#include <stdlib.h>
#include <locale.h>
#include "mbctype.h"

#ifdef MB_CAPABLE
typedef enum { ESCAPE, DOLLAR, BRACKET, AT, B, J, 
               NUL, JIS_CHAR, OTHER, JIS_C_NUM } JIS_CHAR_TYPE;
typedef enum { ASCII, A_ESC, A_ESC_DL, JIS, JIS_1, JIS_2, J_ESC, J_ESC_BR,
               J2_ESC, J2_ESC_BR, DONE, INV, JIS_S_NUM } JIS_STATE; 
typedef enum { COPY_A, COPY_J, COPY_J2, MAKE_A, MAKE_J, NOOP, EMPTY, ERROR } JIS_ACTION;

/************************************************************************************** 
 * state/action tables for processing JIS encoding
 * Where possible, switches to JIS are grouped with proceding JIS characters and switches
 * to ASCII are grouped with preceding JIS characters.  Thus, maximum returned length
 * is 2 (switch to JIS) + 2 (JIS characters) + 2 (switch back to ASCII) = 6.
 *************************************************************************************/

static JIS_STATE JIS_state_table[JIS_S_NUM][JIS_C_NUM] = {
/*              ESCAPE   DOLLAR    BRACKET   AT       B       J        NUL      JIS_CHAR  OTHER */
/* ASCII */   { A_ESC,   DONE,     DONE,     DONE,    DONE,   DONE,    DONE,    DONE,     DONE },
/* A_ESC */   { DONE,    A_ESC_DL, DONE,     DONE,    DONE,   DONE,    DONE,    DONE,     DONE },
/* A_ESC_DL */{ DONE,    DONE,     DONE,     JIS,     JIS,    DONE,    DONE,    DONE,     DONE }, 
/* JIS */     { J_ESC,   JIS_1,    JIS_1,    JIS_1,   JIS_1,  JIS_1,   INV,     JIS_1,    INV },
/* JIS_1 */   { INV,     JIS_2,    JIS_2,    JIS_2,   JIS_2,  JIS_2,   INV,     JIS_2,    INV },
/* JIS_2 */   { J2_ESC,  DONE,     DONE,     DONE,    DONE,   DONE,    INV,     DONE,     DONE },
/* J_ESC */   { INV,     INV,      J_ESC_BR, INV,     INV,    INV,     INV,     INV,      INV },
/* J_ESC_BR */{ INV,     INV,      INV,      INV,     ASCII,  ASCII,   INV,     INV,      INV },
/* J2_ESC */  { INV,     INV,      J2_ESC_BR,INV,     INV,    INV,     INV,     INV,      INV },
/* J2_ESC_BR*/{ INV,     INV,      INV,      INV,     DONE,   DONE,    INV,     INV,      INV },
};

static JIS_ACTION JIS_action_table[JIS_S_NUM][JIS_C_NUM] = {
/*              ESCAPE   DOLLAR    BRACKET   AT       B        J        NUL      JIS_CHAR  OTHER */
/* ASCII */   { NOOP,    COPY_A,   COPY_A,   COPY_A,  COPY_A,  COPY_A,  EMPTY,   COPY_A,  COPY_A},
/* A_ESC */   { COPY_A,  NOOP,     COPY_A,   COPY_A,  COPY_A,  COPY_A,  COPY_A,  COPY_A,  COPY_A},
/* A_ESC_DL */{ COPY_A,  COPY_A,   COPY_A,   MAKE_J,  MAKE_J,  COPY_A,  COPY_A,  COPY_A,  COPY_A},
/* JIS */     { NOOP,    NOOP,     NOOP,     NOOP,    NOOP,    NOOP,    ERROR,   NOOP,    ERROR },
/* JIS_1 */   { ERROR,   NOOP,     NOOP,     NOOP,    NOOP,    NOOP,    ERROR,   NOOP,    ERROR },
/* JIS_2 */   { NOOP,    COPY_J2,  COPY_J2,  COPY_J2, COPY_J2, COPY_J2, ERROR,   COPY_J2, COPY_J2},
/* J_ESC */   { ERROR,   ERROR,    NOOP,     ERROR,   ERROR,   ERROR,   ERROR,   ERROR,   ERROR },
/* J_ESC_BR */{ ERROR,   ERROR,    ERROR,    ERROR,   NOOP,    NOOP,    ERROR,   ERROR,   ERROR },
/* J2_ESC */  { ERROR,   ERROR,    NOOP,     ERROR,   ERROR,   ERROR,   ERROR,   ERROR,   ERROR },
/* J2_ESC_BR*/{ ERROR,   ERROR,    ERROR,    ERROR,   COPY_J,  COPY_J,  ERROR,   ERROR,   ERROR },
};
#endif /* MB_CAPABLE */

int
_DEFUN (_mbtowc_r, (r, pwc, s, n, state),
        struct _reent *r   _AND
        wchar_t       *pwc _AND 
        const char    *s   _AND        
        size_t         n   _AND
        int           *state)
{
  wchar_t dummy;
  unsigned char *t = (unsigned char *)s;

  if (pwc == NULL)
    pwc = &dummy;

  if (s != NULL && n == 0)
    return -1;

#ifdef MB_CAPABLE
  if (r->_current_locale == NULL ||
      (strlen (r->_current_locale) <= 1))
    { /* fall-through */ }
  else if (!strcmp (r->_current_locale, "C-SJIS"))
    {
      int char1;
      if (s == NULL)
        return 0;  /* not state-dependent */
      char1 = *t;
      if (_issjis1 (char1))
        {
          int char2 = t[1];
          if (n <= 1)
            return -1;
          if (_issjis2 (char2))
            {
              *pwc = (((wchar_t)*t) << 8) + (wchar_t)(*(t+1));
              return 2;
            }
          else  
            return -1;
        }
    }
  else if (!strcmp (r->_current_locale, "C-EUCJP"))
    {
      int char1;
      if (s == NULL)
        return 0;  /* not state-dependent */
      char1 = *t;
      if (_iseucjp (char1))
        {
          int char2 = t[1];     
          if (n <= 1)
            return -1;
          if (_iseucjp (char2))
            {
              *pwc = (((wchar_t)*t) << 8) + (wchar_t)(*(t+1));
              return 2;
            }
          else
            return -1;
        }
    }
  else if (!strcmp (r->_current_locale, "C-JIS"))
    {
      JIS_STATE curr_state;
      JIS_ACTION action;
      JIS_CHAR_TYPE ch;
      unsigned char *ptr;
      int i, curr_ch;
 
      if (s == NULL)
        {
          *state = 0;
          return 1;  /* state-dependent */
        }

      curr_state = (*state == 0 ? ASCII : JIS);
      ptr = t;

      for (i = 0; i < n; ++i)
        {
          curr_ch = t[i];
          switch (curr_ch)
            {
	    case ESC_CHAR:
              ch = ESCAPE;
              break;
	    case '$':
              ch = DOLLAR;
              break;
            case '@':
              ch = AT;
              break;
            case '(':
	      ch = BRACKET;
              break;
            case 'B':
              ch = B;
              break;
            case 'J':
              ch = J;
              break;
            case '\0':
              ch = NUL;
              break;
            default:
              if (_isjis (curr_ch))
                ch = JIS_CHAR;
              else
                ch = OTHER;
	    }

          action = JIS_action_table[curr_state][ch];
          curr_state = JIS_state_table[curr_state][ch];
        
          switch (action)
            {
            case NOOP:
              break;
            case EMPTY:
              *state = 0;
              *pwc = (wchar_t)0;
              return i;
            case COPY_A:
	      *state = 0;
              *pwc = (wchar_t)*ptr;
              return (i + 1);
            case COPY_J:
              *state = 0;
              *pwc = (((wchar_t)*ptr) << 8) + (wchar_t)(*(ptr+1));
              return (i + 1);
            case COPY_J2:
              *state = 1;
              *pwc = (((wchar_t)*ptr) << 8) + (wchar_t)(*(ptr+1));
              return (ptr - t) + 2;
            case MAKE_A:
            case MAKE_J:
              ptr = (char *)(t + i + 1);
              break;
            case ERROR:
            default:
              return -1;
            }

        }

      return -1;  /* n < bytes needed */
    }
#endif /* MB_CAPABLE */               

  /* otherwise this must be the "C" locale or unknown locale */
  if (s == NULL)
    return 0;  /* not state-dependent */

  *pwc = (wchar_t)*t;
  
  if (*t == '\0')
    return 0;

  return 1;
}