feat(sts-viewer): implement drag-and-drop for inventory items

Adds interactive drag-and-drop functionality to the inventory spawner,
allowing users to move items within the grid.

- Implements `InventoryItemSpawnerCallbacks` to handle item movement
- Adds `moveItem` utility to update inventory state via signals
- Integrates `dragDropEventEffect` for item interaction
- Updates `InventoryTestScene` to demonstrate movement
- Adjusts text colors in `GRID_CONFIG` for better visibility

packages/sts-like-viewer/src/config/index.ts

@@ -42,7 +42,7 @@ export const GRID_CONFIG = {
   /** Title text style */
   TITLE_STYLE: {
     fontSize: "24px",
-    color: "#ffffff",
+    color: "#888",
     fontStyle: "bold",
   } as const,
   /** Subtitle/hint text style */
@@ -53,7 +53,7 @@ export const GRID_CONFIG = {
   /** Item name text style */
   ITEM_NAME_STYLE: {
     fontSize: "11px",
-    color: "#ffffff",
+    color: "#888",
     fontStyle: "bold",
   } as const,
 } as const;

packages/sts-like-viewer/src/scenes/InventoryItemSpawner.ts

@@ -1,5 +1,10 @@
 import Phaser from "phaser";
-import { spawnEffect, type Spawner } from "boardgame-phaser";
+import {
+  spawnEffect,
+  dragDropEventEffect,
+  DragDropEventType,
+  type Spawner,
+} from "boardgame-phaser";
 import { GRID_CONFIG, ITEM_COLORS } from "@/config";
 import type {
   GameItemMeta,
@@ -7,15 +12,27 @@ import type {
 } from "boardgame-core/samples/slay-the-spire-like";
 import type { InventorySignal } from "@/state/inventory";
 
+export interface InventoryItemSpawnerCallbacks {
+  onMoveItem: (itemId: string, newX: number, newY: number) => void;
+}
+
 export class InventoryItemSpawner implements Spawner<
   [string, InventoryItem<GameItemMeta>],
   Phaser.GameObjects.Container
 > {
+  private dragState: {
+    itemId: string;
+    startX: number;
+    startY: number;
+    container: Phaser.GameObjects.Container;
+  } | null = null;
+
   constructor(
     private scene: Phaser.Scene,
     private inventorySignal: InventorySignal,
     private gridOffsetX: number,
     private gridOffsetY: number,
+    private callbacks: InventoryItemSpawnerCallbacks,
   ) {}
 
   *getData(): Iterable<[string, InventoryItem<GameItemMeta>]> {
@@ -46,6 +63,11 @@ export class InventoryItemSpawner implements Spawner<
     return cells;
   }
 
+  private getItemColor(itemId: string): number {
+    const hash = itemId.split("").reduce((acc, c) => acc + c.charCodeAt(0), 0);
+    return ITEM_COLORS[hash % ITEM_COLORS.length];
+  }
+
   onSpawn(
     entry: [string, InventoryItem<GameItemMeta>],
   ): Phaser.GameObjects.Container | null {
@@ -73,7 +95,7 @@ export class InventoryItemSpawner implements Spawner<
       const firstCell = cells[0];
       const px = this.gridOffsetX + firstCell.x * GRID_CONFIG.VIEWER_CELL_SIZE;
       const py = this.gridOffsetY + firstCell.y * GRID_CONFIG.VIEWER_CELL_SIZE;
-      const itemName = item.meta?.itemData.name ?? item.id;
+      const itemName = item.meta?.itemData.name ?? itemId;
 
       const text = this.scene.add.text(
         px + GRID_CONFIG.VIEWER_CELL_SIZE / 2,
@@ -84,13 +106,104 @@ export class InventoryItemSpawner implements Spawner<
       text.setOrigin(0.5);
 
       container.add([graphics, text]);
+      container.setPosition(px, py);
     } else {
       container.add(graphics);
     }
 
+    // Make container interactive for drag-and-drop
+    container.setInteractive(
+      new Phaser.Geom.Rectangle(
+        0,
+        0,
+        GRID_CONFIG.VIEWER_CELL_SIZE,
+        GRID_CONFIG.VIEWER_CELL_SIZE,
+      ),
+      Phaser.Geom.Rectangle.Contains,
+    );
+    container.setScrollFactor(0);
+    container.setSize(
+      GRID_CONFIG.VIEWER_CELL_SIZE * (item.shape?.width ?? 1),
+      GRID_CONFIG.VIEWER_CELL_SIZE * (item.shape?.height ?? 1),
+    );
+
+    // Setup drag handling
+    dragDropEventEffect(container, (event) => {
+      if (event.type === DragDropEventType.DOWN) {
+        // Start drag
+        this.dragState = {
+          itemId,
+          startX: container.x,
+          startY: container.y,
+          container,
+        };
+        container.setAlpha(0.7);
+      } else if (event.type === DragDropEventType.MOVE) {
+        // Update drag position
+        if (this.dragState?.itemId === itemId) {
+          container.x += event.deltaX;
+          container.y += event.deltaY;
+        }
+      } else if (event.type === DragDropEventType.UP) {
+        // End drag
+        if (this.dragState?.itemId === itemId) {
+          container.setAlpha(1);
+          this.handleDragEnd(itemId, container);
+          this.dragState = null;
+        }
+      }
+    });
+
     return container;
   }
 
+  private handleDragEnd(
+    itemId: string,
+    container: Phaser.GameObjects.Container,
+  ): void {
+    const inventory = this.inventorySignal.value;
+    const item = inventory.items.get(itemId);
+    if (!item) return;
+
+    const cellSize = GRID_CONFIG.VIEWER_CELL_SIZE;
+    const shapeWidth = item.shape?.width ?? 1;
+    const shapeHeight = item.shape?.height ?? 1;
+
+    // Calculate target grid position based on container center
+    const targetX = Math.round((container.x - cellSize / 2) / cellSize);
+    const targetY = Math.round((container.y - cellSize / 2) / cellSize);
+
+    // Clamp to inventory bounds
+    const clampedX = Math.max(
+      0,
+      Math.min(targetX, inventory.width - shapeWidth),
+    );
+    const clampedY = Math.max(
+      0,
+      Math.min(targetY, inventory.height - shapeHeight),
+    );
+
+    // If position changed, notify callback
+    if (
+      clampedX !== item.transform.offset.x ||
+      clampedY !== item.transform.offset.y
+    ) {
+      this.callbacks.onMoveItem(itemId, clampedX, clampedY);
+    } else {
+      // Snap back to original position
+      const originalX = this.gridOffsetX + item.transform.offset.x * cellSize;
+      const originalY = this.gridOffsetY + item.transform.offset.y * cellSize;
+
+      this.scene.tweens.add({
+        targets: container,
+        x: originalX,
+        y: originalY,
+        duration: 150,
+        ease: "Power2",
+      });
+    }
+  }
+
   onUpdate(
     entry: [string, InventoryItem<GameItemMeta>],
     obj: Phaser.GameObjects.Container,
@@ -103,6 +216,8 @@ export class InventoryItemSpawner implements Spawner<
       const px = this.gridOffsetX + firstCell.x * GRID_CONFIG.VIEWER_CELL_SIZE;
       const py = this.gridOffsetY + firstCell.y * GRID_CONFIG.VIEWER_CELL_SIZE;
 
+      // Don't animate if currently dragging this item
+      if (this.dragState?.itemId !== entry[0]) {
         this.scene.tweens.add({
           targets: obj,
           x: px,
@@ -112,6 +227,7 @@ export class InventoryItemSpawner implements Spawner<
         });
       }
     }
+  }
 
   onDespawn(obj: Phaser.GameObjects.Container): void {
     this.scene.tweens.add({
@@ -123,11 +239,6 @@ export class InventoryItemSpawner implements Spawner<
       onComplete: () => obj.destroy(),
     });
   }
-
-  private getItemColor(itemId: string): number {
-    const hash = itemId.split("").reduce((acc, c) => acc + c.charCodeAt(0), 0);
-    return ITEM_COLORS[hash % ITEM_COLORS.length];
-  }
 }
 
 export function createInventoryItemSpawner(
@@ -135,8 +246,15 @@ export function createInventoryItemSpawner(
   inventorySignal: InventorySignal,
   gridOffsetX: number,
   gridOffsetY: number,
+  callbacks: InventoryItemSpawnerCallbacks,
 ) {
   return spawnEffect(
-    new InventoryItemSpawner(scene, inventorySignal, gridOffsetX, gridOffsetY),
+    new InventoryItemSpawner(
+      scene,
+      inventorySignal,
+      gridOffsetX,
+      gridOffsetY,
+      callbacks,
+    ),
   );
 }

packages/sts-like-viewer/src/scenes/InventoryTestScene.ts

@@ -1,7 +1,7 @@
 import { ReactiveScene } from "boardgame-phaser";
 import { createButton } from "@/utils/createButton";
 import { GRID_CONFIG } from "@/config";
-import { createInventorySignal } from "@/state/inventory";
+import { createInventorySignal, moveItem } from "@/state/inventory";
 import { createItemIn, data } from "boardgame-core/samples/slay-the-spire-like";
 import { createInventoryItemSpawner } from "./InventoryItemSpawner";
 import { SceneKey } from "./types";
@@ -45,7 +45,7 @@ export class InventoryTestScene extends ReactiveScene {
       .text(
         width / 2,
         height - 40,
-        "Items update reactively via signals",
+        "Drag items to move them",
         GRID_CONFIG.SUBTITLE_STYLE,
       )
       .setOrigin(0.5);
@@ -90,6 +90,11 @@ export class InventoryTestScene extends ReactiveScene {
       this.inventorySignal,
       this.gridOffsetX,
       this.gridOffsetY,
+      {
+        onMoveItem: (itemId: string, newX: number, newY: number) => {
+          moveItem(this.inventorySignal, itemId, newX, newY);
+        },
+      },
     );
     this.disposables.add(spawner);
   }

packages/sts-like-viewer/src/state/inventory.ts

@@ -4,6 +4,9 @@ import {
   createItemIn,
   data,
   GameItemMeta,
+  placeItem,
+  removeItemFromGrid,
+  validatePlacement,
 } from "boardgame-core/samples/slay-the-spire-like";
 
 function genId() {
@@ -16,9 +19,43 @@ export function createInventorySignal() {
   const inventory = createGridInventory<GameItemMeta>(4, 6);
 
   const startingItems = data.desert.getStartingItems();
-  for (const data of startingItems) {
-    createItemIn(inventory, `${data.id}-${genId()}`, data);
+  for (const d of startingItems) {
+    createItemIn(inventory, `${d.id}-${genId()}`, d);
   }
 
   return mutableSignal(inventory);
 }
+
+/**
+ * Move an item to a new position in the inventory.
+ * Returns true if the move was successful, false if the new position is invalid.
+ */
+export function moveItem(
+  inventorySignal: InventorySignal,
+  itemId: string,
+  newX: number,
+  newY: number,
+): boolean {
+  const inventory = inventorySignal.value;
+  const item = inventory.items.get(itemId);
+
+  if (!item) {
+    return false;
+  }
+
+  const newTransform = {
+    ...item.transform,
+    offset: { x: newX, y: newY },
+  };
+  const validation = validatePlacement(inventory, item.shape, newTransform);
+  if (!validation.valid) return false;
+
+  inventorySignal.produce((inv) => {
+    const item = inv.items.get(itemId)!;
+    removeItemFromGrid(inv, itemId);
+    item.transform = newTransform;
+    placeItem(inv, item);
+  });
+
+  return true;
+}