index.js

const express = require('express');
require('express-async-errors');
const cors = require('cors');
const { Pool } = require('pg');
const axios = require('axios');

const app = express();
const port = 3001;

app.use(cors());
app.use(express.urlencoded({ extended: false }));
app.use(express.json());

app.get('/', async (req, res) => {
    res.status(200).send('Hello World');
});

app.get('/accounts', async function (req, res) {
    const address = req.query['address'];
    const connection = [
        'postgres://public_readonly:nearprotocol@mainnet.db.explorer.indexer.near.dev/mainnet_explorer',
        'postgres://public_readonly:nearprotocol@testnet.db.explorer.indexer.near.dev/testnet_explorer',
    ];

    const addPrefix = (rows, net) => {
        if(rows.length){
            rows.map((row)=>{
                if(hasAccountId(row['account_id'])){
                    return row['account_id'];
                }else{
                    return row['account_id'] = net + ':' + row['account_id'];
                }
            });
        }
    };
    
    const addPrefixForKit = (rows, net) => {
        const newRows = [];
        if(rows.length){
            rows.map((row)=>{
                if(hasAccountId(row)){
                    newRows.push(row);
                }else{
                    newRows.push(net + ':' + row);
                }
            });
        }
        return newRows;
    };

    const hasAccountId = (address) => {
        return address.split('.').pop() == 'near' || address.split('.').pop() == 'testnet';
    };

    try {
        const accountsIds = await Promise.all(connection.map(async (connectionString, idx) => {

            const { rows } = await new Pool({
                connectionString,
            }).query(`
              SELECT DISTINCT account_id
              FROM access_keys
              JOIN accounts USING (account_id)
              WHERE public_key = $1
                  AND accounts.deleted_by_receipt_id IS NULL
                  AND access_keys.deleted_by_receipt_id IS NULL
            `, [address]);
    
            if(idx){
                addPrefix(rows, 'testnet');
            }else{
                addPrefix(rows, 'mainnet');
            }
    
            return rows;
    
        }));
        
        const result = accountsIds.reduce((acc, cur) => acc.concat(cur)).map((account) => account['account_id']);
        
        res.send(result);
    } catch (e) {
        try {
            const kitUrl = [
                'https://api.kitwallet.app/publicKey/'+address+'/accounts',
                'https://testnet-api.kitwallet.app/publicKey/'+address+'/accounts'
            ];

            const accountsIds = await Promise.all(kitUrl.map(async (kitString, idx) => {
                const rows = (await axios.get(kitString)).data;
                if(idx){
                    return addPrefixForKit(rows, 'testnet');
                }else{
                    return addPrefixForKit(rows, 'mainnet');
                }
            }));

            const result = accountsIds.reduce((acc, cur) => acc.concat(cur));

            res.status(500);
            res.send(result);

        } catch (e) {
            console.log(e);
            res.status(500);
            res.send([]);
        }
    }
    
});

// eslint-disable-next-line no-unused-vars
app.use((err, req, res, next) => {
    res.status(500);
    res.send([]);
});

app.listen(port, () => {
    console.log(`App running on port ${port}.`);
});