import { PathConfig, PathConfigMap, validatePathConfig } from '@react-navigation/core';
import type { NavigationState, PartialState, Route } from '@react-navigation/routers';
import Constants from 'expo-constants';
import * as queryString from 'query-string';

import { matchDeepDynamicRouteName, matchDynamicName, matchGroupName } from '../matchers';

type Options<ParamList extends object> = {
  initialRouteName?: string;
  screens: PathConfigMap<ParamList>;
};

export type State = NavigationState | Omit<PartialState<NavigationState>, 'stale'>;

type StringifyConfig = Record<string, (value: any) => string>;

type ConfigItem = {
  pattern?: string;
  stringify?: StringifyConfig;
  screens?: Record<string, ConfigItem>;
  // Used as fallback for groups
  initialRouteName?: string;
};

type CustomRoute = Route<string> & {
  state?: State;
};

const DEFAULT_SCREENS: PathConfigMap<object> = {};

const getActiveRoute = (state: State): { name: string; params?: object } => {
  const route =
    typeof state.index === 'number'
      ? state.routes[state.index]
      : state.routes[state.routes.length - 1];

  if (route.state) {
    return getActiveRoute(route.state);
  }

  if (route && isInvalidParams(route.params)) {
    return getActiveRoute(createFakeState(route.params));
  }

  return route;
};

function createFakeState(params: StateAsParams) {
  return {
    stale: false,
    type: 'UNKNOWN',
    key: 'UNKNOWN',
    index: 0,
    routeNames: [],
    routes: [
      {
        key: 'UNKNOWN',
        name: params.screen,
        params: params.params,
        path: params.path,
      },
    ],
  };
}

function segmentMatchesConvention(segment: string): boolean {
  return (
    segment === 'index' ||
    matchDynamicName(segment) != null ||
    matchGroupName(segment) != null ||
    matchDeepDynamicRouteName(segment) != null
  );
}

function encodeURIComponentPreservingBrackets(str: string) {
  return encodeURIComponent(str).replace(/%5B/g, '[').replace(/%5D/g, ']');
}

/**
 * Utility to serialize a navigation state object to a path string.
 *
 * @example
 * ```js
 * getPathFromState(
 *   {
 *     routes: [
 *       {
 *         name: 'Chat',
 *         params: { author: 'Jane', id: 42 },
 *       },
 *     ],
 *   },
 *   {
 *     screens: {
 *       Chat: {
 *         path: 'chat/:author/:id',
 *         stringify: { author: author => author.toLowerCase() }
 *       }
 *     }
 *   }
 * )
 * ```
 *
 * @param state Navigation state to serialize.
 * @param options Extra options to fine-tune how to serialize the path.
 * @returns Path representing the state, e.g. /foo/bar?count=42.
 */
export default function getPathFromState<ParamList extends object>(
  state: State,
  _options?: Options<ParamList> & {
    preserveGroups?: boolean;
    preserveDynamicRoutes?: boolean;
  }
): string {
  return getPathDataFromState(state, _options).path;
}

export function getPathDataFromState<ParamList extends object>(
  state: State,
  _options: Options<ParamList> & {
    preserveGroups?: boolean;
    preserveDynamicRoutes?: boolean;
  } = { screens: DEFAULT_SCREENS }
) {
  if (state == null) {
    throw Error("Got 'undefined' for the navigation state. You must pass a valid state object.");
  }

  const { preserveGroups, preserveDynamicRoutes, ...options } = _options;

  validatePathConfig(options);

  // Expo Router disallows usage without a linking config.
  if (Object.is(options.screens, DEFAULT_SCREENS)) {
    throw Error("You must pass a 'screens' object to 'getPathFromState' to generate a path.");
  }

  return getPathFromResolvedState(
    JSON.parse(JSON.stringify(state)),
    // Create a normalized configs object which will be easier to use
    createNormalizedConfigs(options.screens),
    { preserveGroups, preserveDynamicRoutes }
  );
}

function processParamsWithUserSettings(configItem: ConfigItem, params: Record<string, any>) {
  const stringify = configItem?.stringify;

  return Object.fromEntries(
    Object.entries(params).map(([key, value]) => [
      key,
      // TODO: Strip nullish values here.
      stringify?.[key]
        ? stringify[key](value)
        : // Preserve rest params
        Array.isArray(value)
        ? value
        : String(value),
    ])
  );
}

export function deepEqual(a: any, b: any) {
  if (a === b) {
    return true;
  }

  if (Array.isArray(a) && Array.isArray(b)) {
    if (a.length !== b.length) {
      return false;
    }

    for (let i = 0; i < a.length; i++) {
      if (!deepEqual(a[i], b[i])) {
        return false;
      }
    }

    return true;
  }

  if (typeof a === 'object' && typeof b === 'object') {
    const keysA = Object.keys(a);
    const keysB = Object.keys(b);

    if (keysA.length !== keysB.length) {
      return false;
    }

    for (const key of keysA) {
      if (!deepEqual(a[key], b[key])) {
        return false;
      }
    }

    return true;
  }

  return false;
}

function walkConfigItems(
  route: CustomRoute,
  focusedRoute: {
    name: string;
    params?: object;
  },
  configs: Record<string, ConfigItem>,
  {
    preserveDynamicRoutes,
  }: {
    preserveDynamicRoutes?: boolean;
  }
) {
  // NOTE(EvanBacon): Fill in current route using state that was passed as params.
  if (!route.state && isInvalidParams(route.params)) {
    route.state = createFakeState(route.params);
  }

  let pattern: string | null = null;
  let focusedParams: Record<string, any> | undefined;

  const collectedParams: Record<string, any> = {};

  while (route.name in configs) {
    const configItem = configs[route.name];
    const inputPattern = configItem.pattern;

    if (inputPattern == null) {
      // This should never happen in Expo Router.
      throw new Error('Unexpected: No pattern found for route ' + route.name);
    }
    pattern = inputPattern;

    if (route.params) {
      const params = processParamsWithUserSettings(configItem, route.params);
      // TODO: Does this need to be a null check?
      if (pattern) {
        Object.assign(collectedParams, params);
      }
      if (deepEqual(focusedRoute, route)) {
        if (preserveDynamicRoutes) {
          focusedParams = params;
        } else {
          // If this is the focused route, keep the params for later use
          // We save it here since it's been stringified already
          focusedParams = getParamsWithConventionsCollapsed({
            params,
            pattern,
            routeName: route.name,
          });
        }
      }
    }

    if (!route.state && isInvalidParams(route.params)) {
      route.state = createFakeState(route.params);
    }

    // If there is no `screens` property or no nested state, we return pattern
    if (!configItem.screens || route.state === undefined) {
      if (
        configItem.initialRouteName &&
        configItem.screens &&
        configItem.initialRouteName in configItem.screens &&
        configItem.screens[configItem.initialRouteName]?.pattern
      ) {
        const initialRouteConfig = configItem.screens[configItem.initialRouteName];

        // NOTE(EvanBacon): Big hack to support initial route changes in tab bars.
        pattern = initialRouteConfig.pattern!;
        if (focusedParams) {
          if (!preserveDynamicRoutes) {
            // If this is the focused route, keep the params for later use
            // We save it here since it's been stringified already
            focusedParams = getParamsWithConventionsCollapsed({
              params: focusedParams,
              pattern,
              routeName: route.name,
            });
          }
        }
      }
      break;
    }

    const index = route.state.index ?? route.state.routes.length - 1;

    const nextRoute = route.state.routes[index];
    const nestedScreens = configItem.screens;

    // if there is config for next route name, we go deeper
    if (nestedScreens && nextRoute.name in nestedScreens) {
      route = nextRoute as CustomRoute;
      configs = nestedScreens;
    } else {
      // If not, there is no sense in going deeper in config
      break;
    }
  }

  if (pattern == null) {
    throw new Error(
      `No pattern found for route "${route.name}". Options are: ${Object.keys(configs).join(', ')}.`
    );
  }

  if (pattern && !focusedParams && focusedRoute.params) {
    if (preserveDynamicRoutes) {
      focusedParams = focusedRoute.params;
    } else {
      // If this is the focused route, keep the params for later use
      // We save it here since it's been stringified already
      focusedParams = getParamsWithConventionsCollapsed({
        params: focusedRoute.params,
        pattern,
        routeName: route.name,
      });
    }
    Object.assign(focusedParams, collectedParams);
  }

  return {
    pattern,
    nextRoute: route,
    focusedParams,
    params: collectedParams,
  };
}

function getPathFromResolvedState(
  state: State,
  configs: Record<string, ConfigItem>,
  {
    preserveGroups,
    preserveDynamicRoutes,
  }: { preserveGroups?: boolean; preserveDynamicRoutes?: boolean }
) {
  let path = '';
  let current: State = state;

  const allParams: Record<string, any> = {};

  while (current) {
    path += '/';

    // Make mutable copies to ensure we don't leak state outside of the function.
    const route = current.routes[current.index ?? 0] as CustomRoute;

    // NOTE(EvanBacon): Fill in current route using state that was passed as params.
    // if (isInvalidParams(route.params)) {
    if (!route.state && isInvalidParams(route.params)) {
      route.state = createFakeState(route.params);
    }

    const { pattern, params, nextRoute, focusedParams } = walkConfigItems(
      route,
      getActiveRoute(current),
      { ...configs },
      { preserveDynamicRoutes }
    );

    Object.assign(allParams, params);

    path += getPathWithConventionsCollapsed({
      pattern,
      routePath: nextRoute.path,
      params: allParams,
      initialRouteName: configs[nextRoute.name]?.initialRouteName,
      preserveGroups,
      preserveDynamicRoutes,
    });

    if (
      nextRoute.state &&
      // NOTE(EvanBacon): The upstream implementation allows for sending in synthetic states (states that weren't generated by `getStateFromPath`)
      // and any invalid routes will simply be ignored.
      // Because of this, we need to check if the next route is valid before continuing, otherwise our more strict
      // implementation will throw an error.
      configs[nextRoute.state.routes?.[nextRoute.state?.index ?? 0]?.name]
    ) {
      // Continue looping with the next state if available.
      current = nextRoute.state;
    } else {
      // Finished crawling state.

      // Check for query params before exiting.
      if (focusedParams) {
        for (const param in focusedParams) {
          // TODO: This is not good. We shouldn't squat strings named "undefined".
          if (focusedParams[param] === 'undefined') {
            // eslint-disable-next-line @typescript-eslint/no-dynamic-delete
            delete focusedParams[param];
          }
        }

        const query = queryString.stringify(focusedParams, { sort: false });
        if (query) {
          path += `?${query}`;
        }
      }
      break;
    }
  }

  return { path: appendBasePath(basicSanitizePath(path)), params: decodeParams(allParams) };
}

function decodeParams(params: Record<string, string>) {
  const parsed: Record<string, any> = {};

  for (const [key, value] of Object.entries(params)) {
    parsed[key] = decodeURIComponent(value);
  }

  return parsed;
}

function getPathWithConventionsCollapsed({
  pattern,
  routePath,
  params,
  preserveGroups,
  preserveDynamicRoutes,
  initialRouteName,
}: {
  pattern: string;
  routePath?: string;
  params: Record<string, any>;
  preserveGroups?: boolean;
  preserveDynamicRoutes?: boolean;
  initialRouteName?: string;
}) {
  const segments = pattern.split('/');
  return segments
    .map((p, i) => {
      const name = getParamName(p);

      // We don't know what to show for wildcard patterns
      // Showing the route name seems ok, though whatever we show here will be incorrect
      // Since the page doesn't actually exist
      if (p.startsWith('*')) {
        if (preserveDynamicRoutes) {
          return `[...${name}]`;
        }
        if (params[name]) {
          if (Array.isArray(params[name])) {
            return params[name].join('/');
          }
          return params[name];
        }
        if (i === 0) {
          // This can occur when a wildcard matches all routes and the given path was `/`.
          return routePath;
        }
        // remove existing segments from route.path and return it
        // this is used for nested wildcard routes. Without this, the path would add
        // all nested segments to the beginning of the wildcard route.
        return routePath
          ?.split('/')
          .slice(i + 1)
          .join('/');
      }

      // If the path has a pattern for a param, put the param in the path
      if (p.startsWith(':')) {
        if (preserveDynamicRoutes) {
          return `[${name}]`;
        }
        // Optional params without value assigned in route.params should be ignored
        return params[name];
      }

      if (!preserveGroups && matchGroupName(p) != null) {
        // When the last part is a group it could be a shared URL
        // if the route has an initialRouteName defined, then we should
        // use that as the component path as we can assume it will be shown.
        if (segments.length - 1 === i) {
          if (initialRouteName) {
            // Return an empty string if the init route is ambiguous.
            if (segmentMatchesConvention(initialRouteName)) {
              return '';
            }
            return encodeURIComponentPreservingBrackets(initialRouteName);
          }
        }
        return '';
      }
      // Preserve dynamic syntax for rehydration
      return encodeURIComponentPreservingBrackets(p);
    })
    .map((v) => v ?? '')
    .join('/');
}

/** Given a set of query params and a pattern with possible conventions, collapse the conventions and return the remaining params. */
function getParamsWithConventionsCollapsed({
  pattern,
  routeName,
  params,
}: {
  pattern: string;
  /** Route name is required for matching the wildcard route. This is specific to Expo Router. */
  routeName: string;
  params: object;
}): Record<string, string> {
  const processedParams: Record<string, string> = { ...params };

  // Remove the params present in the pattern since we'll only use the rest for query string

  const segments = pattern.split('/');

  // Dynamic Routes
  segments
    .filter((segment) => segment.startsWith(':'))
    .forEach((segment) => {
      const name = getParamName(segment);
      delete processedParams[name];
    });

  // Deep Dynamic Routes
  if (segments.some((segment) => segment.startsWith('*'))) {
    // NOTE(EvanBacon): Drop the param name matching the wildcard route name -- this is specific to Expo Router.
    const name = matchDeepDynamicRouteName(routeName) ?? routeName;
    delete processedParams[name];
  }

  return processedParams;
}

// Remove multiple as well as trailing slashes
function basicSanitizePath(path: string) {
  // Remove duplicate slashes like `foo//bar` -> `foo/bar`
  const simplifiedPath = path.replace(/\/+/g, '/');
  if (simplifiedPath.length <= 1) {
    return simplifiedPath;
  }
  // Remove trailing slash like `foo/bar/` -> `foo/bar`
  return simplifiedPath.replace(/\/$/, '');
}

type StateAsParams = {
  initial: boolean;
  path?: string;
  screen: string;
  params: Record<string, any>;
};

// TODO: Make StackRouter not do this...
// Detect if the params came from StackRouter using `params` to pass around internal state.
function isInvalidParams(params?: Record<string, any>): params is StateAsParams {
  if (!params) {
    return false;
  }

  if ('params' in params && typeof params.params === 'object' && !!params.params) {
    return true;
  }

  return (
    'initial' in params &&
    typeof params.initial === 'boolean' &&
    // "path" in params &&
    'screen' in params
  );
}

const getParamName = (pattern: string) => pattern.replace(/^[:*]/, '').replace(/\?$/, '');

const joinPaths = (...paths: string[]): string =>
  ([] as string[])
    .concat(...paths.map((p) => p.split('/')))
    .filter(Boolean)
    .join('/');

const createConfigItem = (
  config: PathConfig<object> | string,
  parentPattern?: string
): ConfigItem => {
  if (typeof config === 'string') {
    // If a string is specified as the value of the key(e.g. Foo: '/path'), use it as the pattern
    const pattern = parentPattern ? joinPaths(parentPattern, config) : config;

    return { pattern };
  }

  if (config.exact && config.path === undefined) {
    throw new Error(
      "A 'path' needs to be specified when specifying 'exact: true'. If you don't want this screen in the URL, specify it as empty string, e.g. `path: ''`."
    );
  }

  // If an object is specified as the value (e.g. Foo: { ... }),
  // It can have `path` property and `screens` prop which has nested configs
  const pattern =
    config.exact !== true ? joinPaths(parentPattern || '', config.path || '') : config.path || '';

  const screens = config.screens ? createNormalizedConfigs(config.screens, pattern) : undefined;

  return {
    // Normalize pattern to remove any leading, trailing slashes, duplicate slashes etc.
    pattern: pattern?.split('/').filter(Boolean).join('/'),
    stringify: config.stringify,
    screens,
    initialRouteName: config.initialRouteName,
  };
};

const createNormalizedConfigs = (
  options: PathConfigMap<object>,
  pattern?: string
): Record<string, ConfigItem> =>
  Object.fromEntries(
    Object.entries(options).map(([name, c]) => [name, createConfigItem(c, pattern)])
  );

export function appendBasePath(
  path: string,
  assetPrefix: string | undefined = Constants.expoConfig?.experiments?.basePath
) {
  if (process.env.NODE_ENV !== 'development') {
    if (assetPrefix) {
      return `/${assetPrefix.replace(/^\/+/, '').replace(/\/$/, '')}${path}`;
    }
  }
  return path;
}