/*
 * [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.
 */
package org.antlr.codegen;

import org.antlr.Tool;
import org.antlr.analysis.Label;
import org.antlr.runtime.Token;
import org.stringtemplate.v4.ST;
import org.antlr.tool.Grammar;

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

/** The code generator for ANTLR can usually be retargeted just by providing
 *  a new X.stg file for language X, however, sometimes the files that must
 *  be generated vary enough that some X-specific functionality is required.
 *  For example, in C, you must generate header files whereas in Java you do not.
 *  Other languages may want to keep DFA separate from the main
 *  generated recognizer file.
 *
 *  The notion of a Code Generator target abstracts out the creation
 *  of the various files.  As new language targets get added to the ANTLR
 *  system, this target class may have to be altered to handle more
 *  functionality.  Eventually, just about all language generation issues
 *  will be expressible in terms of these methods.
 *
 *  If org.antlr.codegen.XTarget class exists, it is used else
 *  Target base class is used.  I am using a superclass rather than an
 *  interface for this target concept because I can add functionality
 *  later without breaking previously written targets (extra interface
 *  methods would force adding dummy functions to all code generator
 *  target classes).
 *
 */
public class Target {

	/** For pure strings of Java 16-bit unicode char, how can we display
	 *  it in the target language as a literal.  Useful for dumping
	 *  predicates and such that may refer to chars that need to be escaped
	 *  when represented as strings.  Also, templates need to be escaped so
	 *  that the target language can hold them as a string.
	 *
	 *  I have defined (via the constructor) the set of typical escapes,
	 *  but your Target subclass is free to alter the translated chars or
	 *  add more definitions.  This is nonstatic so each target can have
	 *  a different set in memory at same time.
	 */
	protected String[] targetCharValueEscape = new String[255];

	public Target() {
		targetCharValueEscape['\n'] = "\\n";
		targetCharValueEscape['\r'] = "\\r";
		targetCharValueEscape['\t'] = "\\t";
		targetCharValueEscape['\b'] = "\\b";
		targetCharValueEscape['\f'] = "\\f";
		targetCharValueEscape['\\'] = "\\\\";
		targetCharValueEscape['\''] = "\\'";
		targetCharValueEscape['"'] = "\\\"";
	}

	protected void genRecognizerFile(Tool tool,
									 CodeGenerator generator,
									 Grammar grammar,
									 ST outputFileST)
		throws IOException
	{
		String fileName =
			generator.getRecognizerFileName(grammar.name, grammar.type);
		generator.write(outputFileST, fileName);
	}

	protected void genRecognizerHeaderFile(Tool tool,
										   CodeGenerator generator,
										   Grammar grammar,
										   ST headerFileST,
										   String extName) // e.g., ".h"
		throws IOException
	{
		// no header file by default
	}

	protected void performGrammarAnalysis(CodeGenerator generator,
										  Grammar grammar)
	{
		// Build NFAs from the grammar AST
		grammar.buildNFA();

		// Create the DFA predictors for each decision
		grammar.createLookaheadDFAs();
	}

	/** Is scope in @scope::name {action} valid for this kind of grammar?
	 *  Targets like C++ may want to allow new scopes like headerfile or
	 *  some such.  The action names themselves are not policed at the
	 *  moment so targets can add template actions w/o having to recompile
	 *  ANTLR.
	 */
	public boolean isValidActionScope(int grammarType, String scope) {
		switch (grammarType) {
			case Grammar.LEXER :
				if ( scope.equals("lexer") ) {return true;}
				break;
			case Grammar.PARSER :
				if ( scope.equals("parser") ) {return true;}
				break;
			case Grammar.COMBINED :
				if ( scope.equals("parser") ) {return true;}
				if ( scope.equals("lexer") ) {return true;}
				break;
			case Grammar.TREE_PARSER :
				if ( scope.equals("treeparser") ) {return true;}
				break;
		}
		return false;
	}

	/** Target must be able to override the labels used for token types */
	public String getTokenTypeAsTargetLabel(CodeGenerator generator, int 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;
	}

	/** Convert from an ANTLR char literal found in a grammar file to
	 *  an equivalent char literal in the target language.  For most
	 *  languages, this means leaving 'x' as 'x'.  Actually, we need
	 *  to escape '\u000A' so that it doesn't get converted to \n by
	 *  the compiler.  Convert the literal to the char value and then
	 *  to an appropriate target char literal.
	 *
	 *  Expect single quotes around the incoming literal.
	 */
	public String getTargetCharLiteralFromANTLRCharLiteral(
		CodeGenerator generator,
		String literal)
	{
		StringBuffer buf = new StringBuffer();
		buf.append('\'');
		int c = Grammar.getCharValueFromGrammarCharLiteral(literal);
		if ( c<Label.MIN_CHAR_VALUE ) {
			return "'\u0000'";
		}
		if ( c<targetCharValueEscape.length &&
			 targetCharValueEscape[c]!=null )
		{
			buf.append(targetCharValueEscape[c]);
		}
		else if ( Character.UnicodeBlock.of((char)c)==
				  Character.UnicodeBlock.BASIC_LATIN &&
				  !Character.isISOControl((char)c) )
		{
			// normal char
			buf.append((char)c);
		}
		else {
			// must be something unprintable...use \\uXXXX
			// turn on the bit above max "\\uFFFF" value so that we pad with zeros
			// then only take last 4 digits
			String hex = Integer.toHexString(c|0x10000).toUpperCase().substring(1,5);
			buf.append("\\u");
			buf.append(hex);
		}

		buf.append('\'');
		return buf.toString();
	}

	/** Convert from an ANTLR string literal found in a grammar file to
	 *  an equivalent string literal in the target language.  For Java, this
	 *  is the translation 'a\n"' -> "a\n\"".  Expect single quotes
	 *  around the incoming literal.  Just flip the quotes and replace
	 *  double quotes with \"
     * 
     *  Note that we have decided to allow poeple to use '\"' without
     *  penalty, so we must build the target string in a loop as Utils.replae
     *  cannot handle both \" and " without a lot of messing around.
     * 
	 */
	public String getTargetStringLiteralFromANTLRStringLiteral(
		CodeGenerator generator,
		String literal)
	{
        StringBuilder sb = new StringBuilder();
        StringBuffer is = new StringBuffer(literal);
        
        // Opening quote
        //
        sb.append('"');
        
        for (int i = 1; i < is.length() -1; i++) {
            if  (is.charAt(i) == '\\') {
                // Anything escaped is what it is! We assume that
                // people know how to escape characters correctly. However
                // we catch anything that does not need an escape in Java (which
                // is what the default implementation is dealing with and remove 
                // the escape. The C target does this for instance.
                //
                switch (is.charAt(i+1)) {
                    // Pass through any escapes that Java also needs
                    //
                    case    '"':
                    case    'n':
                    case    'r':
                    case    't':
                    case    'b':
                    case    'f':
                    case    '\\':
                    case    'u':    // Assume unnnn
                        sb.append('\\');    // Pass the escape through
                        break;
                    default:
                        // Remove the escape by virtue of not adding it here
                        // Thus \' becomes ' and so on
                        //
                        break;
                }
                
                // Go past the \ character
                //
                i++;
            } else {
                // Chracters that don't need \ in ANTLR 'strings' but do in Java
                //
                if (is.charAt(i) == '"') {
                    // We need to escape " in Java
                    //
                    sb.append('\\');
                }
            }
            // Add in the next character, which may have been escaped
            //
            sb.append(is.charAt(i));   
        }
        
        // Append closing " and return
        //
        sb.append('"');
        
		return sb.toString();
	}

	/** Given a random string of Java unicode chars, return a new string with
	 *  optionally appropriate quote characters for target language and possibly
	 *  with some escaped characters.  For example, if the incoming string has
	 *  actual newline characters, the output of this method would convert them
	 *  to the two char sequence \n for Java, C, C++, ...  The new string has
	 *  double-quotes around it as well.  Example String in memory:
	 *
	 *     a"[newlinechar]b'c[carriagereturnchar]d[tab]e\f
	 *
	 *  would be converted to the valid Java s:
	 *
	 *     "a\"\nb'c\rd\te\\f"
	 *
	 *  or
	 *
	 *     a\"\nb'c\rd\te\\f
	 *
	 *  depending on the quoted arg.
	 */
	public String getTargetStringLiteralFromString(String s, boolean quoted) {
		if ( s==null ) {
			return null;
		}

		StringBuffer buf = new StringBuffer();
		if ( quoted ) {
			buf.append('"');
		}
		for (int i=0; i<s.length(); i++) {
			int c = s.charAt(i);
			if ( c!='\'' && // don't escape single quotes in strings for java
				 c<targetCharValueEscape.length &&
				 targetCharValueEscape[c]!=null )
			{
				buf.append(targetCharValueEscape[c]);
			}
			else {
				buf.append((char)c);
			}
		}
		if ( quoted ) {
			buf.append('"');
		}
		return buf.toString();
	}

	public String getTargetStringLiteralFromString(String s) {
		return getTargetStringLiteralFromString(s, false);
	}

	/** Convert long to 0xNNNNNNNNNNNNNNNN by default for spitting out
	 *  with bitsets.  I.e., convert bytes to hex string.
	 */
	public String getTarget64BitStringFromValue(long word) {
		int numHexDigits = 8*2;
		StringBuffer buf = new StringBuffer(numHexDigits+2);
		buf.append("0x");
		String digits = Long.toHexString(word);
		digits = digits.toUpperCase();
		int padding = numHexDigits - digits.length();
		// pad left with zeros
		for (int i=1; i<=padding; i++) {
			buf.append('0');
		}
		buf.append(digits);
		return buf.toString();
	}

	public String encodeIntAsCharEscape(int v) {
		if ( v<=127 ) {
			return "\\"+Integer.toOctalString(v);
		}
		String hex = Integer.toHexString(v|0x10000).substring(1,5);
		return "\\u"+hex;
	}

	/** Some targets only support ASCII or 8-bit chars/strings.  For example,
	 *  C++ will probably want to return 0xFF here.
	 */
	public int getMaxCharValue(CodeGenerator generator) {
		return Label.MAX_CHAR_VALUE;
	}

	/** Give target a chance to do some postprocessing on actions.
	 *  Python for example will have to fix the indention.
	 */
	public List postProcessAction(List chunks, Token actionToken) {
		return chunks;
	}

}