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

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

/* Wrapper provided by the module (available when built with ZLIB_DEBUG) */
extern void test_check_match(deflate_state *s, IPos start, IPos match, int length);

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

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

/* Helper to initialize a deflate stream and return its internal state */
static deflate_state* init_state(z_stream *strm) {
    memset(strm, 0, sizeof(*strm));
    int ret = deflateInit(strm, Z_DEFAULT_COMPRESSION);
    TEST_ASSERT_EQUAL_INT(Z_OK, ret);
    TEST_ASSERT_NOT_NULL(strm->state);
    return (deflate_state*)strm->state;
}

/* Test 1: Basic equal regions within the window should pass without error */
void test_check_match_basic_equal(void) {
    z_stream strm;
    deflate_state *s = init_state(&strm);

    /* Choose indices well within the allocated window */
    const IPos match = 50;
    const IPos start = 100;
    const int length = 9;
    const unsigned char seq[] = { 'H','e','l','l','o','Z','l','i','b' };

    /* Ensure window is allocated and large enough, then place equal data */
    TEST_ASSERT_NOT_NULL(s->window);
    memcpy(s->window + match, seq, length);
    memcpy(s->window + start, seq, length);

    /* Should not abort (valid match) */
    test_check_match(s, start, match, length);

    TEST_ASSERT_EQUAL_INT(Z_OK, deflateEnd(&strm));
}

/* Test 2: Special case when match == (IPos)-1; compare length-1 bytes after increment */
void test_check_match_match_minus_one_case(void) {
    z_stream strm;
    deflate_state *s = init_state(&strm);

    /* We will call with match == -1, so check_match will compare:
       back = window[0 .. len-2]
       here = window[start+1 .. start+len-1]  */
    const IPos match = (IPos)-1;
    const IPos start = 10;
    const int length = 6; /* check_match will compare length-1 bytes == 5 */

    const unsigned char pattern[] = { 1, 2, 3, 4, 5 };
    TEST_ASSERT_NOT_NULL(s->window);

    /* Set the two compared regions equal according to the function's logic */
    memcpy(s->window + 0, pattern, sizeof(pattern));                  /* back (after ++), indexes 0..4 */
    memcpy(s->window + (start + 1), pattern, sizeof(pattern));        /* here (after ++), indexes 11..15 */

    /* Should not abort (valid match given the semantics) */
    test_check_match(s, start, match, length);

    TEST_ASSERT_EQUAL_INT(Z_OK, deflateEnd(&strm));
}

/* Test 3: Boundary case with length == 1 */
void test_check_match_length_one(void) {
    z_stream strm;
    deflate_state *s = init_state(&strm);

    const IPos match = 42;
    const IPos start = 1234;
    const int length = 1;

    TEST_ASSERT_NOT_NULL(s->window);

    /* Ensure single byte equality */
    s->window[match] = (Byte)'Q';
    s->window[start] = (Byte)'Q';

    /* Should not abort */
    test_check_match(s, start, match, length);

    TEST_ASSERT_EQUAL_INT(Z_OK, deflateEnd(&strm));
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_check_match_basic_equal);
    RUN_TEST(test_check_match_match_minus_one_case);
    RUN_TEST(test_check_match_length_one);
    return UNITY_END();
}