Add instructions + example client for devnet

contracts/examples/hello-world/README.md

@@ -0,0 +1,61 @@
+# chainlink-solana
+
+## Running the example on devnet
+
+Generate a new wallet:
+
+```
+solana-keygen new -o id.json
+solana-keygen pubkey id.json
+```
+
+Airdrop some tokens:
+
+```
+solana airdrop 4 <RECIPIENT_ACCOUNT_ADDRESS> --url https://api.devnet.solana.com
+```
+
+Build and deploy the contract:
+
+```
+anchor build
+anchor deploy --provider.cluster devnet
+```
+
+Extract the `program_id` and insert it into `client.js`
+
+```
+solana-keygen pubkey target/deploy/hello_world-keypair.json
+```
+
+Now run the Node.JS client:
+
+```
+ANCHOR_PROVIDER_URL=https://api.devnet.solana.com ANCHOR_WALLET=id.json node client.js
+Running client...
+Fetching transaction logs...
+[
+  'Program <PROGRAM_ID> invoke [1]',
+  'Program log: Instruction: Execute',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g invoke [2]',
+  'Program log: Instruction: Query',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g consumed 2916 of 196135 compute units',
+  'Program return: DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g 6NQDALZQ7mEAAAAAQH32BQAAAAAAAAAAAAAAAA==',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g success',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g invoke [2]',
+  'Program log: Instruction: Query',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g consumed 2943 of 189793 compute units',
+  'Program return: DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g CgAAAFVTRFQgLyBVU0Q=',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g success',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g invoke [2]',
+  'Program log: Instruction: Query',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g consumed 2332 of 183111 compute units',
+  'Program return: DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g CA==',
+  'Program DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g success',
+  'Program log: USDT / USD price is 1.00040000',
+  'Program ENzTWES9dJhCDh2cBdxysQyzBUTxUqokPcojSj5phykw consumed 21585 of 200000 compute units',
+  'Program return: DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g CA==',
+  'Program ENzTWES9dJhCDh2cBdxysQyzBUTxUqokPcojSj5phykw success'
+]
+Success
+```

contracts/examples/hello-world/client.js

@@ -0,0 +1,42 @@
+const anchor = require("@project-serum/anchor");
+
+// devnet IDs
+const CHAINLINK_PROGRAM_ID = "DWqYEinRbZWtuq1DiDYvmexAKFoyjSyazZZUvdgPHT5g";
+// USDT/USD
+const CHAINLINK_FEED = "CwBg8pxL73LvuJ781cWBGF1e64G2z7AbZ22J2g8Lp35a";
+
+const provider = anchor.Provider.env();
+
+// Configure the cluster.
+anchor.setProvider(provider);
+
+async function main() {
+  // #region main
+  // Read the generated IDL.
+  const idl = JSON.parse(
+    require("fs").readFileSync("./target/idl/hello_world.json", "utf8")
+  );
+
+  // Address of the deployed program.
+  const programId = new anchor.web3.PublicKey("<YOUR-PROGRAM-ID>");
+
+  // Generate the program client from IDL.
+  const program = new anchor.Program(idl, programId);
+
+  // Execute the RPC.
+  let tx = await program.rpc.execute({
+    accounts: {
+      chainlinkFeed: CHAINLINK_FEED,
+      chainlinkProgram: CHAINLINK_PROGRAM_ID
+    },
+    options: { commitment: "confirmed" },
+  });
+
+  console.log("Fetching transaction logs...");
+  let t = await provider.connection.getConfirmedTransaction(tx, "confirmed");
+  console.log(t.meta.logMessages);
+  // #endregion main
+}
+
+console.log("Running client...");
+main().then(() => console.log("Success"));

contracts/examples/hello-world/programs/hello-world/src/lib.rs

@@ -4,8 +4,6 @@ use chainlink_solana as chainlink;
 
 declare_id!("Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS");
 
-const DECIMALS: u32 = 18;
-
 struct Decimal {
     pub value: i128,
     pub decimals: u32,
@@ -42,8 +40,18 @@ pub mod hello_world {
             ctx.accounts.chainlink_feed.to_account_info(),
         )?;
 
-        let decimal = Decimal::new(round.answer, DECIMALS);
-        msg!("Price is {}", decimal);
+        let description = chainlink::description(
+            ctx.accounts.chainlink_program.to_account_info(),
+            ctx.accounts.chainlink_feed.to_account_info(),
+        )?;
+
+        let decimals = chainlink::decimals(
+            ctx.accounts.chainlink_program.to_account_info(),
+            ctx.accounts.chainlink_feed.to_account_info(),
+        )?;
+
+        let decimal = Decimal::new(round.answer, u32::from(decimals));
+        msg!("{} price is {}", description, decimal);
         Ok(())
     }
 }