export type DeletionStep = 'warning' | 'confirm' | 'code';

export type DeletionDialogState = {
  step: DeletionStep;
  confirmationCode: string;
  codeReceived: boolean;
  scheduledDate: string;
  isLoading: boolean;
  error: string | null;
};

export type DeletionDialogAction =
  | { type: 'CONTINUE_TO_CONFIRM' }
  | { type: 'GO_BACK_TO_WARNING' }
  | { type: 'REQUEST_DELETION'; payload: { scheduledDate: string } }
  | { type: 'UPDATE_CODE'; payload: { code: string } }
  | { type: 'TOGGLE_CODE_RECEIVED' }
  | { type: 'SET_LOADING'; payload: boolean }
  | { type: 'SET_ERROR'; payload: string | null }
  | { type: 'RESET' };

export const initialState: DeletionDialogState = {
  step: 'warning',
  confirmationCode: '',
  codeReceived: false,
  scheduledDate: '',
  isLoading: false,
  error: null
};

export function deletionDialogReducer(
  state: DeletionDialogState,
  action: DeletionDialogAction
): DeletionDialogState {
  switch (action.type) {
    case 'CONTINUE_TO_CONFIRM':
      return { ...state, step: 'confirm' };
      
    case 'GO_BACK_TO_WARNING':
      return { ...state, step: 'warning', error: null };
      
    case 'REQUEST_DELETION':
      return {
        ...state,
        step: 'code',
        scheduledDate: action.payload.scheduledDate,
        isLoading: false,
        error: null
      };
      
    case 'UPDATE_CODE':
      // Only allow digits, max 6
      const sanitized = action.payload.code.replace(/\D/g, '').slice(0, 6);
      return { ...state, confirmationCode: sanitized };
      
    case 'TOGGLE_CODE_RECEIVED':
      return { ...state, codeReceived: !state.codeReceived };
      
    case 'SET_LOADING':
      return { ...state, isLoading: action.payload };
      
    case 'SET_ERROR':
      return { ...state, error: action.payload, isLoading: false };
      
    case 'RESET':
      return initialState;
      
    default:
      // Exhaustive check
      const _exhaustive: never = action;
      return state;
  }
}

// Validation helpers
export const canProceedToConfirm = (state: DeletionDialogState): boolean => {
  return state.step === 'warning' && !state.isLoading;
};

export const canRequestDeletion = (state: DeletionDialogState): boolean => {
  return state.step === 'confirm' && !state.isLoading;
};

export const canConfirmDeletion = (state: DeletionDialogState): boolean => {
  return (
    state.step === 'code' &&
    state.confirmationCode.length === 6 &&
    state.codeReceived &&
    !state.isLoading
  );
};