import {
  EMPTY,
  Observable,
  Observer,
  ReplaySubject,
  Subscription,
  TimeoutError,
  concat,
  interval,
  of,
  timer,
} from "rxjs";
import { DisconnectedDevice, DisconnectedDeviceDuringOperation } from "@ledgerhq/errors";
import { catchError, debounce, delayWhen, filter, switchMap, tap, timeout } from "rxjs/operators";
import { Device } from "./types";
import { getDeviceModel } from "@ledgerhq/devices";
import { ConnectManagerTimeout } from "../../errors";
import { LocalTracer } from "@ledgerhq/logs";
import { LOG_TYPE } from "..";
import { getEnv } from "@ledgerhq/live-env";

export enum ImplementationType {
  event = "enum",
  polling = "polling",
}

type ImplementationEvent =
  | {
      type: "deviceChange";
      device?: Device | undefined | null;
    }
  | {
      type: "unresponsiveDevice";
    }
  | {
      type: "error";
      error: Error;
    };

type PollingImplementationConfig = {
  pollingFrequency: number;
  initialWaitTime: number;
  reconnectWaitTime: number;
  connectionTimeout: number;
};

type PollingImplementationParams<Request, EmittedEvents> = {
  deviceSubject: ReplaySubject<Device | null | undefined>;
  task: (params: { deviceId: string; request: Request }) => Observable<EmittedEvents>;
  request: Request;
  config?: PollingImplementationConfig;
  // retryableWithDelayDisconnectedErrors has default value of [DisconnectedDevice, DisconnectedDeviceDuringOperation]
  // used to filter which error(s) retry polling after a delay, reconnectWaitTime
  retryableWithDelayDisconnectedErrors?: ReadonlyArray<ErrorConstructor>;
};

const defaultRetryableWithDelayDisconnectedErrors: ReadonlyArray<ErrorConstructor> = [
  DisconnectedDevice,
  DisconnectedDeviceDuringOperation,
];

export const defaultImplementationConfig: PollingImplementationConfig = {
  pollingFrequency: 2000,
  initialWaitTime: 5000,
  reconnectWaitTime: 5000,
  connectionTimeout: getEnv("DETOX") ? 60000 : 20000,
};
type Implementation = <EmittedEvent, GenericRequestType>(
  params: PollingImplementationParams<GenericRequestType, EmittedEvent>,
) => Observable<EmittedEvent | ImplementationEvent>;

export type EmittedEvent<T> = {
  type: string;
} & T;

/**
 * Returns a polling implementation function that repeatedly performs a given task
 * with a given request, with a specified polling frequency and wait times until a
 * KO or OK end state is reached. This emulates the event based connection paradigm
 * from the USB stack in a BLE setting.
 * @template EmittedEvent - Type of the events emitted by the task's observable.
 * @template GenericRequestType - Type of the request to be passed to the task.
 **/
const pollingImplementation: Implementation = <SpecificType, GenericRequestType>(
  params: PollingImplementationParams<GenericRequestType, SpecificType>,
): Observable<SpecificType | ImplementationEvent> =>
  new Observable((subscriber: Observer<EmittedEvent<SpecificType> | ImplementationEvent>) => {
    const { deviceSubject, task, request, config = defaultImplementationConfig } = params;
    const { pollingFrequency, initialWaitTime, reconnectWaitTime, connectionTimeout } = config;
    const tracer = new LocalTracer(LOG_TYPE, { function: "pollingImplementation" });
    tracer.trace("Setting up device action polling implementation", { config });

    let shouldStopPolling = false;
    let connectSub: Subscription;
    let loopTimeout: NodeJS.Timeout | null;
    let firstRound = true;

    let currentDevice: Device;
    const deviceSubjectSub = deviceSubject.subscribe(device => {
      currentDevice = device || currentDevice;
    });

    // Cover case where our device job never gets a transport instance
    // it will signal back to the consumer that we don't have a device.
    let initialTimeout: NodeJS.Timeout | null = setTimeout(() => {
      return subscriber.next({
        type: "deviceChange",
        device: undefined,
      });
    }, initialWaitTime);

    // Runs every time we get a new device.
    function actionLoop() {
      if (currentDevice) {
        const productName = getDeviceModel(currentDevice.modelId).productName;

        connectSub = concat(
          of({
            type: "deviceChange",
            device: currentDevice,
            replaceable: !firstRound,
          }),
          task({ deviceId: currentDevice.deviceId, request }),
        )
          .pipe(
            // Any event should clear the initialTimeout.
            tap((_: any) => {
              if (initialTimeout) {
                clearTimeout(initialTimeout);
                initialTimeout = null;
              }
            }),

            // More than `connectionTimeout` time of silence, is considered
            // a failed connection. Depending on the flow this may mean we'd have
            // to emit an `alive` kind of event.
            timeout(connectionTimeout),

            filter((event: EmittedEvent<SpecificType> | ImplementationEvent) => {
              if ("type" in event) {
                return event.type !== "unresponsiveDevice";
              }
              return false;
            }),

            catchError((error: Error) => {
              const maybeRemappedError =
                error instanceof TimeoutError
                  ? (new ConnectManagerTimeout(undefined, {
                      // TODO make this configurable
                      productName,
                    }) as Error)
                  : error;

              tracer.trace(`Error when running task in polling implementation: ${error}`, {
                error,
                maybeRemappedError,
              });

              return of({
                type: "error",
                error: maybeRemappedError,
              } as ImplementationEvent);
            }),

            debounce((event: EmittedEvent<SpecificType> | ImplementationEvent) => {
              if (event.type === "error" && "error" in event) {
                const allowedRetryableErrors =
                  params.retryableWithDelayDisconnectedErrors ||
                  defaultRetryableWithDelayDisconnectedErrors;
                const error = event.error as unknown;
                if (allowedRetryableErrors.find(e => error instanceof e)) {
                  // Delay emission of allowed disconnects to allow reconnection.
                  return timer(reconnectWaitTime);
                }
                // Other errors should cancel the loop.
                shouldStopPolling = true;
              }
              // All other events pass through.
              return of(null);
            }),
          )
          .subscribe({
            next: (event: any) => {
              subscriber.next(event);
            },
            error: (e: any) => {
              subscriber.error(e);
            },
            complete: () => {
              if (shouldStopPolling) return;
              firstRound = false; // For proper debouncing.
              loopTimeout = setTimeout(actionLoop, pollingFrequency);
            },
          });
      } else {
        // We currently don't have a device, try again.
        loopTimeout = setTimeout(actionLoop, pollingFrequency);
      }
    }

    // Delay the first loop run in order to be async.
    loopTimeout = setTimeout(actionLoop, 0);

    // Get rid of pending timeouts and subscriptions.
    return function cleanup() {
      if (deviceSubjectSub) deviceSubjectSub.unsubscribe();
      if (connectSub) connectSub.unsubscribe();

      if (initialTimeout) clearTimeout(initialTimeout);
      if (loopTimeout) clearTimeout(loopTimeout);
    };
  });

const eventImplementation: Implementation = <SpecificType, GenericRequestType>(
  params: PollingImplementationParams<GenericRequestType, SpecificType>,
): Observable<EmittedEvent<SpecificType> | ImplementationEvent> => {
  const { deviceSubject, task, request, config = defaultImplementationConfig } = params;
  const { reconnectWaitTime } = config;
  return new Observable(
    (subscriber: Observer<EmittedEvent<SpecificType> | ImplementationEvent>) => {
      const connectSub = deviceSubject
        .pipe(
          debounce(device => timer(!device ? reconnectWaitTime : 0)),
          switchMap(device => {
            const initialEvent = of({
              type: "deviceChange",
              device,
            });

            return concat(
              initialEvent,
              !device ? EMPTY : task({ deviceId: device.deviceId, request }),
            );
          }),
          catchError((error: Error) =>
            of({
              type: "error",
              error,
            }),
          ),
          // NB An error is a dead-end as far as the task is concerned, and by delaying
          // the emission of the event we prevent instant failures from showing flashing
          // UI that looks like a glitch. For instance, if the device is locked and we retry
          // this would allow a better UX, 800ms before a failure is totally acceptable.
          delayWhen((e: any) =>
            e.type === "error" || e.type === "lockedDevice" ? interval(800) : interval(0),
          ),
        )
        .subscribe({
          next: (event: any) => {
            subscriber.next(event);
          },
          error: (e: any) => {
            subscriber.error(e);
          },
          complete: () => {},
        });

      // Get rid of subscriptions.
      return function cleanup() {
        if (connectSub) connectSub.unsubscribe();
      };
    },
  );
};

const getImplementation = (currentMode: string): Implementation =>
  currentMode === "polling" ? pollingImplementation : eventImplementation;

export { pollingImplementation, eventImplementation, getImplementation };