/*--

 * Copyright 2010 René M. de Bloois

 *

 * Licensed 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 solidstack.httpserver;



import java.io.IOException;

import java.io.InputStream;



import solidstack.io.FatalIOException;





public class HttpHeaderTokenizer

{

	/**

	 * The reader used to read from and push back characters.

	 */

	protected InputStream in;





	/**

	 * Constructs a new instance of the HttpHeaderTokenizer.

	 *

	 * @param in The input.

	 */

	public HttpHeaderTokenizer( InputStream in )

	{

		this.in = in;

	}



	/**

	 * Is the given character a whitespace?

	 *

	 * @param ch The character to check.

	 * @return True if the characters is whitespace, false otherwise.

	 */

	protected boolean isWhitespace( int ch )

	{

		switch( ch )

		{

			case ' ':

			case '\t':

				return true;

		}

		return false;

	}



	public String getLine()

	{

		try

		{

			StringBuilder result = new StringBuilder();

			while( true )

			{

				int ch = this.in.read();

				if( ch == -1 )

					throw new HttpException( "Unexpected end of line" );

				if( ch == '\r' )

					continue;

				if( ch == '\n' )

					return result.toString();

				result.append( (char)ch );

			}

		}

		catch( IOException e )

		{

			throw new FatalIOException( e );

		}

	}



	public Token getField()

	{

		try

		{

			int ch = this.in.read();



			// Ignore whitespace

			while( isWhitespace( ch ) && ch != -1 )

				ch = this.in.read();



			// Ignore carriage return

			if( ch == '\r' )

				ch = this.in.read();



			// Empty line means end of input for the header

			if( ch == '\n' )

				return new Token( null );



			StringBuilder result = new StringBuilder();

			while( ch != ':' && !isWhitespace( ch ) )

			{

				if( ch == -1 )

					throw new HttpException( "Unexpected end of statement" );

				if( ch == '\n' )

					throw new HttpException( "Unexpected end of line" );

				result.append( (char)ch );

				ch = this.in.read();

			}



			// Ignore whitespace

			while( isWhitespace( ch ) && ch != -1 )

				ch = this.in.read();



			if( ch != ':' )

				throw new HttpException( "Expecting a :" );



			// Return the result

			if( result.length() == 0 )

				throw new HttpException( "Empty header field" );



			return new Token( result.toString() );

		}

		catch( IOException e )

		{

			throw new FatalIOException( e );

		}

	}



	public Token getValue()

	{

		try

		{

			// Read whitespace

			int ch = this.in.read();

			while( isWhitespace( ch ) )

				ch = this.in.read();



			// Read everything until end-of-line

			StringBuilder result = new StringBuilder();

			while( true )

			{

				if( ch == -1 )

					throw new HttpException( "Unexpected end-of-input" );

				if( ch == '\n' ) // TODO Multiline header field values (space or tab)

					return new Token( result.toString() );

				if( ch != '\r' ) // ignore carriage return

					result.append( (char)ch );

				ch = this.in.read();

			}

		}

		catch( IOException e )

		{

			throw new FatalIOException( e );

		}

	}

}