tool/src/main/java/org/antlr/codegen/PythonTarget.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*

Please excuse my obvious lack of Java experience. The code here is probably
full of WTFs - though IMHO Java is the Real WTF(TM) here...

 */

package org.antlr.codegen;

import org.antlr.runtime.Token;
import org.antlr.tool.Grammar;

import java.util.ArrayList;
import java.util.List;

public class PythonTarget extends Target {
    @Override
    public boolean useBaseTemplatesForSynPredFragments() {
        return false;
    }
    /** Target must be able to override the labels used for token types */
	@Override
    public String getTokenTypeAsTargetLabel(CodeGenerator generator,
					    int ttype) {
	// use ints for predefined types;
	// <invalid> <EOR> <DOWN> <UP>
	if ( ttype >= 0 && ttype <= 3 ) {
	    return String.valueOf(ttype);
	}

	String name = generator.grammar.getTokenDisplayName(ttype);

	// If name is a literal, return the token type instead
	if ( name.charAt(0)=='\'' ) {
	    return String.valueOf(ttype);
	}

	return name;
    }

	@Override
    public String getTargetCharLiteralFromANTLRCharLiteral(
            CodeGenerator generator,
            String literal) {
	int c = Grammar.getCharValueFromGrammarCharLiteral(literal);
	return String.valueOf(c);
    }

    private List<String> splitLines(String text) {
		ArrayList<String> l = new ArrayList<String>();
		int idx = 0;

		while ( true ) {
			int eol = text.indexOf("\n", idx);
			if ( eol == -1 ) {
				l.add(text.substring(idx));
				break;
			}
			else {
				l.add(text.substring(idx, eol+1));
				idx = eol+1;
			}
		}

		return l;
    }

	@Override
    public List<Object> postProcessAction(List<Object> chunks, Token actionToken) {
		/* TODO
		   - check for and report TAB usage
		 */

		//System.out.println("\n*** Action at " + actionToken.getLine() + ":" + actionToken.getColumn());

		/* First I create a new list of chunks. String chunks are splitted into
		   lines and some whitespace my be added at the beginning.

		   As a result I get a list of chunks
		   - where the first line starts at column 0
		   - where every LF is at the end of a string chunk
		*/

		List<Object> nChunks = new ArrayList<Object>();
		for (int i = 0; i < chunks.size(); i++) {
			Object chunk = chunks.get(i);

			if ( chunk instanceof String ) {
				String text = (String)chunks.get(i);
				if ( nChunks.isEmpty() && actionToken.getCharPositionInLine() >= 0 ) {
					// first chunk and some 'virtual' WS at beginning
					// prepend to this chunk

					String ws = "";
					for ( int j = 0 ; j < actionToken.getCharPositionInLine() ; j++ ) {
						ws += " ";
					}
					text = ws + text;
				}

				nChunks.addAll(splitLines(text));
			}
			else {
				if ( nChunks.isEmpty() && actionToken.getCharPositionInLine() >= 0 ) {
					// first chunk and some 'virtual' WS at beginning
					// add as a chunk of its own

					String ws = "";
					for ( int j = 0 ; j <= actionToken.getCharPositionInLine() ; j++ ) {
						ws += " ";
					}
					nChunks.add(ws);
				}

				nChunks.add(chunk);
			}
		}

		int lineNo = actionToken.getLine();
		int col = 0;

		// strip trailing empty lines
		int lastChunk = nChunks.size() - 1;
		while ( lastChunk > 0
				&& nChunks.get(lastChunk) instanceof String
				&& ((String)nChunks.get(lastChunk)).trim().length() == 0 )
			lastChunk--;

		// string leading empty lines
		int firstChunk = 0;
		while ( firstChunk <= lastChunk
				&& nChunks.get(firstChunk) instanceof String
				&& ((String)nChunks.get(firstChunk)).trim().length() == 0
				&& ((String)nChunks.get(firstChunk)).endsWith("\n") ) {
			lineNo++;
			firstChunk++;
		}

		int indent = -1;
		for ( int i = firstChunk ; i <= lastChunk ; i++ ) {
			Object chunk = nChunks.get(i);

			//System.out.println(lineNo + ":" + col + " " + quote(chunk.toString()));

			if ( chunk instanceof String ) {
				String text = (String)chunk;

				if ( col == 0 ) {
					if ( indent == -1 ) {
						// first non-blank line
						// count number of leading whitespaces

						indent = 0;
						for ( int j = 0; j < text.length(); j++ ) {
							if ( !Character.isWhitespace(text.charAt(j)) )
								break;
			
							indent++;
						}
					}

					if ( text.length() >= indent ) {
						int j;
						for ( j = 0; j < indent ; j++ ) {
							if ( !Character.isWhitespace(text.charAt(j)) ) {
								// should do real error reporting here...
								System.err.println("Warning: badly indented line " + lineNo + " in action:");
								System.err.println(text);
								break;
							}
						}

						nChunks.set(i, text.substring(j));
					}
					else if ( text.trim().length() > 0 ) {
						// should do real error reporting here...
						System.err.println("Warning: badly indented line " + lineNo + " in action:");
						System.err.println(text);
					}
				}

				if ( text.endsWith("\n") ) {
					lineNo++;
					col = 0;
				}
				else {
					col += text.length();
				}
			}
			else {
				// not really correct, but all I need is col to increment...
				col += 1;
			}
		}

		return nChunks;
    }
}