/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package groovy.console.ui.text

import groovy.transform.CompileStatic

import javax.swing.AbstractAction
import javax.swing.JTextPane
import javax.swing.text.AttributeSet
import javax.swing.text.SimpleAttributeSet
import java.awt.event.ActionEvent

/**
 * Inserts a newline that preserves the indentation of the current line.
 */
@CompileStatic
class AutoIndentAction extends AbstractAction {
    private static final long serialVersionUID = -2680684287296849370L

    /**
     * Attributes used for inserted text.
     */
    AttributeSet simpleAttributeSet = new SimpleAttributeSet()

    /**
     * Inserts a newline and copies the leading whitespace of the current line.
     *
     * @param evt the action event providing the target text pane
     */
    void actionPerformed(ActionEvent evt) {
        JTextPane inputArea = (JTextPane) evt.source
        def rootElement = inputArea.document.defaultRootElement
        def cursorPos = inputArea.getCaretPosition()
        int rowNum = rootElement.getElementIndex(cursorPos)
        def rowElement = rootElement.getElement(rowNum)
        int startOffset = rowElement.startOffset, endOffset = rowElement.endOffset
        String rowContent = inputArea.document.getText(startOffset, endOffset - startOffset)
        String contentBeforeCursor = inputArea.document.getText(startOffset, cursorPos - startOffset)

        String whitespaceStr = ''
        rowContent.eachMatch(~/(?m)^(\s*).*\n$/) { all, ws ->
            whitespaceStr = ws
        }
        if (contentBeforeCursor ==~ /(\s)*/) {
            whitespaceStr = contentBeforeCursor
        }

        inputArea.document.insertString(cursorPos, '\n' + whitespaceStr, simpleAttributeSet)
    }
}
