/**
 * Persistence for the half-written dump in the create modal.
 *
 * The modal is dismissable by Escape, a backdrop click and the ✕, and it holds
 * a URL, a title, a rich-text "why", categories and a visibility choice — so a
 * stray keystroke used to destroy a few minutes of writing. Everything except
 * the attached file (a `File` cannot survive a reload) is mirrored here on each
 * change and restored the next time the modal opens; a successful post clears
 * it.
 *
 * Deliberately a single draft rather than one per tab: someone who closed the
 * modal by accident wants the thing they were just writing, wherever they
 * reopen it.
 */

const STORAGE_KEY = "gerbeur.dumpDraft";

export interface DumpDraft {
  url: string;
  title: string;
  /** Whether `title` was typed by the poster, rather than taken from the preview. */
  titleFromUser: boolean;
  comment: string;
  isPublic: boolean;
  categoryIds: string[];
}

export const EMPTY_DUMP_DRAFT: DumpDraft = {
  url: "",
  title: "",
  titleFromUser: false,
  comment: "",
  isPublic: true,
  categoryIds: [],
};

/** Whether a draft holds anything worth restoring or warning about. */
export function isDumpDraftEmpty(draft: DumpDraft): boolean {
  return !draft.url.trim() && !draft.comment.trim() &&
    !(draft.titleFromUser && draft.title.trim()) &&
    draft.categoryIds.length === 0 && draft.isPublic;
}

export function loadDumpDraft(): DumpDraft | null {
  let raw: string | null;
  try {
    raw = localStorage.getItem(STORAGE_KEY);
  } catch {
    return null; // Storage disabled (private mode, blocked cookies) — no drafts.
  }
  if (!raw) return null;

  try {
    const parsed = JSON.parse(raw) as Partial<DumpDraft>;
    const draft: DumpDraft = {
      url: typeof parsed.url === "string" ? parsed.url : "",
      title: typeof parsed.title === "string" ? parsed.title : "",
      titleFromUser: parsed.titleFromUser === true,
      comment: typeof parsed.comment === "string" ? parsed.comment : "",
      isPublic: parsed.isPublic !== false,
      categoryIds: Array.isArray(parsed.categoryIds)
        ? parsed.categoryIds.filter((id): id is string => typeof id === "string")
        : [],
    };
    return isDumpDraftEmpty(draft) ? null : draft;
  } catch {
    return null;
  }
}

export function saveDumpDraft(draft: DumpDraft): void {
  try {
    if (isDumpDraftEmpty(draft)) localStorage.removeItem(STORAGE_KEY);
    else localStorage.setItem(STORAGE_KEY, JSON.stringify(draft));
  } catch {
    // Storage full or unavailable — the draft is a convenience, never a
    // precondition for posting, so a failure here is silent by design.
  }
}

export function clearDumpDraft(): void {
  try {
    localStorage.removeItem(STORAGE_KEY);
  } catch { /* see saveDumpDraft */ }
}