/*******************************************************************************
 * Copyright (c) 2000, 2018 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.core;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.StringTokenizer;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.Platform;
import org.eclipse.debug.core.DebugPlugin;
import org.eclipse.debug.core.ILogicalStructureType;
import org.eclipse.debug.core.model.IValue;

/**
 * Manages logical structure extensions
 *
 * @since 3.0
 */
public class LogicalStructureManager {

	private static LogicalStructureManager fgDefault;
	private List<LogicalStructureType> fTypes = null;
	private List<LogicalStructureProvider> fTypeProviders;

	/**
	 * Map containing the user's selection for each combination of logical
	 * structure types.
	 * key: String - Comma-separated list of ints representing a combination of structure types.
	 *               These integers are indeces into the fStructureTypeIds array.
	 * value: Integer - One of the ints from the combo key (the one chosen by the user) or -1 if
	 *                  the user has chosen not to display any structures for this combination
	 */
	private Map<String, Integer> fStructureTypeSelections = null;
	/**
	 * List of known type identifiers. An identifier's index in this list is used as
	 * its ID number. This list is maintained as a space-saving measure so that the various
	 * combinations of structure types can be persisted using indeces instead of storing the
	 * full index strings.
	 */
	private List<String> fStructureTypeIds = null;

	/**
	 * Preference key used for storing the user's selected structure for each combination
	 * or structures. The preference value is stored in the form:
	 * int,int,...,int|int,int,...int|...
	 * Where int is an integer index of a structure in the array of known structures.
	 */
	public static final String PREF_STRUCTURE_SELECTIONS= "selectedStructures"; //$NON-NLS-1$
	/**
	 * Preference key used for storing the array of known structures. The preference
	 * value is in the form:
	 * string,string,string,...,string,
	 * Where string is an identifier of a logical structure.
	 */
	public static final String PREF_STRUCTURE_IDS= "allStructures"; //$NON-NLS-1$

	public static LogicalStructureManager getDefault() {
		if (fgDefault == null) {
			fgDefault = new LogicalStructureManager();
		}
		return fgDefault;
	}

	/**
	 * Returns the logical structure types that are applicable to the given value.
	 * @param value the value
	 * @return the logical structure types that are applicable to the given value
	 */
	public ILogicalStructureType[] getLogicalStructureTypes(IValue value) {
		initialize();
		// looks in the logical structure types
		List<ILogicalStructureType> select = new ArrayList<>();
		for (ILogicalStructureType type : fTypes) {
			if (type.providesLogicalStructure(value)) {
				select.add(type);
			}
		}
		// asks the logical structure providers
		for (LogicalStructureProvider provider : fTypeProviders) {
			ILogicalStructureType[] types = provider.getLogicalStructures(value);
			Collections.addAll(select, types);
		}
		return select.toArray(new ILogicalStructureType[select.size()]);
	}

	/**
	 * Loads the map of structure selections from the preference store.
	 */
	private void loadStructureTypeSelections() {
		fStructureTypeSelections = new HashMap<>();
		String selections= Platform.getPreferencesService().getString(DebugPlugin.getUniqueIdentifier(), PREF_STRUCTURE_SELECTIONS, IInternalDebugCoreConstants.EMPTY_STRING, null);
		// selections are stored in the form:
		// selection|selection|...selection|
		StringTokenizer tokenizer= new StringTokenizer(selections, "|"); //$NON-NLS-1$
		while (tokenizer.hasMoreTokens()) {
			String selection = tokenizer.nextToken();
			// selection string is of the form:
			// id,id,...,selectedid
			int i = selection.lastIndexOf(',');
			if (i > 0 && i < selection.length() - 1) {
				String comboKey= selection.substring(0, i + 1);
				String selected= selection.substring(i + 1, selection.length());
				fStructureTypeSelections.put(comboKey, Integer.valueOf(Integer.parseInt(selected)));
			}
		}
	}

	/**
	 * Stores the map of structure selections to the preference store
	 */
	private void storeStructureTypeSelections() {
		StringBuilder buffer= new StringBuilder();
		for (Entry<String, Integer> entry : fStructureTypeSelections.entrySet()) {
			buffer.append(entry.getKey());
			buffer.append(entry.getValue());
			buffer.append('|');
		}
		Preferences.setString(DebugPlugin.getUniqueIdentifier(), PREF_STRUCTURE_SELECTIONS, buffer.toString(), null);
	}

	/**
	 * Loads the collection of known structures identifiers from the preference store
	 */
	private void loadStructureTypeIds() {
		fStructureTypeIds = new ArrayList<>();
		// Types are stored as a comma-separated, ordered list.
		String types= Platform.getPreferencesService().getString(DebugPlugin.getUniqueIdentifier(), PREF_STRUCTURE_IDS, IInternalDebugCoreConstants.EMPTY_STRING, null);
		StringTokenizer tokenizer= new StringTokenizer(types, ","); //$NON-NLS-1$
		while (tokenizer.hasMoreTokens()) {
			String id= tokenizer.nextToken();
			if (id.length() > 0) {
				fStructureTypeIds.add(id);
			}
		}
	}

	/**
	 * Stores the collection of known structure identifiers to the preference store
	 */
	private void storeStructureTypeIds() {
		StringBuilder buffer= new StringBuilder();
		for (String id : fStructureTypeIds) {
			buffer.append(id).append(',');
		}
		Preferences.setString(DebugPlugin.getUniqueIdentifier(), PREF_STRUCTURE_IDS, buffer.toString(), null);
	}

	/**
	 * Returns the structure that the user has chosen from among the given
	 * collection of structures or <code>null</code> if the user has chosen
	 * to display none.
	 * @param structureTypes the collection of structures available
	 * @return the structure that the user has chosen from among the given collection
	 *  or <code>null</code> if the user has chosen to display none
	 */
	public ILogicalStructureType getSelectedStructureType(ILogicalStructureType[] structureTypes) {
		if (structureTypes.length == 0) {
			return null;
		}
		String combo= getComboString(structureTypes);
		// Lookup the combo
		Integer index = fStructureTypeSelections.get(combo);
		if (index == null) {
			// If the user hasn't explicitly chosen anything for this
			// combo yet, just return the first type.
			return structureTypes[0];
		} else if (index.intValue() == -1) {
			// An index of -1 means the user has deselected all structures for this combo
			return null;
		}
		// If an index is stored for this combo, retrieve the id at the index
		String id= fStructureTypeIds.get(index.intValue());
		for (ILogicalStructureType type : structureTypes) {
			if (type.getId().equals(id)) {
			// Return the type with the retrieved id
				return type;
			}
		}
		return structureTypes[0];
	}

	/**
	 *
	 * @param types the array of types
	 * @param selected the type that is selected for the given combo or <code>null</code>
	 *  if the user has de-selected any structure for the given combo
	 */
	public void setEnabledType(ILogicalStructureType[] types, ILogicalStructureType selected) {
		String combo= getComboString(types);
		int index= -1; // Initialize to "none selected"
		if (selected != null) {
			index= fStructureTypeIds.indexOf(selected.getId());
		}
		Integer integer= Integer.valueOf(index);
		fStructureTypeSelections.put(combo, integer);
		storeStructureTypeSelections();
		storeStructureTypeIds();
	}

	/**
	 * Returns the string representing the given combination of logical
	 * structure types. This string will be a series of comma-separated
	 * indices representing the various types. If any of the given types
	 * don't have indices associated with them, this method will create
	 * the appropriate index.
	 * @param types the logical structure types
	 * @return the string representing the given combination of logical
	 *  structure types
	 */
	protected String getComboString(ILogicalStructureType[] types) {
		StringBuilder comboKey= new StringBuilder();
		for (ILogicalStructureType type : types) {
			int typeIndex = fStructureTypeIds.indexOf(type.getId());
			if (typeIndex == -1) {
				typeIndex= fStructureTypeIds.size();
				fStructureTypeIds.add(type.getId());
			}
			comboKey.append(typeIndex).append(',');
		}
		return comboKey.toString();
	}

	private synchronized void initialize() {
		if (fTypes == null) {
			//get the logical structure types from the extension points
			IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(DebugPlugin.getUniqueIdentifier(), DebugPlugin.EXTENSION_POINT_LOGICAL_STRUCTURE_TYPES);
			IConfigurationElement[] extensions = point.getConfigurationElements();
			fTypes = new ArrayList<>(extensions.length);
			for (IConfigurationElement extension : extensions) {
				LogicalStructureType type;
				try {
					type = new LogicalStructureType(extension);
					fTypes.add(type);
				} catch (CoreException e) {
					DebugPlugin.log(e);
				}
			}
			// get the logical structure providers from the extension point
			point= Platform.getExtensionRegistry().getExtensionPoint(DebugPlugin.getUniqueIdentifier(), DebugPlugin.EXTENSION_POINT_LOGICAL_STRUCTURE_PROVIDERS);
			extensions= point.getConfigurationElements();
			fTypeProviders = new ArrayList<>(extensions.length);
			for (IConfigurationElement extension : extensions) {
				try {
					fTypeProviders.add(new LogicalStructureProvider(extension));
				} catch (CoreException e) {
					DebugPlugin.log(e);
				}
			}
		}
		if (fStructureTypeSelections == null) {
			loadStructureTypeSelections();
		}
		if (fStructureTypeIds == null) {
			loadStructureTypeIds();
		}
	}
}