refactor: Introduce a layered architecture for card interactions, separating drag logic, and selection handling.

frontend/src/desktop/CardDragLogic.ts

@@ -0,0 +1,24 @@
+import { LayoutStore } from './LayoutSystem';
+
+const capturedCards = new Set<string>();
+
+export const handleDragMove = (store: LayoutStore, selection: string[], delta: { x: number, y: number }) => {
+    selection.forEach(id => {
+        const card = store.items.get(id);
+        if (card) {
+            if (!capturedCards.has(id)) {
+                card.captureDragStart();
+                capturedCards.add(id);
+            }
+
+            card.update({
+                x: card.dragStartX + delta.x,
+                y: card.dragStartY + delta.y
+            });
+        }
+    });
+};
+
+export const handleDragEnd = () => {
+    capturedCards.clear();
+};

frontend/src/desktop/DesktopWorkspace.tsx

@@ -15,6 +15,7 @@ import '../styles/workspace/workspace-layout.css';
 import '../styles/workspace/workspace-items.css';
 import '../styles/workspace/workspace-cards.css';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
+import { createDocumentEntryKey } from '../app/entryKey';
 import type { Identifier } from '../types/identifiers';
 import type { DocumentsListEntry, Document } from '../types/documents';
 
@@ -56,10 +57,16 @@ export interface DesktopWorkspaceProps {
 }
 
 // Wrapper to handle hooks per card
-const DesktopDocumentContainer: React.FC<React.ComponentProps<typeof DesktopDocumentCard>> = React.memo((props) => {
-  const { layoutCard, selected } = props;
+const DesktopDocumentContainer: React.FC<React.ComponentProps<typeof DesktopDocumentCard> & {
+  onSelect: (ids: string[], extend?: boolean) => void;
+  onDeselect: (ids: string[]) => void;
+  onDocumentActivate?: (id: string) => void;
+  selection: string[];
+}> = React.memo((props) => {
+  const { layoutCard, selected, onSelect, onDeselect, onDocumentActivate, selection } = props;
+
   // We assume layoutCard is always present in this context
-  const cardPointerHandlers = useCardPointer(layoutCard!, !!selected);
+  const cardPointerHandlers = useCardPointer(layoutCard!, !!selected, selection, onSelect, onDeselect, onDocumentActivate);
 
   return (
     <DesktopDocumentCard
@@ -94,22 +101,18 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
 
   // Selection Context
   const {
-    selectedDocumentIds: contextSelectedIds,
-    setSelectedDocumentIds,
+    selectedDocumentIds,
+    setSelectedEntries,
     clearSelection,
   } = useWorkspaceSelectionContext();
 
-  const [localSelectedIds, setLocalSelectedIds] = useState<Identifier[]>([]);
-  const selectedDocumentIds = contextSelectedIds || localSelectedIds;
-
   const handleSelectionChange = useCallback((ids: Identifier[]) => {
-    if (setSelectedDocumentIds) {
-      setSelectedDocumentIds(ids);
-    } else {
-      setLocalSelectedIds(ids);
+    if (setSelectedEntries) {
+      const keys = ids.map(id => createDocumentEntryKey(id));
+      setSelectedEntries(keys);
     }
     onSelectionChange?.(ids);
-  }, [setSelectedDocumentIds, onSelectionChange]);
+  }, [setSelectedEntries, onSelectionChange]);
 
   const onClearSelection = useCallback(() => {
     clearSelection ? clearSelection() : handleSelectionChange([]);
@@ -207,7 +210,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
                 ensureAssetUrl={ensureAssetUrl}
                 getDocumentAsset={getDocumentAsset}
                 handleNavigatorSnapshot={() => { }}
-                onDocumentActivate={onDocumentActivate}
+                onDocumentActivate={(id) => { onDocumentActivate?.({ id } as DeskDocument) }}
                 layoutCard={layoutCard}
                 onTagDragEnter={tagInteractions.handleTagDragEnterDoc}
                 onTagDragOver={tagInteractions.handleTagDragOverDoc}
@@ -220,6 +223,21 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
                 tagTargetActive={tagDropTargetId === docId}
                 tagTargetPending={pendingTagDocId === docId}
                 pendingRemovalTag={pendingRemovalTag}
+                onSelect={(ids, extend = false) => {
+                  if (!extend) {
+                    handleSelectionChange(ids);
+                  } else {
+                    const newSelection = new Set(selectedDocumentIds);
+                    ids.forEach(id => newSelection.add(id));
+                    handleSelectionChange(Array.from(newSelection));
+                  }
+                }}
+                onDeselect={(ids) => {
+                  const newSelection = new Set(selectedDocumentIds);
+                  ids.forEach(id => newSelection.delete(id));
+                  handleSelectionChange(Array.from(newSelection));
+                }}
+                selection={selectedDocumentIds}
               />
             );
           })}

frontend/src/desktop/LayoutSystem.ts

@@ -22,9 +22,13 @@ export class LayoutCard implements LayoutCardState {
 
     private _innerRadius: number = 0;
     private _outerRadius: number = 0;
+    public store: LayoutStore;
+    public dragStartX: number = 0;
+    public dragStartY: number = 0;
 
-    constructor(id: string, initialData: Partial<LayoutCardState> = {}, ref: HTMLElement | null = null) {
+    constructor(id: string, store: LayoutStore, initialData: Partial<LayoutCardState> = {}, ref: HTMLElement | null = null) {
         this.id = id;
+        this.store = store;
         Object.assign(this, initialData);
         this.ref = ref;
         this.recalculateRadii();
@@ -35,6 +39,11 @@ export class LayoutCard implements LayoutCardState {
         this.applyTransform();
     }
 
+    captureDragStart() {
+        this.dragStartX = this.x;
+        this.dragStartY = this.y;
+    }
+
     update(changes: Partial<LayoutCardState>) {
         Object.assign(this, changes);
         if (changes.width !== undefined || changes.height !== undefined) {
@@ -43,19 +52,113 @@ export class LayoutCard implements LayoutCardState {
         this.applyTransform();
     }
 
+    isUnobstructed(): boolean {
+        for (const other of this.store.items.values()) {
+            if (other.id === this.id) continue;
+            if (other.z <= this.z) continue;
+
+            const dx = other.x - this.x;
+            const dy = other.y - this.y;
+            const distance = Math.sqrt(dx * dx + dy * dy);
+
+            // Broad phase: check outer radii
+            if (distance < this.outerRadius + other.outerRadius) {
+                // Narrow phase: SAT intersection test
+                if (this.intersects(other)) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    bringToFront() {
+        this.z = this.store.zCounter++;
+    }
+
+    private getVertices(): { x: number; y: number }[] {
+        const rad = (this.rotation * Math.PI) / 180;
+        const cos = Math.cos(rad);
+        const sin = Math.sin(rad);
+        const hw = this.width / 2;
+        const hh = this.height / 2;
+
+        // Corners relative to center, then rotated, then translated
+        // (-hw, -hh), (hw, -hh), (hw, hh), (-hw, hh)
+        const corners = [
+            { x: -hw, y: -hh },
+            { x: hw, y: -hh },
+            { x: hw, y: hh },
+            { x: -hw, y: hh }
+        ];
+
+        return corners.map(p => ({
+            x: (p.x * cos - p.y * sin) + this.x,
+            y: (p.x * sin + p.y * cos) + this.y
+        }));
+    }
+
+    private getAxes(): { x: number; y: number }[] {
+        const rad = (this.rotation * Math.PI) / 180;
+        const cos = Math.cos(rad);
+        const sin = Math.sin(rad);
+        // Normals of the edges (local x and y axes)
+        return [
+            { x: cos, y: sin },
+            { x: -sin, y: cos }
+        ];
+    }
+
+    private intersects(other: LayoutCard): boolean {
+        const verticesA = this.getVertices();
+        const verticesB = other.getVertices();
+        const axes = [...this.getAxes(), ...other.getAxes()];
+
+        for (const axis of axes) {
+            const pA = this.project(verticesA, axis);
+            const pB = this.project(verticesB, axis);
+
+            if (pA.max < pB.min || pB.max < pA.min) {
+                return false; // Gap found, no intersection
+            }
+        }
+        return true;
+    }
+
+    private project(vertices: { x: number; y: number }[], axis: { x: number; y: number }) {
+        let min = Infinity;
+        let max = -Infinity;
+        for (const v of vertices) {
+            const dot = v.x * axis.x + v.y * axis.y;
+            if (dot < min) min = dot;
+            if (dot > max) max = dot;
+        }
+        return { min, max };
+    }
+
     private recalculateRadii() {
         this._innerRadius = Math.min(this.width, this.height) / 2;
         this._outerRadius = Math.sqrt(this.width * this.width + this.height * this.height) / 2;
     }
 
+    private rafId: number | null = null;
+
     private applyTransform() {
-        if (this.ref) {
-            this.ref.style.transform =
-                `translate3d(${this.x}px, ${this.y}px, 0) rotate(${this.rotation}deg)`;
-            this.ref.style.zIndex = String(this.z);
-            this.ref.style.width = `${this.width}px`;
-            this.ref.style.height = `${this.height}px`;
+        if (this.rafId) {
+            cancelAnimationFrame(this.rafId);
         }
+
+        this.rafId = requestAnimationFrame(() => {
+            if (this.ref) {
+                this.ref.style.transform =
+                    `translate3d(${this.x}px, ${this.y}px, 0) rotate(${this.rotation}deg)`;
+                this.ref.style.zIndex = String(this.z);
+                this.ref.style.width = `${this.width}px`;
+                this.ref.style.height = `${this.height}px`;
+            }
+            this.rafId = null;
+        });
     }
 
     toSnapshot(): LayoutCardState {
@@ -101,12 +204,13 @@ export class LayoutStore {
             const y = Math.random() * 500;
             const rotation = Math.random() * 10 - 5;
 
-            card = new LayoutCard(id, {
+            card = new LayoutCard(id, this, {
                 x,
                 y,
                 rotation,
                 width,
-                height
+                height,
+                z: this.zCounter++
             }, ref);
             this.items.set(id, card);
         } else {
@@ -125,18 +229,6 @@ export class LayoutStore {
         this.items.delete(id);
     }
 
-    update(id: string, updates: Partial<LayoutCardState>) {
-        const card = this.items.get(id);
-        if (card) {
-            if (updates.z) this.zCounter = Math.max(this.zCounter, updates.z);
-            card.update(updates);
-        }
-    }
-
-    bringToFront(id: string) {
-        this.update(id, { z: ++this.zCounter });
-    }
-
     getCardsInCircle(x: number, y: number, radius: number): LayoutCard[] {
         const result: LayoutCard[] = [];
         for (const card of this.items.values()) {

frontend/src/desktop/useCardPointer.ts

@@ -1,23 +1,102 @@
-import React, { useCallback } from 'react';
+import React, { useCallback, useRef } from 'react';
 
 import { LayoutCard } from './LayoutSystem';
+import { handleDragMove, handleDragEnd } from './CardDragLogic';
+
+const DRAG_THRESHOLD = 3;
+
+type PointerState = 'idle' | 'click' | 'drag';
+
+export const useCardPointer = (
+    card: LayoutCard,
+    isSelected: boolean,
+    selection: string[],
+    onSelect: (ids: string[], extend?: boolean) => void,
+    onDeselect: (ids: string[]) => void,
+    onDocumentActivate?: (id: string) => void
+) => {
+    const [state, setState] = React.useState<PointerState>('idle');
+    const initialPosition = useRef<{ x: number, y: number } | null>(null);
+
+    const updateState = useCallback((e: React.PointerEvent) => {
+        if (state === 'click' && initialPosition.current) {
+            const dx = e.clientX - initialPosition.current.x;
+            const dy = e.clientY - initialPosition.current.y;
+            const distance = Math.sqrt(dx * dx + dy * dy);
+
+            if (distance > DRAG_THRESHOLD) {
+                setState('drag-start');
+            }
+        }
+    }, [state]);
 
-export const useCardPointer = (card: LayoutCard, isSelected: boolean) => {
     const onPointerDown = useCallback((e: React.PointerEvent) => {
-        console.log('Pointer down on card', card.id, card.rotation, card.z, isSelected, e);
-    }, [card, isSelected]);
+        // Only left click
+        if (e.button !== 0) return;
+
+        (e.target as Element).setPointerCapture(e.pointerId);
+        setState('click');
+        initialPosition.current = { x: e.clientX, y: e.clientY };
+    }, []);
 
     const onPointerMove = useCallback((e: React.PointerEvent) => {
-        console.log('Pointer move on card', card.id, card.rotation, e);
-    }, [card]);
+        const hasModifier = e.metaKey || e.ctrlKey || e.shiftKey;
+        updateState(e);
+
+        if (state === 'drag-start') {
+            if (!isSelected) {
+                onSelect([card.id], hasModifier);
+
+                if (!hasModifier) {
+                    card.bringToFront();
+                }
+            }
+
+            setState('drag');
+        }
+
+        if (state === 'drag' && initialPosition.current) {
+            const delta = {
+                x: e.clientX - initialPosition.current.x,
+                y: e.clientY - initialPosition.current.y
+            };
+
+            handleDragMove(card.store, selection, delta);
+        }
+    }, [card, state, updateState, isSelected, selection, onSelect]);
 
     const onPointerUp = useCallback((e: React.PointerEvent) => {
-        console.log('Pointer up on card', card.id, card.rotation, e);
-    }, [card]);
+        const hasModifier = e.metaKey || e.ctrlKey || e.shiftKey;
+        updateState(e);
+
+        if (state === 'drag' || state === 'drag-start') {
+            handleDragEnd();
+        } else if (state === 'click') {
+            if (isSelected) {
+                const isUnobstructed = card.isUnobstructed();
+
+                if (hasModifier) {
+                    onDeselect([card.id]);
+                } else if (isUnobstructed) {
+                    onDocumentActivate?.(card.id);
+                }
+            } else {
+                onSelect([card.id], hasModifier);
+
+                if (!hasModifier) {
+                    card.bringToFront();
+                }
+            }
+        }
+
+        setState('idle');
+        initialPosition.current = null;
+        (e.target as Element).releasePointerCapture(e.pointerId);
+    }, [card, state, isSelected, onSelect, onDeselect, onDocumentActivate, updateState]);
 
     return {
         onPointerDown,
         onPointerMove,
-        onPointerUp,
+        onPointerUp
     };
 };