Add inventory.

src/item/CMakeLists.txt

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+# Copyright (c) 2025 Dominic Masters
+# 
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+# Sources
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    item.c
+    inventory.c
+)

src/item/inventory.c

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+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "inventory.h"
+#include "util/memory.h"
+#include "assert/assert.h"
+
+void inventoryInit(
+  inventory_t* inventory,
+  inventorystack_t* storage,
+  uint8_t storageSize
+) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(storage, "Storage pointer is NULL.");
+  assertTrue(storageSize > 0, "Storage size must be greater than zero.");
+
+  inventory->storage = storage;
+  inventory->storageSize = storageSize;
+
+  // Zero item ids.
+  memoryZero(inventory->storage, sizeof(inventorystack_t) * storageSize);
+}
+
+bool_t inventoryItemExists(const inventory_t *inventory, const itemid_t item) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(inventory->storage, "Storage pointer is NULL.");
+  assertTrue(inventory->storageSize > 0, "Storage too small.");
+  assertTrue(item != ITEM_ID_NULL, "Item ID cannot be ITEM_ID_NULL.");
+  
+  inventorystack_t *stack = inventory->storage;
+  inventorystack_t *end = stack + inventory->storageSize;
+  do {
+    if(stack->item == ITEM_ID_NULL) break;
+    if(stack->item != item) continue;
+    assertTrue(stack->quantity > 0, "Item has quantity zero.");
+    return true;
+  } while(++stack < end);
+
+  return false;
+}
+
+void inventorySet(
+  inventory_t *inventory,
+  const itemid_t item,
+  const uint8_t quantity
+) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(inventory->storage, "Storage pointer is NULL.");
+  assertTrue(inventory->storageSize > 0, "Storage too small.");
+  assertTrue(item != ITEM_ID_NULL, "Item ID cannot be ITEM_ID_NULL.");
+
+  // If quantity 0, remove.
+  if(quantity == 0) return inventoryRemove(inventory, item);
+
+  // Search for existing stack.
+  inventorystack_t *stack = inventory->storage;
+  inventorystack_t *end = stack + inventory->storageSize;
+  do {
+    // Not in inventory yet, add as new stack.
+    if(stack->item == ITEM_ID_NULL) {
+      stack->item = item;
+      stack->quantity = quantity;
+      return;
+    }
+
+    // Not the stack we're looking for.
+    if(stack->item != item) continue;
+
+    // Update existing stack.
+    stack->quantity = quantity;
+    return;
+  } while(++stack < end);
+
+  // No space in the inventory.
+  assertUnreachable("Inventory is full, cannot set more items.");
+}
+
+void inventoryAdd(
+  inventory_t *inventory,
+  const itemid_t item,
+  const uint8_t quantity
+) {
+  uint8_t current = inventoryGetCount(inventory, item);
+  uint16_t newQuantity = (uint16_t)current + (uint16_t)quantity;
+
+  assertTrue(
+    newQuantity <= UINT8_MAX,
+    "Cannot add item, would overflow maximum quantity."
+  );
+
+  inventorySet(inventory, item, (uint8_t)newQuantity);
+}
+
+void inventoryRemove(inventory_t *inventory, const itemid_t item) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(inventory->storage, "Storage pointer is NULL.");
+  assertTrue(inventory->storageSize > 0, "Storage too small.");
+  assertTrue(item != ITEM_ID_NULL, "Item ID cannot be ITEM_ID_NULL.");
+
+  inventorystack_t *stack = inventory->storage;
+  inventorystack_t *end = stack + inventory->storageSize;
+
+  // Search for existing stack.
+  do {
+    // End of inventory, item not present.
+    if(stack->item == ITEM_ID_NULL) break;
+
+    // Not matching stack.
+    if(stack->item != item) continue;
+
+    // Match found, shift everything else down
+    memoryMove(stack, stack + 1, end - (stack + 1));
+
+    // Clear last stack.
+    inventorystack_t *last = end - 1;
+    last->item = ITEM_ID_NULL;
+
+    break;
+  } while(++stack < end);
+}
+
+uint8_t inventoryGetCount(const inventory_t *inventory, const itemid_t item) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(inventory->storage, "Storage pointer is NULL.");
+  assertTrue(inventory->storageSize > 0, "Storage too small.");
+  assertTrue(item != ITEM_ID_NULL, "Item ID cannot be ITEM_ID_NULL.");
+
+  inventorystack_t *stack = inventory->storage;
+  inventorystack_t *end = stack + inventory->storageSize;
+  do {
+    // End of inventory, item not present.
+    if(stack->item == ITEM_ID_NULL) break;
+
+    // Not matching stack.
+    if(stack->item != item) continue;
+
+    // Match found, return quantity.
+    return stack->quantity;
+  } while(++stack < end);
+
+  return 0;
+}
+
+bool_t inventoryIsFull(const inventory_t *inventory) {
+  assertNotNull(inventory, "Inventory pointer is NULL.");
+  assertNotNull(inventory->storage, "Storage pointer is NULL.");
+  assertTrue(inventory->storageSize > 0, "Storage too small.");
+
+  inventorystack_t *stack = inventory->storage;
+  inventorystack_t *end = stack + inventory->storageSize;
+  do {
+    // Found empty stack, not full.
+    if(stack->item == ITEM_ID_NULL) return false;
+  } while(++stack < end);
+
+  return true;
+}
+
+bool_t inventoryItemFull(const inventory_t *inventory, const itemid_t item) {
+  return inventoryGetCount(inventory, item) == ITEM_STACK_QUANTITY_MAX;
+}

src/item/inventory.h

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+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "item.h"
+
+#define ITEM_STACK_QUANTITY_MAX UINT8_MAX
+
+typedef struct {
+  itemid_t item;
+  uint8_t quantity;
+} inventorystack_t;
+
+typedef struct {
+  inventorystack_t *storage;
+  uint8_t storageSize;
+} inventory_t;
+
+/**
+ * Initializes an inventory.
+ * 
+ * @param inventory The inventory to initialize.
+ * @param storage The storage array for the inventory.
+ * @param storageSize The size of the storage array.
+ */
+void inventoryInit(
+  inventory_t* inventory,
+  inventorystack_t* storage,
+  uint8_t storageSize
+);
+
+/**
+ * Checks if a specific item exists in the inventory (and has quantity > 0).
+ * 
+ * @param inventory The inventory to check.
+ * @param item The item ID to check.
+ * @return true if the item exists, false otherwise.
+ */
+bool_t inventoryItemExists(const inventory_t *inventory, const itemid_t item);
+
+/**
+ * Sets the quantity of a specific item in the inventory.
+ * 
+ * @param inventory The inventory to modify.
+ * @param item The item ID to set.
+ * @param quantity The quantity to set.
+ */
+void inventorySet(
+  inventory_t *inventory,
+  const itemid_t item,
+  const uint8_t quantity
+);
+
+/**
+ * Adds a specific quantity of an item to the inventory.
+ * 
+ * @param inventory The inventory to modify.
+ * @param item The item ID to add.
+ * @param quantity The quantity to add.
+ */
+void inventoryAdd(
+  inventory_t *inventory,
+  const itemid_t item,
+  const uint8_t quantity
+);
+
+/**
+ * Removes an item from the inventory.
+ * 
+ * @param inventory The inventory to modify.
+ * @param item The item ID to remove.
+ */
+void inventoryRemove(inventory_t *inventory, const itemid_t item);
+
+/**
+ * Gets the count of a specific item in the inventory.
+ * 
+ * @param inventory The inventory to check.
+ * @param item The item ID to check.
+ * @return The count of the item in the inventory.
+ */
+uint8_t inventoryGetCount(const inventory_t *inventory, const itemid_t item);
+
+/**
+ * Checks if the inventory is full.
+ * 
+ * @param inventory The inventory to check.
+ * @return true if full, false otherwise.
+ */
+bool_t inventoryIsFull(const inventory_t *inventory);
+
+/**
+ * Checks if a specific item stack is full in the inventory.
+ * 
+ * @param inventory The inventory to check.
+ * @param item The item ID to check.
+ * @return true if the item stack is full, false otherwise.
+ */
+bool_t inventoryItemFull(const inventory_t *inventory, const itemid_t item);

src/item/item.c

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+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "item.h"
+
+const item_t ITEMS[] = {
+  [ITEM_ID_NULL] = {
+    .type = ITEM_TYPE_NULL
+  },
+
+  // Potion
+  [ITEM_ID_POTION] = {
+    .type = ITEM_TYPE_MEDICINE
+  },
+};

src/item/item.h

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+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "itemtype.h"
+
+typedef struct {
+  itemtype_t type;
+} item_t;
+
+typedef uint8_t itemid_t;
+
+#define ITEM_ID_NULL 0
+#define ITEM_ID_POTION 1
+#define ITEM_ID_POTATO 2
+
+extern const item_t ITEMS[];

src/item/itemtype.h

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+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "dusk.h"
+
+typedef enum {
+  ITEM_TYPE_NULL,
+
+  ITEM_TYPE_MEDICINE,
+  ITEM_TYPE_INGREDIENT,
+  ITEM_TYPE_KEYITEM,
+
+  ITEM_TYPE_COUNT
+} itemtype_t;