Restricted message length to 256 chars, in case black hat hackers are tempted. Also set max blocks validation to 10

README.md

@@ -53,3 +53,112 @@ The one constant is `deployment-info.json`.
 ## License
 
 [Open BSV License](./LICENSE.txt)
+
+# Locksmith
+
+### "For those of us who think purposely freezing our money for a cause is cool."
+
+### Locksmith is a Bitcoin SV (BSV) application that lets users lock a small amount of satoshis in a smart contract until a specified future block height. This time-lock is accompanied by a custom message and cannot be redeemed until the blockchain reaches the unlock height.
+
+## Features
+
+- Lock 10–1000 satoshis for 1–10 blocks.
+- Attach a personal message to each lock.
+- View current active locks and the number of blocks remaining.
+- Automatically redeem funds once the lock expires.
+- Lookup service and topic manager to manage the overlay.
+
+## Tech Stack
+
+| Layer          | Technology                                |
+|----------------|--------------------------------------------|
+| Frontend       | React + TypeScript + MUI                  |
+| Smart Contract | sCrypt (Locksmith contract)               |
+| Blockchain     | Bitcoin SV (via `@bsv/sdk`, `@bsv/overlay`) |
+| Backend        | Node.js + Express + MongoDB               |
+| Storage        | MongoDB (lock metadata)                   |
+| Overlay        | LookupService + TopicManager via `@bsv/overlay` |
+
+## Screenshots
+
+The frontend allows you to lock satoshis with a reason and see other users' active locks when it is deployed using CARS (see above).
+![App page](https://github.com/user-attachments/assets/9363c9a5-0535-4805-a376-a0322aeef074)
+
+## Getting Started
+
+### Prerequisites
+
+- Node.js ≥ v18
+- MongoDB running locally or remotely
+- [BRC-100](https://github.com/bitcoin-sv/BRCs/blob/master/wallet/0100.md) Wallet integration (get your [Metanet Desktop](https://github.com/bitcoin-sv/metanet-desktop/releases) wallet)
+- Docker (optional, but integral if using LARS (see above))
+
+## Frontend Setup
+```bash
+cd frontend
+npm i
+npm run start
+Visit: http://localhost:8090
+```
+## Backend Setup
+```bash
+cd backend
+npm i
+npm run build
+npm run start
+Server runs on: http://localhost:8080
+```
+
+## Contracts
+### Locksmith 
+Built using: ([sCrypt.io](https://scrypt.io/))
+```ts
+class Locksmith extends SmartContract {
+  @prop() address: Addr
+  @prop() lockUntilHeight: bigint
+  @prop() message: ByteString
+
+  @method(SigHash.ANYONECANPAY_NONE)
+  unlock(sig: Sig, pubKey: PubKey) {
+    assert(lock conditions...)
+  }
+}
+```
+## The contract enforces:
+- Lock until a future block height
+- Signature verification
+- Message attachment for context
+
+## Lock Flow
+### Lock funds
+- User inputs satoshis, block duration, and message.
+- Transaction is created using `walletClient.createAction()`.
+- Funds are locked in a smart contract and broadcast via `SHIPBroadcaster()`.
+
+### Monitor locks
+- The frontend polls the overlay every 10 seconds.
+- Active locks are displayed with their remaining blocks.
+
+### Unlock funds
+- When the lock expires, the app automatically constructs and broadcasts a redeeming transaction using `walletClient.createAction()` and the original contract and signature.
+
+## Overlay 
+[documentation](https://docs.projectbabbage.com/docs/concepts/overlays)
+- Two overlay components handle indexing and filtering:
+- LookupService: Tracks active locks in the MongoDB.
+- TopicManager: Identifies outputs created using the Locksmith contract.
+
+## Directory Structure
+```css
+locksmith/
+├── frontend/
+│   └── App.tsx
+├── backend/
+│   ├── src/
+│   │   ├── contracts/Locksmith.ts
+│   │   ├── lookup-services/
+│   │   └── topic-managers/
+├── artifacts/
+├── types/
+├── mod.ts
+```

frontend/src/App.tsx

@@ -6,7 +6,7 @@ import {
   LinearProgress,
   Container
 } from '@mui/material'
-import { lock, startBackgroundUnlockWatchman } from './utils/utils'
+import { lock, startBackgroundUnlockWatchman, truncate } from './utils/utils'
 import { NoMncModal } from 'metanet-react-prompt'
 import { LookupResolver, Transaction, Utils, WalletClient } from '@bsv/sdk'
 import { HodlockerToken, Token } from './types/types'
@@ -242,14 +242,16 @@ export const App: React.FC = () => {
           <br />
           <TextField
             disabled={loading}
-            label="Your message:"
+            label="Your message 1 -> 256 chars:"
             value={message}
             fullWidth
             rows={8}
             multiline
-            onChange={(e: {
-              target: { value: React.SetStateAction<string> }
-            }) => setMessage(e.target.value)}
+            inputProps={{ maxLength: 256 }}
+            onChange={(e: React.ChangeEvent<HTMLInputElement>) => {
+              const truncated = truncate(e.target.value, 256)
+              setMessage(truncated)
+            }}
           />
           <br />
           <br />

frontend/src/utils/utils.ts

@@ -65,8 +65,8 @@ export const lock = async (
   setHodlocker: React.Dispatch<React.SetStateAction<HodlockerToken[]>>,
   hodlocker: HodlockerToken[]
 ): Promise<string | undefined> => {
-  if (lockBlockCount < 0) {
-    throw new Error('Lock block count must be zero or positive')
+  if (lockBlockCount < 1 || lockBlockCount > 10) {
+    throw new Error('Lock block count must be positive and less than 10')
   }
   if (satoshis < 10 || satoshis > 1000) {
     throw new Error(
@@ -76,6 +76,9 @@ export const lock = async (
   if (message.length < 1) {
     throw new Error('Message is required for the lock')
   }
+  if (message.length > 260) {
+    throw new Error('Message is too long')
+  }
 
   const currentBlockHeightObj = await constants.walletClient.getHeight()
   const lockBlockHeight = currentBlockHeightObj.height + lockBlockCount