export type CanvasDraft = { base: string; snapshot: string };
const key = (projectId: string) => `canvas-unsynced:${projectId}`;

export function readCanvasDraft(projectId: string): CanvasDraft | null {
  try {
    const value = JSON.parse(localStorage.getItem(key(projectId)) || "null");
    return typeof value?.base === "string" && typeof value?.snapshot === "string" ? value : null;
  } catch {
    return null;
  }
}

export function writeCanvasDraft(projectId: string, draft: CanvasDraft): boolean {
  try {
    localStorage.setItem(key(projectId), JSON.stringify(draft));
    return true;
  } catch {
    return false;
  }
}

export function clearCanvasDraft(projectId: string) {
  try {
    localStorage.removeItem(key(projectId));
  } catch {
    // Keep the current in-memory canvas when browser storage is unavailable.
  }
}

const composerKey = (chatId: string) => `canvas-unsent-message:${chatId}`;
export function writeCanvasComposerDraft(chatId: string, draft: { text: string; attachments: unknown[] }) {
  try {
    localStorage.setItem(composerKey(chatId), JSON.stringify(draft));
    return true;
  } catch {
    return false;
  }
}

export function readCanvasComposerDraft<T>(chatId: string): { text: string; attachments: T[] } | null {
  try {
    const value = JSON.parse(localStorage.getItem(composerKey(chatId)) || "null");
    return typeof value?.text === "string" && Array.isArray(value?.attachments) ? value : null;
  } catch {
    return null;
  }
}

export function clearCanvasComposerDraft(chatId: string) {
  try {
    localStorage.removeItem(composerKey(chatId));
  } catch {
    // Keep the current editor contents when browser storage is unavailable.
  }
}