/*
  Universal iconv implementation for OS/2.

  Andrey Vasilkin, 2016.
*/

#define INCL_DOSMODULEMGR     /* Module Manager values */
#define INCL_DOSERRORS        /* Error values */
#include <os2.h>

#include "geniconv.h"

//#define DEBUG

#ifdef DEBUG
# include <stdio.h>
# define debug(s,...) printf(__func__"(): "##s"\n" ,##__VA_ARGS__)
#else
# define debug(s,...)
#endif

// Exports from os2iconv.c.
extern iconv_t _System os2_iconv_open(const char* tocode, const char* fromcode);
extern size_t _System os2_iconv(iconv_t cd, char* * inbuf,
                                size_t *inbytesleft, char* * outbuf,
                                size_t *outbytesleft);
extern int _System os2_iconv_close(iconv_t cd);

// Functions pointers types.
typedef iconv_t _System (*FNICONV_OPEN)(const char* tocode, const char* fromcode);
typedef size_t _System (*FNICONV)(iconv_t cd, char* * inbuf,
                                  size_t *inbytesleft, char* * outbuf,
                                  size_t *outbytesleft);
typedef int _System (*FNICONV_CLOSE)(iconv_t cd);

// Used DLL module handle.
static HMODULE         hmIconv = NULLHANDLE;
// Functions pointers.
static FNICONV_OPEN    fn_iconv_open = NULL;
static FNICONV         fn_iconv = NULL;
static FNICONV_CLOSE   fn_iconv_close = NULL;


static BOOL _loadDLL(PSZ pszName, PSZ pszIconvOpen, PSZ pszIconv,
                     PSZ pszIconvClose)
{
  ULONG      ulRC;
  CHAR       acError[256];

  ulRC = DosLoadModule( acError, sizeof(acError), pszName, &hmIconv );
  if ( ulRC != NO_ERROR )
  {
    debug( "DLL not loaded: %s", &acError );
    return FALSE;
  }

  do
  {
    ulRC = DosQueryProcAddr( hmIconv, 0, pszIconvOpen, (PFN *)&fn_iconv_open );
    if ( ulRC != NO_ERROR )
    {
      debug( "Error: cannot find entry %s in %s", pszIconvOpen, pszName );
      break;
    }

    ulRC = DosQueryProcAddr( hmIconv, 0, pszIconv, (PFN *)&fn_iconv );
    if ( ulRC != NO_ERROR )
    {
      debug( "Error: cannot find entry %s in %s", pszIconv, pszName );
      break;
    }

    ulRC = DosQueryProcAddr( hmIconv, 0, pszIconvClose, (PFN *)&fn_iconv_close );
    if ( ulRC != NO_ERROR )
    {
      debug( "Error: cannot find entry %s in %s", pszIconvClose, pszName );
      break;
    }

    debug( "DLL %s used", pszName );
    return TRUE;
  }
  while( FALSE );

  DosFreeModule( hmIconv );
  hmIconv = NULLHANDLE;
  return FALSE;
}

static void _init()
{
  if ( fn_iconv_open != NULL )
    // Already was initialized.
    return;

  // Try to load kiconv.dll, iconv2.dll or iconv.dll.
  if ( !_loadDLL( "KICONV", "_libiconv_open", "_libiconv", "_libiconv_close" )
       && !_loadDLL( "ICONV2", "_libiconv_open", "_libiconv", "_libiconv_close" )
       && !_loadDLL( "ICONV", "_iconv_open", "_iconv", "_iconv_close" ) )
  {
    // No one DLL was loaded - use OS/2 conversion objects API.

    debug( "Uni*() API used" );
    fn_iconv_open  = os2_iconv_open;
    fn_iconv       = os2_iconv;
    fn_iconv_close = os2_iconv_close;
  }
}


//           Public routines.
//           ----------------

// Non-standard function for iconv to unload the used dynamic library.
void libiconv_clean()
{
  if ( hmIconv != NULLHANDLE )
  {
    DosFreeModule( hmIconv );
    hmIconv = NULLHANDLE;

    fn_iconv_open  = NULL;
    fn_iconv       = NULL;
    fn_iconv_close = NULL;
  }
}

iconv_t libiconv_open(const char* tocode, const char* fromcode)
{
  _init();
  return fn_iconv_open( tocode, fromcode );
}

size_t libiconv(iconv_t cd, char* * inbuf, size_t *inbytesleft,
                char* * outbuf, size_t *outbytesleft)
{
  return fn_iconv( cd, inbuf, inbytesleft, outbuf, outbytesleft );
}

int libiconv_close(iconv_t cd)
{
  return fn_iconv_close( cd );
}