/**
 * @file       use-annotation-selection.tsx — Phase 5.1 annotation selection store
 * @scope      apps/studio/use-annotation-selection.tsx
 * @purpose    Parallel to `use-selection-set`, but holds annotation stroke IDs
 *             instead of DOM-element selections. Annotation IDs are local
 *             identifiers (`s_*`) generated by `rid()` — they never live in
 *             `_active.json` and don't post upstream to the dev-server shell.
 *
 * In-memory only. Scope is per canvas mount: when the iframe reloads, the
 * selection resets (the strokes themselves persist via `.annotations.svg`).
 */

import {
  createContext,
  type ReactNode,
  useCallback,
  useContext,
  useMemo,
  useRef,
  useState,
} from 'react';

export interface AnnotationSelectionValue {
  selectedIds: string[];
  replace: (id: string | string[]) => void;
  add: (id: string | string[]) => void;
  toggle: (id: string) => void;
  clear: () => void;
  contains: (id: string) => boolean;
}

const AnnotationSelectionContext = createContext<AnnotationSelectionValue | null>(null);

function dedupe(ids: string[]): string[] {
  const out: string[] = [];
  const seen = new Set<string>();
  for (const id of ids) {
    if (seen.has(id)) continue;
    seen.add(id);
    out.push(id);
  }
  return out;
}

export function AnnotationSelectionProvider({ children }: { children: ReactNode }) {
  const [selectedIds, setSelectedIds] = useState<string[]>([]);

  const replace = useCallback((id: string | string[]) => {
    const next = dedupe(Array.isArray(id) ? id : [id]);
    setSelectedIds(next);
  }, []);

  const add = useCallback((id: string | string[]) => {
    const incoming = Array.isArray(id) ? id : [id];
    setSelectedIds((prev) => dedupe([...prev, ...incoming]));
  }, []);

  const toggle = useCallback((id: string) => {
    setSelectedIds((prev) => (prev.includes(id) ? prev.filter((x) => x !== id) : [...prev, id]));
  }, []);

  const clear = useCallback(() => {
    setSelectedIds([]);
  }, []);

  // Read live from state at call time so multi-step flows in the same tick
  // (e.g. a router callback that adds then asks `contains`) see the staged
  // result instead of a stale closure capture. MUST be a real useRef — the
  // pre-FigJam-v3 code created a fresh `{ current }` object literal every
  // render, so the stable useCallback closure kept reading the FIRST render's
  // (empty) selection forever: `contains()` always returned false, which
  // silently broke hull/multi-drag and click-keeps-selection (user-gate
  // finding, 2026-06-11).
  const containsRef = useRef<string[]>(selectedIds);
  containsRef.current = selectedIds;
  const contains = useCallback((id: string) => containsRef.current.includes(id), []);

  const value = useMemo<AnnotationSelectionValue>(
    () => ({ selectedIds, replace, add, toggle, clear, contains }),
    [selectedIds, replace, add, toggle, clear, contains]
  );

  return (
    <AnnotationSelectionContext.Provider value={value}>
      {children}
    </AnnotationSelectionContext.Provider>
  );
}

export function useAnnotationSelection(): AnnotationSelectionValue {
  const ctx = useContext(AnnotationSelectionContext);
  if (!ctx) {
    throw new Error('useAnnotationSelection must be used inside <AnnotationSelectionProvider>');
  }
  return ctx;
}

export function useAnnotationSelectionOptional(): AnnotationSelectionValue | null {
  return useContext(AnnotationSelectionContext);
}