/** * Zustand store for sidebar thread multi-selection state. * * Supports Cmd/Ctrl+Click (toggle individual), Shift+Click (range select), * and bulk actions on the selected set. */ import type { ThreadId } from "@t3tools/contracts";import { create } from "zustand"; export interface ThreadSelectionState {  /** Currently selected thread IDs. */  selectedThreadIds: ReadonlySet<ThreadId>;  /** The thread ID that anchors shift-click range selection. */  anchorThreadId: ThreadId | null;} interface ThreadSelectionStore extends ThreadSelectionState {  /** Toggle a single thread in the selection (Cmd/Ctrl+Click). */  toggleThread: (threadId: ThreadId) => void;  /**   * Select a range of threads (Shift+Click).   * Requires the ordered list of thread IDs within the same project   * so the store can compute which threads fall between anchor and target.   */  rangeSelectTo: (threadId: ThreadId, orderedThreadIds: readonly ThreadId[]) => void;  /** Clear all selection state. */  clearSelection: () => void;  /** Remove specific thread IDs from the selection (e.g. after deletion). */  removeFromSelection: (threadIds: readonly ThreadId[]) => void;  /** Set the anchor thread without adding it to the selection (e.g. on plain-click navigate). */  setAnchor: (threadId: ThreadId) => void;  /** Check if any threads are selected. */  hasSelection: () => boolean;} const EMPTY_SET = new Set<ThreadId>(); export const useThreadSelectionStore = create<ThreadSelectionStore>((set, get) => ({  selectedThreadIds: EMPTY_SET,  anchorThreadId: null,   toggleThread: (threadId) => {    set((state) => {      const next = new Set(state.selectedThreadIds);      if (next.has(threadId)) {        next.delete(threadId);      } else {        next.add(threadId);      }      return {        selectedThreadIds: next,        anchorThreadId: next.has(threadId) ? threadId : state.anchorThreadId,      };    });  },   rangeSelectTo: (threadId, orderedThreadIds) => {    set((state) => {      const anchor = state.anchorThreadId;      if (anchor === null) {        // No anchor yet — treat as a single toggle        const next = new Set(state.selectedThreadIds);        next.add(threadId);        return { selectedThreadIds: next, anchorThreadId: threadId };      }       const anchorIndex = orderedThreadIds.indexOf(anchor);      const targetIndex = orderedThreadIds.indexOf(threadId);      if (anchorIndex === -1 || targetIndex === -1) {        // Anchor or target not in this list (different project?) — fallback to toggle        const next = new Set(state.selectedThreadIds);        next.add(threadId);        return { selectedThreadIds: next, anchorThreadId: threadId };      }       const start = Math.min(anchorIndex, targetIndex);      const end = Math.max(anchorIndex, targetIndex);      const next = new Set(state.selectedThreadIds);      for (let i = start; i <= end; i++) {        const id = orderedThreadIds[i];        if (id !== undefined) {          next.add(id);        }      }      // Keep anchor stable so subsequent shift-clicks extend from the same point      return { selectedThreadIds: next, anchorThreadId: anchor };    });  },   clearSelection: () => {    const state = get();    if (state.selectedThreadIds.size === 0 && state.anchorThreadId === null) return;    set({ selectedThreadIds: EMPTY_SET, anchorThreadId: null });  },   setAnchor: (threadId) => {    if (get().anchorThreadId === threadId) return;    set({ anchorThreadId: threadId });  },   removeFromSelection: (threadIds) => {    set((state) => {      const toRemove = new Set(threadIds);      let changed = false;      const next = new Set<ThreadId>();      for (const id of state.selectedThreadIds) {        if (toRemove.has(id)) {          changed = true;        } else {          next.add(id);        }      }      if (!changed) return state;      const newAnchor =        state.anchorThreadId !== null && toRemove.has(state.anchorThreadId)          ? null          : state.anchorThreadId;      return { selectedThreadIds: next, anchorThreadId: newAnchor };    });  },   hasSelection: () => get().selectedThreadIds.size > 0,}));