ObjectActionHandler.js

const { AbstractActionHandler } = require("demux")

// Initial state
let state = {
    volumeBySymbol: {},
    totalTransfers: 0,
    indexState: {
        blockNumber: 0,
        blockHash: "",
        isReplay: false,
        handlerVersionName: "v1",
    },
}

const stateHistory = {}
const stateHistoryMaxLength = 300

class ObjectActionHandler extends AbstractActionHandler {
    async handleWithState(handle) {
        await handle(state)
        const { blockNumber } = state.indexState
        stateHistory[blockNumber] = JSON.parse(JSON.stringify(state))
        if (blockNumber > stateHistoryMaxLength && stateHistory[blockNumber - stateHistoryMaxLength]) {
            delete stateHistory[blockNumber - stateHistoryMaxLength]
        }
    }

    async loadIndexState() {
        return state.indexState
    }

    async updateIndexState(stateObj, block, isReplay, handlerVersionName) {
        stateObj.indexState.blockNumber = block.blockInfo.blockNumber
        stateObj.indexState.blockHash = block.blockInfo.blockHash
        stateObj.indexState.isReplay = isReplay
        stateObj.indexState.handlerVersionName = handlerVersionName
    }

    async rollbackTo(blockNumber) {
        const latestBlockNumber = state.indexState.blockNumber
        const toDelete = [...Array(latestBlockNumber - (blockNumber)).keys()].map(n => n + blockNumber + 1)
        for (const n of toDelete) {
            delete stateHistory[n]
        }
        state = stateHistory[blockNumber]
    }

    async setup() {
    }
}

module.exports = ObjectActionHandler