.getId())) {
                	IValue logicalValue = getLogicalStructureCache().getLogicalStructure(type, value);
                	previousStructureIds.add(type.getId());
                	return getLogicalValue(logicalValue, previousStructureIds, context);
                }
            }
        }
        return value;
    }

    /**
     * Returns the logical structure cache to use to store calculated structures.  If the cache does not
     * exist yet, one is created and a debug event listener is added to clear the cache on RESUME and
     * TERMINATE events.
     *
     * @return the logical structure cache to use
     */
    protected synchronized LogicalStructureCache getLogicalStructureCache(){
    	if (fgLogicalCache == null){
    		fgLogicalCache = new LogicalStructureCache();
    		// Add a listener to clear the cache when resuming, terminating, or suspending
    		DebugPlugin.getDefault().addDebugEventListener(new IDebugEventSetListener(){
				@Override
				public void handleDebugEvents(DebugEvent[] events) {
					for (int i = 0; i < events.length; i++) {
						if (events[i].getKind() == DebugEvent.TERMINATE){
							fgLogicalCache.clear();
							break;
						} else if (events[i].getKind() == DebugEvent.RESUME && events[i].getDetail() != DebugEvent.EVALUATION_IMPLICIT){
							fgLogicalCache.clear();
							break;
						} else if (events[i].getKind() == DebugEvent.SUSPEND && events[i].getDetail() != DebugEvent.EVALUATION_IMPLICIT){
								fgLogicalCache.clear();
								break;
						} else if (events[i].getKind() == DebugEvent.CHANGE && events[i].getDetail() == DebugEvent.CONTENT){
							fgLogicalCache.clear();
							break;
						}
					}
				}
    		});
    	}
    	return fgLogicalCache;
    }

}
