import { web3Factory } from '@0x/dev-utils';
import { Web3ProviderEngine } from '@0x/subproviders';
import R = require('ramda');
import 'reflect-metadata';
import { Connection, createConnection, Repository } from 'typeorm';

import { ExchangeEventsSource } from '../data_sources/contract-wrappers/exchange_events';
import { ExchangeFillEvent } from '../entities';
import { deployConfig } from '../ormconfig';
import { parseExchangeEvents } from '../parsers/events';
import { handleError } from '../utils';

const EXCHANGE_START_BLOCK = 6271590; // Block number when the Exchange contract was deployed to mainnet.
const START_BLOCK_OFFSET = 1000; // Number of blocks before the last known block to consider when updating fill events.
const BATCH_SAVE_SIZE = 1000; // Number of events to save at once.

let connection: Connection;

(async () => {
    connection = await createConnection(deployConfig);
    const provider = web3Factory.getRpcProvider({
        rpcUrl: 'https://mainnet.infura.io',
    });
    await getExchangeEventsAsync(provider);
    process.exit(0);
})().catch(handleError);

async function getExchangeEventsAsync(provider: Web3ProviderEngine): Promise<void> {
    console.log('Checking existing event logs...');
    const eventsRepository = connection.getRepository(ExchangeFillEvent);
    const startBlock = await getStartBlockAsync(eventsRepository);
    console.log(`Getting event logs starting at ${startBlock}...`);
    const exchangeEvents = new ExchangeEventsSource(provider, 1);
    const eventLogs = await exchangeEvents.getFillEventsAsync(startBlock);
    console.log('Parsing events...');
    const events = parseExchangeEvents(eventLogs);
    console.log(`Retrieved and parsed ${events.length} total events.`);
    console.log('Saving events...');
    // Split the events into batches of size BATCH_SAVE_SIZE and save each batch
    // in a single request. This reduces round-trip latency to the DB. We need
    // to batch this way because saving an extremely large number of events in a
    // single request causes problems.
    for (const eventsBatch of R.splitEvery(BATCH_SAVE_SIZE, events)) {
        await eventsRepository.save(eventsBatch);
    }
    const totalEvents = await eventsRepository.count();
    console.log(`Done saving events. There are now ${totalEvents} total events.`);
}

async function getStartBlockAsync(eventsRepository: Repository<ExchangeFillEvent>): Promise<number> {
    const fillEventCount = await eventsRepository.count();
    if (fillEventCount === 0) {
        console.log('No existing fill events found.');
        return EXCHANGE_START_BLOCK;
    }
    const queryResult = await connection.query(
        'SELECT block_number FROM exchange_fill_events ORDER BY block_number DESC LIMIT 1',
    );
    const lastKnownBlock = queryResult[0].block_number;
    return lastKnownBlock - START_BLOCK_OFFSET;
}