#include "unity/unity.h"
#include "zlib.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

/* Unity setup/teardown */
void setUp(void) {
    /* Setup code here, or leave empty */
}
void tearDown(void) {
    /* Cleanup code here, or leave empty */
}

/* Helper: create a unique temporary filename with .gz suffix.
   Returns a heap-allocated string that must be freed by the caller. */
static char* make_temp_gz_path(void) {
    char base[L_tmpnam];
    char fallback[64];
    char *result;
    if (tmpnam(base) == NULL) {
        /* Fallback: use time + rand */
        srand((unsigned)time(NULL));
        snprintf(fallback, sizeof(fallback), "tmp_gzeof_%lu_%u",
                 (unsigned long)time(NULL), (unsigned)rand());
        snprintf(base, sizeof(base), "%s", fallback);
    }
    size_t len = strlen(base) + 3; /* + ".gz" and null */
    result = (char*)malloc(len + 1);
    if (!result) return NULL;
    snprintf(result, len + 1, "%s.gz", base);
    return result;
}

/* Helper: write content to a gzip file (overwrites if exists). */
static void write_gz_file(const char *path, const void *data, unsigned len) {
    gzFile f = gzopen(path, "wb");
    TEST_ASSERT_MESSAGE(f != NULL, "gzopen for write failed");
    int wrote = gzwrite(f, data, len);
    TEST_ASSERT_EQUAL_INT((int)len, wrote);
    int rc = gzclose(f);
    TEST_ASSERT_EQUAL_INT(0, rc);
}

/* Test: gzeof(NULL) returns 0 */
static void test_gzeof_null_returns_zero(void) {
    TEST_ASSERT_EQUAL_INT(0, gzeof(NULL));
}

/* Test: gzeof on write-mode handle is always 0 */
static void test_gzeof_write_mode_returns_zero(void) {
    char *path = make_temp_gz_path();
    TEST_ASSERT_NOT_NULL(path);

    gzFile f = gzopen(path, "wb");
    TEST_ASSERT_NOT_NULL(f);

    /* Before writing */
    TEST_ASSERT_EQUAL_INT(0, gzeof(f));

    /* After writing some data */
    const char *msg = "writing some data";
    int wrote = gzwrite(f, msg, (unsigned)strlen(msg));
    TEST_ASSERT_EQUAL_INT((int)strlen(msg), wrote);
    TEST_ASSERT_EQUAL_INT(0, gzeof(f));

    /* Close and cleanup */
    TEST_ASSERT_EQUAL_INT(0, gzclose(f));
    remove(path);
    free(path);
}

/* Test: gzeof on read-mode remains 0 until reading past end */
static void test_gzeof_read_mode_past_end_behavior(void) {
    char *path = make_temp_gz_path();
    TEST_ASSERT_NOT_NULL(path);

    const char *content = "hello";
    write_gz_file(path, content, (unsigned)strlen(content));

    gzFile f = gzopen(path, "rb");
    TEST_ASSERT_NOT_NULL(f);

    /* Before any read */
    TEST_ASSERT_EQUAL_INT(0, gzeof(f));

    /* Partial read */
    char buf[3];
    int n = gzread(f, buf, 3);
    TEST_ASSERT_EQUAL_INT(3, n);
    TEST_ASSERT_EQUAL_INT(0, gzeof(f)); /* not past end yet */

    /* Read remaining bytes (2 more) */
    char buf2[4] = {0};
    int n2 = gzread(f, buf2, 2);
    TEST_ASSERT_EQUAL_INT(2, n2);

    /* Now attempt to read one more byte to go past end */
    int c = gzgetc(f);
    TEST_ASSERT_EQUAL_INT(-1, c);
    TEST_ASSERT_NOT_EQUAL(0, gzeof(f)); /* now past end */

    /* Cleanup */
    TEST_ASSERT_EQUAL_INT(0, gzclose(f));
    remove(path);
    free(path);
}

/* Test: gzclearerr resets gzeof from non-zero back to zero */
static void test_gzeof_cleared_by_gzclearerr(void) {
    char *path = make_temp_gz_path();
    TEST_ASSERT_NOT_NULL(path);

    const char *content = "abc";
    write_gz_file(path, content, (unsigned)strlen(content));

    gzFile f = gzopen(path, "rb");
    TEST_ASSERT_NOT_NULL(f);

    /* Consume all data */
    char buf[8];
    int n = gzread(f, buf, (unsigned)strlen(content));
    TEST_ASSERT_EQUAL_INT((int)strlen(content), n);

    /* Force read past end */
    TEST_ASSERT_EQUAL_INT(-1, gzgetc(f));
    TEST_ASSERT_NOT_EQUAL(0, gzeof(f));

    /* Clear and check */
    gzclearerr(f);
    TEST_ASSERT_EQUAL_INT(0, gzeof(f));

    /* Reading past end again makes it non-zero again */
    TEST_ASSERT_EQUAL_INT(-1, gzgetc(f));
    TEST_ASSERT_NOT_EQUAL(0, gzeof(f));

    TEST_ASSERT_EQUAL_INT(0, gzclose(f));
    remove(path);
    free(path);
}

/* Test: gzrewind resets so that gzeof becomes 0 again */
static void test_gzeof_reset_by_gzrewind(void) {
    char *path = make_temp_gz_path();
    TEST_ASSERT_NOT_NULL(path);

    const char *content = "ABCDEFG";
    write_gz_file(path, content, (unsigned)strlen(content));

    gzFile f = gzopen(path, "rb");
    TEST_ASSERT_NOT_NULL(f);

    /* Read to end */
    char buf[16];
    int n = gzread(f, buf, sizeof(buf));
    TEST_ASSERT_EQUAL_INT((int)strlen(content), n);

    /* Force read past end so gzeof is non-zero */
    TEST_ASSERT_EQUAL_INT(-1, gzgetc(f));
    TEST_ASSERT_NOT_EQUAL(0, gzeof(f));

    /* Rewind and confirm gzeof reset */
    TEST_ASSERT_EQUAL_INT(0, gzrewind(f));
    TEST_ASSERT_EQUAL_INT(0, gzeof(f));

    /* Close and cleanup */
    TEST_ASSERT_EQUAL_INT(0, gzclose(f));
    remove(path);
    free(path);
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_gzeof_null_returns_zero);
    RUN_TEST(test_gzeof_write_mode_returns_zero);
    RUN_TEST(test_gzeof_read_mode_past_end_behavior);
    RUN_TEST(test_gzeof_cleared_by_gzclearerr);
    RUN_TEST(test_gzeof_reset_by_gzrewind);
    return UNITY_END();
}