import { DataPacket, DataPacket_Kind, RpcRequest } from '@livekit/protocol';
import { EventEmitter } from 'events';
import type TypedEmitter from 'typed-emitter';
import { type StructuredLogger } from '../../../logger';
import { CLIENT_PROTOCOL_DATA_STREAM_RPC } from '../../../version';
import { type TextStreamReader } from '../../data-stream/incoming/StreamReader';
import type OutgoingDataStreamManager from '../../data-stream/outgoing/OutgoingDataStreamManager';
import type Participant from '../../participant/Participant';
import { Future, compareVersions } from '../../utils';
import {
  MAX_V1_PAYLOAD_BYTES,
  type PerformRpcParams,
  RPC_REQUEST_DATA_STREAM_TOPIC,
  RPC_VERSION_V1,
  RPC_VERSION_V2,
  RpcError,
  RpcRequestAttrs,
  byteLength,
} from '../utils';
import type { RpcClientManagerCallbacks } from './events';

/**
 * Manages the client (caller) side of RPC: sending requests, tracking pending
 * ack/response state, and handling incoming ack/response packets.
 * @internal
 */
export default class RpcClientManager extends (EventEmitter as new () => TypedEmitter<RpcClientManagerCallbacks>) {
  private log: StructuredLogger;

  private outgoingDataStreamManager: OutgoingDataStreamManager;

  private getRemoteParticipantClientProtocol: (identity: Participant['identity']) => number;

  private getServerVersion: () => string | undefined;

  private pendingAcks = new Map<string, { resolve: () => void; participantIdentity: string }>();

  private pendingResponses = new Map<
    string /* request id */,
    {
      completionFuture: Future<string, RpcError>;
      participantIdentity: string;
    }
  >();

  constructor(
    log: StructuredLogger,
    outgoingDataStreamManager: OutgoingDataStreamManager,
    getRemoteParticipantClientProtocol: (identity: Participant['identity']) => number,
    getServerVersion: () => string | undefined,
  ) {
    super();
    this.log = log;
    this.outgoingDataStreamManager = outgoingDataStreamManager;
    this.getRemoteParticipantClientProtocol = getRemoteParticipantClientProtocol;
    this.getServerVersion = getServerVersion;
  }

  async performRpc({
    destinationIdentity,
    method,
    payload,
    responseTimeout: responseTimeoutMs = 15000,
  }: PerformRpcParams): Promise<[id: string, completionPromise: Promise<string>]> {
    const maxRoundTripLatencyMs = 7000;
    const minEffectiveTimeoutMs = maxRoundTripLatencyMs + 1000;

    const remoteClientProtocol = this.getRemoteParticipantClientProtocol(destinationIdentity);
    const payloadBytes = byteLength(payload);

    // Only enforce the legacy size limit when on rpc v1
    if (
      payloadBytes > MAX_V1_PAYLOAD_BYTES &&
      remoteClientProtocol < CLIENT_PROTOCOL_DATA_STREAM_RPC
    ) {
      throw RpcError.builtIn('REQUEST_PAYLOAD_TOO_LARGE');
    }

    const serverVersion = this.getServerVersion();
    if (serverVersion && compareVersions(serverVersion, '1.8.0') < 0) {
      throw RpcError.builtIn('UNSUPPORTED_SERVER');
    }

    const effectiveTimeoutMs = Math.max(responseTimeoutMs, minEffectiveTimeoutMs);
    const id = crypto.randomUUID();

    const completionFuture = new Future<string, RpcError>();

    let responseTimeoutId: ReturnType<typeof setTimeout> | null = null;
    const ackTimeoutId = setTimeout(() => {
      this.pendingAcks.delete(id);
      completionFuture.reject?.(RpcError.builtIn('CONNECTION_TIMEOUT'));
      this.pendingResponses.delete(id);
      if (responseTimeoutId !== null) {
        clearTimeout(responseTimeoutId);
      }
    }, maxRoundTripLatencyMs);

    this.pendingAcks.set(id, {
      resolve: () => {
        clearTimeout(ackTimeoutId);
      },
      participantIdentity: destinationIdentity,
    });

    this.pendingResponses.set(id, {
      completionFuture,
      participantIdentity: destinationIdentity,
    });

    await this.publishRpcRequest(
      destinationIdentity,
      id,
      method,
      payload,
      effectiveTimeoutMs,
      remoteClientProtocol,
    );

    responseTimeoutId = setTimeout(() => {
      this.pendingResponses.delete(id);
      completionFuture.reject?.(RpcError.builtIn('RESPONSE_TIMEOUT'));
    }, responseTimeoutMs);

    const completionPromise = completionFuture.promise.finally(() => {
      clearTimeout(responseTimeoutId);

      if (this.pendingAcks.has(id)) {
        this.log.warn('RPC response received before ack', id);
        this.pendingAcks.delete(id);
        clearTimeout(ackTimeoutId);
      }
    });

    return [id, completionPromise];
  }

  private async publishRpcRequest(
    destinationIdentity: string,
    requestId: string,
    method: string,
    payload: string,
    responseTimeout: number,
    remoteClientProtocol: number,
  ) {
    if (remoteClientProtocol >= CLIENT_PROTOCOL_DATA_STREAM_RPC) {
      // Send payload as a data stream - a "version 2" rpc request.
      await this.outgoingDataStreamManager.sendText(payload, {
        topic: RPC_REQUEST_DATA_STREAM_TOPIC,
        destinationIdentities: [destinationIdentity],
        attributes: {
          [RpcRequestAttrs.RPC_REQUEST_ID]: requestId,
          [RpcRequestAttrs.RPC_REQUEST_METHOD]: method,
          [RpcRequestAttrs.RPC_REQUEST_RESPONSE_TIMEOUT_MS]: `${responseTimeout}`,
          [RpcRequestAttrs.RPC_REQUEST_VERSION]: `${RPC_VERSION_V2}`,
        },
      });
      return;
    }

    // Fallback to sending a literal RpcRequest - a "version 1" rpc request.
    this.emit('sendDataPacket', {
      packet: new DataPacket({
        destinationIdentities: [destinationIdentity],
        kind: DataPacket_Kind.RELIABLE,
        value: {
          case: 'rpcRequest',
          value: new RpcRequest({
            id: requestId,
            method,
            payload,
            responseTimeoutMs: responseTimeout,
            version: RPC_VERSION_V1,
          }),
        },
      }),
    });
  }

  /**
   * Handle an incoming data stream containing an RPC response payload.
   * @internal
   */
  async handleIncomingDataStream(
    reader: TextStreamReader,
    senderIdentity: Participant['identity'],
    attributes: Record<string, string>,
  ) {
    const associatedRequestId = attributes[RpcRequestAttrs.RPC_REQUEST_ID];
    if (!associatedRequestId) {
      this.log.warn(`RPC data stream malformed: ${RpcRequestAttrs.RPC_REQUEST_ID} not set.`);
      // NOTE: no response can be sent here, because there's no request id so associate
      // so logging is the best we can do here.
      return;
    }

    const pending = this.pendingResponses.get(associatedRequestId);
    if (pending && pending.participantIdentity !== senderIdentity) {
      this.log.warn(
        `RPC response stream for ${associatedRequestId} arrived from unexpected sender ${senderIdentity}, expected ${pending.participantIdentity}. Ignoring.`,
      );
      return;
    }

    let payload: string;
    try {
      payload = await reader.readAll();
    } catch (e) {
      this.log.warn(`Error reading RPC response payload: ${e}`);
      this.handleIncomingRpcResponseFailure(
        associatedRequestId,
        RpcError.builtIn('APPLICATION_ERROR', 'Error reading RPC response payload', { cause: e }),
      );
      return;
    }

    this.handleIncomingRpcResponseSuccess(associatedRequestId, payload);
  }

  /** @internal */
  handleIncomingRpcResponseSuccess(requestId: string, payload: string) {
    const handler = this.pendingResponses.get(requestId);
    if (handler) {
      handler.completionFuture.resolve?.(payload);
      this.pendingResponses.delete(requestId);
    } else {
      this.log.error('Response received for unexpected RPC request', requestId);
    }
  }

  /** @internal */
  handleIncomingRpcResponseFailure(requestId: string, error: RpcError) {
    const handler = this.pendingResponses.get(requestId);
    if (handler) {
      handler.completionFuture.reject?.(error);
      this.pendingResponses.delete(requestId);
    } else {
      this.log.error('Response received for unexpected RPC request', requestId);
    }
  }

  /** @internal */
  handleIncomingRpcAck(requestId: string) {
    const handler = this.pendingAcks.get(requestId);
    if (handler) {
      handler.resolve();
      this.pendingAcks.delete(requestId);
    } else {
      this.log.error(`Ack received for unexpected RPC request: ${requestId}`);
    }
  }

  /** @internal */
  handleParticipantDisconnected(participantIdentity: string) {
    for (const [id, { participantIdentity: pendingIdentity }] of this.pendingAcks) {
      if (pendingIdentity === participantIdentity) {
        this.pendingAcks.delete(id);
      }
    }

    for (const [id, { participantIdentity: pendingIdentity, completionFuture }] of this
      .pendingResponses) {
      if (pendingIdentity === participantIdentity) {
        completionFuture.reject?.(RpcError.builtIn('RECIPIENT_DISCONNECTED'));
        this.pendingResponses.delete(id);
      }
    }
  }
}