//! Cross-program invocation.
//!
//! Solana programs may call other programs, termed [_cross-program
//! invocations_][cpi] (CPI), with the [`invoke`] and [`invoke_signed`]
//! functions.
//!
//! This crate does not support overwriting syscall stubs for offchain code.
//! If you want to overwrite syscall stubs, use the wrapper functions in
//! [`rialo_s_program::program`].
//!
//! [`invoke`]: invoke
//! [`invoke_signed`]: invoke_signed
//! [cpi]: https://solana.com/docs/core/cpi
//! [`rialo_s_program::program`]: https://docs.rs/solana-program/latest/rialo_s_program/program/

#![allow(unsafe_code)]

use rialo_s_account_info::AccountInfo;
use rialo_s_instruction::{AccountMeta, Instruction};
use rialo_s_program_error::ProgramResult;
use rialo_s_pubkey::Pubkey;
#[cfg(target_os = "solana")]
pub mod syscalls;

/// Invoke a cross-program instruction.
///
/// Invoking one program from another program requires an [`Instruction`]
/// containing the program ID of the other program, instruction data that
/// will be understood by the other program, and a list of [`AccountInfo`]s
/// corresponding to all of the accounts accessed by the other program. Because
/// the only way for a program to acquire `AccountInfo` values is by receiving
/// them from the runtime at the [program entrypoint][entrypoint!], any account
/// required by the callee program must transitively be required by the caller
/// program, and provided by _its_ caller. The same is true of the program ID of
/// the called program.
///
/// [entrypoint!]: https://docs.rs/solana-entrypoint/latest/solana_entrypoint/macro.entrypoint.html
///
/// The `Instruction` is usually built from within the calling program, but may
/// be deserialized from an external source.
///
/// This function will not return if the called program returns anything other
/// than success. If the callee returns an error or aborts then the entire
/// transaction will immediately fail. To return data as the result of a
/// cross-program invocation use the [`set_return_data`] / [`get_return_data`]
/// functions, or have the callee write to a dedicated account for that purpose.
///
/// A program may directly call itself recursively, but may not be indirectly
/// called recursively (reentered) by another program. Indirect reentrancy will
/// cause the transaction to immediately fail.
///
/// # Validation of shared data between programs
///
/// The `AccountInfo` structures passed to this function contain data that is
/// directly accessed by the runtime and is copied to and from the memory space
/// of the called program. Some of that data, the [`AccountInfo::kelvins`] and
/// [`AccountInfo::data`] fields, may be mutated as a side-effect of the called
/// program, if that program has writable access to the given account.
///
/// These two fields are stored in [`RefCell`]s to enforce the aliasing
/// discipline for mutated values required by the Rust language. Prior to
/// invoking the runtime, this routine will test that each `RefCell` is
/// borrowable as required by the callee and return an error if not.
///
/// The CPU cost of these runtime checks can be avoided with the unsafe
/// [`invoke_unchecked`] function.
///
/// [`RefCell`]: std::cell::RefCell
///
/// # Errors
///
/// If the called program completes successfully and violates no runtime
/// invariants, then this function will return successfully. If the callee
/// completes and returns a [`ProgramError`], then the transaction will
/// immediately fail. Control will not return to the caller.
///
/// Various runtime invariants are checked before the callee is invoked and
/// before returning control to the caller. If any of these invariants are
/// violated then the transaction will immediately fail. A non-exhaustive list
/// of these invariants includes:
///
/// - The sum of kelvins owned by all referenced accounts has not changed.
/// - A program has not debited kelvins from an account it does not own.
/// - A program has not otherwise written to an account that it does not own.
/// - A program has not written to an account that is not writable.
/// - The size of account data has not exceeded applicable limits.
///
/// If the invoked program does not exist or is not executable then
/// the transaction will immediately fail.
///
/// If any of the `RefCell`s within the provided `AccountInfo`s cannot be
/// borrowed in accordance with the call's requirements, an error of
/// [`ProgramError::AccountBorrowFailed`] is returned.
///
/// [`ProgramError`]: https://docs.rs/solana-program-error/latest/rialo_s_program_error/enum.ProgramError.html
/// [`ProgramError::AccountBorrowFailed`]: https://docs.rs/solana-program-error/latest/rialo_s_program_error/enum.ProgramError.html#variant.AccountBorrowFailed
///
/// # Examples
///
/// A simple example of transferring kelvins via CPI:
///
/// ```
/// use rialo_s_cpi::invoke;
/// use rialo_s_account_info::{next_account_info, AccountInfo};
/// use rialo_s_program_entrypoint::entrypoint;
/// use rialo_s_program_error::ProgramResult;
/// use rialo_s_pubkey::Pubkey;
/// use rialo_s_sdk_ids::system_program;
/// use rialo_s_system_interface::instruction as system_instruction;
///
/// entrypoint!(process_instruction);
///
/// fn process_instruction(
///     program_id: &Pubkey,
///     accounts: &[AccountInfo],
///     instruction_data: &[u8],
/// ) -> ProgramResult {
///     let account_info_iter = &mut accounts.iter();
///
///     let payer = next_account_info(account_info_iter)?;
///     let recipient = next_account_info(account_info_iter)?;
///     // The system program is a required account to invoke a system
///     // instruction, even though we don't use it directly.
///     let system_program_account = next_account_info(account_info_iter)?;
///
///     assert!(payer.is_writable);
///     assert!(payer.is_signer);
///     assert!(recipient.is_writable);
///     assert!(system_program::check_id(system_program_account.key));
///
///     let kelvins = 1000000;
///
///     invoke(
///         &system_instruction::transfer(payer.key, recipient.key, kelvins),
///         &[payer.clone(), recipient.clone(), system_program_account.clone()],
///     )
/// }
/// ```
pub fn invoke(instruction: &Instruction, account_infos: &[AccountInfo<'_>]) -> ProgramResult {
    invoke_signed(instruction, account_infos, &[])
}

/// Invoke a cross-program instruction but don't enforce Rust's aliasing rules.
///
/// This function is like [`invoke`] except that it does not check that
/// [`RefCell`]s within [`AccountInfo`]s are properly borrowable as described in
/// the documentation for that function. Those checks consume CPU cycles that
/// this function avoids.
///
/// [`RefCell`]: std::cell::RefCell
///
/// # Safety
///
/// __This function is incorrectly missing an `unsafe` declaration.__
///
/// If any of the writable accounts passed to the callee contain data that is
/// borrowed within the calling program, and that data is written to by the
/// callee, then Rust's aliasing rules will be violated and cause undefined
/// behavior.
pub fn invoke_unchecked(
    instruction: &Instruction,
    account_infos: &[AccountInfo<'_>],
) -> ProgramResult {
    invoke_signed_unchecked(instruction, account_infos, &[])
}

/// Invoke a cross-program instruction with program signatures.
///
/// This function is like [`invoke`] with the additional ability to virtually
/// sign an invocation on behalf of one or more [program derived addresses][pda] (PDAs)
/// controlled by the calling program, allowing the callee to mutate them, or
/// otherwise confirm that a PDA program key has authorized the actions of the
/// callee.
///
/// There is no cryptographic signing involved &mdash; PDA signing is a runtime
/// construct that allows the calling program to control accounts as if it could
/// cryptographically sign for them; and the callee to treat the account as if it
/// was cryptographically signed.
///
/// The `signer_seeds` parameter is a slice of `u8` slices where the inner
/// slices represent the seeds plus the _bump seed_ used to derive (with
/// [`Pubkey::find_program_address`]) one of the PDAs within the `account_infos`
/// slice of `AccountInfo`s. During invocation, the runtime will re-derive the
/// PDA from the seeds and the calling program's ID, and if it matches one of
/// the accounts in `account_info`, will consider that account "signed".
///
/// [pda]: https://solana.com/docs/core/cpi#program-derived-addresses
/// [`Pubkey::find_program_address`]: https://docs.rs/solana-pubkey/latest/rialo_s_pubkey/struct.Pubkey.html#method.find_program_address
///
/// See the documentation for [`Pubkey::find_program_address`] for more
/// about program derived addresses.
///
/// # Examples
///
/// A simple example of creating an account for a PDA:
///
/// ```
/// use rialo_s_cpi::invoke_signed;
/// use rialo_s_account_info::{next_account_info, AccountInfo};
/// use rialo_s_program_entrypoint::entrypoint;
/// use rialo_s_program_error::ProgramResult;
/// use rialo_s_pubkey::Pubkey;
/// use rialo_s_sdk_ids::system_program;
/// use rialo_s_system_interface::instruction as system_instruction;
///
/// entrypoint!(process_instruction);
///
/// fn process_instruction(
///     program_id: &Pubkey,
///     accounts: &[AccountInfo],
///     instruction_data: &[u8],
/// ) -> ProgramResult {
///     let account_info_iter = &mut accounts.iter();
///     let payer = next_account_info(account_info_iter)?;
///     let vault_pda = next_account_info(account_info_iter)?;
///     let system_program = next_account_info(account_info_iter)?;
///
///     assert!(payer.is_writable);
///     assert!(payer.is_signer);
///     assert!(vault_pda.is_writable);
///     assert_eq!(vault_pda.owner, &system_program::ID);
///     assert!(system_program::check_id(system_program.key));
///
///     let vault_bump_seed = instruction_data[0];
///     let vault_seeds = &[b"vault", payer.key.as_ref(), &[vault_bump_seed]];
///     let expected_vault_pda = Pubkey::create_program_address(vault_seeds, program_id)?;
///
///     assert_eq!(vault_pda.key, &expected_vault_pda);
///
///     let kelvins = 10000000;
///     let vault_size = 16;
///
///     invoke_signed(
///         &system_instruction::create_account(
///             &payer.key,
///             &vault_pda.key,
///             kelvins,
///             vault_size,
///             &program_id,
///         ),
///         &[
///             payer.clone(),
///             vault_pda.clone(),
///         ],
///         &[
///             &[
///                 b"vault",
///                 payer.key.as_ref(),
///                 &[vault_bump_seed],
///             ],
///         ]
///     )?;
///     Ok(())
/// }
/// ```
pub fn invoke_signed(
    instruction: &Instruction,
    account_infos: &[AccountInfo<'_>],
    signers_seeds: &[&[&[u8]]],
) -> ProgramResult {
    // Check that the account RefCells are consistent with the request
    for account_meta in instruction.accounts.iter() {
        for account_info in account_infos.iter() {
            if account_meta.pubkey == *account_info.key {
                if account_meta.is_writable {
                    let _ = account_info.try_borrow_mut_kelvins()?;
                    let _ = account_info.try_borrow_mut_data()?;
                } else {
                    let _ = account_info.try_borrow_kelvins()?;
                    let _ = account_info.try_borrow_data()?;
                }
                break;
            }
        }
    }

    invoke_signed_unchecked(instruction, account_infos, signers_seeds)
}

/// Copied from `rialo_s_program_entrypoint::SUCCESS`
/// to avoid a `rialo_s_program_entrypoint` dependency
const _SUCCESS: u64 = 0;
#[cfg(test)]
static_assertions::const_assert_eq!(_SUCCESS, rialo_s_program_entrypoint::SUCCESS);

/// Marshalled `AccountInfo` containing raw pointers to VM memory.
///
/// Allows the RISC-V executor to extract account info for CPI calls.
#[repr(C)]
pub struct HostAccountInfo {
    pub key: Pubkey,
    pub kelvins: *mut u64,
    pub data_ptr: *mut u8,
    pub data_len: usize,
    pub data_len_ptr: *mut u8,
    pub owner: *mut Pubkey,
    pub rent_epoch: u64,
    pub is_signer: bool,
    pub is_writable: bool,
    pub executable: bool,
}

impl From<&AccountInfo<'_>> for HostAccountInfo {
    fn from(account: &AccountInfo<'_>) -> Self {
        let kelvins_ptr: &mut u64 = &mut account.kelvins.borrow_mut();
        let data_ref: &mut [u8] = &mut account.data.borrow_mut();
        let data_ptr = data_ref.as_mut_ptr();
        let data_len = data_ref.len();
        let data_len_ptr = account.data.as_ptr() as *const u64 as u64 + 8;

        HostAccountInfo {
            key: *account.key,
            kelvins: kelvins_ptr,
            data_ptr,
            data_len,
            data_len_ptr: data_len_ptr as *mut u8,
            owner: account.owner as *const _ as *mut Pubkey,
            rent_epoch: account.rent_epoch,
            is_signer: account.is_signer,
            is_writable: account.is_writable,
            executable: account.executable,
        }
    }
}

/// Marshal `&[AccountInfo]` into `Vec<HostAccountInfo>` suitable for RISC-V unmarshalling.
pub fn marshal_accounts(accounts: &[AccountInfo<'_>]) -> Vec<HostAccountInfo> {
    accounts.iter().map(HostAccountInfo::from).collect()
}

/// Marshalled `Instruction` containing raw pointers to VM memory.
///
/// Allows the RISC-V executor to extract account info for CPI calls.
#[repr(C)]
pub struct HostInstruction {
    pub program_id: Pubkey,
    pub accounts_ptr: *const AccountMeta,
    pub accounts_len: usize,
    pub data_ptr: *const u8,
    pub data_len: usize,
}

/// Marshal an `Instruction` into a `HostInstruction` suitable for RISC-V unmarshalling.
pub fn marshal_instruction(instruction: &Instruction) -> HostInstruction {
    HostInstruction {
        program_id: instruction.program_id,
        accounts_ptr: instruction.accounts.as_ptr(),
        accounts_len: instruction.accounts.len(),
        data_ptr: instruction.data.as_ptr(),
        data_len: instruction.data.len(),
    }
}

/// Invoke a cross-program instruction with signatures but don't enforce Rust's
/// aliasing rules.
///
/// This function is like [`invoke_signed`] except that it does not check that
/// [`RefCell`]s within [`AccountInfo`]s are properly borrowable as described in
/// the documentation for that function. Those checks consume CPU cycles that
/// this function avoids.
///
/// [`RefCell`]: std::cell::RefCell
///
/// # Safety
///
/// __This function is incorrectly missing an `unsafe` declaration.__
///
/// If any of the writable accounts passed to the callee contain data that is
/// borrowed within the calling program, and that data is written to by the
/// callee, then Rust's aliasing rules will be violated and cause undefined
/// behavior.
#[allow(unused_variables)]
pub fn invoke_signed_unchecked(
    instruction: &Instruction,
    account_infos: &[AccountInfo<'_>],
    signers_seeds: &[&[&[u8]]],
) -> ProgramResult {
    #[cfg(all(target_os = "solana", not(target_arch = "riscv64")))]
    {
        let instruction =
            rialo_s_stable_layout::stable_instruction::StableInstruction::from(instruction.clone());
        let result = unsafe {
            crate::syscalls::rlo_invoke_signed_rust(
                &instruction as *const _ as *const u8,
                account_infos as *const _ as *const u8,
                account_infos.len() as u64,
                signers_seeds as *const _ as *const u8,
                signers_seeds.len() as u64,
            )
        };
        match result {
            _SUCCESS => Ok(()),
            _ => Err(result.into()),
        }
    }

    #[cfg(all(target_os = "solana", target_arch = "riscv64"))]
    {
        let instruction = marshal_instruction(instruction);
        let instruction_ptr: *const HostInstruction = &instruction;

        let accounts = marshal_accounts(account_infos);
        let account_infos = accounts.as_ptr();
        let account_sizes = accounts.len();

        let result = unsafe {
            crate::syscalls::rlo_invoke_signed_rust(
                instruction_ptr as *const _ as *const u8,
                account_infos as *const _ as *const u8,
                account_sizes as u64,
                signers_seeds as *const _ as *const u8,
                signers_seeds.len() as u64,
            )
        };
        match result {
            _SUCCESS => Ok(()),
            _ => Err(result.into()),
        }
    }

    #[cfg(not(target_os = "solana"))]
    Ok(())
}

/// Maximum size that can be set using [`set_return_data`].
pub const MAX_RETURN_DATA: usize = 1024;

/// Set the running program's return data.
///
/// Return data is a dedicated per-transaction buffer for data passed
/// from cross-program invoked programs back to their caller.
///
/// The maximum size of return data is [`MAX_RETURN_DATA`]. Return data is
/// retrieved by the caller with [`get_return_data`].
#[allow(unused_variables)]
pub fn set_return_data(data: &[u8]) {
    #[cfg(target_os = "solana")]
    unsafe {
        crate::syscalls::rlo_set_return_data(data.as_ptr(), data.len() as u64)
    };
}

/// Get the return data from an invoked program.
///
/// For every transaction there is a single buffer with maximum length
/// [`MAX_RETURN_DATA`], paired with a [`Pubkey`] representing the program ID of
/// the program that most recently set the return data. Thus the return data is
/// a global resource and care must be taken to ensure that it represents what
/// is expected: called programs are free to set or not set the return data; and
/// the return data may represent values set by programs multiple calls down the
/// call stack, depending on the circumstances of transaction execution.
///
/// Return data is set by the callee with [`set_return_data`].
///
/// Return data is cleared before every CPI invocation &mdash; a program that
/// has invoked no other programs can expect the return data to be `None`; if no
/// return data was set by the previous CPI invocation, then this function
/// returns `None`.
///
/// Return data is not cleared after returning from CPI invocations &mdash; a
/// program that has called another program may retrieve return data that was
/// not set by the called program, but instead set by a program further down the
/// call stack; or, if a program calls itself recursively, it is possible that
/// the return data was not set by the immediate call to that program, but by a
/// subsequent recursive call to that program. Likewise, an external RPC caller
/// may see return data that was not set by the program it is directly calling,
/// but by a program that program called.
///
/// For more about return data see the [documentation for the return data proposal][rdp].
///
/// [rdp]: https://docs.solanalabs.com/proposals/return-data
pub fn get_return_data() -> Option<(Pubkey, Vec<u8>)> {
    #[cfg(target_os = "solana")]
    {
        use std::cmp::min;

        let mut buf = [0u8; MAX_RETURN_DATA];
        let mut program_id = Pubkey::default();

        let size = unsafe {
            crate::syscalls::rlo_get_return_data(
                buf.as_mut_ptr(),
                buf.len() as u64,
                &mut program_id,
            )
        };

        if size == 0 {
            None
        } else {
            let size = min(size as usize, MAX_RETURN_DATA);
            Some((program_id, buf[..size as usize].to_vec()))
        }
    }

    #[cfg(not(target_os = "solana"))]
    None
}
