package cz.davza.studentadventure.objects;

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

/**
 * Tests ItemCollectionBase behaviour through PlayerInventory.
 * Inventory capacity = 20 bulk units.
 * Book bulk = 3, EnergyDrink bulk = 2, StickyNote bulk = 1.
 */
class ItemCollectionBaseTest {

    private PlayerInventory inventory;

    @BeforeEach
    void setUp() {
        inventory = new PlayerInventory(20);
    }

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

    @Test
    void addItemIncreasesUsedCapacity() {
        inventory.Add(new Book(), 1);
        assertEquals(20 - 3, inventory.GetRemainingCapacity());
    }

    @Test
    void addMultipleItemsStackUnderSameKey() {
        inventory.Add(new Book(), 2);
        ItemStack stack = inventory.GetByItemCode("book");
        assertNotNull(stack);
        assertEquals(2, stack.getAmount());
    }

    @Test
    void addReturnsZeroWhenAllFit() {
        int leftOver = inventory.Add(new Book(), 2); // costs 6 bulk, capacity 20
        assertEquals(0, leftOver);
    }

    @Test
    void addReturnsLeftoverWhenCapacityExceeded() {
        // capacity 20, book bulk 3 → can fit 6 books (18 bulk), 7th won't fit
        int leftOver = inventory.Add(new Book(), 7);
        assertEquals(1, leftOver);
    }

    @Test
    void addToExistingStackMergesCorrectly() {
        inventory.Add(new Book(), 2);
        inventory.Add(new Book(), 1);
        ItemStack stack = inventory.GetByItemCode("book");
        assertEquals(3, stack.getAmount());
    }

    @Test
    void addZeroBulkItemAlwaysFits() {
        // StickyNote has bulk 1 actually — test with a full inventory of high-bulk items
        // fill to 18 bulk (6 books), then add sticky note (bulk 1) — still 2 bulk remaining
        inventory.Add(new Book(), 6);
        int leftOver = inventory.Add(new StickyNote("test"), 1);
        assertEquals(0, leftOver);
    }

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

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

    @Test
    void removeDecrementsUsedCapacity() {
        inventory.Add(new Book(), 2); // 6 bulk used
        inventory.Remove("book", 1); // 3 bulk freed
        assertEquals(20 - 3, inventory.GetRemainingCapacity());
    }

    @Test
    void removeEntireStackClearsEntry() {
        inventory.Add(new Book(), 2);
        inventory.Remove("book", 2);
        assertNull(inventory.GetByItemCode("book"));
    }

    @Test
    void removeMoreThanStackSizeClearsEntry() {
        inventory.Add(new Book(), 1);
        inventory.Remove("book", 99);
        assertNull(inventory.GetByItemCode("book"));
    }

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

    @Test
    void removeRestoresCapacityCorrectly() {
        inventory.Add(new EnergyDrink(), 3); // 6 bulk used
        inventory.Remove("energy_drink", 3); // all removed
        assertEquals(20, inventory.GetRemainingCapacity());
    }

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

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

    @Test
    void getByItemCodeReturnsCorrectStack() {
        inventory.Add(new Book(), 2);
        ItemStack stack = inventory.GetByItemCode("book");
        assertNotNull(stack);
        assertEquals("book", stack.getItem().getCode());
    }

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

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

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

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

    @Test
    void emptyClearsAllItems() {
        inventory.Add(new Book(), 2);
        inventory.Add(new EnergyDrink(), 1);
        inventory.Empty();
        assertNull(inventory.GetByItemCode("book"));
        assertNull(inventory.GetByItemCode("energy_drink"));
    }

    @Test
    void emptyResetsUsedCapacity() {
        inventory.Add(new Book(), 3);
        inventory.Empty();
        assertEquals(20, inventory.GetRemainingCapacity());
    }

    // ── GetItems ─────────────────────────────────────────────────────────────

    @Test
    void getItemsReturnsOnlyOccupiedEntries() {
        inventory.Add(new Book(), 1);
        inventory.Add(new EnergyDrink(), 1);
        assertEquals(2, inventory.GetItems().size());
    }

    @Test
    void getItemsIsEmptyWhenInventoryEmpty() {
        assertTrue(inventory.GetItems().isEmpty());
    }
}