package cz.davza.studentadventure.objects;

import cz.davza.studentadventure.Items.Book;
import cz.davza.studentadventure.Items.EnergyDrink;
import cz.davza.studentadventure.interfaces.IItem;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class ItemCollectionTest {

    private PlayerInventory inventory;
    private IItem book;
    private IItem drink;

    @BeforeEach
    void setUp() {
        inventory = new PlayerInventory(20); // capacity of 20 bulk
        book  = new Book();       // bulk = 3
        drink = new EnergyDrink();// bulk = 2
    }

    // ── Add ──────────────────────────────────────────────────────────

    @Test
    void addItemStoresIt() {
        inventory.Add(book, 1);
        assertNotNull(inventory.GetByItemCode("book"));
    }

    @Test
    void addItemReturnsZeroLeftoverWhenFits() {
        int leftOver = inventory.Add(book, 1);
        assertEquals(0, leftOver);
    }

    @Test
    void addItemDecreasesRemainingCapacity() {
        inventory.Add(book, 1); // bulk 3
        assertEquals(17, inventory.GetRemainingCapacity());
    }

    @Test
    void addMultipleOfSameItemStacksTogether() {
        inventory.Add(book, 2);
        assertEquals(2, inventory.GetByItemCode("book").getAmount());
    }

    @Test
    void addReturnsLeftoverWhenCapacityExceeded() {
        // capacity 20, book bulk 3 → fits 6 (uses 18), 7th overflows
        int leftOver = inventory.Add(book, 7);
        assertEquals(1, leftOver);
    }

    @Test
    void addDifferentItemsTrackSeparately() {
        inventory.Add(book, 1);
        inventory.Add(drink, 1);
        assertNotNull(inventory.GetByItemCode("book"));
        assertNotNull(inventory.GetByItemCode("energy_drink"));
    }

    @Test
    void addZeroItemsDoesNothing() {
        // capacity / bulk = 20/3 = 6, asking for 0 → canInsert = min(0, 6) = 0
        inventory.Add(book, 0);
        assertNull(inventory.GetByItemCode("book"));
        assertEquals(20, inventory.GetRemainingCapacity());
    }

    // ── Remove ───────────────────────────────────────────────────────

    @Test
    void removeReducesStackAmount() {
        inventory.Add(book, 3);
        inventory.Remove("book", 1);
        assertEquals(2, inventory.GetByItemCode("book").getAmount());
    }

    @Test
    void removeRestoresCapacity() {
        inventory.Add(book, 2); // uses 6
        inventory.Remove("book", 1); // frees 3
        assertEquals(17, inventory.GetRemainingCapacity());
    }

    @Test
    void removeEntireStackCleansUpEntry() {
        inventory.Add(book, 1);
        inventory.Remove("book", 1);
        assertNull(inventory.GetByItemCode("book"));
    }

    @Test
    void removeMoreThanStackRemovesAll() {
        inventory.Add(book, 2);
        inventory.Remove("book", 10);
        assertNull(inventory.GetByItemCode("book"));
    }

    @Test
    void removeMissingCodeIsNoOp() {
        assertDoesNotThrow(() -> inventory.Remove("nonexistent", 1));
    }

    @Test
    void removeFullyRestoresCapacityToInitial() {
        inventory.Add(book, 2);
        inventory.Remove("book", 2);
        assertEquals(20, inventory.GetRemainingCapacity());
    }

    // ── GetByItemCode ─────────────────────────────────────────────────

    @Test
    void getByItemCodeReturnsNullForMissingItem() {
        assertNull(inventory.GetByItemCode("book"));
    }

    @Test
    void getByItemCodeReturnsCorrectStack() {
        inventory.Add(drink, 3);
        ItemStack stack = inventory.GetByItemCode("energy_drink");
        assertNotNull(stack);
        assertEquals(3, stack.getAmount());
    }

    // ── Capacity ──────────────────────────────────────────────────────

    @Test
    void getRemainingCapacityStartsAtMax() {
        assertEquals(20, inventory.GetRemainingCapacity());
    }

    @Test
    void getCapacityReturnsInitialSize() {
        assertEquals(20, inventory.GetCapacity());
    }

    // ── Empty ─────────────────────────────────────────────────────────

    @Test
    void emptyRemovesAllItems() {
        inventory.Add(book, 2);
        inventory.Add(drink, 1);
        inventory.Empty();
        assertTrue(inventory.GetItems().isEmpty());
    }

    @Test
    void emptyResetsUsedCapacity() {
        inventory.Add(book, 2);
        inventory.Empty();
        assertEquals(20, inventory.GetRemainingCapacity());
    }
}