Feat/add price slot check (In on-chain programs) (#16)

Adds `get_current_price_status` to Price struct which returns the current price status. If run on-chain with the current slot it checks whether price information has got stale or not. `get_current_price` uses this function to make the interface consistent.

Additional changes:
- Moves `test_instr` for testing to `common.rs` (as it's used in the test for this feature) and renamed it to `test_instr_exex_ok` to be more clear.
- Adds Borsh SerDe traits to PriceStatus as it is used for testing instructions.
- Makes Ema fields public. It was required for creating testing Price object.

README.md

@@ -71,6 +71,12 @@ The price is returned along with a confidence interval that represents the degre
 Both values are represented as fixed-point numbers, `a * 10^e`. 
 The method will return `None` if the price is not currently available.
 
+The status of the price feed determines if the price is available. You can get the current status using:
+
+```rust
+let price_status: PriceStatus = price_account.get_current_price_status();
+```
+
 ### Non-USD prices 
 
 Most assets in Pyth are priced in USD.

examples/get_accounts.rs

@@ -66,7 +66,9 @@ fn main() {
       // print key and reference data for this Product
       println!( "product_account .. {:?}", prod_pkey );
       for (key, val) in prod_acct.iter() {
-        println!( "  {:.<16} {}", key, val );
+        if key.len() > 0 {
+          println!( "  {:.<16} {}", key, val );
+        }
       }
 
       // print all Prices that correspond to this Product
@@ -92,7 +94,7 @@ fn main() {
 
           println!( "    price_type ... {}", get_price_type(&pa.ptype));
           println!( "    exponent ..... {}", pa.expo );
-          println!( "    status ....... {}", get_status(&pa.agg.status));
+          println!( "    status ....... {}", get_status(&pa.get_current_price_status()));
           println!( "    corp_act ..... {}", get_corp_act(&pa.agg.corp_act));
 
           println!( "    num_qt ....... {}", pa.num_qt );

src/instruction.rs

@@ -1,5 +1,9 @@
 //! Program instructions for end-to-end testing and instruction counts
 
+use bytemuck::bytes_of;
+
+use crate::{PriceStatus, Price};
+
 use {
   crate::id,
   borsh::{BorshDeserialize, BorshSerialize},
@@ -34,6 +38,13 @@ pub enum PythClientInstruction {
   ///
   /// No accounts required for this instruction
   Noop,
+
+  PriceStatusCheck {
+    // A Price serialized as a vector of bytes. This field is stored as a vector of bytes (instead of a Price)
+    // so that we do not have to add Borsh serialization to all structs, which is expensive.
+    price_account_data: Vec<u8>,  
+    expected_price_status: PriceStatus
+  }
 }
 
 pub fn divide(numerator: PriceConf, denominator: PriceConf) -> Instruction {
@@ -94,3 +105,14 @@ pub fn noop() -> Instruction {
     data: PythClientInstruction::Noop.try_to_vec().unwrap(),
   }
 }
+
+// Returns ok if price account status matches given expected price status.
+pub fn price_status_check(price: &Price, expected_price_status: PriceStatus) -> Instruction {
+  Instruction {
+    program_id: id(), 
+    accounts: vec![],
+    data: PythClientInstruction::PriceStatusCheck { price_account_data: bytes_of(price).to_vec(), expected_price_status }
+      .try_to_vec()
+      .unwrap(),
+  }
+}

src/lib.rs

@@ -13,20 +13,25 @@ pub mod processor;
 pub mod instruction;
 
 use std::mem::size_of;
+use borsh::{BorshSerialize, BorshDeserialize};
 use bytemuck::{
   cast_slice, from_bytes, try_cast_slice,
   Pod, PodCastError, Zeroable,
 };
 
+#[cfg(target_arch = "bpf")]
+use solana_program::{clock::Clock, sysvar::Sysvar};
+
 solana_program::declare_id!("PythC11111111111111111111111111111111111111");
 
-pub const MAGIC          : u32   = 0xa1b2c3d4;
-pub const VERSION_2      : u32   = 2;
-pub const VERSION        : u32   = VERSION_2;
-pub const MAP_TABLE_SIZE : usize = 640;
-pub const PROD_ACCT_SIZE : usize = 512;
-pub const PROD_HDR_SIZE  : usize = 48;
-pub const PROD_ATTR_SIZE : usize = PROD_ACCT_SIZE - PROD_HDR_SIZE;
+pub const MAGIC               : u32   = 0xa1b2c3d4;
+pub const VERSION_2           : u32   = 2;
+pub const VERSION             : u32   = VERSION_2;
+pub const MAP_TABLE_SIZE      : usize = 640;
+pub const PROD_ACCT_SIZE      : usize = 512;
+pub const PROD_HDR_SIZE       : usize = 48;
+pub const PROD_ATTR_SIZE      : usize = PROD_ACCT_SIZE - PROD_HDR_SIZE;
+pub const MAX_SLOT_DIFFERENCE : u64   = 25; 
 
 /// The type of Pyth account determines what data it contains
 #[derive(Copy, Clone)]
@@ -40,7 +45,7 @@ pub enum AccountType
 }
 
 /// The current status of a price feed.
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, PartialEq, BorshSerialize, BorshDeserialize, Debug)]
 #[repr(C)]
 pub enum PriceStatus
 {
@@ -146,11 +151,15 @@ unsafe impl Pod for Product {}
 #[repr(C)]
 pub struct PriceInfo
 {
-  /// the current price
+  /// the current price. 
+  /// For the aggregate price use price.get_current_price() whenever possible. It has more checks to make sure price is valid.
   pub price      : i64,
-  /// confidence interval around the price
+  /// confidence interval around the price.
+  /// For the aggregate confidence use price.get_current_price() whenever possible. It has more checks to make sure price is valid.
   pub conf       : u64,
-  /// status of price (Trading is valid)
+  /// status of price (Trading is valid).
+  /// For the aggregate status use price.get_current_status() whenever possible.
+  /// Price data can sometimes go stale and the function handles the status in such cases.
   pub status     : PriceStatus,
   /// notification of any corporate action
   pub corp_act   : CorpAction,
@@ -180,9 +189,9 @@ pub struct Ema
   /// The current value of the EMA
   pub val        : i64,
   /// numerator state for next update
-  numer          : i64,
+  pub numer          : i64,
   /// denominator state for next update
-  denom          : i64
+  pub denom          : i64
 }
 
 /// Price accounts represent a continuously-updating price feed for a product.
@@ -243,13 +252,26 @@ unsafe impl Zeroable for Price {}
 unsafe impl Pod for Price {}
 
 impl Price {
+  /**
+   * Get the current status of the aggregate price.
+   * If this lib is used on-chain it will mark price status as unknown if price has not been updated for a while.
+   */
+  pub fn get_current_price_status(&self) -> PriceStatus {
+    #[cfg(target_arch = "bpf")]
+    if matches!(self.agg.status, PriceStatus::Trading) &&
+      Clock::get().unwrap().slot - self.agg.pub_slot > MAX_SLOT_DIFFERENCE {
+      return PriceStatus::Unknown;
+    }
+    self.agg.status
+  }
+
   /**
    * Get the current price and confidence interval as fixed-point numbers of the form a * 10^e.
    * Returns a struct containing the current price, confidence interval, and the exponent for both
    * numbers. Returns `None` if price information is currently unavailable for any reason.
    */
   pub fn get_current_price(&self) -> Option<PriceConf> {
-    if !matches!(self.agg.status, PriceStatus::Trading) {
+    if !matches!(self.get_current_price_status(), PriceStatus::Trading) {
       None
     } else {
       Some(PriceConf {
@@ -394,6 +416,7 @@ pub fn load_price(data: &[u8]) -> Result<&Price, PythError> {
   return Ok(pyth_price);
 }
 
+
 pub struct AttributeIter<'a> {
     attrs: &'a [u8],
 }

src/processor.rs

@@ -5,10 +5,11 @@ use solana_program::{
   account_info::AccountInfo,
   entrypoint::ProgramResult,
   pubkey::Pubkey,
+  program_error::ProgramError
 };
 
 use crate::{
-  instruction::PythClientInstruction,
+  instruction::PythClientInstruction, load_price,
 };
 
 pub fn process_instruction(
@@ -41,5 +42,14 @@ pub fn process_instruction(
     PythClientInstruction::Noop => {
       Ok(())
     }
+    PythClientInstruction::PriceStatusCheck { price_account_data, expected_price_status } => {
+      let price = load_price(&price_account_data[..])?;
+
+      if price.get_current_price_status() == expected_price_status {
+        Ok(())
+      } else {
+        Err(ProgramError::Custom(0))
+      }
+    }
   }
 }

tests/common.rs

@@ -0,0 +1,24 @@
+use {
+    pyth_client::id,
+    pyth_client::processor::process_instruction,
+    solana_program::instruction::Instruction,
+    solana_program_test::*,
+    solana_sdk::{signature::Signer, transaction::Transaction},
+};
+
+// Panics if running instruction fails
+pub async fn test_instr_exec_ok(instr: Instruction) {
+    let (mut banks_client, payer, recent_blockhash) = ProgramTest::new(
+        "pyth_client",
+        id(),
+        processor!(process_instruction),
+    )
+        .start()
+        .await;
+    let mut transaction = Transaction::new_with_payer(
+        &[instr],
+        Some(&payer.pubkey()),
+    );
+    transaction.sign(&[&payer], recent_blockhash);
+    banks_client.process_transaction(transaction).await.unwrap()
+}

tests/instruction_count.rs

@@ -1,26 +1,10 @@
 use {
-    pyth_client::{id, instruction, PriceConf},
-    pyth_client::processor::process_instruction,
-    solana_program::instruction::Instruction,
+    pyth_client::{instruction, PriceConf},
     solana_program_test::*,
-    solana_sdk::{signature::Signer, transaction::Transaction},
 };
 
-async fn test_instr(instr: Instruction) {
-    let (mut banks_client, payer, recent_blockhash) = ProgramTest::new(
-        "pyth_client",
-        id(),
-        processor!(process_instruction),
-    )
-        .start()
-        .await;
-    let mut transaction = Transaction::new_with_payer(
-        &[instr],
-        Some(&payer.pubkey()),
-    );
-    transaction.sign(&[&payer], recent_blockhash);
-    banks_client.process_transaction(transaction).await.unwrap();
-}
+mod common;
+use common::test_instr_exec_ok;
 
 fn pc(price: i64, conf: u64, expo: i32) -> PriceConf {
     PriceConf {
@@ -32,71 +16,71 @@ fn pc(price: i64, conf: u64, expo: i32) -> PriceConf {
 
 #[tokio::test]
 async fn test_noop() {
-    test_instr(instruction::noop()).await;
+    test_instr_exec_ok(instruction::noop()).await;
 }
 
 #[tokio::test]
 async fn test_scale_to_exponent_down() {
-    test_instr(instruction::scale_to_exponent(pc(1, u64::MAX, -1000), 1000)).await
+    test_instr_exec_ok(instruction::scale_to_exponent(pc(1, u64::MAX, -1000), 1000)).await
 }
 
 #[tokio::test]
 async fn test_scale_to_exponent_up() {
-    test_instr(instruction::scale_to_exponent(pc(1, u64::MAX, 1000), -1000)).await
+    test_instr_exec_ok(instruction::scale_to_exponent(pc(1, u64::MAX, 1000), -1000)).await
 }
 
 #[tokio::test]
 async fn test_scale_to_exponent_best_case() {
-    test_instr(instruction::scale_to_exponent(pc(1, u64::MAX, 10), 10)).await
+    test_instr_exec_ok(instruction::scale_to_exponent(pc(1, u64::MAX, 10), 10)).await
 }
 
 #[tokio::test]
 async fn test_normalize_max_conf() {
-    test_instr(instruction::normalize(pc(1, u64::MAX, 0))).await
+    test_instr_exec_ok(instruction::normalize(pc(1, u64::MAX, 0))).await
 }
 
 #[tokio::test]
 async fn test_normalize_max_price() {
-    test_instr(instruction::normalize(pc(i64::MAX, 1, 0))).await
+    test_instr_exec_ok(instruction::normalize(pc(i64::MAX, 1, 0))).await
 }
 
 #[tokio::test]
 async fn test_normalize_min_price() {
-    test_instr(instruction::normalize(pc(i64::MIN, 1, 0))).await
+    test_instr_exec_ok(instruction::normalize(pc(i64::MIN, 1, 0))).await
 }
 
 #[tokio::test]
 async fn test_normalize_best_case() {
-    test_instr(instruction::normalize(pc(1, 1, 0))).await
+    test_instr_exec_ok(instruction::normalize(pc(1, 1, 0))).await
 }
 
 #[tokio::test]
 async fn test_div_max_price() {
-    test_instr(instruction::divide(
+    test_instr_exec_ok(instruction::divide(
         pc(i64::MAX, 1, 0),
         pc(1, 1, 0)
     )).await;
 }
 
 #[tokio::test]
 async fn test_div_max_price_2() {
-    test_instr(instruction::divide(
+    test_instr_exec_ok(instruction::divide(
         pc(i64::MAX, 1, 0),
         pc(i64::MAX, 1, 0)
     )).await;
 }
 
 #[tokio::test]
 async fn test_mul_max_price() {
-    test_instr(instruction::multiply(
+    test_instr_exec_ok(instruction::multiply(
         pc(i64::MAX, 1, 2),
         pc(123, 1, 2),
     )).await;
 }
 
 #[tokio::test]
 async fn test_mul_max_price_2() {
-    test_instr(instruction::multiply(
+    test_instr_exec_ok(instruction::multiply(
         pc(i64::MAX, 1, 2),
         pc(i64::MAX, 1, 2),
     )).await;