//! Executor engine implementation for Brainfuck interpreter.
//!
//! This predominantly allows implementation of a [`u16`] executor.

use std::io::Read;

use num_traits::{One, Unsigned, WrappingAdd, WrappingSub, Zero};

use crate::executor::{self, Error};

/// Generic engine implementation for the Brainfuck interpreter.
pub trait Engine {
	/// Inner type of the Tape.
	type TapeInner: Clone + Copy + Unsigned + WrappingAdd + WrappingSub + One + Zero;

	/// Read one byte from stdin.
	///
	/// # Errors
	///
	/// This function will return an error if it is unable to read from stdin,
	/// or if it indexes out of bounds.
	fn read_byte() -> Result<Self::TapeInner, Error>;

	/// Write the provided byte to stdout.
	///
	/// # Errors
	///
	/// This function will return an error if it is unable to write a byte to
	/// stdout.
	fn write_byte(byte: Self::TapeInner) -> Result<(), Error>;
}

impl Engine for executor::U8 {
	type TapeInner = u8;

	fn read_byte() -> Result<u8, Error> {
		let mut input: [u8; 1] = [0; 1];

		std::io::stdin().read_exact(&mut input)?;

		Ok(input[0])
	}

	fn write_byte(byte: u8) -> Result<(), Error> {
		print!("{}", char::from(byte));

		Ok(())
	}
}

impl Engine for executor::U16 {
	type TapeInner = u16;

	fn read_byte() -> Result<u16, Error> {
		let mut input: [u8; 2] = [0; 2];

		std::io::stdin().read_exact(&mut input)?;

		let number = ((u16::from(input[0])) << 8i32) | u16::from(input[1]);

		Ok(number)
	}

	fn write_byte(byte: u16) -> Result<(), Error> {
		print!("{}", String::from_utf16_lossy(&[byte]));

		Ok(())
	}
}