DEV Community: Anton Tyshchenko

How I Made a Free Automated PDF Invoice Maker for Batch Billing All My Contractors

Anton Tyshchenko — Tue, 14 Apr 2026 15:39:58 +0000

Why I needed this in the first place

I run a platform for distributing game graphics called Craftpix. Everyone we work with is a contractor. Incredibly creative people who, to put it mildly, have no interest in paperwork. I outsourced bookkeeping and auditing to a team in Singapore. They have their own dashboard and their accountants are meticulous about collecting everything the audit requires. But the invoices for every single transaction are on me.

In theory that means collecting invoices from each contractor. In practice it would be a nightmare. What saved me is that Hong Kong allows self-billing: I can issue invoices on behalf of my contractors for transactions that have already been completed, without any involvement on their end.

But even with all the details and Google Docs templates on hand, every invoice still needs updated dates and figures. A pointless waste of time. It makes no difference whether I do it or someone else does. It simply should not exist.

I am genuinely glad that e-invoicing is picking up in more countries. That is the future. But while we still live in a world where PDF invoices are a legal requirement, you work with what you have.

Client and contractor data: who is responsible for what

When you receive someone's personal data, you become their data controller. That means you are responsible for tracking where that data goes next.

If you send invoice details to a third-party server-side generator, you are now obligated to read through the Data Processing Agreement of that service. And nobody guarantees things will not go wrong. SaaS services leak data regularly: here is a recent example, and here is another one. Your clients' and contractors' personal data could easily end up on that list.

When we built our invoice generator, we made a clear decision from the start: user data is none of our business. Nothing goes to the server. Generation happens entirely in the browser using plain JS, and all data stays there. You can open the Network tab and verify for yourself that no personal data leaves your machine.

The generator is still a form though: one document at a time. So I wrote a small addition that takes an array of invoice data and generates all of them in one go. I keep the array saved, run it once a month, update the numbers, done. All the details stay in place.

Setup: running the generator

Open Free PDF Invoice Maker and the browser console. I use Chrome: on Mac it is Cmd + Option + J, on Windows Ctrl + Shift + J. Go to the Console tab, paste the code below and hit Enter.

(() => {
    // grab the invoice API exposed by gdoc.io on the window object
    const { store, invoice } = window.invoiceAPI;

    // expose batchInvoice globally so you can call it from the console
    window.batchInvoice = async (invoices) => {
        for (const inv of invoices) {

            // reset the form before filling in the next invoice
            invoice.new();

            // fill in all invoice fields via the store
            store.set({
                'inv.number': inv.number,
                'currency': inv.currency,
                'date.value': inv.date,
                'dueDate.value': inv.dueDate,
                'paymentTerms.value': inv.paymentTerms,
                'poNumber.value': inv.poNumber,
                'from.value': inv.from,
                'billTo.value': inv.billTo,
                'notes.value': inv.notes,
                'terms.value': inv.terms,

                // tax, discount and shipping are optional:
                // if you pass a value, the field gets enabled automatically
                'tax.enabled': inv.tax != null ? '1' : '0',
                'tax.value': inv.tax || 0,
                'discount.enabled': inv.discount != null ? '1' : '0',
                'discount.value': inv.discount || 0,
                'discount.mode': inv.discountMode || 'abs', // 'abs' for fixed amount, 'pct' for percent
                'shipping.enabled': inv.shipping != null ? '1' : '0',
                'shipping.value': inv.shipping || 0,
                'amountPaid.value': inv.amountPaid || 0,
            });

            // each line item needs a unique key — built from timestamp + random suffix
            inv.items.forEach(item => {
                const id = Date.now().toString(36) + Math.random().toString(36).slice(2, 6);
                store.set({
                    [`items.${id}.name`]: item.name,
                    [`items.${id}.qty`]: item.qty,
                    [`items.${id}.price`]: item.price,
                });
            });

            // save state, then trigger PDF download
            invoice.save();
            await invoice.pdf();
        }
        console.log(`✅ ${invoices.length} invoices generated`);
    };
    return '🌋 gdoc.io Invoice Volcano activated! Feed batchInvoice([...]) and watch it erupt';
})();

The generator is ready. Now pass it your data array and hit Enter again.

Each invoice object supports the following fields:

Field	Required	Description
`number`	yes	Invoice number
`currency`	yes	Currency symbol, e.g. `$`, `€`, `£`
`date`	yes	Invoice date in `YYYY-MM-DD` format
`dueDate`	no	Payment due date in `YYYY-MM-DD` format
`paymentTerms`	no	e.g. `Net 30`, `Net 60`
`poNumber`	no	Purchase order number
`from`	yes	Sender details. Use `\n` for line breaks
`billTo`	yes	Recipient details. Use `\n` for line breaks
`items`	yes	Array of line items, each with `name`, `qty`, and `price`
`discount`	no	Discount value. Requires `discountMode`
`discountMode`	no	`pct` for percentage, `abs` for fixed amount
`tax`	no	Tax rate in percent
`shipping`	no	Shipping cost
`amountPaid`	no	Amount already paid, shown as a deduction
`notes`	no	Payment instructions or any additional notes
`terms`	no	Terms and conditions

batchInvoice([
    {
        number: '001',            // invoice number
        currency: '$',            // currency symbol shown on the invoice
        date: '2026-04-11',       // invoice date (YYYY-MM-DD)
        dueDate: '2026-05-11',    // payment due date
        paymentTerms: 'Net 30',   // payment terms label
        poNumber: 'PO-2026-001',  // purchase order number (optional)
        from: 'Acme Corp\n100 Main St\nNew York, NY 10001',    // sender details, use \n for line breaks
        billTo: 'TechStart Inc\n456 Oak Ave\nBoston, MA 02101', // recipient details
        items: [
            // each item: service/product name, quantity, unit price
            { name: 'Frontend Development', qty: 40, price: 120 },
            { name: 'Backend API',          qty: 30, price: 150 },
        ],
        discount: 15,           // discount value
        discountMode: 'pct',    // 'pct' = percentage, 'abs' = fixed amount
        tax: 10,                // tax rate in percent
        amountPaid: 5000,       // amount already paid (shown as a deduction)
        notes: 'Wire: Bank of America\nAcc: 1234567890', // payment instructions or any notes
        terms: 'Late payments subject to 1.5% monthly interest', // terms and conditions
    },
    {
        number: '002',
        currency: '€',
        date: '2026-04-11',
        dueDate: '2026-06-11',
        paymentTerms: 'Net 60',
        from: 'Digital Studio GmbH\nBerlinstr. 42\nBerlin, 10115',
        billTo: 'MegaShop EU\n8 Rue de Rivoli\nParis, 75001',
        items: [
            { name: 'UI/UX Design',     qty: 20, price: 95 },
            { name: 'Brand Guidelines', qty: 1,  price: 2500 },
        ],
        discount: 400,          // fixed discount of €400
        discountMode: 'abs',
        tax: 19,
        shipping: 50,           // shipping cost (optional)
        notes: 'IBAN: DE89 3704 0044 0532 0130 00',
        terms: 'Payment within 60 days',
    },
]);

Generation starts automatically. Depending on your OS and browser settings, files will either land straight in your downloads folder or the browser will ask for permission on each one.

Used to be an hour of repetitive work every month. Now I open the array file, update the dates and numbers, run it — the whole thing takes a couple of minutes.

The full script is also on GitHub if you want to grab it directly.

[Boost]

Anton Tyshchenko — Thu, 10 Jul 2025 17:54:42 +0000

Anton Tyshchenko for Yoka Games

May 22 '25

We Acquired the Rights to a Hardcore Platformer and Released It as a Free Browser Game [Personal Experience]

#gamedev #unity3d #html5games #gameporting

Comments 4

2 min read

We Acquired the Rights to a Hardcore Platformer and Released It as a Free Browser Game [Personal Experience]

Anton Tyshchenko — Thu, 22 May 2025 04:16:25 +0000

Pukan, Bye-Bye! is a minimalist hardcore platformer where death at every step isn’t a bug but a core mechanic. The game has long been available on various platforms, including Steam and consoles, and now it’s freely accessible in the browser at yoka.net (Yoka Games).

Wanted to Enter Game Development — Without Lengthy Development

It all started with a desire to dive into the gaming industry but without spending months creating a game from scratch. I wasn’t planning to immediately develop a large indie project or launch a team. I wanted to go through the entire cycle “from release to publication” using an existing game.

I was acquainted with Artalasky — the author of Pukan, Bye-Bye! — through collaboration on the Craftpix.net project. I knew he already had several completed games, and one of them fit my needs perfectly. We quickly found common ground, discussed the details, and I acquired a sublicense for the web version of the game.

Why I Chose Construct Over Unity

The original game was developed in Unity. However, Unity WebGL turned out to be entirely unsuitable for my needs: fast loading, instant start, cross-device compatibility. The final build was over 40 megabytes — players simply wouldn’t wait for it to load.

I needed an engine that:

produces micro-builds (a few megabytes),
launches instantly,
is perfectly suited for the browser.

I chose Construct, with which I already had experience. Rebuilding the game from scratch turned out to be the only viable solution.

How We Rebuilt Everything Manually

We had all the Unity source files — from graphics to levels. But the code, physics, character behavior, interface, effects — everything had to be redone.

The developer Alven took on the task of porting, and he released a detailed video on his channel about how it all happened. He meticulously recreated the mechanics:

controls considering inertia, sliding, and air behavior;
all traps, which were implemented in Unity through animations;
visual effects, as much as Construct’s capabilities allowed.

The result — 166 hours of pure work. The finished game weighs only 1.5 MB and works excellently in the browser on both PC and mobile devices. We even implemented mobile controls from scratch.

What I Aimed to Achieve

This project became my entry into game development from a producer’s perspective. I wanted to gain quick and practical experience in game distribution: understand how releases work, what publication channels exist, where to gather feedback, and how publishers operate at a basic level.

Additionally, I wanted to assess what kind of team is actually needed to create and release a small but complete project like Pukan, Bye-Bye!.

What Came Out of It

Pukan, Bye-Bye! is now available for free — no downloads, no lags:

Pukan Bye-bye! free-to-play

How to Create an Auto-Failover Load Balancer for 100% Uptime (Tutorial)

Anton Tyshchenko — Sun, 29 Dec 2024 06:05:19 +0000

Recently, my primary server unexpectedly went offline due to unplanned maintenance at the data center. The downtime led to a significant loss of traffic and ad revenue, and I couldn’t intervene in time. This experience made me realize the importance of a robust failover system, especially for situations when immediate action isn’t possible—like during the night or while traveling.

I sought a straightforward yet dependable solution to ensure nearly 100% uptime, even if one server failed. The goal was to minimize configuration complexity while maximizing reliability. To achieve this, I configured automated site replication across two virtual servers and deployed a failover Load Balancer to seamlessly redirect traffic to the backup server in case of primary server downtime.

This tutorial is designed for anyone looking to quickly set up a failover system without needing extensive knowledge of network configurations. The steps are straightforward and easy to follow, ideal for users familiar with basic SSH commands. Whether you’re a developer, a website owner, or someone new to server management, this guide will help you save time and ensure your project’s reliability.

What is load balancer for?

It receives incoming requests and distributes them among multiple servers. The Load Balancer continuously monitors each server’s status and automatically removes any that go offline, ensuring users are always directed to a functional server.

Tools and Services Used

Two virtual machines on DigitalOcean: Provides a scalable and reliable cloud environment.
Cloudflare for Load Balancer: Ensures efficient traffic distribution and failover support.
Debian 11 for the virtual machines: A stable and widely used Linux distribution.
ISPManager (trial): A user-friendly control panel to simplify server management.”

Create Droplets

When setting up a Droplet, consider the following key factors:

Location: Choose a region that is geographically close to your target audience to reduce latency.
Operating System: Debian 11 x64, as this tutorial is specifically tailored for this version.
RAM: At least 2 GB, which is the minimum requirement for the smooth operation of ispmanager.

The screenshot shows an example of the minimal configuration.

Choose Authentication Method : Password

I created two virtual machines right away to demonstrate the process. If you already have a live website, you only need one backup virtual machine.

Installing ispmanager

Before installing ispmanager, you need to adjust the hostname to meet the control panel’s requirements. To do this, edit the following file:

sudo nano /etc/hostname

Here you can see the hostname we set when creating the virtual machine: in my case, it’s debian-s1 and debian-s2. Simply add .ltd at the end to form a valid domain name.

sudo nano /etc/hosts

In this file, you need to find the line that specifies the virtual machine name you set when creating it. For example, we'll use debian-s1 here, but you can replace it with your own:

127.0.1.1 debian-s1 debian-s1
127.0.0.1 localhost

Also, add the .ltd suffix to the first entry, and you'll end up with something like this:

127.0.1.1 debian-s1.ltd debian-s1
127.0.0.1 localhost

After that, we restart the hostname settings.

sudo systemctl restart systemd-hostnamed

Now the system is ready for the control panel installation.

We install wget to download the installer:

apt install wget

Download the ISPmanager installer:

wget https://download.ispmanager.com/install.sh -O install.sh

Run the installation:

sh install.sh

Wait until the following message appears:

Which version would you like to install ?
b) beta version - has the latest functionality
s) stable version - time-proved version

Вам нужно вписать s и нажать enter

Type s and press Enter.

Next, the system will ask you to choose a preferred version. Choose:

1) Ispmanager-lite,pro,host with recommended software

For the choice "Which web server would you like to install?" select:

1) Nginx + Apache

For "Choose database server for ispmanager's internal data," select:

2) MySQL (recommended when maintaining a large number of sites and users)

The panel installation and component configuration will now begin. This process may take about 10 minutes, so feel free to grab a coffee.

After the installation is complete, the console will display a message with your IP:

=================================================
ispmanager-lite-common is installed
Go to the "https://67.205.135.37:1500/ispmgr" to login
Login: root
Password: <root password>
=================================================

Connecting a Website

Next, log in to the control panel at https://your_server_IP:1500/ispmgr. You can activate the trial version of the control panel at https://www.ispmanager.com/.

After logging in, create a user with the same name as the one on your primary server from which the files will be copied.

Configuring the Backup Server to Connect to the Primary Server

Before setting up synchronization, you need to create an SSH access key for your primary server. On the backup server, run:

ssh-keygen -t rsa -b 4096 -C "rsync_backup"

You can leave the password blank.

Next, send this key to the primary server:

ssh-copy-id -i ~/.ssh/id_rsa.pub -p 22 root@IP-address_of_main_server

Great! Your backup server can now connect to the primary server without a password. It's time to create bash scripts for automatic copying.

Setting Up Automatic Copying

To automatically copy the website files and database, you need to create two scripts and configure a cron job. Here’s how:

File Synchronization

Create a folder for the scripts:

mkdir -p /root/scripts/

Create a script for copying files:

nano /root/scripts/copy_files.sh

With the following content:

rsync -avz -e "ssh -p 22" root@IP-address_of_main_server:/var/www/USER_FOLDER/data/www/DOMAIN.LTD/ /var/www/USER_FOLDER/data/www/DOMAIN.LTD/

Replace the placeholders with your data:

IP-address_of_main_server
USER_FOLDER
DOMAIN.LTD

If you want to exclude certain data from synchronization, add these operators after rsync:

--exclude 'wp-config.php' to exclude a specific file
--exclude 'wp-content/cache/' to exclude a folder’s contents

Database Synchronization

Create a script for copying the database:

nano /root/scripts/backup_db.sh

With the following content:

#!/bin/bash

# Settings
PRIMARY_HOST="192.168.1.1"
PRIMARY_HOST_PORT="22"
PRIMARY_HOST_USER="root"

PRIMARY_DB_USER="db-user"
PRIMARY_DB_PASSWORD="******"
PRIMARY_DB="data-base-name"

SECONDARY_HOST="localhost"
SECONDARY_DB_USER="db-user"
SECONDARY_DB_PASSWORD="******"
SECONDARY_DB="data-base-name"

echo "$(date) - Starting database synchronization"

# hecking the availability of the Primary server
if ! ssh -q -p $PRIMARY_HOST_PORT $PRIMARY_HOST_USER@$PRIMARY_HOST exit; then
    echo "$(date) - Primary server ($PRIMARY_HOST) is unreachable. Sync aborted."
    exit 1
fi

# Exporting data from the Primary server
echo "$(date) - Exporting data from primary server..."
ssh -p $PRIMARY_HOST_PORT $PRIMARY_HOST_USER@$PRIMARY_HOST "mysqldump -u $PRIMARY_DB_USER -p'$PRIMARY_DB_PASSWORD' $PRIMARY_DB" > /tmp/$PRIMARY_DB.sql

if [ $? -ne 0 ]; then
    echo "$(date) - Failed to export data from primary server. Sync aborted."
    exit 1
fi

# Importing data to the SECONDARY_HOST
echo "$(date) - Importing data to secondary server..."
mysql -u $SECONDARY_DB_USER -p"$SECONDARY_DB_PASSWORD" $SECONDARY_DB < /tmp/$PRIMARY_DB.sql

if [ $? -eq 0 ]; then
    echo "$(date) - Database synchronization completed successfully."

        # Check if the directory exists
        if [ -d "$TARGET_DIR" ]; then
            # Remove all contents of the directory
            rm -rf "${TARGET_DIR:?}"/*
            echo "Contents of $TARGET_DIR have been removed."
        else
            echo "Directory $TARGET_DIR does not exist."
        fi
else
    echo "$(date) - Database synchronization failed."
    exit 1
fi

# Deleting the temporary file
rm -f /tmp/$PRIMARY_DB.sql

Note: This script is not suitable for large databases or systems with frequent updates. It works best for resources with occasional updates.

Setting Up a CRON Job for Synchronization

Set the frequency of the synchronization scripts based on how fresh you want the backup server data to be. For my site, which updates only during the day, I chose daily synchronization during off-hours.

To create a cron job, run:

nano /var/spool/cron/crontabs/root

Add the following lines to the end of the file:

## Daily MySQL copy (5:00 AM Bangkok time)
0 22 * * * bash /root/scripts/backup_db.sh
## Daily site copy (5:05 AM Bangkok time)
5 22 * * * bash /root/scripts/copy_files.sh

For an initial copy of the site and its database, run these commands once:

bash /root/scripts/backup_db.sh
bash /root/scripts/copy_files.sh

Congratulations! If you’ve reached this point, you now have a fully operational backup server. The last step is to activate the Load Balancer for failover in case the primary server goes down.

Setting Up the Load Balancer

This section explains how to set up a Load Balancer using Cloudflare. I assume your site is already connected to Cloudflare and DNS records are configured. If not, complete the basic setup first.

To make the system activate only when the primary server fails, follow these steps:

Create one Load Balancer;
Configure two server pools;
Add one endpoint per pool.

Go to the Traffic / Load Balancing section for your site.

Creating Monitors

First, create a monitor to check the server’s status via a link. Enter a URL that is not cached and reflects the essential components of the system (e.g., database connection, working script, nginx). For my setup, I use the login page. Don’t forget to check "Don't verify SSL/TLS certificates (insecure)".

Creating Endpoints

Endpoints are the connected servers. It’s essential to create one endpoint for each server: one as the primary and the other as the failover.

During Load Balancer setup, you can customize names for the Pool Name and Endpoint Name fields for convenience. Ensure the Endpoint Address fields contain the IP addresses of your primary and backup servers. In the Header Value field, enter your domain in the format domain.ltd (e.g., example.com). These settings will ensure proper traffic distribution.

Also, select the previously created monitor for server health checks. In the Health Check Regions field, specify the region where most of your audience is located to ensure health checks are performed close to users. Set the Health Threshold value to 1, meaning the pool is considered available with at least one working server.

Creating the Load Balancer

Finally, consolidate everything into a unified system. Below are screenshots of the working configuration:

Hostname

Enter your main domain in the format domain.ltd.

Endpoints

Assign your primary server to "Endpoints in this Load Balancer" and your backup server to "Fallback Pool".

Monitors

Add the previously created monitor.

Traffic Steering

Leave the default setting "Off: Cloudflare will route pools in failover order."

Click Next at each step until you reach the Save button.

Congratulations! Now you can test the setup: disable the primary server and ensure the system correctly redirects traffic to the backup server. If you have any questions, feel free to leave them in the comments—I’ll be happy to help!