/*  file: utf7.l  */

%{

#ifdef __MSDOS__
#  include <dir.h>
#  include <fcntl.h>
#  include <io.h>
#else
#  include <unistd.h>
#endif
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

int
    printcode = 0;

unsigned int
    outcode [2],
    instep,
    outstep;

char
    *programname;

void
    get_programname (char const *argv0),
    syntax (void),
    errit (char const *format, ...),
    utf (void),
    nextout (void),
    outchar (long unsigned);

#ifdef __MSDOS__
#define strcasecmp(s1, s2) (stricmp(s1, s2))
#endif

#define YY_NO_UNPUT
#define YY_SKIP_YYWRAP
#ifdef yywrap
#  undef yywrap
#endif
int yywrap()
{
    return 1;
}

%}

%Start _utf

%%

<INITIAL>"+-"                   { fputc ('+', stdout); }
<INITIAL>"+"			{ instep = outstep = 0;
                                  BEGIN _utf; }

<_utf>[A-Za-z0-9+/]		{ utf (); }
<_utf>"-"			{ BEGIN INITIAL; }
<_utf>.|\n			{ fputc (yytext [0], stdout);
                                  BEGIN INITIAL; }

%%

void utf ()
{
    unsigned
        i,
        c;

    i = yytext [0];
    if (i >= 'A' && i <= 'Z')
        c = i - 'A';
    else if (i >= 'a' && i <= 'z')
        c = i + 26 - 'a';
    else if (i >= '0' && i <= '9')
        c = i + 52 - '0';
    else if (i == '+')
        c = 62;
    else if (i == '/')
        c = 63;

    switch (instep) {
        case 0:
            outcode [outstep] = (c << 2);
            break;
        case 1:
            outcode [outstep] |= (c >> 4);
            nextout ();
            outcode [outstep] = (c << 4);
            break;
        case 2:
            outcode [outstep] |= (c >> 2);
            nextout ();
            outcode [outstep] = (c << 6);
            break;
        case 3:
            outcode [outstep] |= c;
            nextout ();
            break;
    }
    if (++instep == 4)
        instep = 0;
}

void nextout ()
{
    unsigned
        c;

    if (outstep == 0) {
        outstep = 1;
    } else {
        outstep = 0;
        c = ((outcode [0] & 0xFF) << 8) | (outcode [1] & 0xFF);
        outchar (c);
    }
}

void outchar (long unsigned c)
{
    int
        i;
    char
        *s;

    /*
     * iso-8859-1
     */
    if (c < 256) {
        fputc (c, stdout);
        return;
    }

    /*
     * iso-8859-15
     */
    i = 0;
    switch (c) {
        case 0x20Ac: i = 0xA4; break;    /* euro */
        case 0x0160: i = 0xA6; break;    /* S caron */
        case 0x0161: i = 0xA8; break; 	 /* s caron */
        case 0x017D: i = 0xB4; break;    /* Z caron */
        case 0x017E: i = 0xB8; break;    /* z caron */
        case 0x0152: i = 0xBC; break;    /* OE ligature */
        case 0x0153: i = 0xBD; break;    /* oe ligature */
        case 0x0178: i = 0xBE; break;    /* Y diaeresis */
    }
    if (i) {
        fputc (i, stdout);
        return;
    }

    /*
     * substitutions
     */
    s = NULL;
    switch (c) {
        case 0x0132: s = "IJ"; break;
        case 0x0133: s = "ij"; break;
    }
    if (s) {
        fputs (s, stdout);
        return;
    }

    if (printcode) {
        if (c < 0x10000)
            printf ("U+%04X", (unsigned) c);
        else
            printf ("U+%08lX", c);
    }  else
        fputc (191, stdout);
}

int main (int argc, char *argv [])
{
    get_programname (argv [0]);

    while (argc > 1)
        if (! strcmp (argv [1], "-c")) {
            printcode = 1;
            argv++;
            argc--;
	} else
            break;

    switch (argc) {
        case 1:
            if (isatty (fileno (stdin)))
                syntax ();
            yyin = stdin;
            break;
        case 2:
            yyin = fopen (argv [1], "r");
            if (! yyin)
                errit ("Opening file \"%s\": %s", argv [1], strerror (errno));
            break;
        default:
            syntax ();
    }

    yylex ();

    if (yyin != stdin)
        fclose (yyin);

    return 0;
}

void get_programname (char const *argv0)
{
#ifdef __MSDOS__
    char
        name [MAXFILE];
    fnsplit (argv0, NULL, NULL, name, NULL);
    programname = strdup (name);
#else   /* unix */
    char
        *p;
    p = strrchr (argv0, '/');
    if (p)
        programname = strdup (p + 1);
    else
        programname = strdup (argv0);
#endif    
}

void errit (char const *format, ...)
{
    va_list
        list;

    fprintf (stderr, "\nError %s: ", programname);

    va_start (list, format);
    vfprintf (stderr, format, list);

    fprintf (stderr, "\n\n");

    exit (1);
}

void syntax ()
{
    fprintf (
        stderr,
        "\n"
        "Syntax: %s [-c] [utf-7 encoded file]\n"
        "\n"
        "The file will be translated to iso-8859-1 *and* iso-8859-15\n"
	"\n"
	"  -c : print U+code for characters not in iso-8859-1/15\n"
        "\n",
        programname
    );

    exit (1);
}