Fis-Retransmission/services/grpc.service.method.ts

import * as grpc from '@grpc/grpc-js';
import { Subject, Subscription } from "rxjs";
import { Message, ConnectionAttribute, GrpcConnectionType, ConnectionState, MessageLog, ConnectionStatus } from "../interfaces/general.interface";
import { Status } from '@grpc/grpc-js/build/src/constants';
import { message_proto } from './protos/server.proto'
import * as _ from 'lodash'
export class GrpcServiceMethod {
    private server: grpc.Server | any
    private messageToBeSendOver: Message | any
    private clientRequest: Subject<ConnectionAttribute> = new Subject()
    private localServerStatus: Subject<any> = new Subject()

    // keep track of all the incoming channel request from the servers
    public getClientRequest() {
        return this.clientRequest
    }

    // keep track of all the incoming channel request from the servers
    public getLocalServerStatus() {
        return this.localServerStatus
    }

    public async create(connectionAttribute: ConnectionAttribute): Promise<any> {
        return new Promise((resolve, reject) => {
            this.createGrpcInstance({ instanceType: 'server' }, connectionAttribute)
            this.createGrpcInstance({ instanceType: 'client' }, connectionAttribute)
            resolve('Just putting it here for now....')
        })
    }

    private async generateAdditionalAttributes(connectionAttribute: ConnectionAttribute, clientInfo?: any, localInfo?: any) {
        // if (clientInfo) {
        //     connectionAttribute.inComing.StreamID = clientInfo.StreamID
        //     connectionAttribute.inComing.PublisherID = clientInfo.PublisherID
        //     connectionAttribute.inComing.SubscriberID = clientInfo.SubscriberID
        // }
        // if (localInfo) {
        //     connectionAttribute.outGoing.StreamID = localInfo.StreamID
        //     connectionAttribute.outGoing.PublisherID = localInfo.PublisherID
        //     connectionAttribute.outGoing.SubscriberID = localInfo.SubscriberID
        // }
        // if (connectionAttribute.outGoing.StreamID && connectionAttribute.inComing.StreamID) {
        //     connectionAttribute.ConnectionID.local = connectionAttribute.outGoing.StreamID + connectionAttribute.inComing.StreamID
        //     connectionAttribute.ConnectionID.remote = connectionAttribute.inComing.StreamID + connectionAttribute.outGoing.StreamID
        // }
    }

    private async createGrpcInstance(grpcType: GrpcConnectionType, connectionAttribute: ConnectionAttribute) {
        // Reconnection Logic here
        while (true) {
            try {
                let recreatePromise = new Promise((resolve) => {
                    if (grpcType.instanceType == 'server') {
                        this.createServerStreamingServer(connectionAttribute).then(() => {
                            resolve('recreate')
                        })
                    }
                    if (grpcType.instanceType == 'client') {
                        this.createServerStreamingClient(connectionAttribute).then(() => {
                            resolve('recreate')
                        })
                    }
                })
                await recreatePromise
            } catch (error) {
                console.error('Connection attempt failed:', error);
            }
            await new Promise(resolve => setTimeout(resolve, 1000)); // Wait for 1 second before the next attempt
            // timeout generate message to trigger this reconnection
        }
    }

    // Create Server Instance to stream all application Outgoing messages
    public async createServerStreamingServer(connectionAttribute: ConnectionAttribute): Promise<any> { // '0.0.0.0:3001'
        return new Promise((resolve, reject) => {
            try {
                if (!this.server) {
                    this.server = new grpc.Server()
                    this.localServerStatus.next({
                        connectionStatus: 'ON',
                        serverName: connectionAttribute.outGoing.PublisherID,
                        message: `${connectionAttribute.outGoing.serverUrl} started.`
                    })
                } else {
                    console.log(`Grpc server alrady started.`)
                }

                this.server.addService(message_proto.Message.service, {
                    HandleMessage: (call) => {
                        let clientInfo: ConnectionAttribute = JSON.parse(call.request.message)
                        this.clientRequest.next(clientInfo)

                        console.log(`Initializing stream. Opening Channel... Confirmation from ${call.request.id}`)

                        if (connectionAttribute.outGoing.MessageToBePublished) {
                            let subscription: Subscription = connectionAttribute.outGoing.MessageToBePublished.subscribe({
                                next: (response: Message) => {
                                    console.log(`Sending from GRPC server: ${(response.message as MessageLog).appData.msgId} `)
                                    let message = {
                                        id: response.id,
                                        message: JSON.stringify(response.message)
                                    }
                                    call.write(message)
                                },
                                error: err => {
                                    console.error(err)
                                    subscription.unsubscribe()
                                    resolve('')
                                },
                                complete: () => {
                                    console.log(`Stream response completed for ${call.request.id}`)
                                    subscription.unsubscribe()
                                    resolve('')
                                }
                            })
                            let report: ConnectionState = {
                                status: 'DIRECT_PUBLISH'
                            }
                            connectionAttribute.connectionStatus!.next(report)
                        }
                    },
                    Check: (_, callback) => {
                        // for now it is just sending the status message over to tell the client it is alive
                        // For simplicity, always return "SERVING" as status
                        callback(null, { status: 'SERVING' });
                    },
                });
                // Bind and start the server
                this.server.bindAsync(connectionAttribute.outGoing.serverUrl, grpc.ServerCredentials.createInsecure(), () => {
                    console.log(`gRPC server is running on ${connectionAttribute.outGoing.serverUrl}`);
                    this.server.start();
                });
            }
            catch (error) {
                resolve(error)
            }
        })
    }

    // Send a request over to the other server to open a channel for this server to emit/stream messages over
    public async createServerStreamingClient(connectionAttribute: ConnectionAttribute): Promise<string> {
        return new Promise(async (resolve, reject) => {
            const client = new message_proto.Message(connectionAttribute.inComing.serverUrl, grpc.credentials.createInsecure());
            let localInfo: ConnectionAttribute = { // need to make a new copy where it doesn't reference the subjects, otherwise circular ref error
                ConnectionID: connectionAttribute.ConnectionID,
                outGoing: {
                    StreamID: connectionAttribute.outGoing.StreamID,
                    PublisherID: connectionAttribute.outGoing.PublisherID,
                    SubscriberID: connectionAttribute.outGoing.SubscriberID,
                    serverUrl: connectionAttribute.outGoing.serverUrl,
                    MessageToBePublished: null,
                    MessageToBeReceived: null
                },
                inComing: {
                    StreamID: connectionAttribute.inComing.StreamID,
                    PublisherID: connectionAttribute.inComing.PublisherID,
                    SubscriberID: connectionAttribute.inComing.SubscriberID,
                    serverUrl: connectionAttribute.inComing.serverUrl,
                    MessageToBePublished: null,
                    MessageToBeReceived: null
                },
                connectionStatus: null
            }
            let call = client.HandleMessage({ id: connectionAttribute.inComing.serverUrl, message: JSON.stringify(localInfo) })

            console.log(`Sending request to ${connectionAttribute.inComing.serverUrl} to open response channel...`)

            call.on('status', (status: Status) => {
                if (status == grpc.status.OK) { // only returns a status when there's error. Otherwise it just waits
                    console.log(`Message trasmission operation is successful`)
                    // RPC completed successfully
                } if (status == grpc.status.UNAVAILABLE) {
                    let report: ConnectionState = {
                        status: 'BUFFER',
                        reason: `Server doesn't seem to be alive. Error returned.`,
                        payload: this.messageToBeSendOver ?? `There's no message at the moment...`
                    }
                    connectionAttribute.connectionStatus!.next(report)
                    resolve('No connection established. Server is not responding..')
                }
            });

            call.on('data', (data: any) => {
                let response: Message = {
                    id: data.id,
                    message: JSON.parse(data.message)
                }
                if (connectionAttribute.inComing.MessageToBeReceived) {
                    connectionAttribute.inComing.MessageToBeReceived.next(response)
                }
            });

            call.on('error', (err) => {
                console.error(err)
                resolve('')
            });
        })
    }


    // THis is no longer necesarry after the introduction of connection Attribute. But it is still useful for checking for the other side's health
    public async checkConnectionHealth(client: any, statusControl: Subject<ConnectionState>, alreadyHealthCheck: boolean): Promise<boolean> {
        return new Promise((resolve, reject) => {
            client.Check({}, (error, response) => {
                if (response) {
                    console.log(`GRPC Health check status: ${response.status} Server Connected`);
                    // Intepret the response status and implement code logic or handler
                    resolve(response.status)
                } else {
                    if (alreadyHealthCheck == false) console.error(`Health check failed: ${error}`);
                    reject(false)
                }
            })
        })
    }
}



// https://github.com/grpc/proposal/blob/master/L5-node-client-interceptors.md