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

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>

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

/* Helpers */
static int make_temp_file(char *out_path, size_t out_size) {
    if (out_size < 32) {
        return -1;
    }
    /* Create a template for mkstemp */
    snprintf(out_path, out_size, "/tmp/zlib_gzdopen_ut_%ld_XXXXXX", (long)getpid());
    int fd = mkstemp(out_path);
    return fd;
}

static int write_string_gz(const char *path, const char *s) {
    gzFile g = gzopen(path, "wb");
    if (g == NULL) return -1;
    int w = gzwrite(g, s, (unsigned)strlen(s));
    int zc = gzclose(g);
    if (w <= 0 || zc != Z_OK) return -1;
    return 0;
}

static int read_all_gz(const char *path, char *buf, size_t buf_size, int *out_len) {
    *out_len = 0;
    gzFile g = gzopen(path, "rb");
    if (g == NULL) return -1;
    int total = 0;
    for (;;) {
        int n = gzread(g, buf + total, (unsigned)(buf_size - (size_t)total));
        if (n < 0) {
            gzclose(g);
            return -1;
        }
        if (n == 0) break;
        total += n;
        if ((size_t)total >= buf_size) break;
    }
    int zc = gzclose(g);
    if (zc != Z_OK) return -1;
    *out_len = total;
    return 0;
}

/* Tests */

void test_gzdopen_invalid_fd_returns_null(void) {
    gzFile g = gzdopen(-1, "rb");
    TEST_ASSERT_NULL(g);
}

void test_gzdopen_write_and_close_closes_fd(void) {
    char path[128];
    int fd = make_temp_file(path, sizeof(path));
    TEST_ASSERT_NOT_EQUAL(-1, fd);

    /* Open gzip on provided fd and write some data */
    gzFile g = gzdopen(fd, "wb");
    TEST_ASSERT_NOT_NULL(g);

    const char *msg = "hello world";
    int w = gzwrite(g, msg, (unsigned)strlen(msg));
    TEST_ASSERT_TRUE(w > 0);

    int zc = gzclose(g);
    TEST_ASSERT_EQUAL_INT(Z_OK, zc);

    /* After gzclose, the provided fd should be closed by zlib */
    errno = 0;
    ssize_t wr = write(fd, "X", 1);
    TEST_ASSERT_EQUAL_INT(-1, (int)wr);

    /* Cleanup */
    unlink(path);
}

void test_gzdopen_read_existing_gz_file(void) {
    char path[128];
    int fd_tmp = make_temp_file(path, sizeof(path));
    TEST_ASSERT_NOT_EQUAL(-1, fd_tmp);
    close(fd_tmp);

    const char *payload = "abcdef";
    TEST_ASSERT_EQUAL_INT(0, write_string_gz(path, payload));

    int fd = open(path, O_RDONLY);
    TEST_ASSERT_NOT_EQUAL(-1, fd);

    gzFile g = gzdopen(fd, "rb");
    TEST_ASSERT_NOT_NULL(g);

    char buf[64];
    int total = 0;
    for (;;) {
        int n = gzread(g, buf + total, (unsigned)(sizeof(buf) - (size_t)total));
        TEST_ASSERT_TRUE(n >= 0);
        if (n == 0) break;
        total += n;
        if ((size_t)total >= sizeof(buf)) break;
    }

    TEST_ASSERT_EQUAL_INT((int)strlen(payload), total);
    TEST_ASSERT_EQUAL_INT(0, memcmp(buf, payload, (size_t)total));

    int zc = gzclose(g);
    TEST_ASSERT_EQUAL_INT(Z_OK, zc);

    unlink(path);
}

void test_gzdopen_plus_mode_rejected_fd_not_closed(void) {
    char path[128];
    int fd = make_temp_file(path, sizeof(path));
    TEST_ASSERT_NOT_EQUAL(-1, fd);

    gzFile g = gzdopen(fd, "wb+"); /* '+' is not allowed */
    TEST_ASSERT_NULL(g);

    /* Ensure fd remains open (write should succeed) */
    errno = 0;
    const char c = 'Z';
    ssize_t wr = write(fd, &c, 1);
    TEST_ASSERT_EQUAL_INT(1, (int)wr);

    close(fd);
    unlink(path);
}

void test_gzdopen_append_mode_appends_and_can_be_read_as_concatenated_streams(void) {
    char path[128];
    int fd_tmp = make_temp_file(path, sizeof(path));
    TEST_ASSERT_NOT_EQUAL(-1, fd_tmp);
    close(fd_tmp);

    const char *first = "first";
    const char *second = "second";
    TEST_ASSERT_EQUAL_INT(0, write_string_gz(path, first));

    int fd = open(path, O_WRONLY);
    TEST_ASSERT_NOT_EQUAL(-1, fd);

    gzFile g = gzdopen(fd, "ab");
    TEST_ASSERT_NOT_NULL(g);

    int w = gzwrite(g, second, (unsigned)strlen(second));
    TEST_ASSERT_TRUE(w > 0);
    int zc = gzclose(g);
    TEST_ASSERT_EQUAL_INT(Z_OK, zc);

    char buf[128];
    int len = 0;
    TEST_ASSERT_EQUAL_INT(0, read_all_gz(path, buf, sizeof(buf), &len));
    TEST_ASSERT_EQUAL_INT((int)(strlen(first) + strlen(second)), len);
    TEST_ASSERT_EQUAL_INT(0, memcmp(buf, "firstsecond", (size_t)len));

    unlink(path);
}

void test_gzdopen_invalid_mode_without_r_w_a_returns_null_and_fd_open(void) {
    char path[128];
    int fd = make_temp_file(path, sizeof(path));
    TEST_ASSERT_NOT_EQUAL(-1, fd);

    gzFile g = gzdopen(fd, "q"); /* no r/w/a, should be rejected */
    TEST_ASSERT_NULL(g);

    /* Ensure fd remains open */
    const char c = 'Y';
    ssize_t wr = write(fd, &c, 1);
    TEST_ASSERT_EQUAL_INT(1, (int)wr);

    close(fd);
    unlink(path);
}

/* Test runner */
int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_gzdopen_invalid_fd_returns_null);
    RUN_TEST(test_gzdopen_write_and_close_closes_fd);
    RUN_TEST(test_gzdopen_read_existing_gz_file);
    RUN_TEST(test_gzdopen_plus_mode_rejected_fd_not_closed);
    RUN_TEST(test_gzdopen_append_mode_appends_and_can_be_read_as_concatenated_streams);
    RUN_TEST(test_gzdopen_invalid_mode_without_r_w_a_returns_null_and_fd_open);
    return UNITY_END();
}