/*******************************************************************************
 *  Copyright (c) 2019 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.jdt.internal.debug.ui.variables;

import java.util.HashMap;
import java.util.Map;
import java.util.Stack;
import java.util.regex.Pattern;

import org.eclipse.debug.internal.ui.SWTFactory;
import org.eclipse.debug.internal.ui.views.variables.details.DefaultDetailPane;
import org.eclipse.jdt.debug.core.IJavaVariable;
import org.eclipse.jdt.internal.debug.ui.ExpressionInformationControlCreator;
import org.eclipse.jdt.internal.debug.ui.JDIDebugUIPlugin;
import org.eclipse.jdt.internal.debug.ui.propertypages.PropertyPageMessages;
import org.eclipse.jface.dialogs.DialogSettings;
import org.eclipse.jface.dialogs.IDialogSettings;
import org.eclipse.jface.text.source.SourceViewer;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.FocusListener;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;

/**
 * Java Variable detail pane.
 *
 * @since 3.10
 */
public class JavaVariablesDetailPane extends DefaultDetailPane {

	/**
	 * Identifier for this Java Variable detail pane editor
	 */
	public static final String JAVA_VARIABLE_DETAIL_PANE_VARIABLES = JDIDebugUIPlugin.getUniqueIdentifier() + ".JAVA_VARIABLE_DETAIL_PANE_VARIABLES"; //$NON-NLS-1$
	public static final String NAME = PropertyPageMessages.JavaVariableDetailsPane_name;
	public static final String DESCRIPTION = PropertyPageMessages.JavaVariableDetailsPane_description;

	private FocusListener focusListener;
	private Combo fExpressionHistory;
	private IDialogSettings fExpressionHistoryDialogSettings;
	private Map<IJavaVariable, Stack<String>> fLocalExpressionHistory;
	private int fSeparatorIndex;
	private static final int MAX_HISTORY_SIZE = 10;
	private static final String DS_SECTION_EXPRESSION_HISTORY = "expressionHistory"; //$NON-NLS-1$
	private static final String DS_KEY_HISTORY_ENTRY_COUNT = "expressionHistoryEntryCount"; //$NON-NLS-1$
	private static final String DS_KEY_HISTORY_ENTRY_PREFIX = "expressionHistoryEntry_"; //$NON-NLS-1$
	private static final Pattern NEWLINE_PATTERN = Pattern.compile("\r\n|\r|\n"); //$NON-NLS-1$ ;

	private IJavaVariable fVariable;
	public JavaVariablesDetailPane() {
		fExpressionHistoryDialogSettings = DialogSettings.getOrCreateSection(JDIDebugUIPlugin.getDefault().getDialogSettings(), DS_SECTION_EXPRESSION_HISTORY);
	}

	@Override
	public Control createControl(Composite parent) {
		if (!isInView()) {
			Control c = super.createControl(parent);
			c.setBackground(ExpressionInformationControlCreator.getSystemBackgroundColor());
			return c;
		}
		if (fExpressionHistoryDialogSettings != null) {
			fLocalExpressionHistory = new HashMap<>();
			fExpressionHistory = SWTFactory.createCombo(parent, SWT.DROP_DOWN | SWT.READ_ONLY, 1, null);
			fExpressionHistory.addSelectionListener(new SelectionAdapter() {
				@Override
				public void widgetSelected(SelectionEvent e) {
					int historyIndex = fExpressionHistory.getSelectionIndex() - 1;
					if (historyIndex >= 0 && historyIndex != fSeparatorIndex && getSourceViewer() != null) {
						getSourceViewer().getDocument().set(getExpressionHistory()[historyIndex]);
					}
				}
			});
			GridData data = new GridData(GridData.FILL_HORIZONTAL);
			data.widthHint = 10;
			fExpressionHistory.setLayoutData(data);
			fExpressionHistory.setEnabled(false);
		}
		Control newControl = super.createControl(parent);
		SourceViewer viewer = getSourceViewer();
		focusListener = new FocusListener() {

			@Override
			public void focusLost(FocusEvent e) {
				updateExpressionHistories();
				initializeExpressionHistoryDropDown();
			}

			@Override
			public void focusGained(FocusEvent e) {

			}
		};
		viewer.getTextWidget().addFocusListener(focusListener);
		return newControl;
	}

	/**
	 * Initializes the Expression history drop-down with values.
	 */
	private void initializeExpressionHistoryDropDown() {
		fExpressionHistory.setItems(getExpressionHistoryLabels());
		String userHint = PropertyPageMessages.JavaVariableDetailsPane_choosePreviousExpression;
		fExpressionHistory.add(userHint, 0);
		fExpressionHistory.setText(userHint);
	}

	/**
	 * Returns the Expression history labels for the current variale.
	 *
	 * @return an array of strings containing the Expression history labels
	 */
	private String[] getExpressionHistoryLabels() {
		String[] expressions = getExpressionHistory();
		String[] labels = new String[expressions.length];
		for (int i = 0; i < expressions.length; i++) {
			labels[i] = NEWLINE_PATTERN.matcher(expressions[i]).replaceAll(" "); //$NON-NLS-1$
		}
		return labels;
	}

	/**
	 * Returns the Expression history entries for the current variable.
	 *
	 * @return an array of strings containing the history of Expressions
	 */
	private String[] getExpressionHistory() {
		fSeparatorIndex = -1;

		// Get global history
		String[] globalItems = readExpressionHistory(fExpressionHistoryDialogSettings);

		// Get local history
		Stack<String> localHistory = fLocalExpressionHistory.get(fVariable);
		if (localHistory == null) {
			return globalItems;
		}

		// Create combined history
		int localHistorySize = Math.min(localHistory.size(), MAX_HISTORY_SIZE);
		String[] historyItems = new String[localHistorySize + globalItems.length + 1];
		for (int i = 0; i < localHistorySize; i++) {
			historyItems[i] = localHistory.get(localHistory.size() - i - 1);
		}
		fSeparatorIndex = localHistorySize;
		historyItems[localHistorySize] = getSeparatorLabel();
		System.arraycopy(globalItems, 0, historyItems, localHistorySize + 1, globalItems.length);
		return historyItems;
	}

	/**
	 * Updates the local and global Expression histories.
	 */
	private void updateExpressionHistories() {
		String newItem = getSourceViewer().getDocument().get();
		if (newItem.length() == 0) {
			return;
		}

		// Update local history
		Stack<String> localHistory = fLocalExpressionHistory.get(fVariable);
		if (localHistory == null) {
			localHistory = new Stack<>();
			fLocalExpressionHistory.put(fVariable, localHistory);
		}

		localHistory.remove(newItem);
		localHistory.push(newItem);

		// Update global history
		String[] globalItems = readExpressionHistory(fExpressionHistoryDialogSettings);
		if (globalItems.length > 0 && newItem.equals(globalItems[0])) {
			return;
		}

		if (globalItems.length == 0) {
			globalItems = new String[1];
		} else {
			String[] tempItems = new String[globalItems.length + 1];
			System.arraycopy(globalItems, 0, tempItems, 1, globalItems.length);
			globalItems = tempItems;
		}
		globalItems[0] = newItem;
		storeExpressionHistory(globalItems, fExpressionHistoryDialogSettings);
	}

	/**
	 * Reads the Expression history from the given dialog settings.
	 *
	 * @param dialogSettings
	 *            the dialog settings
	 * @return the Expression history
	 */
	private static String[] readExpressionHistory(IDialogSettings dialogSettings) {
		int count = 0;
		try {
			count = dialogSettings.getInt(DS_KEY_HISTORY_ENTRY_COUNT);
		} catch (NumberFormatException ex) {
			// No history yet
		}
		count = Math.min(count, MAX_HISTORY_SIZE);
		String[] expressions = new String[count];
		for (int i = 0; i < count; i++) {
			expressions[i] = dialogSettings.get(DS_KEY_HISTORY_ENTRY_PREFIX + i);
		}
		return expressions;
	}

	/**
	 * Writes the given Expressions into the given dialog settings.
	 *
	 * @param expressions
	 *            an array of strings containing the Expressions
	 * @param dialogSettings
	 *            the dialog settings
	 */
	private static void storeExpressionHistory(String[] expressions, IDialogSettings dialogSettings) {
		int length = Math.min(expressions.length, MAX_HISTORY_SIZE);
		int count = 0;
		outer: for (int i = 0; i < length; i++) {
			for (int j = 0; j < i; j++) {
				if (expressions[i].equals(expressions[j])) {
					break outer;
				}
			}
			dialogSettings.put(DS_KEY_HISTORY_ENTRY_PREFIX + count, expressions[i]);
			count = count + 1;
		}
		dialogSettings.put(DS_KEY_HISTORY_ENTRY_COUNT, count);
	}

	/**
	 * Returns the label for the history separator.
	 *
	 * @return the label for the history separator
	 */
	private String getSeparatorLabel() {
		int borderWidth = fExpressionHistory.computeTrim(0, 0, 0, 0).width;
		Rectangle rect = fExpressionHistory.getBounds();
		int width = rect.width - borderWidth;

		GC gc = new GC(fExpressionHistory);
		gc.setFont(fExpressionHistory.getFont());

		int fSeparatorWidth = gc.getAdvanceWidth('-');
		String separatorLabel = PropertyPageMessages.JavaVariableDetailsPane_historySeparator;
		int fMessageLength = gc.textExtent(separatorLabel).x;

		gc.dispose();

		StringBuilder dashes = new StringBuilder();
		int chars = (((width - fMessageLength) / fSeparatorWidth) / 2) - 2;
		for (int i = 0; i < chars; i++) {
			dashes.append('-');
		}

		StringBuilder result = new StringBuilder();
		result.append(dashes);
		result.append(" " + separatorLabel + " "); //$NON-NLS-1$//$NON-NLS-2$
		result.append(dashes);
		return result.toString().trim();
	}

	@Override
	public String getDescription() {
		return DESCRIPTION;
	}

	@Override
	public String getID() {
		return JAVA_VARIABLE_DETAIL_PANE_VARIABLES;
	}

	@Override
	public String getName() {
		return NAME;
	}

	@Override
	public void display(IStructuredSelection selection) {
		if (fExpressionHistory != null && selection != null && selection.getFirstElement() instanceof IJavaVariable) {
			IJavaVariable variable = (IJavaVariable) (selection.getFirstElement());
			if (fVariable == null || !fVariable.equals(variable)) {
				fVariable = variable;
				fExpressionHistory.setEnabled(true);
				initializeExpressionHistoryDropDown();
			}
		}
		super.display(selection);
	}

	/**
	 * Clears the Java variable detail viewer, removes all text.
	 */
	@Override
	protected void clearSourceViewer(){
		fVariable = null;
		if (fExpressionHistory != null) {
			fExpressionHistory.setEnabled(false);
		}
		super.clearSourceViewer();
	}

	@Override
	public void dispose() {
		if (fExpressionHistory != null) {
			fExpressionHistory.dispose();
		}
		if (fLocalExpressionHistory != null) {
			fLocalExpressionHistory.clear();
		}
		if (focusListener != null && getSourceViewer() != null && getSourceViewer().getTextWidget() != null) {
			getSourceViewer().getTextWidget().removeFocusListener(focusListener);
		}
		super.dispose();
	}
}