/* -*- mode: objc; coding: utf-8 -*- */
/* Étoilisp/Mulklisp, a Common Lisp subset for the Étoilé runtime.
 * Copyright (C) 2008  Matthias Andreas Benkard.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#import "MLKReader.h"
#import "MLKCharacter.h"
#import "MLKReadtable.h"
#import "MLKEndOfFileError.h"
#import "MLKReaderError.h"
#import "MLKDynamicContext.h"
#import "MLKEnvironment.h"
#import "MLKPackage.h"

#import <Foundation/NSArray.h>
#import <Foundation/NSString.h>


@implementation MLKReader
+(id) readFromStream:(MLKStream *)stream
            eofError:(BOOL)eofError
            eofValue:(id)eofValue
           recursive:(BOOL)recursive
  preserveWhitespace:(BOOL)preserveWhitespace
{
  unichar ch;
  NSMutableString *token;
  MLKReadtable *readtable;
  BOOL escaped;

  readtable = [[[MLKDynamicContext currentContext] environment]
                valueForBinding:[[MLKPackage commonLisp]
                                  intern:@"*READTABLE*"]];
  
 start:
  if ([stream isEOF])
    {
      if (eofError)
        [[[MLKEndOfFileError alloc] initWithStream:stream] raise];
      else
        return eofValue;
    }

  ch = [stream readChar];
  if ([readtable isWhitespaceCharacter:ch])
    goto start;
  
  if ([readtable isMacroCharacter:ch])
    {
      NSArray *returnValues;
      MLKClosure *macrofun = [readtable macroFunctionForCharacter:ch];
      NSArray *args = [NSArray arrayWithObjects:
                                 stream,
                                 [MLKCharacter characterWithUnichar:ch],
                               nil];
      if ([args count] != 2)
        {
          args = [NSMutableArray arrayWithCapacity:2];
          [((NSMutableArray*)args) addObject:stream];
          [((NSMutableArray*)args) addObject:[MLKCharacter
                                               characterWithUnichar:ch]];
        }
      returnValues = [macrofun applyToArray:args];
      if ([returnValues count])
        return [returnValues objectAtIndex:0];
      else
        goto start;
    }
  
  escaped = NO;
  
  if ([readtable isSingleEscapeCharacter:ch])
    {
      if ([stream isEOF])
        [[[MLKEndOfFileError alloc] initWithStream:stream] raise];

      token = [NSMutableString stringWithCapacity:8];
      [token appendFormat:@"%C", [stream readChar]];
    }

  if ([readtable isMultipleEscapeCharacter:ch])
    {
      token = [NSMutableString stringWithCapacity:8];      
      escaped = YES;
    }

  if ([readtable isConstituentCharacter:ch])
    {
      token = [NSMutableString stringWithCapacity:8];
      [token appendFormat:@"%C", [stream readChar]];
    }

  while (![stream isEOF])
    {
      ch = [stream readChar];
      if ([readtable isConstituentCharacter:ch] ||
          [readtable isNonTerminatingMacroCharacter:ch] ||
          (escaped && [readtable isWhitespaceCharacter:ch]))
        {
          if (escaped)
            [token appendFormat:@"%C", ch];
          else
            [token appendFormat:@"%C", [readtable charWithReadtableCase:ch]];
        }
      else if ([readtable isSingleEscapeCharacter:ch])
        {
          if ([stream isEOF])
            [[[MLKEndOfFileError alloc] initWithStream:stream] raise];
          
          token = [NSMutableString stringWithCapacity:8];
          [token appendFormat:@"%C", [stream readChar]];
        }
      else if ([readtable isMultipleEscapeCharacter:ch])
        escaped = !escaped;
      else if ([readtable isTerminatingMacroCharacter:ch])
        {
          [stream unreadChar];
          break;
        }
      else if ([readtable isWhitespaceCharacter:ch])
        {
          if (preserveWhitespace)
            [stream unreadChar];
          break;
        }
      else if ([readtable isInvalidCharacter:ch])
        {
          [[[MLKReaderError alloc] initWithStream:stream] raise];
        }
    }

  // FIXME: Check the token for invalid syntax.
  return token;
}
@end