setup reclaim order

interface/src/data/intent.rs

@@ -24,14 +24,15 @@ use solana_program_error::ProgramError;
 use solana_pubkey::Pubkey;
 
 /// Direction of the trade.
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Default)]
 #[repr(u8)]
 pub enum OrderKind {
+    #[default]
     Sell = 0,
     Buy = 1,
 }
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Default)]
 pub struct OrderIntent {
     /// Account authorized to create and invalidate this order and whose
     /// signature authenticates it. For off-chain orders this is the Ed25519

interface/src/data/order.rs

@@ -22,14 +22,18 @@ use core::mem::size_of;
 
 use arrayref::{array_refs, mut_array_refs};
 use derive_more::Deref;
+use solana_account_view::AccountView;
+use solana_address::Address;
 use solana_hash::Hash;
 use solana_program_error::ProgramError;
 use solana_pubkey::Pubkey;
 
 use crate::data::intent::{self, EncodedOrderIntent, OrderIntent};
+use crate::pda::order::order_pda_signer_seeds;
+use crate::SettlementError;
 
 /// Idiomatic representation of an order PDA's body.
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Default)]
 pub struct OrderAccount {
     /// `false` = the order is still active and can be filled; `true` = the
     /// order has been cancelled by the owner and must not be filled.
@@ -51,6 +55,33 @@ pub struct OrderAccount {
     pub intent: OrderIntent,
 }
 
+impl OrderAccount {
+    /// Load and decode the order at the given PDA, and confirm
+    /// the PDA is reached by its own data and the provided bump
+    pub fn load_from_pda(
+        order_pda: &AccountView,
+        program_id: &Address,
+        bump: u8,
+    ) -> Result<Self, ProgramError> {
+        let (account, uid) = {
+            let data = order_pda.try_borrow()?;
+            let bytes: &[u8; EncodedOrderAccount::SIZE] = (&*data)
+                .try_into()
+                .map_err(|_| ProgramError::InvalidAccountData)?;
+            EncodedOrderAccount::decode_and_hash(bytes)?
+        };
+
+        let expected =
+            Address::create_program_address(&order_pda_signer_seeds(&uid, &[bump]), program_id)
+                .map_err(|_| SettlementError::AccountNotDerivable)?;
+        if &expected != order_pda.address() {
+            return Err(SettlementError::AccountNotDerivable.into());
+        }
+
+        Ok(account)
+    }
+}
+
 /// Canonical 200-byte representation of an [`OrderAccount`]. The bytes
 /// written to/read from the order PDA's data area.
 ///
@@ -388,6 +419,72 @@ mod tests {
         assert_eq!(err, ProgramError::InvalidAccountData);
     }
 
+    mod load_from_pda {
+        use super::*;
+        use crate::instruction::fixtures::fake_account_with_data;
+        use crate::pda::order::find_order_pda;
+
+        const PROGRAM_ID: Address = Address::new_from_array([9; 32]);
+
+        #[test]
+        fn accepts_the_canonical_pda() {
+            let account = sample_account(false);
+            let (pda_address, bump) = find_order_pda(&PROGRAM_ID, &account.intent.uid());
+            let order_pda = fake_account_with_data(
+                pda_address,
+                &EncodedOrderAccount::from(account.clone())[..],
+            );
+
+            let loaded = OrderAccount::load_from_pda(&order_pda, &PROGRAM_ID, bump)
+                .expect("canonical PDA must load");
+            assert_eq!(loaded, account);
+        }
+
+        #[test]
+        fn rejects_a_non_canonical_address() {
+            let account = sample_account(false);
+            let (_, bump) = find_order_pda(&PROGRAM_ID, &account.intent.uid());
+            // An address unrelated to the intent's canonical seeds.
+            let wrong_address = Pubkey::new_from_array([0x42; 32]);
+            let order_pda =
+                fake_account_with_data(wrong_address, &EncodedOrderAccount::from(account)[..]);
+
+            let err = OrderAccount::load_from_pda(&order_pda, &PROGRAM_ID, bump)
+                .expect_err("a non-canonical address must be rejected");
+            assert_eq!(err, SettlementError::AccountNotDerivable.into());
+        }
+
+        #[test]
+        fn rejects_a_wrong_bump() {
+            let account = sample_account(false);
+            let (pda_address, bump) = find_order_pda(&PROGRAM_ID, &account.intent.uid());
+            let order_pda =
+                fake_account_with_data(pda_address, &EncodedOrderAccount::from(account)[..]);
+
+            // Any bump other than the canonical one either derives a
+            // different address or fails to derive one at all (falling on
+            // curve); either way, the PDA can no longer be proven canonical.
+            let wrong_bump = bump.wrapping_sub(1);
+            let err = OrderAccount::load_from_pda(&order_pda, &PROGRAM_ID, wrong_bump)
+                .expect_err("a non-canonical bump must be rejected");
+            assert_eq!(err, SettlementError::AccountNotDerivable.into());
+        }
+
+        #[test]
+        fn propagates_decode_errors() {
+            let account = sample_account(false);
+            let (pda_address, bump) = find_order_pda(&PROGRAM_ID, &account.intent.uid());
+            let mut bytes: [u8; EncodedOrderAccount::SIZE] =
+                EncodedOrderAccount::from(account).into();
+            bytes[CANCELLED_OFFSET] = 0xff;
+            let order_pda = fake_account_with_data(pda_address, &bytes);
+
+            let err = OrderAccount::load_from_pda(&order_pda, &PROGRAM_ID, bump)
+                .expect_err("a corrupt account must fail to decode");
+            assert_eq!(err, ProgramError::InvalidAccountData);
+        }
+    }
+
     #[test]
     fn direct_write_account_matches_order_account_decoding() {
         let cancelled = true;

interface/src/instruction/mod.rs

@@ -12,6 +12,7 @@ use crate::{recover_discriminator, SettlementInstruction};
 pub mod create_buffer;
 pub mod create_order;
 pub mod initialize;
+pub mod reclaim_order;
 pub mod settle;
 
 /// Shared components for parsing generic instruction input.
@@ -51,6 +52,7 @@ pub trait InstructionInputParsing<'a>: Sized {
 pub mod fixtures {
     use solana_account_view::{AccountView, RuntimeAccount};
     use solana_address::Address;
+    use std::{mem, ptr};
 
     /// Build an `AccountView` based on the input `RuntimeAccount` and whose
     /// data region is empty.
@@ -85,11 +87,75 @@ pub mod fixtures {
         unsafe { AccountView::new_unchecked(backing as *mut RuntimeAccount) }
     }
 
+    /// Adapted from pinocchio's crate-private test helper; kept structurally
+    /// close for comparison:
+    /// https://docs.rs/crate/pinocchio/0.11.1/source/src/sysvars/slot_hashes/test_utils.rs#120-160
+    ///
+    /// Allocate a heap-backed `AccountView` whose data region is initialized with
+    /// `data`, whose address is `address`, and whose borrow flag is `borrow_state`.
+    ///
+    /// The function also returns the backing `Vec<u64>` so the caller can keep it
+    /// alive for the duration of the test (otherwise the memory would be freed and
+    /// the raw pointer inside `AccountView` would dangle).
+    ///
+    /// # Safety
+    /// The caller must ensure the returned `AccountView` is used only for reading
+    /// or according to borrow rules because the Solana runtime invariants are not
+    /// fully enforced in this hand-rolled representation.
+    #[allow(
+        clippy::arithmetic_side_effects,
+        reason = "the function is mostly vendored and don't want to introduce unnecessary changes"
+    )]
+    pub unsafe fn make_account_view(
+        address: Address,
+        data: &[u8],
+        borrow_state: u8,
+    ) -> (AccountView, Vec<u64>) {
+        // pinocchio writes a hand-rolled `AccountLayout` mirror and casts the
+        // pointer to `*mut RuntimeAccount`, because inside that crate the
+        // account struct's fields are private and its tests cannot set them by
+        // name. Here we instead write a real `RuntimeAccount`, since
+        // `solana_account_view::RuntimeAccount` has public fields and a
+        // `Default` impl.
+        let hdr_size = mem::size_of::<RuntimeAccount>();
+        let total = hdr_size + data.len();
+        let words = total.div_ceil(8);
+        let mut backing: Vec<u64> = vec![0u64; words];
+        assert!(
+            mem::align_of::<u64>() >= mem::align_of::<RuntimeAccount>(),
+            "`backing` should be properly aligned to store a `RuntimeAccount` instance"
+        );
+
+        let hdr_ptr = backing.as_mut_ptr() as *mut RuntimeAccount;
+        ptr::write(
+            hdr_ptr,
+            RuntimeAccount {
+                address,
+                borrow_state,
+                data_len: data.len() as u64,
+                ..Default::default()
+            },
+        );
+
+        ptr::copy_nonoverlapping(
+            data.as_ptr(),
+            (hdr_ptr as *mut u8).add(hdr_size),
+            data.len(),
+        );
+
+        (AccountView::new_unchecked(hdr_ptr), backing)
+    }
+
+    /// Create an account view storing the input data.
+    pub fn fake_account_with_data(address: Address, data: &[u8]) -> AccountView {
+        let (account, backing) =
+            unsafe { make_account_view(address, data, solana_account_view::NOT_BORROWED) };
+        core::mem::forget(backing);
+        account
+    }
+
     pub fn fake_account(address: Address) -> AccountView {
-        fake_account_from(RuntimeAccount {
-            address,
-            ..Default::default()
-        })
+        fake_account_with_data(address, &[])
     }
 
     pub fn fake_account_from_array(address_array: [u8; 32]) -> AccountView {