refactor(web): extract allocation drag session

apps/web/src/hooks/timelineAllocationDragSession.ts

@@ -0,0 +1,48 @@
+type MutableCurrent<T> = {
+  current: T;
+};
+
+type AttachDocumentMouseDrag = (
+  documentTarget: Document,
+  onMove: (event: MouseEvent) => void,
+  onUp: (event: MouseEvent) => void,
+) => () => void;
+
+type BeginAllocationDragSessionParams<TState> = {
+  state: TState;
+  cleanupRef: MutableCurrent<(() => void) | null>;
+  stateRef: MutableCurrent<TState>;
+  setState: (state: TState) => void;
+  documentTarget: Document;
+  attachDrag: AttachDocumentMouseDrag;
+  updatePosition: (clientX: number) => void;
+  finalize: (clientX: number) => Promise<void> | void;
+};
+
+export function beginAllocationDragSession<TState>({
+  state,
+  cleanupRef,
+  stateRef,
+  setState,
+  documentTarget,
+  attachDrag,
+  updatePosition,
+  finalize,
+}: BeginAllocationDragSessionParams<TState>) {
+  stateRef.current = state;
+  setState(state);
+  cleanupRef.current?.();
+
+  function handleMove(event: MouseEvent) {
+    updatePosition(event.clientX);
+  }
+
+  function handleUp(event: MouseEvent) {
+    cleanupRef.current?.();
+    cleanupRef.current = null;
+    void finalize(event.clientX);
+    event.preventDefault();
+  }
+
+  cleanupRef.current = attachDrag(documentTarget, handleMove, handleUp);
+}