Refactor state PDA accessors

bench-report.json

@@ -29,10 +29,10 @@
     "create_buffers/max_buffers_in_one_instruction": 176947,
     "create_order/happy_path_creates_order_pda_with_expected_body": 4976,
     "initialize/happy_path_initializes_state_pda_with_expected_data": 4526,
-    "reclaim_buffer/funded_buffer_is_skipped": 6299,
-    "reclaim_buffer/happy_path_reclaims_empty_buffer_to_the_authority_itself": 7447,
-    "reclaim_buffer/max_buffers_in_one_instruction": 136501,
-    "reclaim_buffer/reclaims_multiple_buffers_skipping_funded": 18043,
+    "reclaim_buffer/funded_buffer_is_skipped": 6324,
+    "reclaim_buffer/happy_path_reclaims_empty_buffer_to_the_authority_itself": 7472,
+    "reclaim_buffer/max_buffers_in_one_instruction": 136526,
+    "reclaim_buffer/reclaims_multiple_buffers_skipping_funded": 18068,
     "reclaim_order/happy_path_returns_lamports_and_closes_pda": 2183,
     "settle/finalizes_with_no_pushes": 7062,
     "settle/pulls_from_multiple_orders": 19921,
@@ -43,9 +43,9 @@
     "settle/pushes_several_orders_from_one_buffer": 17609,
     "settle/settles_a_single_order": 12384,
     "settle/settles_multiple_orders": 22894,
-    "transfer_authority/manager_can_transfer_manager": 3170,
-    "transfer_authority/manager_can_transfer_reclaim_authority": 3172,
-    "transfer_authority/reclaim_authority_can_transfer_itself": 3175
+    "transfer_authority/manager_can_transfer_manager": 3174,
+    "transfer_authority/manager_can_transfer_reclaim_authority": 3176,
+    "transfer_authority/reclaim_authority_can_transfer_itself": 3180
   },
   "transaction_bytes": {
     "create_buffers/happy_path_creates_initialized_buffer_token_account": 303,

client/src/lib.rs

@@ -4,3 +4,4 @@ pub use cow_settlement_interface;
 
 pub mod instructions;
 pub mod parse;
+pub mod pda;

client/src/pda/mod.rs

@@ -0,0 +1,3 @@
+//! Off-chain decoders for the settlement program's PDAs.
+
+pub mod state;

client/src/pda/state.rs

@@ -0,0 +1,76 @@
+//! Off-chain decoded snapshot of a settlement state account.
+
+use cow_settlement_interface::{data::state::StateAccount, Pubkey, Role};
+use solana_program_error::ProgramError;
+
+/// An owned, decoded snapshot of a settlement state account.
+/// Similar to [`StateAccount`], but it fully owns its data.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct DecodedStateAccount {
+    pub manager: Pubkey,
+    pub reclaim_authority: Pubkey,
+}
+
+impl TryFrom<&[u8]> for DecodedStateAccount {
+    type Error = ProgramError;
+
+    fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
+        let state = StateAccount::attach(bytes)?;
+        Ok(Self {
+            manager: state.authority(Role::Manager),
+            reclaim_authority: state.authority(Role::ReclaimAuthority),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use cow_settlement_interface::data::state::{StateInitArgs, WIDTH_HEADER};
+    use cow_settlement_interface::fixtures::pubkey_from_seed;
+
+    fn state_bytes(manager: &Pubkey, reclaim_authority: &Pubkey) -> [u8; WIDTH_HEADER] {
+        let mut bytes = [0u8; WIDTH_HEADER];
+        StateAccount::initialize(
+            &mut bytes[..],
+            &StateInitArgs {
+                manager: *manager,
+                reclaim_authority: *reclaim_authority,
+            },
+        )
+        .expect("header fits");
+        bytes
+    }
+
+    #[test]
+    fn decodes_the_header() {
+        let manager = pubkey_from_seed("manager");
+        let reclaim_authority = pubkey_from_seed("reclaim authority");
+        let bytes = state_bytes(&manager, &reclaim_authority);
+
+        let decoded = DecodedStateAccount::try_from(&bytes[..]).expect("valid state account");
+        assert_eq!(
+            decoded,
+            DecodedStateAccount {
+                manager,
+                reclaim_authority,
+            },
+        );
+    }
+
+    #[test]
+    fn rejects_non_state_account() {
+        // A zeroed buffer: right length, but its leading byte isn't the state
+        // discriminator.
+        let bytes = [0u8; WIDTH_HEADER];
+        assert!(DecodedStateAccount::try_from(&bytes[..]).is_err());
+    }
+
+    #[test]
+    fn rejects_too_short_account() {
+        let manager = pubkey_from_seed("manager");
+        let reclaim_authority = pubkey_from_seed("reclaim authority");
+        let bytes = state_bytes(&manager, &reclaim_authority);
+        assert!(DecodedStateAccount::try_from(&bytes[..WIDTH_HEADER - 1]).is_err());
+    }
+}