import * as grpc from '@grpc/grpc-js';
import { Subject, Subscription, take, takeUntil } from 'rxjs';
import { ColorCode, GrpcConnectionType, MessageLog, ReportStatus } from '../interfaces/general.interface';
import { Status } from '@grpc/grpc-js/build/src/constants';
const message_proto = require('./protos/server.proto')

export class GrpcService {
    private grpcServerConnection: any = {}

    constructor() { }

    public async stopServer(serverUrl: string): Promise<any> {
        return new Promise((resolve, reject) => {
            if (this.grpcServerConnection[serverUrl]) {
                console.log(`Shutting down the gRPC server:${serverUrl} ...`);
                // this.grpcServerConnection[serverUrl].tryShutdown(() => {
                //     console.log(`Server ${serverUrl} has been gracefully stopped.`);
                //     resolve('')
                // })
                resolve(this.grpcServerConnection[serverUrl].forceShutdown())
                console.log(`Server ${serverUrl} is forced to shut down!`)
                // simply removing the reference to the GrpcService instance associated with the specific serverUrl from the grpcServerConnection object.
                // However, the gRPC server instance itself continues to run as long as it has not been explicitly shut down using methods like tryShutdown.
                console.log(`Deleting grpc connection instance:${serverUrl} .....`)
                delete this.grpcServerConnection[serverUrl];
            } else {
                console.log(`Server${serverUrl} is not running.`);
                reject()
            }
        })
    }

    public getAllGrpcServerConnectionInstance(): any {
        console.log(this.grpcServerConnection)
        return this.grpcServerConnection
    }

    // To be migrated into a service in the immediate future
    public async createGrpcInstance(serverUrl: string, messageToBePublished: Subject<MessageLog>, reportStatus: Subject<ReportStatus>, connectionType: GrpcConnectionType) {
        let messageToBeTransmitted: Subject<MessageLog> = messageToBePublished
        let statusControl: Subject<ReportStatus> = reportStatus
        let consecutiveResolutions = 0;
        let lastResolutionTime = Date.now();
        let alreadyHealthCheck: boolean = false
        let yellowErrorEmission: boolean = false
        let redErrorEmission: boolean = false

        while (true) {
            try {
                if (connectionType.instanceType == 'client' && connectionType.serviceMethod == 'bidirectional') {
                    await this.createBidirectionalStreamingClient(serverUrl, alreadyHealthCheck, messageToBeTransmitted, statusControl);
                }
                if (connectionType.instanceType == 'client' && connectionType.serviceMethod == 'server streaming') {
                    await this.createServerStreamingClient(serverUrl, alreadyHealthCheck, messageToBeTransmitted, statusControl);
                }
                if (connectionType.instanceType == 'server' && connectionType.serviceMethod == 'bidirectional') {
                    await this.createGrpcBidirectionalServer(serverUrl, messageToBeTransmitted, statusControl)
                }
                if (connectionType.instanceType == 'server' && connectionType.serviceMethod == 'server streaming') {
                    await this.createServerStreamingServer(serverUrl, alreadyHealthCheck, messageToBePublished, statusControl)
                }
                // If connection resolves (indicating failure), increment the count
                consecutiveResolutions++;
                // console.log(`Reconnection Attempt: ${consecutiveResolutions}`)
                alreadyHealthCheck = true


                // If there are x consecutive resolutions, log an error and break the loop
                if (consecutiveResolutions >= parseInt(process.env.ReconnectionAttempt as string) && redErrorEmission == false) {
                    redErrorEmission = true
                    console.error(`Connection failed ${consecutiveResolutions} times. Stopping connection attempts.`);
                    let error: ReportStatus = {
                        code: ColorCode.RED,
                        message: 'Initiate Doomsday protocol....'
                    }
                    statusControl.next(error)
                }
                if (consecutiveResolutions < parseInt(process.env.ReconnectionAttempt as string) && yellowErrorEmission == false) {
                    yellowErrorEmission = true
                    let error: ReportStatus = {
                        code: ColorCode.YELLOW,
                        // message: `Reconnection Attempt: ${consecutiveResolutions}. Server has yet to respond`
                        message: `Attempting reconnection... Server has yet to respond`
                    }
                    statusControl.next(error);
                }
            } catch (error) {
                // Connection did not resolve, reset the count
                consecutiveResolutions = 0;
                console.error('Connection attempt failed:', error);
            }

            // Check for a pause of more than 3 seconds since the last resolution attempt
            const currentTime = Date.now();
            const timeSinceLastResolution = currentTime - lastResolutionTime;
            if (timeSinceLastResolution > 2000) {
                consecutiveResolutions = 0;
                yellowErrorEmission = false
                redErrorEmission = false
                alreadyHealthCheck = false
            }

            // Update the last resolution time
            lastResolutionTime = currentTime;

            await new Promise(resolve => setTimeout(resolve, 1000)); // Wait for 1 second before the next attempt
            // timeout generate message to trigger this reconnection
        }
    }

    private async createGrpcBidirectionalServer(serverUrl: string, messageToBeStream: Subject<any>, statusControl: Subject<ReportStatus>): Promise<any> { // '0.0.0.0:3001'
        return new Promise((resolve, reject) => {
            try {
                // https://github.com/grpc/proposal/blob/master/L5-node-client-interceptors.md
                let server: grpc.Server = new grpc.Server();
                // Add the streamingData function to the gRPC service
                // Define your message_proto.Message service methods

                server.addService(message_proto.Message.service, {
                    sendMessageStream: (call) => {
                        console.log(`Client connected from: ${call.getPeer()}`);
                        let report: ReportStatus = {
                            code: ColorCode.GREEN,
                            message: `Client connected!!`
                        }
                        statusControl.next(report)

                        // Right now this is being broadcast.
                        let subscription: Subscription = messageToBeStream.subscribe({
                            next: (payload: any) => {
                                let noConnection = call.cancelled // check connection for each and every message
                                if (noConnection === true) { // that means there's no connection, beccause the cancel operation is determined to check 
                                    let report: ReportStatus = {
                                        code: ColorCode.YELLOW,
                                        message: `Client is not alive.....`,
                                        payload: payload
                                    }
                                    statusControl.next(report) // no connection. Tell buffer service to stop releasing messages
                                    subscription.unsubscribe() // i still dont understand why i wrote this here
                                } else {
                                    console.log(`Sending ${payload.appData.msgId}`)
                                    let message: string = JSON.stringify(payload)
                                    call.write({ message })
                                }
                            },
                            error: err => console.error(err),
                            complete: () => { } //it will never complete
                        })

                        call.on('data', (data: any) => {
                            // console.log(data) // it does return in string format
                            let payload = JSON.parse(data.message)
                            console.log(`Received Message from Client: ${payload.appData?.msgId}`);
                            // Forward the received message to the RxJS subject
                            // let respmsg: any = {
                            //     msgId: payload.appData?.msgId,
                            //     confirmationMessage: `Message ${payload.appData?.msgId} acknowledged!`
                            // }
                            // let message: string = JSON.stringify(respmsg)
                            // console.log(`Responding to client: ${respmsg.msgId}`);
                            // Note: The parameter here MUST BE STRICTLY be the same letter as defined in proto. Eg: message MessageRequest { string >>'message'<< = 1 }
                            // call.write({ message });
                        });

                        call.on('end', () => {
                            console.log('Client stream ended');
                            // but the stream never ends. THis is not a reliable way to tell if a client is disconnected
                        });

                        call.on('error', (err) => {
                            // Error that may occue during the rpc call. Id there's an error, put a callbacn function there to check the connection for client
                            // emit a yellow report to halt message release. If the server does not reply to the callback function, then emit a red card
                            // the call back function will be to write and then the client should response immediately through test
                        });

                        call.on('close', () => {
                            console.log('Unknown cause for diconnectivity');
                            // Handle client closure, which may be due to errors or manual termination
                        });

                    },

                    Check: (_, callback) => {
                        // health check logic here
                        // 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
                server.bindAsync(serverUrl, grpc.ServerCredentials.createInsecure(), () => {
                    console.log(`gRPC server is running on ${serverUrl}`);
                    server.start();
                });
                this.grpcServerConnection[serverUrl] = server
            }
            catch (error) {
                resolve(error)
            }

        })
    }


    private async createBidirectionalStreamingClient(server: string, alreadyHealthCheck: boolean, messageToBeTransmitted: Subject<any>, statusControl: Subject<ReportStatus>): Promise<string> {
        let subscription: any
        let unsubscribed: boolean = false

        return new Promise(async (resolve, reject) => {
            const client = new message_proto.Message(server, grpc.credentials.createInsecure());
            const call = client.sendMessageStream();

            this.checkConnectionHealth(client, statusControl, alreadyHealthCheck)

            call.on('status', (status: Status) => {
                // console.log(status) // For more info: https://grpc.github.io/grpc/core/md_doc_statuscodes.html
                // https://grpc.io/docs/what-is-grpc/core-concepts/#streaming
                if (status == grpc.status.UNAVAILABLE) { // only returns a status when there's error. Otherwise it just waits
                    resolve('No connection established. Server is not responding..')
                }
            });

            // All the grpc operations are here
            // Subscribe to the RxJS subject to send data to the server
            subscription = messageToBeTransmitted.subscribe({
                next: (payload: any) => {
                    if (!unsubscribed) {
                        console.log(`Sending ${payload.appData.msgId}`)
                        let message: string = JSON.stringify(payload)
                        call.write({ message })
                    }
                },
                error: err => console.error(err),
                complete: () => { } //it will never complete
            });


            call.on('data', (data: any) => {
                let message = JSON.parse(data.message)
                console.log(`Received acknowledgement from Server: ${message.msgId ?? message.appData?.msgId ?? `Invalid`}`);
            });

            call.on('error', (err) => {
                console.log(`Something wrong with RPC call...`)
                if (!unsubscribed && subscription) { // kill subcription to prevent memory leaks
                    subscription.unsubscribe();
                    unsubscribed = true;
                }
                resolve('Server Error');
            });

            call.on('end', () => {
                if (!unsubscribed && subscription) { // kill subcription to prevent memory leaks
                    subscription.unsubscribe();
                    unsubscribed = true;
                }
                resolve('Server Error');
            });

        })
    }

    private async createServerStreamingServer(serverUrl: string, alreadyHealthCheck: boolean, messageToBeStream: Subject<any>, statusControl: Subject<ReportStatus>): Promise<any> { // '0.0.0.0:3001'
        return new Promise((resolve, reject) => {
            try {
                // https://github.com/grpc/proposal/blob/master/L5-node-client-interceptors.md
                let server: grpc.Server = new grpc.Server();
                let onHold: any
                // Add the streamingData function to the gRPC service
                // Define your message_proto.Message service methods

                server.addService(message_proto.Message.service, {
                    HandleMessage: (call) => { // this is for bidirectional streaming. Need to have another one for unary calls for web clients
                        console.log(`Client connected from: ${call.getPeer()}`);
                        // let request = call.request // just putting it here to verify unary call request
                        let report: ReportStatus = {
                            code: ColorCode.GREEN,
                            message: `Client connected!!`
                        }
                        statusControl.next(report)
                        let subscription: Subscription = messageToBeStream.subscribe({
                            next: (payload: any) => {
                                let noConnection = call.cancelled // check connection for each and every message
                                if (noConnection === true) { // that means there's no connection, beccause the cancel operation is determined to check 
                                    let report: ReportStatus = {
                                        code: ColorCode.YELLOW,
                                        message: `Client is not alive.....`,
                                        payload: payload
                                    }
                                    statusControl.next(report)
                                    subscription.unsubscribe()
                                } else {
                                    console.log(`Sending ${payload.appData.msgId}`)
                                    let message: string = JSON.stringify(payload)
                                    call.write({ message })
                                    // onHold = null
                                }
                            },
                            error: err => {
                                console.error(err)
                                let report: ReportStatus = {
                                    code: ColorCode.YELLOW,
                                    message: `Message streaming error`
                                }
                                statusControl.next(report)
                            },
                            complete: () => console.log(``)  //it will never complete
                        })

                        call.on('data', (data: any) => {
                            // console.log(data) // it does return in string format
                            let payload = JSON.parse(data.message)
                            console.log(data)
                            // console.log(`Received Message from Client: ${payload.appData?.msgId}`);
                            // Forward the received message to the RxJS subject
                            let respmsg: any = {
                                msgId: payload.appData?.msgId,
                                confirmationMessage: `Message ${payload.appData?.msgId} acknowledged!`
                            }
                            let message: string = JSON.stringify(respmsg)
                            console.log(`Responding to client: ${respmsg.msgId}`);
                            // Note: The parameter here MUST BE STRICTLY be the same letter as defined in proto. Eg: message MessageRequest { string >>'message'<< = 1 }
                            call.write({ message });
                        });

                        call.on('end', () => {
                            console.log('Client stream ended');
                            // but the stream never ends. THis is not a reliable way to tell if a client is disconnected
                        });

                        call.on('error', (err) => {
                            // Error that may occue during the rpc call. Id there's an error, put a callbacn function there to check the connection for client
                            // emit a yellow report to halt message release. If the server does not reply to the callback function, then emit a red card
                            // the call back function will be to write and then the client should response immediately through test
                        });

                        call.on('close', () => {
                            console.log('Unknown cause for diconnectivity');
                            // Handle client closure, which may be due to errors or manual termination
                        });
                    },

                    Check: (_, callback) => {
                        // health check logic here
                        // 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
                server.bindAsync(serverUrl, grpc.ServerCredentials.createInsecure(), () => {
                    console.log(`gRPC server is running on ${serverUrl}`);
                    server.start();
                });
                this.grpcServerConnection[serverUrl] = server
            }
            catch (error) {
                resolve(error)
            }

        })
    }

    // Create a server streaming call. Please note that the structure of the code would not be the same as bidirectional because of it's unary nature
    private async createServerStreamingClient(server: string, alreadyHealthCheck: boolean, unaryRequestSubject: Subject<any>, statusControl: Subject<ReportStatus>): Promise<string> {
        return new Promise(async (resolve, reject) => {
            const client = new message_proto.Message(server, grpc.credentials.createInsecure());
            this.checkConnectionHealth(client, statusControl, alreadyHealthCheck) // atcually there's no need for this 
            unaryRequestSubject.subscribe({
                next: (request: any) => {
                    let message = {
                        id: '123',
                        message: JSON.stringify(request)
                    }

                    console.log(`Sending request: ${message.id} over to server....`)
                    const call = client.HandleMessage(message)

                    call.on('status', (status: Status) => {
                        // console.log(status) // For more info: https://grpc.github.io/grpc/core/md_doc_statuscodes.html
                        // https://grpc.io/docs/what-is-grpc/core-concepts/#streaming
                        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) {
                            resolve('No connection established. Server is not responding..')
                            let report = {
                                code: ColorCode.YELLOW,
                                message: `Server doesn't seem to be alive. Error returned.`
                            }
                            statusControl.next(report)
                        }
                    });

                    call.on('data', (data: any) => {
                        let message = JSON.parse(data.message)
                        console.log(`Received data from Server: ${message.appData?.msgId ?? `Invalid`}`);
                    });

                    call.on('error', (err) => {
                        let report = {
                            code: ColorCode.YELLOW,
                            message: `Server doesn't seem to be alive. Error returned.`
                        }
                        statusControl.next(report)
                        // resolve(err)
                    });

                    call.on('end', () => { // this is for gracefull || willfull termination from the server
                        let report = {
                            code: ColorCode.YELLOW,
                            message: `Server doesn't seem to be alive. Error returned.`
                        }
                        statusControl.next(report)
                        // subscription.unsubscribe(); // this is not correct i am just destroying the entire operation. i should be terminating the instance to which i think it does by it self
                        // resolve('Server Error');
                    });
                    /* Avoid rsolving at the moment. Because initially it was intended for the bi directional streaming to continue to instantiate the client
                    should there be any rpc errors or internet connection errors. In this case, we just want to listen to incoming unary call without terminating the session
                    A separate resolve will be prepared for the subject should it fails in its operation */
                },
                error: error => {
                    console.error(error),
                        resolve(error)
                },
                complete: () => { } // should not complete since this is an indefinite listening process to transmit requests made by relevant client application
            })


        })
    }

    // Check connection To be Update. This function is destroying my code flow
    private async checkConnectionHealth(client: any, statusControl: Subject<ReportStatus>, 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`);
                    let report: ReportStatus = {
                        code: ColorCode.GREEN,
                        message: `Good to go!!!`
                    }
                    statusControl.next(report)
                } else {
                    if (alreadyHealthCheck == false) console.error(`Health check failed: ${error}`);

                }
            })
        })
    }

}