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

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

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

/* Helpers */

static char *make_temp_filename(char *buf, size_t buflen) {
    /* Use tmpnam to generate a unique name. */
    if (buf == NULL || buflen < L_tmpnam) return NULL;
    char *res = tmpnam(buf);
    if (res == NULL) return NULL;
    /* Ensure it's a normal C string path in buf */
    /* tmpnam writes into buf when provided */
    return buf;
}

static int write_gzip_file(const char *path, const void *data, unsigned len) {
    gzFile gz = gzopen(path, "wb");
    if (gz == NULL) return -1;
    int written = gzwrite(gz, data, (unsigned)len);
    int close_ret = gzclose(gz);
    if (written != (int)len) return -2;
    if (close_ret != Z_OK) return -3;
    return 0;
}

static int corrupt_file_last_byte(const char *path) {
    FILE *fp = fopen(path, "rb+");
    if (!fp) return -1;
    if (fseek(fp, 0, SEEK_END) != 0) { fclose(fp); return -2; }
    long sz = ftell(fp);
    if (sz <= 0) { fclose(fp); return -3; }
    if (fseek(fp, -1L, SEEK_END) != 0) { fclose(fp); return -4; }
    int c = fgetc(fp);
    if (c == EOF) { fclose(fp); return -5; }
    if (fseek(fp, -1L, SEEK_END) != 0) { fclose(fp); return -6; }
    if (fputc((c ^ 0xFF) & 0xFF, fp) == EOF) { fclose(fp); return -7; }
    if (fclose(fp) != 0) return -8;
    return 0;
}

/* Tests */

void test_gzclearerr_null_does_not_crash(void) {
    /* Just ensure it doesn't crash */
    gzclearerr(NULL);
    TEST_ASSERT_TRUE(1); /* If we reached here, no crash */
}

void test_gzclearerr_clears_eof_and_past_after_read_past_end(void) {
    char path[L_tmpnam];
    TEST_ASSERT_NOT_NULL(make_temp_filename(path, sizeof(path)));

    const char *payload = "Hello, world!";
    TEST_ASSERT_EQUAL_INT(0, write_gzip_file(path, payload, (unsigned)strlen(payload)));

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

    /* Read until EOF using gzgetc to ensure we step past end and set 'past' */
    int ch;
    while ((ch = gzgetc(gz)) != -1) {
        /* consume */
    }

    /* At this point, either EOF or error; for a valid gzip, should be EOF */
    int errnum_before = Z_OK;
    const char *msg_before = gzerror(gz, &errnum_before);
    (void)msg_before; /* not strictly needed */
    TEST_ASSERT_EQUAL_INT(Z_OK, errnum_before); /* should be OK at EOF */
    TEST_ASSERT_EQUAL_INT(1, gzeof(gz)); /* 'past' should be true after EOF */

    /* Now clear error/eof */
    gzclearerr(gz);

    int errnum_after = -1;
    const char *msg_after = gzerror(gz, &errnum_after);
    TEST_ASSERT_EQUAL_INT(Z_OK, errnum_after);
    TEST_ASSERT_NOT_NULL(msg_after);
    TEST_ASSERT_EQUAL_STRING("", msg_after);
    TEST_ASSERT_EQUAL_INT(0, gzeof(gz)); /* eof/past cleared */

    TEST_ASSERT_EQUAL_INT(Z_OK, gzclose(gz));
    remove(path);
}

void test_gzclearerr_clears_error_and_message_after_crc_error(void) {
    char path[L_tmpnam];
    TEST_ASSERT_NOT_NULL(make_temp_filename(path, sizeof(path)));

    const char *payload = "This will be corrupted.";
    TEST_ASSERT_EQUAL_INT(0, write_gzip_file(path, payload, (unsigned)strlen(payload)));

    /* Corrupt the file to induce a CRC/data error on read */
    TEST_ASSERT_EQUAL_INT(0, corrupt_file_last_byte(path));

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

    /* Read until error */
    unsigned char buf[64];
    int ret;
    int saw_error = 0;
    while ((ret = gzread(gz, buf, sizeof(buf))) > 0) {
        /* consume */
    }
    if (ret == -1) {
        saw_error = 1;
    }
    TEST_ASSERT_EQUAL_INT(1, saw_error);

    int errnum_before = Z_OK;
    const char *msg_before = gzerror(gz, &errnum_before);
    TEST_ASSERT_NOT_NULL(msg_before);
    TEST_ASSERT_NOT_EQUAL(Z_OK, errnum_before);
    TEST_ASSERT_TRUE(msg_before[0] != '\0'); /* should have a message */

    /* Now clear error */
    gzclearerr(gz);

    int errnum_after = -1;
    const char *msg_after = gzerror(gz, &errnum_after);
    TEST_ASSERT_EQUAL_INT(Z_OK, errnum_after);
    TEST_ASSERT_NOT_NULL(msg_after);
    TEST_ASSERT_EQUAL_STRING("", msg_after);

    /* gzeof() should be 0; error cleared and not at EOF */
    TEST_ASSERT_EQUAL_INT(0, gzeof(gz));

    /* Cleanup */
    TEST_ASSERT_EQUAL_INT(Z_OK, gzclose(gz));
    remove(path);
}

void test_gzclearerr_on_write_mode_noop_and_ok(void) {
    char path[L_tmpnam];
    TEST_ASSERT_NOT_NULL(make_temp_filename(path, sizeof(path)));

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

    /* Ensure starting state is OK */
    int errnum_before = -1;
    const char *msg_before = gzerror(gz, &errnum_before);
    TEST_ASSERT_EQUAL_INT(Z_OK, errnum_before);
    TEST_ASSERT_NOT_NULL(msg_before);

    /* Call gzclearerr; in write mode it should simply ensure err is Z_OK (no eof flags to clear) */
    gzclearerr(gz);

    int errnum_after = -1;
    const char *msg_after = gzerror(gz, &errnum_after);
    TEST_ASSERT_EQUAL_INT(Z_OK, errnum_after);
    TEST_ASSERT_NOT_NULL(msg_after);
    TEST_ASSERT_TRUE(msg_after[0] == '\0' || msg_after == msg_before);

    /* Cleanup */
    TEST_ASSERT_EQUAL_INT(Z_OK, gzclose(gz));
    remove(path);
}

/* Main */
int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_gzclearerr_null_does_not_crash);
    RUN_TEST(test_gzclearerr_clears_eof_and_past_after_read_past_end);
    RUN_TEST(test_gzclearerr_clears_error_and_message_after_crc_error);
    RUN_TEST(test_gzclearerr_on_write_mode_noop_and_ok);
    return UNITY_END();
}