PiggyBank

A time-locked SOL savings dapp built with Ruby on Rails 8. Lock SOL in an on-chain vault for a set duration, watch a live countdown, and unlock when the timer expires — all using the Rails default stack.

Part of the SolRengine project.

Stack

• Ruby on Rails 8 (Hotwire, Turbo, Stimulus, Solid Queue/Cache/Cable)
• SolRengine — Rails framework for Solana dapps
• SQLite (primary + cache + queue + cable)
• Tailwind CSS 4 + esbuild
• @solana/kit for client-side transaction building
• Wallet Standard for wallet discovery
• Custom Anchor program on Solana Devnet

Features

• Wallet Authentication — Sign in with Phantom, Solflare, or Backpack via SIWS (Sign In With Solana)
• Lock SOL — Choose an amount and duration, sign a transaction, and lock SOL in an on-chain program account
• Live Countdown — Each lock shows a real-time countdown with a progress bar that persists across page refreshes
• Unlock — When the timer expires, unlock and your SOL returns to your wallet
• Non-custodial — Your SOL stays in a program-derived account. The app never holds your funds.
• Anchor IDL in Ruby — The solrengine-programs gem parses the Anchor IDL and generates Ruby models for on-chain accounts with Borsh encoding

Setup

bin/setup
bin/rails db:prepare

Development

bin/dev

Starts 4 processes: web server, JS bundler, CSS compiler, and Solid Queue worker.

Open http://localhost:3000 with a Solana wallet extension installed (Phantom, Solflare, or Backpack).

Testing on Devnet

1. Set SOLANA_NETWORK=devnet in .env (default)
2. Get free SOL from the Solana Faucet
3. Connect your wallet and lock some SOL

Environment Variables

Variable	Default	Description
SOLANA_NETWORK	devnet	Network to run on (mainnet, devnet, testnet)
SOLANA_RPC_DEVNET_URL	—	Devnet HTTP RPC endpoint
SOLANA_WS_DEVNET_URL	—	Devnet WebSocket RPC endpoint
APP_DOMAIN	localhost	Domain for SIWS message (production)

Copy .env.example to .env and fill in your RPC endpoints.

Architecture

app/
├── controllers/
│   ├── sessions_controller.rb       # SIWS auth (nonce → sign → verify → session)
│   ├── dashboard_controller.rb      # Lock list with cached RPC queries
│   ├── locks_controller.rb          # Build lock/unlock instruction data
│   └── pages_controller.rb          # Landing page
├── models/
│   ├── user.rb                      # wallet_address identity
│   └── piggy_bank/
│       └── lock.rb                  # On-chain account model (Borsh fields: dst, exp)
├── services/
│   └── piggy_bank/
│       ├── lock_instruction.rb      # Lock instruction builder (Anchor IDL)
│       └── unlock_instruction.rb    # Unlock instruction builder (Anchor IDL)
└── javascript/controllers/
    ├── wallet_controller.js          # Wallet Standard discovery + SIWS sign-in
    ├── piggy_bank_controller.js      # Build tx with @solana/kit + wallet-standard sign
    ├── countdown_controller.js       # Live countdown timer with progress bar
    └── auto_refresh_controller.js    # Idiomorph-based invisible page refresh

How It Works

Authentication

1. Stimulus discovers wallets via Wallet Standard
2. User clicks "Connect Wallet" → wallet popup opens
3. Rails generates a SIWS message with a nonce
4. Wallet signs the message (Ed25519)
5. Rails verifies the signature and creates a session

Locking SOL

1. Client generates a fresh keypair for the lock account
2. Rails builds Borsh-encoded instruction data via the Anchor IDL
3. Stimulus assembles the transaction with @solana/kit
4. Lock keypair signs first, then wallet signs and sends via signAndSendTransaction
5. Dashboard updates with a live countdown

Unlocking SOL

1. Rails builds the unlock instruction using the lock account address
2. Stimulus assembles and sends via wallet-standard
3. SOL returns to the user's wallet

Program

• ID: ZaU8j7XCKSxmmkMvg7NnjrLNK6eiLZbHsJQAc2rFzEN (Devnet)
• IDL: config/idl/piggy_bank.json
• Account: PiggyBank::Lock — 8-byte discriminator + 32-byte pubkey (dst) + 8-byte u64 (expiration)
• Instructions: lock(amt, exp) and unlock()