#include "test_utils.h"

static int test_lseek(const char *path)
{
    printf("\n=== test_lseek ===\n");

    int fd = open(path, O_CREAT | O_RDWR | O_TRUNC, 0644);
    if (fd < 0) { perror("open"); return 1; }

    const char *alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    if (write(fd, alpha, 26) != 26) { perror("write"); return 2; }
    printf("write 26 bytes: %s\n", alpha);

    off_t pos = lseek(fd, 0, SEEK_SET);
    printf("lseek SEEK_SET 0 -> %ld\n", (long)pos);
    char buf[32] = {0};
    ssize_t r = read(fd, buf, 5);
    printf("read 5 bytes: %.*s  (expect: ABCDE)\n", (int)r, buf);

    pos = lseek(fd, 3, SEEK_CUR);
    printf("lseek SEEK_CUR +3 -> %ld\n", (long)pos);
    memset(buf, 0, sizeof(buf));
    r = read(fd, buf, 5);
    printf("read 5 bytes: %.*s  (expect: IJKLM)\n", (int)r, buf);

    pos = lseek(fd, -5, SEEK_END);
    printf("lseek SEEK_END -5 -> %ld\n", (long)pos);
    memset(buf, 0, sizeof(buf));
    r = read(fd, buf, 10);
    printf("read %zd bytes: %.*s  (expect: VWXYZ)\n", r, (int)r, buf);

    pos = lseek(fd, 30, SEEK_SET);
    printf("lseek SEEK_SET 30 -> %ld\n", (long)pos);
    if (write(fd, "!", 1) != 1) { perror("write hole"); return 3; }

    lseek(fd, 26, SEEK_SET);
    memset(buf, 0xAA, sizeof(buf));
    r = read(fd, buf, 5);
    printf("read hole+1: %zd bytes, hole[0]=%02X hole[1]=%02X hole[2]=%02X "
           "hole[3]=%02X last='%c'  (expect: 00 00 00 00 '!')\n",
           r, (unsigned char)buf[0], (unsigned char)buf[1],
           (unsigned char)buf[2], (unsigned char)buf[3], buf[4]);

    close(fd);
    unlink(path);
    return 0;
}

int main(int argc, char **argv)
{
    char path[PATH_MAX];
    make_path(path, sizeof(path), argc >= 2 ? argv[1] : NULL, "file.dat");
    int rc = test_lseek(path);
    return report_result("test_lseek", rc);
}