/*      $OpenBSD: test_fflush.c,v 1.3 2025/06/08 08:53:53 yasuoka Exp $ */

/*
 * Copyright (c) 2025 YASUOKA Masahiko <yasuoka@yasuoka.net>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <assert.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>

/* we use assert() */
#undef  NDEBUG

#define TMPFILENAME     "test_fflush.tmp"

void setup(void);

void test_fflush_read0(void);
void test_fflush_read1(void);
void test_fflush_read2(void);
void test_fflush_read3(void);
void test_fflush_read4(void);
void setupw(void);
void test_fflush_read5(void);
void test_fflush_read6(void);

void
setup(void)
{
        FILE    *fp;

        /* common setup */
        unlink(TMPFILENAME);
        fp = fopen(TMPFILENAME, "w+");
        assert(fp != NULL);
        fputs("Hello world\n", fp);
        fclose(fp);
}

/* fflush work with reading file and seekable */
void
test_fflush_read0(void)
{
        int      r;
        char     buf[80];
        FILE    *fp;

        setup();

        /* In POSIX 2008, fflush() must work with the file object for reading */
        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);
        assert(fgetc(fp) == 'H');
        r = fflush(fp);
        assert(r == 0);

        /* the position is moved to 1 */
        assert(ftell(fp) == 1);

        /* can read rest of that */
        fgets(buf, sizeof(buf), fp);
        assert(strcmp(buf, "ello world\n") == 0);
        r = fclose(fp);
        assert(r == 0);
}

/* fflush work with reading file and seekable + unget */
void
test_fflush_read1(void)
{
        int      r;
        char     buf[80];
        FILE    *fp;

        setup();

        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);
        assert(fgetc(fp) == 'H');
        assert(fgetc(fp) == 'e');
        assert(fgetc(fp) == 'l');
        assert(fgetc(fp) == 'l');
        assert(fgetc(fp) == 'o');

        /* push the 'AAAA' back */
        ungetc('A', fp);
        ungetc('A', fp);
        ungetc('A', fp);
        ungetc('A', fp);

        /* can read rest of that */
        fgets(buf, sizeof(buf), fp);
        assert(strcmp(buf, "AAAA world\n") == 0);
        r = fclose(fp);
        assert(r == 0);

        /* do the same thing + fflush */

        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);
        assert(fgetc(fp) == 'H');
        assert(fgetc(fp) == 'e');
        assert(fgetc(fp) == 'l');
        assert(fgetc(fp) == 'l');
        assert(fgetc(fp) == 'o');

        /* push 'AAAA' back */
        ungetc('A', fp);
        ungetc('A', fp);
        ungetc('A', fp);
        ungetc('A', fp);

        /* then fflush */
        r = fflush(fp);
        assert(r == 0);

        /* fllush() clears the all pushed back chars */

        /* can read rest of that */
        fgets(buf, sizeof(buf), fp);
        assert(strcmp(buf, " world\n") == 0);
        r = fclose(fp);
        assert(r == 0);
}

/* fflush() to reading and non-seekable stream */
void
test_fflush_read2(void)
{
        int      r;
        FILE    *fp;
        char     buf[80];

        /* In POSIX-2008, fflush() must work with the file object for reading */
        fp = popen("echo Hello world", "r");
        assert(fp != NULL);
        assert(fgetc(fp) == 'H');
        r = fflush(fp);
        assert(r == 0);

        /*
         * FILE object for read and NOT seekable.  In that case, fflush does
         * nothing, but must keep the buffer.
         */

        /* can read rest of that */
        fgets(buf, sizeof(buf), fp);
        assert(strcmp(buf, "ello world\n") == 0);
        r = pclose(fp);
        assert(r == 0);
}

/* fflush() to the file which doesn't have any buffer */
void
test_fflush_read3(void)
{
        int      r;
        FILE    *fp;

        setup();

        /* In POSIX-2008, fflush() must work with the file object for reading */
        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);
        r = fflush(fp);
        assert(r == 0);
        r = fclose(fp);
        assert(r == 0);
}

/* freopen() should call fflush() internal */
void
test_fflush_read4(void)
{
        int      r;
        FILE    *fp;
        off_t    pos;
        char     buf[80];

        setup();

        /* In POSIX-2008, fflush() must work with the file object for reading */
        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);

        assert(fgetc(fp) == 'H');       /* read 1 */

        pos = lseek(fileno(fp), 0, SEEK_CUR);
        assert(pos >= 1);
        assert(pos > 1);        /* this test assume the buffer is used */

        /* freopen() should call fflush() internal */
        fp = freopen(TMPFILENAME, "r", fp);
        assert(fp != NULL);

        /* can read rest of that on fp */
        fgets(buf, sizeof(buf), fp);
        assert(strcmp(buf, "Hello world\n") == 0);

        r = fclose(fp);
        assert(r == 0);
}

void
setupw(void)
{
        FILE    *fp;

        /* common setup */
        unlink(TMPFILENAME);
        fp = fopen(TMPFILENAME, "w+");
        assert(fp != NULL);
        /* Konnitiwa Sekai(in Kanji) */
        fputws(L"\u3053\u3093\u306b\u3061\u308f \u4e16\u754c\n", fp);
        fclose(fp);
}

/* fflush work with reading file and seekable + ungetwc */
void
test_fflush_read5(void)
{
        int      r;
        wchar_t  buf[80];
        FILE    *fp;

        setupw();

        fp = fopen(TMPFILENAME, "r");

        assert(fp != NULL);
        assert(fgetwc(fp) == L'\u3053');        /* Ko */
        assert(fgetwc(fp) == L'\u3093');        /* N  */
        assert(fgetwc(fp) == L'\u306b');        /* Ni */
        assert(fgetwc(fp) == L'\u3061');        /* Ti */
        assert(fgetwc(fp) == L'\u308f');        /* Wa */

        /* push 263A(smile) back */
        assert(ungetwc(L'\u263a', fp));

        /* we support 1 push back wchar_t */
        assert(fgetwc(fp) == L'\u263a');

        /* can read reset of that */
        fgetws(buf, sizeof(buf), fp);
        assert(wcscmp(buf, L" \u4e16\u754c\n") == 0);

        r = fclose(fp);
        assert(r == 0);

        /* do the same thing + fflush */
        fp = fopen(TMPFILENAME, "r");

        assert(fp != NULL);
        assert(fgetwc(fp) == L'\u3053');        /* Ko */
        assert(fgetwc(fp) == L'\u3093');        /* N  */
        assert(fgetwc(fp) == L'\u306b');        /* Ni */
        assert(fgetwc(fp) == L'\u3061');        /* Ti */
        assert(fgetwc(fp) == L'\u308f');        /* Wa */

        /* push 263A(smile) back */
        assert(ungetwc(L'\u263a', fp));

        /* we support 1 push back wchar_t */
        assert(fgetwc(fp) == L'\u263a');

        /* then fflush */
        r = fflush(fp);
        assert(r == 0);

        /* fllush() clears the all pushed back chars */

        /* can read rest of that */
        fgetws(buf, sizeof(buf), fp);
        assert(wcscmp(buf, L" \u4e16\u754c\n") == 0);
        r = fclose(fp);
        assert(r == 0);
}

void
test_fflush_read6(void)
{
        int      r, c;
        FILE    *fp;

        setup();
        fp = fopen(TMPFILENAME, "r");
        assert(fp != NULL);

        /*
         * https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html
         * .. any characters pushed back onto the stream by ungetc() or ungetwc()
         * that have not subsequently been read from the stream shall be discarded
         * (without further changing the file offset).
         */

        assert(fgetc(fp) == 'H');
        c = getc(fp);
        ungetc(c, fp);  /* push back the character has been read */
        r = fflush(fp);
        assert(r == 0);
        assert(getc(fp) == c);

        fseek(fp, 0, SEEK_SET);
        assert(fgetc(fp) == 'H');
        c = getc(fp);
        ungetc('X', fp); /* push back the character has not been read */
        r = fflush(fp);
        assert(r == 0);
        assert(getc(fp) == 'l');

        r = fclose(fp);
        assert(r == 0);
}

int
main(int argc, char *argv[])
{
        setlocale(LC_ALL, "C.UTF-8");

        test_fflush_read0();
        test_fflush_read1();
        test_fflush_read2();
        test_fflush_read3();
        test_fflush_read4();
        test_fflush_read5();
        test_fflush_read6();

        exit(0);
}