/*
 This file is part of GNU Taler
 (C) 2022-2024 Taler Systems S.A.

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

import {
  LibtoolVersion,
  ObservableHttpClientLibrary,
  TalerAuthenticationHttpClient,
  TalerBankConversionCacheEviction,
  TalerBankConversionHttpClient,
  TalerCoreBankCacheEviction,
  TalerCoreBankHttpClient,
  TalerCorebankApi,
  TalerError,
  assertUnreachable,
  CacheEvictor,
  ObservabilityEvent,
} from "@gnu-taler/taler-util";
import {
  BrowserFetchHttpLib,
  ErrorLoading,
  useTranslationContext,
} from "@gnu-taler/web-util/browser";
import {
  ComponentChildren,
  FunctionComponent,
  VNode,
  createContext,
  h,
} from "preact";
import { useContext, useEffect, useState } from "preact/hooks";
import {
  revalidateAccountDetails,
  revalidatePublicAccounts,
  revalidateTransactions,
} from "../hooks/account.js";
import {
  revalidateBusinessAccounts,
  revalidateCashouts,
  revalidateConversionInfo,
} from "../hooks/regional.js";

/**
 *
 * @author Sebastian Javier Marchano (sebasjm)
 */

export type Type = {
  url: URL;
  config: TalerCorebankApi.Config;
  bank: TalerCoreBankHttpClient;
  conversion: TalerBankConversionHttpClient;
  authenticator: (user: string) => TalerAuthenticationHttpClient;
  hints: VersionHint[];
  onBackendActivity: (fn: Listener) => Unsuscriber;
  cancelRequest: (eventId: string) => void;
};

// FIXME: below
// @ts-expect-error default value to undefined, should it be another thing?
const Context = createContext<Type>(undefined);

export const useBankCoreApiContext = (): Type => useContext(Context);

export enum VersionHint {
  /**
   * when this flag is on, server is running an old version with cashout before implementing 2fa API
   */
  CASHOUT_BEFORE_2FA,
}

const observers = new Array<(e: ObservabilityEvent) => void>();
type Listener = (e: ObservabilityEvent) => void;
type Unsuscriber = () => void;

const activity = Object.freeze({
  notify: (data: ObservabilityEvent) =>
    observers.forEach((observer) => observer(data)),
  subscribe: (func: Listener): Unsuscriber => {
    observers.push(func);
    return () => {
      observers.forEach((observer, index) => {
        if (observer === func) {
          observers.splice(index, 1);
        }
      });
    };
  },
});

export type ConfigResult =
  | undefined
  | { type: "ok"; config: TalerCorebankApi.Config; hints: VersionHint[] }
  | { type: "incompatible"; result: TalerCorebankApi.Config; supported: string }
  | { type: "error"; error: TalerError };

export const BankCoreApiProvider = ({
  baseUrl,
  children,
  frameOnError,
}: {
  baseUrl: string;
  children: ComponentChildren;
  frameOnError: FunctionComponent<{ children: ComponentChildren }>;
}): VNode => {
  const [checked, setChecked] = useState<ConfigResult>();
  const { i18n } = useTranslationContext();

  const { bankClient, conversionClient, authClient, cancelRequest } =
    buildApiClient(new URL(baseUrl));

  useEffect(() => {
    bankClient
      .getConfig()
      .then((resp) => {
        if (resp.type === "fail") {
          setChecked({ type: "error", error:  TalerError.fromUncheckedDetail(resp.detail) });
        } else if (bankClient.isCompatible(resp.body.version)) {
          setChecked({ type: "ok", config: resp.body, hints: [] });
        } else {
          // this API supports version 3.0.3
          const compare = LibtoolVersion.compare("3:0:3", resp.body.version);
          if (compare?.compatible ?? false) {
            setChecked({
              type: "ok",
              config: resp.body,
              hints: [VersionHint.CASHOUT_BEFORE_2FA],
            });
          } else {
            setChecked({
              type: "incompatible",
              result: resp.body,
              supported: bankClient.PROTOCOL_VERSION,
            });
          }
        }
      })
      .catch((error: unknown) => {
        if (error instanceof TalerError) {
          setChecked({ type: "error", error });
        }
      });
  }, []);

  if (checked === undefined) {
    return h(frameOnError, { children: h("div", {}, "loading...") });
  }
  if (checked.type === "error") {
    return h(frameOnError, {
      children: h(ErrorLoading, { error: checked.error, showDetail: true }),
    });
  }
  if (checked.type === "incompatible") {
    return h(frameOnError, {
      children: h(
        "div",
        {},
        i18n.str`The bank backend is not supported. Supported version "${checked.supported}", server version "${checked.result.version}"`,
      ),
    });
  }
  const value: Type = {
    url: new URL(bankClient.baseUrl),
    config: checked.config,
    bank: bankClient,
    onBackendActivity: activity.subscribe,
    conversion: conversionClient,
    authenticator: authClient,
    cancelRequest,
    hints: checked.hints,
  };
  return h(Context.Provider, {
    value,
    children,
  });
};

/**
 * build http client with cache breaker due to SWR
 * @param url
 * @returns
 */
function buildApiClient(url: URL) {
  const httpFetch = new BrowserFetchHttpLib({
    enableThrottling: true,
    requireTls: false,
  });
  const httpLib = new ObservableHttpClientLibrary(httpFetch, {
    observe(ev) {
      activity.notify(ev);
    },
  });

  function cancelRequest(id: string) {
    httpLib.cancelRequest(id);
  }

  const bankClient = new TalerCoreBankHttpClient(
    url.href,
    httpLib,
    evictBankSwrCache,
  );
  const conversionClient = new TalerBankConversionHttpClient(
    bankClient.getConversionInfoAPI().href,
    httpLib,
    evictConversionSwrCache,
  );
  const authClient = (user: string) =>
    new TalerAuthenticationHttpClient(
      bankClient.getAuthenticationAPI(user).href,
      httpLib,
    );

  return { bankClient, conversionClient, authClient, cancelRequest };
}

export const BankCoreApiProviderTesting = ({
  children,
  state,
  url,
}: {
  children: ComponentChildren;
  state: TalerCorebankApi.Config;
  url: string;
}): VNode => {
  const value: Type = {
    url: new URL(url),
    config: state,
    // @ts-expect-error this API is not being used, not really needed
    bank: undefined,
    hints: [],
  };

  return h(Context.Provider, {
    value,
    children,
  });
};

const evictBankSwrCache: CacheEvictor<TalerCoreBankCacheEviction> = {
  async notifySuccess(op) {
    switch (op) {
      case TalerCoreBankCacheEviction.DELETE_ACCOUNT: {
        await Promise.all([
          revalidatePublicAccounts(),
          revalidateBusinessAccounts(),
        ]);
        return;
      }
      case TalerCoreBankCacheEviction.CREATE_ACCOUNT: {
        // admin balance change on new account
        await Promise.all([
          revalidateAccountDetails(),
          revalidateTransactions(),
          revalidatePublicAccounts(),
          revalidateBusinessAccounts(),
        ]);
        return;
      }
      case TalerCoreBankCacheEviction.UPDATE_ACCOUNT: {
        await Promise.all([revalidateAccountDetails()]);
        return;
      }
      case TalerCoreBankCacheEviction.CREATE_TRANSACTION: {
        await Promise.all([
          revalidateAccountDetails(),
          revalidateTransactions(),
        ]);
        return;
      }
      case TalerCoreBankCacheEviction.CONFIRM_WITHDRAWAL: {
        await Promise.all([
          revalidateAccountDetails(),
          revalidateTransactions(),
        ]);
        return;
      }
      case TalerCoreBankCacheEviction.CREATE_CASHOUT: {
        await Promise.all([
          revalidateAccountDetails(),
          revalidateCashouts(),
          revalidateTransactions(),
        ]);
        return;
      }
      case TalerCoreBankCacheEviction.UPDATE_PASSWORD:
      case TalerCoreBankCacheEviction.ABORT_WITHDRAWAL:
      case TalerCoreBankCacheEviction.CREATE_WITHDRAWAL:
        return;
      default:
        assertUnreachable(op);
    }
  },
};

const evictConversionSwrCache: CacheEvictor<TalerBankConversionCacheEviction> =
  {
    async notifySuccess(op) {
      switch (op) {
        case TalerBankConversionCacheEviction.UPDATE_RATE: {
          await revalidateConversionInfo();
          return;
        }
        default:
          assertUnreachable(op);
      }
    },
  };