@worldbrain/storex-sync/ts/logging-middleware/index.ts

Offline-first syncing between multiple databases using Storex

import { StorageMiddleware } from '@worldbrain/storex/lib/types/middleware'
import { ClientSyncLogStorage } from "../client-sync-log"
import StorageManager from '@worldbrain/storex'
import { ClientSyncLogEntry } from '../client-sync-log/types'
import { OperationProcessorMap, DEFAULT_OPERATION_PROCESSORS } from './operation-processors'

export class SyncLoggingMiddleware implements StorageMiddleware {
    private clientSyncLog : ClientSyncLogStorage
    private storageManager : StorageManager
    private operationProcessors : OperationProcessorMap = DEFAULT_OPERATION_PROCESSORS
    private includeCollections : Set<string>

    constructor(options : {clientSyncLog : ClientSyncLogStorage, storageManager : StorageManager, includeCollections : string[]}) {
        Object.assign(this, { ...options, includeCollections: new Set(options.includeCollections) })
    }
    
    async process({next, operation} : {next : {process: ({operation}) => any}, operation : any[]}) {
        const executeAndLog = (originalOperation, logEntries : ClientSyncLogEntry[]) => {
            const batch = originalOperation instanceof Array ? originalOperation : [originalOperation]
            for (const logEntry of logEntries) {
                batch.push({
                    placeholder: 'logEntry',
                    operation: 'createObject',
                    collection: 'clientSyncLogEntry',
                    args: logEntry
                })
            }
            return next.process({operation: [
                'executeBatch',
                batch
            ]})
        }

        const operationType = (operation[0] as string)
        const operationProcessor = this.operationProcessors[operationType]
        if (operationProcessor) {
            return operationProcessor({
                next, operation, executeAndLog, getNow: () => this._getNow(),
                includeCollections: this.includeCollections,
                storageRegistry: this.storageManager.registry})
        } else {
            return next.process({operation})
        }
    }

    _getNow() {
        return Date.now()
    }
}