hopper-native 0.4.1

//! PDA (Program Derived Address) helpers.
//!
//! Direct syscall-based PDA creation and derivation. No external dependencies.

use crate::account_view::AccountView;
use crate::address::{Address, MAX_SEEDS, MAX_SEED_LEN};
use crate::error::ProgramError;

#[cfg(target_os = "solana")]
const CURVE25519_EDWARDS: u64 = 0;
#[cfg(target_os = "solana")]
const PDA_MARKER_BYTES: &[u8; 21] = crate::address::PDA_MARKER;

/// SHA-based paths must accept exactly the seed domain that the PDA signing
/// syscall accepts. A helper which appends a bump reserves one of the 16 slots.
#[inline(always)]
fn validate_seeds(seeds: &[&[u8]], max_count: usize) -> Result<(), ProgramError> {
    if seeds.len() > max_count || seeds.iter().any(|seed| seed.len() > MAX_SEED_LEN) {
        return Err(ProgramError::InvalidSeeds);
    }
    Ok(())
}

/// Create a program-derived address from seeds and a program ID.
///
/// Returns `Err(InvalidSeeds)` if the derived address falls on the
/// ed25519 curve (not a valid PDA), or if more than [`MAX_SEEDS`] seeds
/// are supplied (matching upstream `Pubkey::create_program_address`
/// semantics, never silently truncating the seed set).
#[inline(always)]
pub fn create_program_address(
    seeds: &[&[u8]],
    program_id: &Address,
) -> Result<Address, ProgramError> {
    validate_seeds(seeds, MAX_SEEDS)?;
    #[cfg(target_os = "solana")]
    {
        // The syscall reads `seeds.len()` (ptr, len) pairs of 8-byte words,
        // which is exactly the in-memory shape of a `&[&[u8]]` on the SBF
        // target (the same layout the Solana SDK and pinocchio hand over).
        // Passing the slice directly replaces the zero-filled 256-byte
        // staging buffer and repack loop the wrapper used to run before
        // every derivation; measured 2026-09-21 on the framework-comparison
        // counter at ~70 CU per call above the syscall's own charge.
        const _: () = assert!(core::mem::size_of::<&[u8]>() == 16);
        let mut result = Address::default();
        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        let rc = unsafe {
            crate::syscalls::sol_create_program_address(
                seeds.as_ptr() as *const u8,
                seeds.len() as u64,
                program_id.as_array().as_ptr(),
                result.0.as_mut_ptr(),
            )
        };
        if rc == 0 {
            Ok(result)
        } else {
            Err(ProgramError::InvalidSeeds)
        }
    }
    #[cfg(not(target_os = "solana"))]
    {
        let _ = (seeds, program_id);
        Err(ProgramError::InvalidSeeds)
    }
}

/// Find a program-derived address and its bump seed.
///
/// Iterates bump seeds 255..=0 until a valid PDA is found.
///
/// # Panics
///
/// Panics if no viable bump exists, 16 or more base seeds are supplied,
/// or a seed exceeds 32 bytes. The bump occupies the final seed slot,
/// matching upstream `Pubkey::find_program_address` semantics.
/// Silently returning a placeholder here would hand callers the all-zero
/// address, the System Program, as if it were their PDA. Use
/// [`based_try_find_program_address`] for the fallible variant.
///
/// `#[inline(always)]` is deliberate: outlining the sibling
/// `verify_pda_sha256_loop` was measured on 2026-07-09 at only −88 bytes
/// of release `.text` for +44..+73 CU on every benched vault row, the
/// call boundary defeats LLVM's per-call-site specialization of the seed
/// staging and bump loop. The size answer to PDA duplication is
/// `bump = stored` (one hash, no search), not outlining the search.
#[inline(always)]
pub fn find_program_address(seeds: &[&[u8]], program_id: &Address) -> (Address, u8) {
    #[cfg(target_os = "solana")]
    {
        match based_try_find_program_address(seeds, program_id) {
            Ok(found) => found,
            Err(_) => panic!("hopper: unable to find a viable program address bump seed"),
        }
    }
    #[cfg(not(target_os = "solana"))]
    {
        let _ = (seeds, program_id);
        panic!(
            "hopper: find_program_address requires the SVM sha256 syscall (target_os = \"solana\")"
        );
    }
}

/// The program-derived address for `seeds` and `bump` under `program_id`,
/// computed with the const SHA-256 so it can be evaluated at compile time.
///
/// This is the hash half of `create_program_address` (seeds, bump, program
/// id, the `ProgramDerivedAddress` marker) without the curve rejection, so
/// callers must pass the canonical bump their client obtained from
/// `find_program_address`; a bump the runtime would skip because its hash
/// lands on the ed25519 curve is not detected here. Static seeds hashed
/// once at compile time turn a runtime PDA check into a 32-byte compare.
/// Panics on 16 or more base seeds or a seed longer than 32 bytes. The bump
/// occupies one of the runtime's 16 seed slots. In a const expression the
/// refusal is a compilation error.
pub const fn program_address_const(seeds: &[&[u8]], bump: u8, program_id: &Address) -> Address {
    assert!(
        seeds.len() < MAX_SEEDS,
        "a PDA takes at most 15 seeds plus its bump"
    );
    let mut hasher = crate::sha256::ConstSha256::new();
    let mut i = 0;
    while i < seeds.len() {
        assert!(
            seeds[i].len() <= crate::address::MAX_SEED_LEN,
            "a PDA seed is at most 32 bytes"
        );
        hasher = hasher.update(seeds[i]);
        i += 1;
    }
    let hash = hasher
        .update(&[bump])
        .update(program_id.as_array())
        .update(crate::address::PDA_MARKER)
        .finalize();
    Address::new_from_array(hash)
}

/// Verify that an expected address matches the PDA hash for the provided seeds.
///
/// The seeds slice must already include the bump byte.
/// This checks hash equality only. It does not establish curve membership,
/// canonicality, account ownership, or an account's initialization history.
#[inline(always)]
pub fn verify_program_address(
    seeds: &[&[u8]],
    program_id: &Address,
    expected: &Address,
) -> Result<(), ProgramError> {
    validate_seeds(seeds, MAX_SEEDS)?;

    #[cfg(target_os = "solana")]
    {
        let n = seeds.len();
        let mut slices = core::mem::MaybeUninit::<[&[u8]; MAX_SEEDS + 2]>::uninit();
        let slice_ptr = slices.as_mut_ptr() as *mut &[u8];

        let mut i = 0;
        while i < n {
            // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
            unsafe { slice_ptr.add(i).write(seeds[i]) };
            i += 1;
        }
        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        unsafe {
            slice_ptr.add(n).write(program_id.as_ref());
            slice_ptr.add(n + 1).write(PDA_MARKER_BYTES.as_slice());
        }

        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        let input = unsafe { core::slice::from_raw_parts(slice_ptr, n + 2) };
        let mut hash = core::mem::MaybeUninit::<[u8; 32]>::uninit();

        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        unsafe {
            crate::syscalls::sol_sha256(
                input as *const _ as *const u8,
                input.len() as u64,
                hash.as_mut_ptr() as *mut u8,
            );
        }

        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        let derived = unsafe { &*(hash.as_ptr() as *const Address) };
        if derived == expected {
            Ok(())
        } else {
            Err(ProgramError::InvalidSeeds)
        }
    }
    #[cfg(not(target_os = "solana"))]
    {
        let _ = (seeds, program_id, expected);
        Err(ProgramError::InvalidSeeds)
    }
}

/// Find a valid PDA by hashing seeds directly and checking curve validity.
///
/// This avoids the `sol_try_find_program_address` syscall and substantially
/// reduces the per-attempt CU cost on SBF.
#[inline(always)]
pub fn based_try_find_program_address(
    seeds: &[&[u8]],
    program_id: &Address,
) -> Result<(Address, u8), ProgramError> {
    validate_seeds(seeds, MAX_SEEDS - 1)?;

    #[cfg(target_os = "solana")]
    {
        let n = seeds.len();
        let mut slices = core::mem::MaybeUninit::<[&[u8]; MAX_SEEDS + 2]>::uninit();
        let slice_ptr = slices.as_mut_ptr() as *mut &[u8];

        let mut i = 0;
        while i < n {
            // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
            unsafe { slice_ptr.add(i).write(seeds[i]) };
            i += 1;
        }
        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        unsafe {
            slice_ptr.add(n + 1).write(program_id.as_ref());
            slice_ptr.add(n + 2).write(PDA_MARKER_BYTES.as_slice());
        }

        let mut hash = core::mem::MaybeUninit::<[u8; 32]>::uninit();
        let mut bump: u64 = u8::MAX as u64;

        loop {
            let bump_seed = [bump as u8];
            // SAFETY: n <= MAX_SEEDS - 1. Install this iteration's immutable
            // seed before constructing the initialized prefix. The syscall
            // consumes it synchronously; no shared seed reference is reused
            // after the next iteration rewrites the descriptor array.
            unsafe {
                slice_ptr
                    .add(n)
                    .write(core::slice::from_raw_parts(bump_seed.as_ptr(), 1))
            };
            let input = unsafe { core::slice::from_raw_parts(slice_ptr, n + 3) };

            // SAFETY: All n + 3 descriptors are initialized, every referenced
            // byte is live for the call, and hash has space for its 32-byte output.
            unsafe {
                crate::syscalls::sol_sha256(
                    input as *const _ as *const u8,
                    input.len() as u64,
                    hash.as_mut_ptr() as *mut u8,
                );
            }

            // SAFETY: `hash` was fully written by sol_sha256 above; the
            // syscall only reads 32 bytes from it.
            // Return code semantics: 0 = the point IS on the ed25519 curve
            // (not a valid PDA), nonzero = off-curve (valid PDA).
            let curve_rc = unsafe {
                crate::syscalls::sol_curve_validate_point(
                    CURVE25519_EDWARDS,
                    hash.as_ptr() as *const u8,
                    core::ptr::null_mut(),
                )
            };

            if curve_rc != 0 {
                return Ok((
                    // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
                    Address::new_from_array(unsafe { hash.assume_init() }),
                    bump as u8,
                ));
            }

            if bump == 0 {
                break;
            }
            bump -= 1;
        }

        Err(ProgramError::InvalidSeeds)
    }
    #[cfg(not(target_os = "solana"))]
    {
        let _ = (seeds, program_id);
        Err(ProgramError::InvalidSeeds)
    }
}

/// Verify that an account's address matches a PDA derived from the given seeds.
///
/// Returns `Ok(())` if the account address matches the derived PDA,
/// or `Err(InvalidSeeds)` if it does not.
#[inline(always)]
pub fn verify_pda(
    account: &AccountView<'_>,
    seeds: &[&[u8]],
    program_id: &Address,
) -> Result<(), ProgramError> {
    let expected = create_program_address(seeds, program_id)?;
    if account.address() == &expected {
        Ok(())
    } else {
        Err(ProgramError::InvalidSeeds)
    }
}

/// Verify a PDA with an explicit bump seed appended to the seeds.
///
/// Appends `&[bump]` to the end of the seed list before verifying via
/// SHA-256 (~200 CU). This is substantially cheaper than the syscall-based
/// `create_program_address` approach (~1500 CU).
///
/// Returns `Err(InvalidSeeds)` for 16 or more base seeds or a seed longer
/// than 32 bytes. The bump counts toward the 16-seed runtime limit.
///
/// # Bump canonicalization
///
/// `bump` must be the **canonical** bump for these seeds, the one
/// `find_program_address` returns and the program stored at init. Passing
/// an attacker-supplied bump (e.g. straight from instruction data) lets
/// multiple addresses verify for the same logical seed set, the classic
/// bump-canonicalization vulnerability. Prefer
/// [`verify_pda_from_stored_bump`], which reads the bump the account
/// itself recorded.
#[inline]
pub fn verify_pda_with_bump(
    account: &AccountView<'_>,
    seeds: &[&[u8]],
    bump: u8,
    program_id: &Address,
) -> Result<(), ProgramError> {
    validate_seeds(seeds, MAX_SEEDS - 1)?;
    // Build a seed list with the bump appended.
    // Stack-allocated: at most 15 base seeds plus the bump.
    let mut full_seeds: [&[u8]; MAX_SEEDS] = [&[]; MAX_SEEDS];
    let num = seeds.len();
    let mut i = 0;
    while i < num {
        full_seeds[i] = seeds[i];
        i += 1;
    }
    let bump_bytes = [bump];
    full_seeds[num] = &bump_bytes;

    verify_program_address(&full_seeds[..num + 1], program_id, account.address())
}

/// Verify that an address matches a PDA derived from the given seeds.
///
/// Unlike `verify_pda` which takes an `AccountView`, this accepts a raw
/// `Address` reference directly. Useful when validating addresses outside
/// of the account parsing flow (e.g. instruction data, cross-program reads).
///
/// The seeds slice must already include the bump byte (like
/// `verify_program_address`). Uses SHA-256 verify-only path (~200 CU)
/// instead of the full `find_program_address` (~1500 CU).
///
/// The included bump must be the **canonical** one for the seed set (see
/// [`verify_pda_with_bump`]'s bump-canonicalization note): verifying with
/// an attacker-supplied bump lets multiple addresses pass for the same
/// logical seeds.
///
/// Returns `Ok(())` if the address matches the derived PDA,
/// or `Err(InvalidSeeds)` if it does not.
#[inline]
pub fn verify_pda_strict(
    expected: &Address,
    seeds: &[&[u8]],
    program_id: &Address,
) -> Result<(), ProgramError> {
    verify_program_address(seeds, program_id, expected)
}

/// Find the bump seed for a known PDA address, skipping curve validation.
///
/// This is a hash-match search, not canonical derivation or an off-curve
/// proof. Mere presence in a transaction or existence on chain does not
/// establish either property. The caller must establish the required PDA
/// provenance separately. Use [`based_try_find_program_address`] and compare
/// its result when a canonical address is required.
///
/// Returns the bump seed, or `Err(InvalidSeeds)` if no bump produces a match.
#[inline(always)]
pub fn find_bump_for_address(
    seeds: &[&[u8]],
    program_id: &Address,
    expected: &Address,
) -> Result<u8, ProgramError> {
    validate_seeds(seeds, MAX_SEEDS - 1)?;

    #[cfg(target_os = "solana")]
    {
        let n = seeds.len();
        let mut slices = core::mem::MaybeUninit::<[&[u8]; MAX_SEEDS + 2]>::uninit();
        let slice_ptr = slices.as_mut_ptr() as *mut &[u8];

        let mut i = 0;
        while i < n {
            // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
            unsafe { slice_ptr.add(i).write(seeds[i]) };
            i += 1;
        }
        // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
        unsafe {
            slice_ptr.add(n + 1).write(program_id.as_ref());
            slice_ptr.add(n + 2).write(PDA_MARKER_BYTES.as_slice());
        }

        let mut hash = core::mem::MaybeUninit::<[u8; 32]>::uninit();
        let mut bump: u64 = u8::MAX as u64;

        loop {
            let bump_seed = [bump as u8];
            // SAFETY: n <= MAX_SEEDS - 1. Install this iteration's immutable
            // seed before constructing the initialized prefix. No shared
            // seed reference is reused after its backing byte changes.
            unsafe {
                slice_ptr
                    .add(n)
                    .write(core::slice::from_raw_parts(bump_seed.as_ptr(), 1))
            };
            let input = unsafe { core::slice::from_raw_parts(slice_ptr, n + 3) };

            // SAFETY: All descriptors and input bytes remain live through the
            // synchronous call, which fills the 32-byte hash output.
            unsafe {
                crate::syscalls::sol_sha256(
                    input as *const _ as *const u8,
                    input.len() as u64,
                    hash.as_mut_ptr() as *mut u8,
                );
            }

            // Address-match shortcut: skip curve check entirely.
            // Matching this address does not establish canonicality or
            // curve membership; those are separate caller obligations.
            // SAFETY: This block is part of Hopper's reviewed zero-copy/backend boundary; surrounding checks and caller contracts uphold the required raw-pointer, layout, and aliasing invariants.
            let derived = unsafe { &*(hash.as_ptr() as *const Address) };
            if derived == expected {
                return Ok(bump as u8);
            }

            if bump == 0 {
                break;
            }
            bump -= 1;
        }

        Err(ProgramError::InvalidSeeds)
    }
    #[cfg(not(target_os = "solana"))]
    {
        let _ = (seeds, program_id, expected);
        Err(ProgramError::InvalidSeeds)
    }
}

/// Read the bump byte directly from account data at a known offset.
///
/// Used with `BUMP_OFFSET` from `hopper_layout!` types to read the stored
/// bump without any derivation. Combined with `verify_program_address`,
/// the total PDA verification cost is ~200 CU vs ~1500 CU for
/// `find_program_address`.
///
/// Returns `Err(AccountDataTooSmall)` if the account data is shorter than
/// `bump_offset + 1`.
#[inline(always)]
pub fn read_bump_from_account(
    account: &AccountView<'_>,
    bump_offset: usize,
) -> Result<u8, ProgramError> {
    let data = account.try_borrow()?;
    if data.len() <= bump_offset {
        return Err(ProgramError::AccountDataTooSmall);
    }
    Ok(data[bump_offset])
}

/// Verify a PDA using the bump stored in account data (cheapest path).
///
/// Reads the bump at `bump_offset`, appends it to seeds, then uses
/// SHA-256 verify-only. Total cost: ~200 CU vs ~1500 CU.
///
/// This is the optimal PDA verification path and should be the default
/// for Hopper programs that store bumps in their account layout.
#[inline]
pub fn verify_pda_from_stored_bump(
    account: &AccountView<'_>,
    seeds: &[&[u8]],
    bump_offset: usize,
    program_id: &Address,
) -> Result<(), ProgramError> {
    validate_seeds(seeds, MAX_SEEDS - 1)?;
    let bump = read_bump_from_account(account, bump_offset)?;

    let mut full_seeds: [&[u8]; MAX_SEEDS] = [&[]; MAX_SEEDS];
    let num = seeds.len();
    let mut i = 0;
    while i < num {
        full_seeds[i] = seeds[i];
        i += 1;
    }
    let bump_bytes = [bump];
    full_seeds[num] = &bump_bytes;

    verify_program_address(&full_seeds[..num + 1], program_id, account.address())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn const_pda_accepts_fifteen_base_seeds() {
        let id = Address::new_from_array([91; 32]);
        let fifteen: [&[u8]; 15] = [&[]; 15];
        assert_eq!(
            program_address_const(&fifteen, 255, &id),
            program_address_const(&[], 255, &id)
        );
    }

    #[test]
    #[should_panic(expected = "at most 15 seeds plus its bump")]
    fn const_pda_reserves_the_bump_slot() {
        let seeds: [&[u8]; 16] = [&[]; 16];
        program_address_const(&seeds, 255, &Address::new_from_array([91; 32]));
    }

    #[test]
    #[should_panic(expected = "at most 32 bytes")]
    fn const_pda_rejects_oversized_seeds() {
        program_address_const(&[&[0; 33]], 255, &Address::new_from_array([91; 32]));
    }
}