import {
  ApolloClient,
  FetchResult,
  InMemoryCache,
  NormalizedCacheObject,
  Reference,
  createHttpLink,
} from "@apollo/client";
import fetch from "cross-fetch";
import jwtDecode from "jwt-decode";

import { JWTToken } from "../core";
import { AuthSDK, auth } from "../core/auth";
import { storage } from "../core/storage";
import { isInternalToken } from "../helpers";
import { TypedTypePolicies } from "./apollo-helpers";
import { ExternalRefreshMutation, RefreshTokenMutation } from "./types";

let client: ApolloClient<NormalizedCacheObject>;
let authClient: AuthSDK;
let refreshPromise:
  | ReturnType<AuthSDK["refreshToken"]>
  | ReturnType<AuthSDK["refreshExternalToken"]>
  | null = null;
const isTokenRefreshExternal = (
  result: RefreshTokenMutation | ExternalRefreshMutation
): result is ExternalRefreshMutation => "externalRefresh" in result;

export type FetchConfig = Partial<{
  /**
   * Enable auto token refreshing. Default to `true`.
   */
  autoTokenRefresh: boolean;
  /**
   * Set a value for skew between local time and token expiration date in
   * seconds (only together with `autoTokenRefresh`). Defaults to `120`.
   */
  tokenRefreshTimeSkew: number;
  /**
   * Refresh token and retry the request when Saleor responds with `Unauthorized` error.
   * Defaults to `true`.
   */
  refreshOnUnauthorized: boolean;
}>;

export const createFetch = ({
  autoTokenRefresh = true,
  tokenRefreshTimeSkew = 120,
  refreshOnUnauthorized = true,
}: FetchConfig = {}) => async (
  input: RequestInfo,
  init: RequestInit = {}
): Promise<Response> => {
  if (!client) {
    throw new Error(
      "Could not find Saleor's client instance. Did you forget to call createSaleorClient()?"
    );
  }

  let token = storage.getAccessToken();

  try {
    if (
      ["refreshToken", "externalRefresh"].includes(
        // INFO: Non-null assertion is enabled because the block is wrapped inside try/catch
        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
        JSON.parse(init.body!.toString()).operationName
      )
    ) {
      return fetch(input, init);
    }
  } catch (e) {}

  if (autoTokenRefresh && token) {
    // auto refresh token before provided time skew (in seconds) until it expires
    const decodedToken = jwtDecode<JWTToken>(token);
    const expirationTime = (decodedToken.exp - tokenRefreshTimeSkew) * 1000;
    const owner = decodedToken.owner;

    try {
      if (refreshPromise) {
        await refreshPromise;
      } else if (Date.now() >= expirationTime) {
        if (isInternalToken(owner)) {
          await authClient.refreshToken();
        } else {
          await authClient.refreshExternalToken();
        }
      }
    } catch (e) {
    } finally {
      refreshPromise = null;
    }
    token = storage.getAccessToken();
  }

  if (token) {
    init.headers = {
      ...init.headers,
      "authorization-bearer": token,
    };
  }

  if (refreshOnUnauthorized && token) {
    const response = await fetch(input, init);
    const data: FetchResult = await response.clone().json();
    const isUnauthenticated = data?.errors?.some(
      error => error.extensions?.exception.code === "ExpiredSignatureError"
    );
    let refreshTokenResponse: FetchResult<
      RefreshTokenMutation | ExternalRefreshMutation,
      Record<string, unknown>,
      Record<string, unknown>
    > | null = null;
    const owner = jwtDecode<JWTToken>(token).owner;

    if (isUnauthenticated) {
      try {
        if (refreshPromise) {
          refreshTokenResponse = await refreshPromise;
        } else {
          refreshPromise = isInternalToken(owner)
            ? authClient.refreshToken()
            : authClient.refreshExternalToken();
          refreshTokenResponse = await refreshPromise;
        }

        if (
          refreshTokenResponse.data &&
          isTokenRefreshExternal(refreshTokenResponse.data)
            ? refreshTokenResponse.data.externalRefresh?.token
            : refreshTokenResponse.data?.tokenRefresh?.token
        ) {
          // check if mutation returns a valid token after refresh and retry the request
          return createFetch({
            autoTokenRefresh: false,
            refreshOnUnauthorized: false,
          })(input, init);
        } else {
          // after Saleor returns ExpiredSignatureError status and token refresh fails
          // we log out the user and return the failed response
          authClient.logout();
        }
      } catch (e) {
      } finally {
        refreshPromise = null;
      }
    }

    return response;
  }

  return fetch(input, init);
};

const getTypePolicies = (autologin: boolean): TypedTypePolicies => ({
  Query: {
    fields: {
      authenticated: {
        read(_, { readField, toReference }): boolean {
          return !!readField(
            "id",
            toReference({
              __typename: "User",
            })
          );
        },
      },
      me: {
        read(_, { toReference, canRead }): Reference | undefined | null {
          const ref = toReference({
            __typename: "User",
          });

          return canRead(ref) ? ref : null;
        },
      },
      authenticating: {
        read(
          read = autologin && !!storage.getRefreshToken(),
          { readField }
        ): boolean {
          if (readField("authenticated")) {
            return false;
          }

          return read;
        },
      },
    },
  },
  User: {
    /**
     * IMPORTANT
     * This works as long as we have 1 User cache object which is the current logged in User.
     * If the client should ever fetch additional Users, this should be removed
     * and the login methods (token create or verify) should be responsible for writing USER query cache manually.
     */
    keyFields: [],
    fields: {
      addresses: {
        merge: false,
      },
    },
  },
});

export const createApolloClient = (
  apiUrl: string,
  autologin: boolean,
  fetchOptions?: FetchConfig
): ApolloClient<NormalizedCacheObject> => {
  const httpLink = createHttpLink({
    fetch: createFetch(fetchOptions),
    uri: apiUrl,
    credentials: "include",
  });

  const cache = new InMemoryCache({
    typePolicies: getTypePolicies(autologin),
  });

  client = new ApolloClient({
    cache,
    link: httpLink,
  });

  /**
   * Refreshing token code should stay under core/auth.ts To get this method available,
   * we need to call "auth()" here. refreshToken mutation doesn't require channel, so it
   * doesn't have to be populated with value.
   */
  authClient = auth({ apolloClient: client, channel: "" });

  return client;
};