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

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

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

/* Helper to fill a buffer with a deterministic pattern */
static void fill_pattern(unsigned char *buf, size_t len) {
    for (size_t i = 0; i < len; i++) {
        buf[i] = (unsigned char)((i * 3u + 7u) & 0xFFu);
    }
}

/* Tests */

void test_crc32_z_null_buf_returns_zero(void) {
    unsigned long r1 = crc32_z(1234UL, NULL, 0);
    TEST_ASSERT_EQUAL_UINT32(0u, (uint32_t)r1);

    unsigned long r2 = crc32_z(0UL, NULL, 5);
    TEST_ASSERT_EQUAL_UINT32(0u, (uint32_t)r2);

    unsigned long r3 = crc32_z(0xFFFFFFFFUL, NULL, 1000);
    TEST_ASSERT_EQUAL_UINT32(0u, (uint32_t)r3);
}

void test_crc32_z_empty_input_returns_initial(void) {
    const unsigned char dummy = 0xAA; /* not used, just to have a pointer if needed */
    (void)dummy;

    unsigned long seeds[] = {0UL, 1UL, 0xFFFFFFFFUL, 0xDEADBEEFUL};
    for (size_t i = 0; i < sizeof(seeds)/sizeof(seeds[0]); i++) {
        unsigned long init = seeds[i];
        unsigned long r = crc32_z(init, (const unsigned char *)"", 0);
        TEST_ASSERT_EQUAL_UINT32((uint32_t)init, (uint32_t)r);
    }
}

void test_crc32_z_known_vector_123456789(void) {
    const unsigned char *msg = (const unsigned char *)"123456789";
    unsigned long r = crc32_z(0UL, msg, 9);
    TEST_ASSERT_EQUAL_HEX32(0xCBF43926u, (uint32_t)r);
}

void test_crc32_z_known_vector_quick_brown(void) {
    const char *s = "The quick brown fox jumps over the lazy dog";
    unsigned long r = crc32_z(0UL, (const unsigned char *)s, (z_size_t)strlen(s));
    TEST_ASSERT_EQUAL_HEX32(0x414FA339u, (uint32_t)r);
}

void test_crc32_z_incremental_vs_one_shot_large(void) {
    const size_t total = 1000;
    unsigned char *buf = (unsigned char *)malloc(total);
    TEST_ASSERT_NOT_NULL(buf);
    fill_pattern(buf, total);

    /* One-shot */
    unsigned long one = crc32_z(0UL, buf, (z_size_t)total);

    /* Incremental: split into uneven segments */
    unsigned long inc = 0UL;
    inc = crc32_z(inc, buf, 13);
    inc = crc32_z(inc, buf + 13, 257);
    inc = crc32_z(inc, buf + 270, 3);
    inc = crc32_z(inc, buf + 273, (z_size_t)(total - 273));

    TEST_ASSERT_EQUAL_UINT32((uint32_t)one, (uint32_t)inc);

    free(buf);
}

void test_crc32_z_nonzero_initial_seed_incremental(void) {
    const size_t total = 250;
    unsigned char *buf = (unsigned char *)malloc(total);
    TEST_ASSERT_NOT_NULL(buf);
    fill_pattern(buf, total);

    unsigned long init = 0xA5A5A5A5UL;

    /* One-shot with non-zero initial seed */
    unsigned long one = crc32_z(init, buf, (z_size_t)total);

    /* Incremental, small chunks */
    unsigned long inc = init;
    size_t pos = 0;
    while (pos < total) {
        size_t chunk = 7;
        if (chunk > total - pos) chunk = total - pos;
        inc = crc32_z(inc, buf + pos, (z_size_t)chunk);
        pos += chunk;
    }

    TEST_ASSERT_EQUAL_UINT32((uint32_t)one, (uint32_t)inc);

    free(buf);
}

void test_crc32_z_input_buffer_unchanged(void) {
    const size_t len = 128;
    unsigned char *buf = (unsigned char *)malloc(len);
    unsigned char *copy = (unsigned char *)malloc(len);
    TEST_ASSERT_NOT_NULL(buf);
    TEST_ASSERT_NOT_NULL(copy);

    fill_pattern(buf, len);
    memcpy(copy, buf, len);

    (void)crc32_z(0UL, buf, (z_size_t)len);

    TEST_ASSERT_EQUAL_UINT8_ARRAY(copy, buf, len);

    free(copy);
    free(buf);
}

void test_crc32_z_unaligned_buffer(void) {
    /* Create a buffer with an extra headroom to allow unaligned starts */
    const size_t total = 260;
    unsigned char *raw = (unsigned char *)malloc(total + 8);
    TEST_ASSERT_NOT_NULL(raw);
    unsigned char *buf = raw + 3; /* create an unaligned pointer intentionally */

    fill_pattern(buf, total);

    /* Compute CRC on slice [1 .. 200] from unaligned base */
    const size_t offset = 1;
    const size_t len = 200;
    unsigned long r_unaligned = crc32_z(0UL, buf + offset, (z_size_t)len);

    /* Copy the same slice to a separate, aligned buffer and compute CRC */
    unsigned char *copy = (unsigned char *)malloc(len);
    TEST_ASSERT_NOT_NULL(copy);
    memcpy(copy, buf + offset, len);
    unsigned long r_aligned = crc32_z(0UL, copy, (z_size_t)len);

    TEST_ASSERT_EQUAL_UINT32((uint32_t)r_aligned, (uint32_t)r_unaligned);

    free(copy);
    free(raw);
}

/* main */
int main(void) {
    UNITY_BEGIN();

    RUN_TEST(test_crc32_z_null_buf_returns_zero);
    RUN_TEST(test_crc32_z_empty_input_returns_initial);
    RUN_TEST(test_crc32_z_known_vector_123456789);
    RUN_TEST(test_crc32_z_known_vector_quick_brown);
    RUN_TEST(test_crc32_z_incremental_vs_one_shot_large);
    RUN_TEST(test_crc32_z_nonzero_initial_seed_incremental);
    RUN_TEST(test_crc32_z_input_buffer_unchanged);
    RUN_TEST(test_crc32_z_unaligned_buffer);

    return UNITY_END();
}