#include <cctype>
#include <cstdlib>
#include <iostream>
#include "errors.h"
#include "lex-string.h"
#include "string16.h"


static uint16 parseInteger( const char *&str, const unsigned base, unsigned maxDigits )
{
  uint16 result = 0;
  
  while (maxDigits--)
    {
      unsigned digit = *str;
      if (isdigit( digit ))
	digit -= '0';
      else if (islower( digit ))
	digit -= 'a' - 10;
      else if (isupper( digit ))
	digit -= 'A' - 10;
      else
	return result;

      if (digit < base)
	{
	  ++str;
	  result *= base;
	  result += digit;
	}
      else
	return result;
    }

  return result;
}


static uint16 convert( const char *&str, const SourcePosn &position )
{
    switch (*str) {
    case '\\':
	switch (*++str) {
	case 'n': ++str; return '\n';
	case 'b': ++str; return '\b';
	case 'r': ++str; return '\r';
	case 't': ++str; return '\t';
	case 'f': ++str; return '\f';
	case '\\': case '"': case '\'':
	    return *str++;
	case '0': case '1': case '2': case '3':
	    return parseInteger( str, 8, 3 );
	case '4': case '5': case '6': case '7':
	    return parseInteger( str, 8, 2 );
	case 'u': {
	    do
		str++;
	    while (*str == 'u');
	    const char * const before = str;
	    const uint16 result = parseInteger( str, 16, 4 );
	    // require exactly four hex digits
	    if (str - before == 4)
		return result;
	}
	default:
	    Error(position) << "illegal escape sequence in literal: \""
			    << (str - 1) << '\"' << endl;
	    return '?';
	}
    default:
	return *str++;
    }
}


uint16 convertCharacter( char *str, size_t length, const SourcePosn &position )
{
    const char *frozen = str;
    str[ length ] = '\0';
    return convert( frozen, position );
}


const string16 convertString( char* str, size_t length, const SourcePosn &position )
{
    const char *frozen = str;
    str[ length ] = '\0';

    string16 result;
    result.reserve( length );

    const char * const end = frozen + length;
    while (frozen < end)
	result += convert( frozen, position );

    return result;
}