/*=============================================================================#
 # Copyright (c) 2021 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.internal.r.ui.pager;

import java.util.ArrayList;

import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.TypedRegion;

import org.eclipse.statet.jcommons.collections.ImCollections;
import org.eclipse.statet.jcommons.collections.ImList;
import org.eclipse.statet.jcommons.lang.NonNullByDefault;


@NonNullByDefault
public class TextFileParser {
	
	
	public static final String DEFAULT_FORMAT_TYPE= IDocument.DEFAULT_CONTENT_TYPE;
	public static final String UNDERLINE_FORMAT_TYPE= "Pager.Underline";
	
	
	private boolean createDefaultRegions= false;
	
	private final StringBuilder cleanTextBuilder= new StringBuilder();
	
	private final ArrayList<ITypedRegion> formatRegions= new ArrayList<>();
	private String cleanText= ""; //$NON-NLS-1$
	
	
	public TextFileParser() {
	}
	
	
	public void setCreateDefaultRegions(final boolean enable) {
		this.createDefaultRegions= enable;
	}
	
	
	public void parse(final String in) {
		this.formatRegions.clear();
		this.cleanTextBuilder.setLength(0);
		
		final int inLength= in.length();
		int offsetDone= 0;
		while (offsetDone < inLength) {
			final int backOffset= in.indexOf(0x08, offsetDone);
			if (backOffset >= 0) {
				this.cleanTextBuilder.append(in, offsetDone, backOffset - 1);
				if (backOffset + 1 == inLength || backOffset == offsetDone) {
					offsetDone= backOffset + 1;
					continue;
				}
				switch (in.charAt(backOffset - 1)) {
				case '_':
					checkDefaultFormat(this.cleanTextBuilder.length());
					offsetDone= readBackspaceFormat(in, backOffset - 1, '_', UNDERLINE_FORMAT_TYPE);
					continue;
				default:
					offsetDone= backOffset + 1;
					continue;
				}
			}
			else {
				if (offsetDone > 0) {
					this.cleanTextBuilder.append(in, offsetDone, inLength);
					offsetDone= inLength;
				}
				break;
			}
		}
		
		this.cleanText= (offsetDone > 0) ? this.cleanTextBuilder.toString() : in;
		checkDefaultFormat(this.cleanText.length());
	}
	
	private void checkDefaultFormat(final int offset) {
		if (!this.createDefaultRegions) {
			return;
		}
		final int lastEndOffset;
		if (this.formatRegions.isEmpty()) {
			lastEndOffset= 0;
		}
		else {
			final ITypedRegion lastFormat= this.formatRegions.get(this.formatRegions.size() - 1);
			lastEndOffset= lastFormat.getOffset() + lastFormat.getLength();
		}
		if (offset > lastEndOffset) {
			this.formatRegions.add(new TypedRegion(
					lastEndOffset, offset - lastEndOffset,
					DEFAULT_FORMAT_TYPE ));
		}
	}
	
	private int readBackspaceFormat(final String in, int offset, final char formatChar,
			final String formatType) {
		final int inLength= in.length();
		final int cleanStartOffset= this.cleanTextBuilder.length();
		
		do {
			this.cleanTextBuilder.append(in.charAt(offset + 2));
			offset+= 3;
		}
		while (offset + 2 < inLength
				&& in.charAt(offset) == formatChar
				&& in.charAt(offset + 1) == 0x08);
		
		this.formatRegions.add(new TypedRegion(
				cleanStartOffset, this.cleanTextBuilder.length() - cleanStartOffset,
				formatType ));
		return offset;
	}
	
	
	public String getCleanText() {
		return this.cleanText;
	}
	
	public ImList<ITypedRegion> getFormatRegions() {
		return ImCollections.toList(this.formatRegions);
	}
	
}