export interface ChatViewPreferences {
  showThinking: boolean;
  showTimestamps: boolean;
  /** Include reasoning, tool summaries, and execution narration in exports. */
  includeExecution: boolean;
}

type ChatViewPreferencePatch = Partial<ChatViewPreferences>;
type StoredChatViewPreferences = Record<string, ChatViewPreferencePatch>;

export const CHAT_VIEW_PREFERENCES_STORAGE_KEY = 'makelore.chat-view-preferences.v1';
export const DEFAULT_CHAT_VIEW_PREFERENCES: ChatViewPreferences = {
  showThinking: true,
  showTimestamps: true,
  includeExecution: false,
};

function browserStorage(): Storage | undefined {
  try {
    return typeof window === 'undefined' ? undefined : window.localStorage;
  } catch {
    return undefined;
  }
}

function readStoredPreferences(storage: Storage | undefined): StoredChatViewPreferences {
  const preferences = Object.create(null) as StoredChatViewPreferences;
  if (!storage) return preferences;

  try {
    const parsed = JSON.parse(storage.getItem(CHAT_VIEW_PREFERENCES_STORAGE_KEY) ?? '{}');
    if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) return preferences;

    for (const [sessionId, candidate] of Object.entries(parsed as Record<string, unknown>)) {
      if (!candidate || typeof candidate !== 'object' || Array.isArray(candidate)) continue;
      const record = candidate as Record<string, unknown>;
      preferences[sessionId] = {
        ...(typeof record.showThinking === 'boolean'
          ? { showThinking: record.showThinking }
          : {}),
        ...(typeof record.showTimestamps === 'boolean'
          ? { showTimestamps: record.showTimestamps }
          : {}),
        ...(typeof record.includeExecution === 'boolean'
          ? { includeExecution: record.includeExecution }
          : {}),
      };
    }
  } catch {
    return preferences;
  }

  return preferences;
}

export function loadChatViewPreferences(
  sessionId: string,
  storage: Storage | undefined = browserStorage(),
): ChatViewPreferences {
  const candidate = readStoredPreferences(storage)[sessionId];
  return {
    showThinking: typeof candidate?.showThinking === 'boolean'
      ? candidate.showThinking
      : DEFAULT_CHAT_VIEW_PREFERENCES.showThinking,
    showTimestamps: typeof candidate?.showTimestamps === 'boolean'
      ? candidate.showTimestamps
      : DEFAULT_CHAT_VIEW_PREFERENCES.showTimestamps,
    includeExecution: typeof candidate?.includeExecution === 'boolean'
      ? candidate.includeExecution
      : DEFAULT_CHAT_VIEW_PREFERENCES.includeExecution,
  };
}

export function saveChatViewPreferences(
  sessionId: string,
  patch: ChatViewPreferencePatch,
  storage: Storage | undefined = browserStorage(),
): ChatViewPreferences {
  const current = loadChatViewPreferences(sessionId, storage);
  const next = {
    showThinking: typeof patch.showThinking === 'boolean'
      ? patch.showThinking
      : current.showThinking,
    showTimestamps: typeof patch.showTimestamps === 'boolean'
      ? patch.showTimestamps
      : current.showTimestamps,
    includeExecution: typeof patch.includeExecution === 'boolean'
      ? patch.includeExecution
      : current.includeExecution,
  };
  if (!storage) return next;

  try {
    const all = readStoredPreferences(storage);
    all[sessionId] = next;
    storage.setItem(CHAT_VIEW_PREFERENCES_STORAGE_KEY, JSON.stringify(all));
  } catch {
    // View preferences are best-effort and must never block the chat UI.
  }

  return next;
}

export function deleteChatViewPreferences(
  sessionId: string,
  storage: Storage | undefined = browserStorage(),
): void {
  if (!storage) return;

  try {
    const all = readStoredPreferences(storage);
    if (!Object.prototype.hasOwnProperty.call(all, sessionId)) return;
    delete all[sessionId];
    if (Object.keys(all).length === 0) {
      storage.removeItem(CHAT_VIEW_PREFERENCES_STORAGE_KEY);
    } else {
      storage.setItem(CHAT_VIEW_PREFERENCES_STORAGE_KEY, JSON.stringify(all));
    }
  } catch {
    // Host deletion already succeeded; unavailable storage must not undo it.
  }
}