Verify that checked ID is smaller than total supply

functions/.gitignore

@@ -1 +1,2 @@
-node_modules/
+node_modules/
+.*

functions/modules/contract.js

@@ -0,0 +1,41 @@
+// Dependencies
+const Web3 = require( 'web3' )
+const functions = require( 'firebase-functions' )
+const { infura } = functions.config()
+
+// Contract data
+const contractAddress = {
+	mainnet: '',
+	rinkeby: '0x2829ba9d76e675b8867E1707A9aB49B280D916c6'
+}
+const ABI = [
+	{
+      "inputs": [],
+      "name": "totalSupply",
+      "outputs": [
+        {
+          "internalType": "uint256",
+          "name": "",
+          "type": "uint256"
+        }
+      ],
+      "stateMutability": "view",
+      "type": "function",
+      "constant": true
+    }
+]
+
+async function getTotalSupply( network='mainnet' ) {
+
+	// Initialise contract connection
+	const web3 = new Web3( `wss://${ network }.infura.io/ws/v3/${ infura.projectid }` )
+	const contract = new web3.eth.Contract( ABI, contractAddress[ network ] )
+
+	// Return the call promise which returns the total supply
+	return contract.methods.totalSupply().call()
+
+}
+
+module.exports = {
+	getTotalSupply: getTotalSupply
+}

functions/modules/mainnet.js

@@ -1,6 +1,7 @@
 const app = require( './express' )()
 const name = require( 'random-name' )
 const { db } = require( './firebase' )
+const { getTotalSupply } = require( './contract' )
 
 // ///////////////////////////////
 // Data sources
@@ -64,6 +65,32 @@ app.get( '/rocketeer/:id', async ( req, res ) => {
     const { id } = req.params
     if( !id ) return res.json( { error: `No ID specified in URL` } )
 
+    // Chech if this is an illegal ID
+    try {
+
+        // Get the last know total supply
+        const { cachedTotalSupply } = await db.collection( 'meta' ).doc( 'contract' ).get().then( doc => doc.data() )
+
+        // If the requested ID is larger than that, check if the new total supply is more
+        if( cachedTotalSupply < id ) {
+
+            // Get net total supply through infura, if infura fails, return the cached value just in case
+            const totalSupply = await getTotalSupply().catch( f => cachedTotalSupply )
+
+            // Write new value to cache
+            await db.collection( 'meta' ).doc( 'contract' ).set( { cachedTotalSupply: totalSupply }, { merge: true } )
+
+            // If the requested ID is larger than total supply, exit
+            if( totalSupply < id ) return res.json( {
+                trace: 'total supply getter',
+                error: 'This Rocketeer does not yet exist.'
+            } )
+
+        }
+    } catch( e ) {
+        return res.json( { trace: 'total supply getter', error: e.message || JSON.stringify( e ) } )
+    }
+
     // Get existing rocketeer if it exists
     try {
 

functions/modules/testnet.js

@@ -1,7 +1,8 @@
 const app = require( './express' )()
+const { getTotalSupply } = require( './contract' )
 
 // Specific Rocketeer instances
-app.get( '/rocketeer/:id', ( req, res ) => res.json( {
+app.get( '/rocketeer/:id', async ( req, res ) => res.json( {
     description: "A testnet Rocketeer",
     external_url: `https://openseacreatures.io/${ req.params.id }`,
     image: "https://rocketpool.net/images/rocket.png",
@@ -14,7 +15,8 @@ app.get( '/rocketeer/:id', ( req, res ) => res.json( {
 
 
 // Collection data
-app.get( '/collection', ( req, res ) => res.json( {
+app.get( '/collection', async ( req, res ) => res.json( {
+	totalSupply: await getTotalSupply( 'rinkeby' ),
     description: "A testnet collection",
     external_url: `https://openseacreatures.io/`,
     image: "https://rocketpool.net/images/rocket.png",

functions/package.json

@@ -18,7 +18,8 @@
     "express": "^4.17.1",
     "firebase-admin": "^9.12.0",
     "firebase-functions": "^3.11.0",
-    "random-name": "^0.1.2"
+    "random-name": "^0.1.2",
+    "web3": "^1.6.0"
   },
   "devDependencies": {
     "@babel/core": "^7.15.8",