docs(near): improve example

Author: Reisen

target_chains/near/README.md

@@ -1,8 +1,8 @@
 # Pyth NEAR
 
 This directory contains the Pyth contract for NEAR, examples, and utilities to deploy. Within the `example/`
-directory you will find an example skeleton NEAR contract that updates and uses a price. You can find
-updates to test with from the Hermes API. Additionally see the `scripts/update.sh` script for an example
+directory you will find an example skeleton NEAR contract that updates and uses several prices. You can find
+payloads to test with from the Hermes API. Additionally see the `scripts/update.sh` script for an example
 of how to manually submit a price update from the CLI.
 
 ## Deployment
@@ -15,6 +15,7 @@ Deploying the NEAR contract has three steps:
    - `sha256sum pyth.wasm` after building the contract.
    - `list(bytes.fromhex(hash))` in Python to get a byte array.
    - Replace the `codehash` field in deploy.sh for the initial codehash.
+   - Replace the sources with the keys expected by the network you're deploying on (testnet vs mainnet).
 
 ## Further Documentation
 

target_chains/near/example/src/lib.rs

@@ -7,16 +7,21 @@ use {
         },
         env,
         is_promise_success,
+        log,
         near_bindgen,
         AccountId,
         Gas,
         PanicOnDefault,
         Promise,
-        PromiseError,
     },
-    pyth::state::PriceIdentifier,
+    pyth::state::{
+        Price,
+        PriceIdentifier,
+    },
 };
 
+/// Our contract simply processes prices, so for now the only state we
+/// need is the Pyth contract ID from which we will be fetching prices.
 #[near_bindgen]
 #[derive(BorshDeserialize, BorshSerialize, PanicOnDefault)]
 pub struct PythExample {
@@ -31,35 +36,64 @@ impl PythExample {
         Self { pyth }
     }
 
-    /// Get a Pyth Price Feed Result.
+    /// Example of submitting an update + request for multiple Price Feeds.
     #[payable]
-    pub fn example_price_usage(&mut self, identifier: PriceIdentifier, data: String) -> Promise {
+    pub fn example_price_usage(
+        &mut self,
+        identifiers: Vec<PriceIdentifier>,
+        data: String,
+    ) -> Promise {
         pyth::ext::ext_pyth::ext(self.pyth.clone())
             .with_static_gas(Gas(30_000_000_000_000))
             .with_attached_deposit(env::attached_deposit())
             .update_price_feeds(data)
             .then(
-                pyth::ext::ext_pyth::ext(self.pyth.clone())
-                    .get_price(identifier)
-                    .then(
-                        Self::ext(env::current_account_id())
-                            .with_static_gas(Gas(10_000_000_000))
-                            .handle_example_price_usage(),
-                    ),
+                Self::ext(env::current_account_id())
+                    .with_static_gas(Gas(10_000_000_000))
+                    .handle_update_callback(identifiers),
             )
     }
 
+    /// Handle the case where prices successfully updated, we can start reads at this point.
     #[payable]
     #[private]
+    pub fn handle_update_callback(&mut self, mut identifiers: Vec<PriceIdentifier>) -> Promise {
+        if !is_promise_success() {
+            panic!("Failed to Update Prices");
+        }
+
+        // Fetch a few prices to use.
+        let price_1 = identifiers.pop().unwrap();
+        let price_2 = identifiers.pop().unwrap();
+        let price_1 = pyth::ext::ext_pyth::ext(self.pyth.clone()).get_price(price_1);
+        let price_2 = pyth::ext::ext_pyth::ext(self.pyth.clone()).get_price(price_2);
+
+        // Start parallel reads.
+        price_1.and(price_2).then(
+            Self::ext(env::current_account_id())
+                .with_static_gas(Gas(10_000_000_000))
+                .handle_results_callback(),
+        )
+    }
+
+    /// Handle results of reading multiple prices, the prices can be accessed using
+    /// NEAR's env::promise_* functions.
+    #[private]
     #[handle_result]
-    pub fn handle_example_price_usage(
-        &mut self,
-        #[callback_result] _r: Result<Option<pyth::state::Price>, PromiseError>,
+    pub fn handle_results_callback(
+        &self,
+        #[callback_result] price_1: Result<Price, near_sdk::PromiseError>,
+        #[callback_result] price_2: Result<Price, near_sdk::PromiseError>,
     ) {
         if !is_promise_success() {
             return;
         }
 
-        // Do things with Price Feed Result.
+        let price_1 = price_1.unwrap();
+        let price_2 = price_2.unwrap();
+
+        // Do something with the prices.
+        log!("{:?}", price_1);
+        log!("{:?}", price_2);
     }
 }