export type OperationKey = 'connection' | 'serverApply' | 'profileAdd' | 'profileRename'
  | 'profileSelect' | 'profileActivate' | 'profileRefresh' | 'profileDelete'
  | 'gatewayAuto' | 'routeRules' | 'diagnosticsSettings' | 'failover';

export interface OperationState {
  status: 'running';
  startedAt: string;
  target: string;
}

export type OperationRegistrySnapshot = Partial<Record<OperationKey, OperationState>>;

const OPERATION_KEYS: readonly OperationKey[] = [
  'connection',
  'serverApply',
  'profileAdd',
  'profileRename',
  'profileSelect',
  'profileActivate',
  'profileRefresh',
  'profileDelete',
  'gatewayAuto',
  'routeRules',
  'diagnosticsSettings',
  'failover',
];

// The backend has one canonical revision and one mutation queue, so the UI mirrors that lock.
export const OPERATION_CONFLICTS = Object.freeze(Object.fromEntries(
  OPERATION_KEYS.map((key) => [key, OPERATION_KEYS.filter((candidate) => candidate !== key)]),
) as unknown as Record<OperationKey, readonly OperationKey[]>);

export function operationBlocked(operations: OperationRegistrySnapshot, key: OperationKey) {
  if (operations[key]?.status === 'running') return true;
  return OPERATION_CONFLICTS[key].some((conflict) => operations[conflict]?.status === 'running');
}

export function createOperationRegistry(
  onChange: (operations: OperationRegistrySnapshot) => void = () => {},
  now = () => new Date().toISOString(),
) {
  let operations: OperationRegistrySnapshot = {};
  const inFlight = new Map<string, Promise<unknown>>();

  function run<T>(key: OperationKey, action: () => T | Promise<T>, target = ''): Promise<T | false> {
    const identity = `${key}:${target}`;
    const existing = inFlight.get(identity);
    if (existing) return existing as Promise<T>;
    if (operationBlocked(operations, key)) return Promise.resolve(false);

    operations = { ...operations, [key]: { status: 'running', startedAt: now(), target } };
    onChange(operations);

    const promise: Promise<T> = Promise.resolve()
      .then(action)
      .finally(() => {
        const { [key]: completed, ...remaining } = operations;
        operations = remaining;
        inFlight.delete(identity);
        onChange(operations);
      });
    inFlight.set(identity, promise as Promise<unknown>);
    return promise;
  }

  return { run, getSnapshot: () => operations };
}