use crate::account::{Account, KeyedAccount};
use crate::instruction::InstructionError;
use crate::pubkey::Pubkey;
use bincode::ErrorKind;

// All native programs export a symbol named process()
pub const ENTRYPOINT: &str = "process";

// Native program ENTRYPOINT prototype
pub type Entrypoint = unsafe extern "C" fn(
    program_id: &Pubkey,
    keyed_accounts: &mut [KeyedAccount],
    data: &[u8],
    tick_height: u64,
) -> Result<(), InstructionError>;

// Convenience macro to define the native program entrypoint.  Supply a fn to this macro that
// conforms to the `Entrypoint` type signature.
#[macro_export]
macro_rules! solana_entrypoint(
    ($entrypoint:ident) => (
        #[no_mangle]
        pub extern "C" fn process(
            program_id: &solana_sdk::pubkey::Pubkey,
            keyed_accounts: &mut [solana_sdk::account::KeyedAccount],
            data: &[u8],
            tick_height: u64
        ) -> Result<(), solana_sdk::instruction::InstructionError> {
            $entrypoint(program_id, keyed_accounts, data, tick_height)
        }
    )
);

/// Conveinence trait to covert bincode errors to instruction errors.
pub trait State<T> {
    fn state(&self) -> Result<T, InstructionError>;
    fn set_state(&mut self, state: &T) -> Result<(), InstructionError>;
}

impl<T> State<T> for Account
where
    T: serde::Serialize + serde::de::DeserializeOwned,
{
    fn state(&self) -> Result<T, InstructionError> {
        self.deserialize_data()
            .map_err(|_| InstructionError::InvalidAccountData)
    }
    fn set_state(&mut self, state: &T) -> Result<(), InstructionError> {
        self.serialize_data(state).map_err(|err| match *err {
            ErrorKind::SizeLimit => InstructionError::AccountDataTooSmall,
            _ => InstructionError::GenericError,
        })
    }
}

impl<'a, T> State<T> for KeyedAccount<'a>
where
    T: serde::Serialize + serde::de::DeserializeOwned,
{
    fn state(&self) -> Result<T, InstructionError> {
        self.account.state()
    }
    fn set_state(&mut self, state: &T) -> Result<(), InstructionError> {
        self.account.set_state(state)
    }
}