Fis-Retransmission/services/fis.retransmission.service.ts

import * as _ from 'lodash'
import mongoose, { Model, Schema } from 'mongoose';
import { Observable, Subject, Subscription, from } from 'rxjs'
import { ColorCode, Message, MessageLog, ReportStatus, Status } from '../interfaces/general.interface'
require('dotenv').config();

// Implement status chain refactoring
export class FisRetransmissionService {
    private mongoUrl: string = process.env.MONGO + 'emergencyStorage'
    private bufferedStorage: Message[] = []
    private mongoConnection: any
    private messageModel: any
    private maximumBufferLength: number = parseInt(process.env.MaxBufferLoad as string) // please configure at environment

    constructor() {
        // Connect to mongoDB. 
        this.manageMongoConnection()
    }

    // Main function that intercepts outgoing messages by communicating || intepreting report status from grpc connection as indicator 
    public handleMessage(applicationOutgoingMessage: Subject<Message>, statusReport: Subject<ReportStatus>): Subject<Message> {
        let releaseMessageSubject: Subject<Message> = new Subject() // Every message subscribed from applicationOutgoingMessage will be released through this subject
        let messageReleaseSubscription: Subscription | null = null
        let messageBufferSubscription: Subscription | null = null
        let messageStreamToMongo: Subscription | null = null
        this.checkBufferLimit(applicationOutgoingMessage, statusReport)
        statusReport.subscribe((report: ReportStatus) => {
            /* Green should release all data from buffer and mongo and also redirect the applicationOutgoingMessage back into the return subject(releaseMessageSubject)
            if there's any. */
            if (report.code == ColorCode.GREEN) { 
                console.log(`Connection status report && ${report.message ?? 'No Message'}`)
                /* Status Chain begins */
                let status: Status = 1
                if (status === 1) {
                    messageStreamToMongo = this.deactivateMongoStreamSubscription(messageStreamToMongo)
                    if (messageStreamToMongo) status = 0
                }
                if (status === 1) {
                    messageBufferSubscription = this.deactivateBufferSubscription(messageBufferSubscription)
                    if (messageBufferSubscription) status = 0
                }
                if (status === 1) {
                    messageReleaseSubscription = this.activateReleaseSubscription(messageReleaseSubscription, applicationOutgoingMessage, releaseMessageSubject)
                    if (!messageReleaseSubscription) status = 0
                }
                if (status === 1) {
                    this.releaseMessageFromLocalBuffer(this.bufferedStorage).then((resObs: Observable<Message>) => {
                        resObs.subscribe({
                            next: message => releaseMessageSubject.next(message),
                            error: err => console.error(err),
                            complete: () => {
                                this.bufferedStorage = []
                                console.log(`Reset buffer Storage count: ${this.bufferedStorage.length}. All messages have been released back into the stream.`)
                            }
                        })
                    }).catch((err) => {
                        status = 0
                        console.error(err)
                    })
                }
                if (status === 1) {
                    this.releaseMessageFromMongoStorage().then((resObs: Subject<Message>) => {
                        resObs.subscribe({
                            next: message => releaseMessageSubject.next(message),
                            error: err => console.error(err),
                            complete: () => console.log(`All Mongo data are transferred `)
                        })
                    }).catch((err) => {
                        status = 0
                        console.error(err)
                    })
                }
                if (status === 0) {
                    console.log(`Something Went Wrong in handling ${ColorCode.RED} report.`)
                }
            }
            /* Start buffering the messages coming in from applicationOutgonigMessages and also stop it from flowing into the release subject */
            if (report.code == ColorCode.YELLOW) {
                if (report.payload) {
                    console.log(`Rebuffering ${report.payload.message?.appData?.msgId} into buffer...`)
                    this.bufferedStorage.push(report.payload)
                }
                console.log(`Connection status report && ${report.message ?? 'No Message'}`)
                let status: Status = 1
                /* Status Chain begins */
                if (status === 1) {
                    messageBufferSubscription = this.activateBufferSubscription(this.bufferedStorage, messageBufferSubscription, applicationOutgoingMessage)
                    if (!messageBufferSubscription) status = 0
                }
                if (status === 1) {
                    messageReleaseSubscription = this.deactivateReleaseSubscription(messageReleaseSubscription)
                    if (messageReleaseSubscription) status = 0
                }
                if (status === 0) {
                    console.log(`Something Went Wrong in handling ${ColorCode.RED} report.`)
                }
            }
            /* Stop buffering the message in local instance, but start saving them in database. Must first transfer the ones in local buffer before redirecting the 
            flow from applicationOutgoingMessage into Mongo */
            if (report.code == ColorCode.RED) {
                console.log(`Connection status report: Server down. ${report.message} lol`)
                let status: Status = 1
                if (status === 1) {
                    messageStreamToMongo = this.activateMongoStreamSubscription(messageStreamToMongo, applicationOutgoingMessage)
                    if (!messageStreamToMongo) status = 0
                }
                if (status === 1) {
                    messageBufferSubscription = this.deactivateBufferSubscription(messageBufferSubscription)
                    if (messageBufferSubscription) status = 0
                }
                if (status === 1) {
                    this.transferBufferedMessageToMongoStorage(this.bufferedStorage, messageBufferSubscription).then((res: any[]) => {
                        if (res.length !== this.bufferedStorage.length || this.bufferedStorage.length > 0) status = -1 // this promise function should return an empty array
                    })
                }
                if (status === 0) {
                    console.log(`Something Went Wrong in handling ${ColorCode.RED} report.`)
                }
            }
            if (!report.code) {
                console.log(`Unknown message...`)
            }
        })
        return releaseMessageSubject
    }

    // IF Buffer exceeds a certain limit, it will trigger RED. Configure in .env file. There's the concern of 2 RED status, one from this and another from other means.
    // Behaviour of this needs to be investigated further
    private checkBufferLimit(message: Subject<Message>, statusReport: Subject<ReportStatus>) {
        let status: Status = 1
        if (status = 1) {
            message.subscribe(() => {
                if (this.bufferedStorage.length >= this.maximumBufferLength) {
                    // for every messges that comes in, check the bufffer size, if it exceesd more than designated amount, push a red report status i
                    console.log(`Buffer length exceeds limit imposed!!!`)
                    let report: ReportStatus = {
                        code: ColorCode.RED,
                        message: `Buffer is exceeding limit. Initiate storage transfer to designated database.`,
                        from: `Error Handling Service`
                    }
                    statusReport.next(report)
                }
            })
        }
    }

    // Release the incoming Messages to be returned to the caller
    private activateReleaseSubscription(messageReleaseSubscription: Subscription | null, applicationOutgoingMessage: Subject<Message>, releaseMessageSubject: Subject<Message>): Subscription | null {
        let status: Status = 1
        if (status = 1) {
            if (!messageReleaseSubscription) {
                messageReleaseSubscription = applicationOutgoingMessage.subscribe({
                    next: (message: Message) => {
                        console.log(`Releasing ${(message.message as MessageLog).appData.msgId}...`);
                        releaseMessageSubject.next(message);
                    },
                    error: (err) => console.error(err),
                    complete: () => { },
                });
                console.log(`Subscription message release activated.`);
            } else {
                status = 0
                console.log(`Subscription message release is already active.`);
            }
        }
        return messageReleaseSubscription
    }

    // Stop the incoming Messages to be returned to caller
    private deactivateReleaseSubscription(messageReleaseSubscription: Subscription | null): Subscription | null {
        let status: Status = 1
        if (status = 1) {
            if (messageReleaseSubscription) {
                messageReleaseSubscription.unsubscribe();
                messageReleaseSubscription = null;
                console.log(`Subscription message release deactivated.`);
            } else {
                console.log(`Subscription message release is already deactivated.`);
            }
        }
        return messageReleaseSubscription
    }

    // Begin to push the incoming messages into local instantarray
    private activateBufferSubscription(bufferStorage: Message[], messageBufferSubscription: Subscription | null, applicationOutgoingMessage: Subject<Message>): Subscription | null {
        let status: Status = 1
        if (status = 1) {
            if (!messageBufferSubscription) {
                messageBufferSubscription = applicationOutgoingMessage.subscribe({
                    next: (message: any) => {
                        console.log(`Buffering ${(message.message as MessageLog).appData.msgId}...  Local array length: ${bufferStorage.length}`);
                        bufferStorage.push(message)
                    },
                    error: (err) => console.error(err),
                    complete: () => { },
                });
                console.log(`Subscription message buffer activated.`);
            } else {
                status = 0
                console.log(`Subscription message buffer is already active.`);
            }
        }
        return messageBufferSubscription
    }

    // Stop pushing the incoming messages into local instantarray
    private deactivateBufferSubscription(messageBufferSubscription: Subscription | null): Subscription | null {
        let status: Status = 1
        if (status) {

            if (messageBufferSubscription) {
                messageBufferSubscription.unsubscribe();
                messageBufferSubscription = null;
                console.log(`Subscription message buffer deactivated.`);
            } else {
                status = 0
                console.log(`Subscription message buffer is already deactivated.`);
            }
        }
        return null
    }

    // Change the streaming direction of the incoming messages into mongo streaming subject( to be saved in local databse )
    private activateMongoStreamSubscription(messageStreamToMongo: Subscription | null, applicationOutgoingMessage: Subject<Message>): Subscription | null {
        let status: Status = 1
        if (status = 1) {
            if (!messageStreamToMongo) {
                messageStreamToMongo = applicationOutgoingMessage.subscribe({
                    next: (message: any) => {
                        console.log(`Saving ${(message.message as MessageLog).appData.msgId}...`);
                        this.saveToMongo(message)
                    },
                    error: (err) => console.error(err),
                    complete: () => { },
                });
                console.log(`Subscription message streaming to Mongo activated.`);
            } else {
                status = 0
                console.log(`Subscription message streaming to Mongo  is already active.`);
            }
        }
        return messageStreamToMongo
    }

    // Stop or cut off the mongo streaming
    private deactivateMongoStreamSubscription(messageStreamToMongo: Subscription | null): Subscription | null {
        let status: Status = 1
        if (status = 1) {
            if (messageStreamToMongo) {
                messageStreamToMongo.unsubscribe();
                messageStreamToMongo = null;
                console.log(`Subscription message streaming to Mongo deactivated.`);
            } else {
                status = 0
                console.log(`Subscription message streaming to Mongo is already deactivated.`);
            }
        }
        return messageStreamToMongo
    }

    // To be used by mongoStreamSubscription to perform the saving execution
    private async saveToMongo(message: Message): Promise<boolean> {
        return new Promise((resolve, reject) => {
            // let messageModel: Model<any> = this.mongoConnection.model('Message', require('../models/message.schema'))
            this.messageModel.create(message).then(() => {
                console.log(`Saved MessageID ${(message.message as MessageLog).appData.msgId} into ${this.mongoUrl}`);
                resolve(true)
            }).catch((err) => {
                console.log(`MongoSaveError: ${err.message}`)
                reject(err)
            })
        })
    }

    // As the name implies, transder all the messages from the local instance into mongoStorage. Local instance should be emptied after transfer is completed
    private async transferBufferedMessageToMongoStorage(bufferedMessage: Message[], messageBufferSubscription: Subscription | null): Promise<Message[]> {
        return new Promise((resolve, reject) => {
            let status: Status = 1
            if (status = 1) {
                let bufferedStorage: Observable<Message> = from(bufferedMessage)
                bufferedStorage.subscribe({
                    next: (message: any) => {
                        this.saveToMongo(message).then((res) => {
                            console.log(`Message ${(message.message as MessageLog).appData.msgId} saved successfully...`)
                        }).catch((err) => console.error(err))
                    },
                    error: (error) => {
                        reject(error)
                        console.error(error)
                    },
                    complete: () => {
                        this.bufferedStorage = []
                        if (messageBufferSubscription) {
                            console.log(`All ${bufferedMessage.length} buffered messages have been sent for transfer to ${this.mongoUrl}. Current length: ${this.bufferedStorage.length}`)
                        }
                        resolve(this.bufferedStorage)
                    }
                })
            }
        })
    }

    // Transfer stored messages from the local instance back into the stream to be returned to the caller.
    private async releaseMessageFromLocalBuffer(bufferedStorage: Message[]): Promise<Observable<Message>> {
        return new Promise((resolve, reject) => {
            let status: Status = 1
            if (status = 1) {
                if (bufferedStorage.length > 1) {
                    let caseVariable = this.bufferedStorage.length > 1;
                    console.log(`Releasing data from local buffer instance. There ${caseVariable ? "is" : "are"} ${this.bufferedStorage.length} messages...`);
                    let returnArrayObs: Observable<Message> = from(bufferedStorage)
                    resolve(returnArrayObs)
                } else {
                    let message = `There is no data in stored in local instance`
                    reject(message)
                }
            }
        })
    }

    // Transder all the stored messages in designated mongo databases. It should be empty after all the data has been transferred.
    private async releaseMessageFromMongoStorage(): Promise<Subject<Message>> {
        return new Promise((resolve, reject) => {
            let status: Status = 1
            if (status = 1) {
                let dataSubject: Subject<Message> = new Subject()
                this.extractAllMessages(dataSubject)
                resolve(dataSubject)
            }
        })
    }

    // Connect to designated mongodatabase.
    private async connectToMongoDatabase(): Promise<any> {
        return new Promise((resolve, reject) => {
            let status: Status = 1
            if (status = 1) {
                console.log(this.mongoUrl)
                this.mongoConnection = mongoose.createConnection(this.mongoUrl)
                this.mongoConnection.on('error', (error) => {
                    console.error('Connection error:', error);
                    resolve('')
                });
                this.mongoConnection.once('open', () => {
                    console.log(`Connected to ${process.env.MONGO}`);
                    this.messageModel = this.mongoConnection.model('Message', require('../models/message.schema'));
                });
            }
        })
    }

    // Manage mongoCOnnectino. The logic used would be different across differnet application. This will loop the process indefinitely os it is always trying to connect to database.
    private async manageMongoConnection(): Promise<boolean> {
        while (true) {
            try {
                await this.connectToMongoDatabase()
            } catch (error) {
                console.log(`Something Wrong occured. Please check at manageMongoConnection`)
            }
            await new Promise(resolve => setTimeout(resolve, 1000)); // Wait for 1 second before the next attempt
        }
    }

    // This will be used to release all the hostage messages once the light is green.
    public async extractAllMessages(subjectArgs: Subject<Message>): Promise<void> {
        // Need to resolve the issue of streaming in a specific order that is sequential
        let status: Status = 1
        if (status = 1) {
            if (this.messageModel) {
                const eventStream = this.messageModel.find().lean().cursor()
                eventStream.on('data', (message) => {
                    // Emit each document to the subject
                    subjectArgs.next(message);
                });
                eventStream.on('end', async () => {
                    // All data has been streamed, complete the subject
                    subjectArgs.complete();
                    // Delete the data once it has been streamed
                    try {
                        await this.messageModel.deleteMany({});
                        console.log('Data in Mongo deleted successfully.');
                    } catch (err) {
                        console.error('Error deleting data:', err);
                    }
                });
            } else {
                status = 0
                console.log(`Error: Message Model is ${this.messageModel}!! Please set up the mongoose connectino properly!`)
            }
        }
    }

}





// Store in json file in this project folder. To be enabled in future
// private async transferMessageToLocalStorage(message: Subject<any>): Promise<void> {
//     let localArray: any[] = this.bufferedStorage
//     let filename = `localstorage.json`;

//     while (localArray.length > 0) {
//         let objectToWrite = this.bufferedStorage[0];
//         await writeMessage(objectToWrite, filename)
//     }
//     message.subscribe((message: any) => {
//         writeMessage(message, filename)
//     })

//     if (localArray.length < 1) this.bufferedStorage = localArray
//     console.log('Local Array is empty. Finished transferring to files.')

//     async function writeMessage(message: any, filename: string) {
//         try {
//             let stringifiedMessage = JSON.stringify(message);
//             await fs.promises.appendFile(filename, stringifiedMessage + "\r\n")
//             console.log(`Successfully transferred ${filename}`);
//             localArray.shift();
//         } catch (err) {
//             console.error(`Error trasferring ${filename}:`, err);
//         }
//     }
// }