"use client";

/**
 * Draft persistence for the wizards, so an OS kill (or an accidental reload)
 * doesn't lose the user's photos, pasted text or options. Best-effort: photo
 * data URLs can be large, so every write is guarded and skipped on quota
 * errors instead of breaking the flow.
 */

export type WizardDraft = {
  v: 1;
  savedAt: number;
  text?: string;
  focus?: string;
  difficulty?: string;
  count?: number;
  folderId?: string;
  images?: Array<{ id: string; name: string; dataUrl: string; bytes: number; width: number; height: number }>;
};

const TTL_MS = 24 * 60 * 60 * 1000;
const MAX_BYTES = 3_000_000;

function keyFor(scope: "deck" | "homework"): string {
  return `freezmo.draft.${scope}.v1`;
}

export function saveWizardDraft(scope: "deck" | "homework", draft: Omit<WizardDraft, "v" | "savedAt">): void {
  try {
    const images = draft.images ?? [];
    const size = images.reduce((sum, image) => sum + image.dataUrl.length, 0);
    const payload: WizardDraft = {
      v: 1,
      savedAt: Date.now(),
      ...draft,
      // Photos over the budget are dropped rather than failing the whole save.
      images: size > MAX_BYTES ? [] : images,
    };
    window.localStorage.setItem(keyFor(scope), JSON.stringify(payload));
  } catch {
    /* quota or private mode — drafts are a nice-to-have */
  }
}

export function loadWizardDraft(scope: "deck" | "homework"): WizardDraft | null {
  try {
    const raw = window.localStorage.getItem(keyFor(scope));
    if (!raw) return null;
    const parsed = JSON.parse(raw) as WizardDraft;
    if (parsed.v !== 1 || Date.now() - parsed.savedAt > TTL_MS) {
      window.localStorage.removeItem(keyFor(scope));
      return null;
    }
    return parsed;
  } catch {
    return null;
  }
}

export function clearWizardDraft(scope: "deck" | "homework"): void {
  try {
    window.localStorage.removeItem(keyFor(scope));
  } catch {
    /* ignore */
  }
}