@atomiqlabs/btc-mempool/src/synchronizer/MempoolBtcRelaySynchronizer.ts

Connector and synchronizer using mempool.space API for bitcoin

import {BtcRelay, BtcStoredHeader, RelaySynchronizer, timeoutPromise} from "@atomiqlabs/base";
import {MempoolBitcoinBlock} from "../mempool/MempoolBitcoinBlock";
import {MempoolBitcoinRpc} from "../mempool/MempoolBitcoinRpc";

/**
 * Mempool.space API based bitcoin relay synchronizer
 *
 * @category Bitcoin
 */
export class MempoolBtcRelaySynchronizer<B extends BtcStoredHeader<any>, TX> implements RelaySynchronizer<B, TX, MempoolBitcoinBlock > {

    bitcoinRpc: MempoolBitcoinRpc;
    btcRelay: BtcRelay<B, TX, MempoolBitcoinBlock>;

    constructor(btcRelay: BtcRelay<B, TX, MempoolBitcoinBlock>, bitcoinRpc: MempoolBitcoinRpc) {
        this.btcRelay = btcRelay;
        this.bitcoinRpc = bitcoinRpc;
    }

    /**
     * @inheritDoc
     */
    async syncToLatestTxs(signer: string, feeRate?: string): Promise<{
        txs: TX[]
        targetCommitedHeader: B,
        computedHeaderMap: {[blockheight: number]: B},
        blockHeaderMap: {[blockheight: number]: MempoolBitcoinBlock},
        btcRelayTipCommitedHeader: B,
        btcRelayTipBlockHeader: MempoolBitcoinBlock,
        latestBlockHeader: MempoolBitcoinBlock,
        startForkId?: number
    }> {
        const tipData = await this.btcRelay.getTipData();
        if(tipData==null) throw new Error("BtcRelay tip data not found - probably not initialized?");

        const latestKnownBlockLogData = await this.btcRelay.retrieveLatestKnownBlockLog();
        if(latestKnownBlockLogData==null) throw new Error("Failed to get latest known block log");
        const {resultStoredHeader, resultBitcoinHeader} = latestKnownBlockLogData;

        let cacheData: {
            forkId: number,
            lastStoredHeader: B,
            tx?: TX,
            computedCommitedHeaders: B[]
        } = {
            forkId: resultStoredHeader.getBlockheight()<tipData.blockheight ? -1 : 0, //Indicate that we will be submitting blocks to fork
            lastStoredHeader: resultStoredHeader,
            computedCommitedHeaders: []
        };

        let spvTipBlockHeader = latestKnownBlockLogData.resultBitcoinHeader;
        let spvTipBlockHeight = spvTipBlockHeader.height;

        const txsList: TX[] = [];
        const blockHeaderMap: {[blockheight: number]: MempoolBitcoinBlock} = {
            [resultBitcoinHeader.getHeight()]: resultBitcoinHeader
        };
        const computedHeaderMap: {[blockheight: number]: B} = {
            [resultStoredHeader.getBlockheight()]: resultStoredHeader
        };
        let startForkId: number | undefined = undefined;

        let forkFee: string | undefined = feeRate;
        let mainFee: string | undefined = feeRate;
        const saveHeaders = async (headerCache: MempoolBitcoinBlock[]) => {
            if(cacheData.forkId===-1) {
                if(mainFee==null) mainFee = await this.btcRelay.getMainFeeRate(signer);
                cacheData = await this.btcRelay.saveNewForkHeaders(signer, headerCache, cacheData.lastStoredHeader, tipData.chainWork, mainFee);
            } else if(cacheData.forkId===0) {
                if(mainFee==null) mainFee = await this.btcRelay.getMainFeeRate(signer);
                cacheData = await this.btcRelay.saveMainHeaders(signer, headerCache, cacheData.lastStoredHeader, mainFee);
            } else {
                if(forkFee==null) forkFee = await this.btcRelay.getForkFeeRate(signer, cacheData.forkId);
                cacheData = await this.btcRelay.saveForkHeaders(signer, headerCache, cacheData.lastStoredHeader, cacheData.forkId, tipData.chainWork, forkFee)
            }
            if(cacheData.forkId!==-1 && cacheData.forkId!==0) startForkId = cacheData.forkId;
            txsList.push(cacheData.tx!);
            for(let storedHeader of cacheData.computedCommitedHeaders) {
                computedHeaderMap[storedHeader.getBlockheight()] = storedHeader;
            }
        };

        let headerCache: MempoolBitcoinBlock[] = [];

        while(true) {
            const retrievedHeaders = await this.bitcoinRpc.getPast15Blocks(spvTipBlockHeight+15);
            let startIndex = retrievedHeaders.findIndex(val => val.height === spvTipBlockHeight);
            if(startIndex === -1) startIndex = retrievedHeaders.length; //Start from the last block

            for(let i=startIndex-1;i>=0;i--) {
                const header = retrievedHeaders[i];

                blockHeaderMap[header.height] = header;
                headerCache.push(header);

                if(cacheData.forkId===0 ?
                    headerCache.length>=this.btcRelay.maxHeadersPerTx :
                    headerCache.length>=this.btcRelay.maxForkHeadersPerTx) {

                    await saveHeaders(headerCache);
                    headerCache = [];
                }
            }

            if(retrievedHeaders.length>0) {
                if(spvTipBlockHeight === retrievedHeaders[0].height) break; //Already at the tip
                spvTipBlockHeight = retrievedHeaders[0].height;
                await timeoutPromise(1000);
            } else break;
        }

        if(headerCache.length>0) await saveHeaders(headerCache);

        if(cacheData.forkId!==0) {
            throw new Error("Unable to synchronize on-chain bitcoin light client! Not enough chainwork at connected RPC.");
        }

        return {
            txs: txsList,
            targetCommitedHeader: cacheData.lastStoredHeader,

            blockHeaderMap,
            computedHeaderMap,

            btcRelayTipCommitedHeader: resultStoredHeader,
            btcRelayTipBlockHeader: resultBitcoinHeader,

            latestBlockHeader: spvTipBlockHeader,
            startForkId
        };
    }

}