#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "numbers.h"

/*
 * Unit-Tests für createNumbers und getDuplicate:
 *  - createNumbers liefert ein gültiges Array
 *  - alle Zahlen liegen im Bereich [1, 2*len]
 *  - genau eine Zahl kommt doppelt vor
 *  - getDuplicate findet genau diese doppelte Zahl
 *  - Fehlerfälle (NULL-Pointer, zu kleine Länge)
 */

static void check_numbers_array(unsigned int *numbers, unsigned int len)
{
    unsigned int maxValue = 2 * len;
    unsigned int *counts;
    unsigned int i;
    unsigned int duplicatesCount = 0;

    assert(numbers != NULL);

    counts = (unsigned int *)calloc(maxValue + 1, sizeof(unsigned int));
    assert(counts != NULL);

    // Werte zählen und Bereich prüfen
    for (i = 0; i < len; ++i)
    {
        unsigned int v = numbers[i];
        assert(v >= 1 && v <= maxValue);
        counts[v]++;
    }

    // Prüfen: genau eine Zahl kommt zweimal vor, alle anderen höchstens einmal
    for (i = 1; i <= maxValue; ++i)
    {
        if (counts[i] == 2)
            duplicatesCount++;
        else
            assert(counts[i] == 0 || counts[i] == 1);
    }

    assert(duplicatesCount == 1);

    free(counts);
}

static void test_createNumbers_and_getDuplicate(unsigned int len)
{
    printf("test_createNumbers_and_getDuplicate(len=%u)...\n", len);

    unsigned int *numbers = createNumbers(len);
    assert(numbers != NULL);

    // Arraystruktur überprüfen
    check_numbers_array(numbers, len);

    // Nochmal zählen, um das Duplikat zu kennen
    unsigned int maxValue = 2 * len;
    unsigned int *counts = (unsigned int *)calloc(maxValue + 1, sizeof(unsigned int));
    assert(counts != NULL);

    for (unsigned int i = 0; i < len; ++i)
    {
        unsigned int v = numbers[i];
        counts[v]++;
    }

    unsigned int expectedDuplicate = 0;
    for (unsigned int v = 1; v <= maxValue; ++v)
    {
        if (counts[v] == 2)
        {
            expectedDuplicate = v;
            break;
        }
    }
    assert(expectedDuplicate != 0);

    // getDuplicate testen
    unsigned int found = getDuplicate(numbers, len);
    assert(found == expectedDuplicate);

    free(counts);
    free(numbers);

    printf("...OK\n");
}

static void test_getDuplicate_error_cases(void)
{
    printf("test_getDuplicate_error_cases...\n");

    // NULL-Array
    unsigned int dup = getDuplicate(NULL, 10);
    assert(dup == 0);

    // Länge < 2
    unsigned int dummy[1] = {42};
    dup = getDuplicate(dummy, 1);
    assert(dup == 0);

    printf("...OK\n");
}

int main(void)
{
    printf("Running numbers unit tests...\n\n");

    // Typische Testfälle mit verschiedenen Längen
    test_createNumbers_and_getDuplicate(5);
    test_createNumbers_and_getDuplicate(10);
    test_createNumbers_and_getDuplicate(20);

    // Fehlerfälle
    test_getDuplicate_error_cases();

    printf("\nAll numbers tests passed.\n");
    return 0;
}