/*
 * filetest — exercise minimal FILE * stream API (fopen/fclose/fputs/
 * fgets/fread/fwrite/fseek/ftell/feof + stdin/stdout/stderr).
 *
 * Steps:
 *   1. fopen("FILE.TXT","w"), fputs+fputc lines, fclose.
 *   2. fopen("FILE.TXT","r"), fgets each line, fclose.
 *   3. fopen("r"), fread block, fseek, ftell, feof, fread again.
 *   4. fputs to stdout (sanity check console pseudo-stream).
 */

#include <stdio.h>
#include <string.h>
#include <errno.h>

int main(void)
{
    const char *path = "FILE.TXT";

    /* ----- 1. Write via fputs + fputc ----- */
    {
        FILE *fp = fopen(path, "w");
        if (!fp) {
            printf("fopen(w) failed: errno=%d (%s)\n", errno, strerror(errno));
            return 1;
        }
        fputs("Hello from FILE*\n", fp);
        fputs("Second line via fputs\n", fp);
        for (int i = '0'; i <= '9'; i++) fputc(i, fp);
        fputc('\n', fp);
        if (fclose(fp) != 0) puts("fclose: error");
    }

    /* ----- 2. Read via fgets ----- */
    {
        FILE *fp = fopen(path, "r");
        if (!fp) {
            printf("fopen(r) failed: errno=%d\n", errno);
            return 1;
        }
        char buf[128];
        int n = 0;
        while (fgets(buf, sizeof buf, fp)) {
            printf("  line %d: %s", ++n, buf);
            if (buf[strlen(buf)-1] != '\n') putchar('\n');
        }
        printf("  total lines: %d, feof=%d\n", n, feof(fp));
        fclose(fp);
    }

    /* ----- 3. fread / fseek / ftell ----- */
    {
        FILE *fp = fopen(path, "r");
        if (!fp) return 1;
        char buf[16];
        size_t got = fread(buf, 1, 16, fp);
        printf("  fread(16) -> %u bytes, ftell=%ld\n",
               (unsigned)got, ftell(fp));
        if (fseek(fp, 0L, SEEK_END) == 0) {
            printf("  file size via fseek(END)+ftell = %ld\n", ftell(fp));
        }
        rewind(fp);
        printf("  rewind: ftell=%ld, feof=%d\n", ftell(fp), feof(fp));
        fclose(fp);
    }

    /* ----- 4. Console pseudo-streams ----- */
    fputs("  fputs to stdout works\n", stdout);
    fputs("  fputs to stderr works\n", stderr);
    fputc('!', stdout); fputc('\n', stdout);

    puts("filetest done.");
    return 0;
}