import { nanoid } from 'nanoid/non-secure';

import type {
  CommonNavigationAction,
  NavigationState,
  PartialState,
} from './types';

function getStateForAction<State extends NavigationState>(
  state: State,
  action: CommonNavigationAction
): State | PartialState<State> | null;
function getStateForAction(
  state: NavigationState,
  action: CommonNavigationAction
) {
  switch (action.type) {
    case 'SET_PARAMS':
    case 'REPLACE_PARAMS': {
      const index = action.source
        ? state.routes.findIndex((r) => r.key === action.source)
        : state.index;

      if (index === -1) {
        return null;
      }

      return {
        ...state,
        routes: state.routes.map((r, i) =>
          i === index
            ? {
                ...r,
                params:
                  action.type === 'REPLACE_PARAMS'
                    ? action.payload.params
                    : { ...r.params, ...action.payload.params },
              }
            : r
        ),
      };
    }

    case 'RESET': {
      const nextState = action.payload;

      if (nextState == null) {
        return null;
      }

      const routeNamesSet = new Set(state.routeNames);

      if (
        nextState.routes.length === 0 ||
        nextState.routes.some(
          (route: { name: string }) => !routeNamesSet.has(route.name)
        )
      ) {
        return null;
      }

      if (nextState.stale === false) {
        if (
          state.routeNames.length !== nextState.routeNames.length ||
          nextState.routeNames.some((name) => !routeNamesSet.has(name)) ||
          !Number.isInteger(nextState.index) ||
          nextState.index < 0 ||
          nextState.index >= nextState.routes.length
        ) {
          return null;
        }

        return {
          ...nextState,
          routes: nextState.routes.map((route) =>
            'key' in route && route.key
              ? route
              : { ...route, key: `${route.name}-${nanoid()}` }
          ),
        };
      }

      return nextState;
    }

    default:
      return null;
  }
}

/**
 * Base router object that can be used when writing custom routers.
 * This provides few helper methods to handle common actions such as `RESET`.
 */
export const BaseRouter = {
  getStateForAction,

  shouldActionChangeFocus(action: CommonNavigationAction) {
    return action.type === 'NAVIGATE' || action.type === 'NAVIGATE_DEPRECATED';
  },
};