compiler/src/main/java/org/apache/etch/compiler/opt/ToString.java

/* $Id$
 *
 * 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 org.apache.etch.compiler.opt;

import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.etch.compiler.EtchGrammarConstants;
import org.apache.etch.compiler.ParseException;
import org.apache.etch.compiler.Token;
import org.apache.etch.compiler.ast.Except;
import org.apache.etch.compiler.ast.Name;
import org.apache.etch.compiler.ast.Opt;
import org.apache.etch.compiler.ast.Struct;


/**
 * Option which sets the string format of a struct or exception.
 */
public class ToString extends Opt
{
	/**
	 * Constructs the ToString.
	 *
	 * @param name
	 * @param args
	 * @throws ParseException
	 */
	public ToString( Name name, Token... args ) throws ParseException
	{
		super( name.name, name.token.beginLine );
		addType( Except.class );
		addType( Struct.class );
		
		if (args.length != 1)
			throw new ParseException( String.format(
				"ToString accepts one string argument at line %d",
				name.token.beginLine ) );
		
		Token arg = args[0];
		if (arg.kind != EtchGrammarConstants.STR)
			throw new ParseException( String.format(
				"ToString accepts one string argument at line %d",
				arg.beginLine ) );
		
		try
		{
			format = parse( arg.image );
		}
		catch ( IOException e )
		{
			throw new ParseException( String.format(
				"ToString: problem with format string at line %d: %s",
				arg.beginLine, e.getMessage() ) );
		}
	}
	
	private final List<FmtItem> format;

	@Override
	public void dump( String indent )
	{
		System.out.printf( "%s@ToString( %s )\n", indent, format );
	}

	@Override
	public String toString()
	{
		return String.format( "@ToString( %s )", format );
	}

	/**
	 * @return the format for the ToString.
	 */
	public List<FmtItem> getFormat()
	{
		return format;
	}
	
	private static List<FmtItem> parse( String s ) throws IOException
	{
		if (s.startsWith( "\"" ))
			s = s.substring( 1 );
		
		if (s.endsWith( "\"" ))
			s = s.substring( 0, s.length()-1 );
		
		List<FmtItem> list = new ArrayList<FmtItem>();
		StringReader rdr = new StringReader( s );
		while (stringItem( list, rdr ) && fieldItem( list, rdr ))
		{
			// nothing else to do.
		}
		return list;
	}

	private static boolean stringItem( List<FmtItem> list, StringReader rdr )
		throws IOException
	{
		StringBuffer sb = new StringBuffer();
		int c;
		boolean escape = false;
		while ((c = rdr.read()) >= 0)
		{
			if (!escape)
			{
				if (c == '{')
				{
					// unescaped brace is start of format item.
					break;
				}
				
				if (c == '\\')
				{
					// unescaped backslash is start of escape
					escape = true;
					continue;
				}
			}
			else
			{
				if (c == 't') c = '\t';
				else if (c == 'r') c = '\r';
				else if (c == 'n') c = '\n';
				else if (c == '{') c = '{';
				else if (c == '\\') c = '\\';
				else throw new IOException( "bad escape. expecting one of t, r, n, {, or \\. got '"+(char) c+"'" );
				escape = false;
			}
			
			sb.append( (char) c );
		}
		
		if (escape)
			throw new IOException( "partial escape at end of string" );
		
		if (sb.length() > 0)
			list.add( new StringItem( sb.toString() ) );
		
		return c >= 0;
	}

	private static boolean fieldItem( List<FmtItem> list, StringReader rdr )
		throws IOException
	{
		StringBuffer sb = new StringBuffer();
		int c;
		while ((c = rdr.read()) >= 0)
		{
			if (c == '}')
				break;
			
			sb.append( (char) c );
		}
		
		if (c != '}')
			throw new IOException( "unclosed field item at end of string" );
		
		if (sb.length() > 0)
			list.add( new FieldItem( sb.toString() ) );
		
		return c >= 0;
	}

	/**
	 * A format item.
	 */
	public interface FmtItem
	{
		/**
		 * @return the value of the format item.
		 */
		public String value();
	}
	
	/**
	 * A string format item.
	 */
	public static class StringItem implements FmtItem
	{
		/**
		 * Constructs the string format item.
		 * @param s the string format item.
		 */
		public StringItem( String s )
		{
			this.s = s;
		}
		
		private final String s;
		
		@Override
		public String toString()
		{
			return "String: '"+s+"'";
		}

		public String value()
		{
			return s;
		}
	}
	
	/**
	 * A field format item.
	 */
	public static class FieldItem implements FmtItem
	{
		/**
		 * Constructs the field format item.
		 * @param s the name of the field.
		 */
		public FieldItem( String s )
		{
			this.s = s;
		}
		
		private final String s;
		
		@Override
		public String toString()
		{
			return "Field: "+s;
		}

		public String value()
		{
			return s;
		}
	}
}