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//! Just-in-time compiles Brainfuck AST to x64 machine code (`--features jit`, nightly only)
//!
//! This uses the [`dynasm`](https://crates.io/search?q=dynasm) crate to generate x86-64
//! machine code from peephole-optimized AST. This is currently the fastest implementation,
//! but it is available only on nightly Rust because `dynasm` uses a plugin.
//!
//! In the `bfi` interpreter, this pass is enabled by default if compiled in.
//! To go even faster, pass the `--unchecked` flag to the `bfi` interpreter to disable
//! memory bounds checking in the generated code. Note that this runs Brainfuck in
//! unsafe mode, which means that programs that move the pointer outside the allocated
//! memory will access and possibly overwrite arbitrary memory locations.

mod loop_balance;
mod analysis;
mod compiler;

pub use self::compiler::{compile, JitCompilable};

use std::io::{Read, Write};
use std::mem;

use dynasmrt;

use common::{BfResult, Error};
use rts::{self, RtsState};
use state::State;
use traits::Interpretable;

/// The representation of a JIT-compiled program.
///
/// Relies on the `dynasmrt` run-time system. [This
/// representation](../../src/bf/jit/mod.rs.html#26-29)
/// is from [the `dynlib-rs` tutorial].
///
/// [the `dynlib-rs` tutorial]: https://censoredusername.github.io/dynasm-rs/language/tutorial.html#advanced-usage
pub struct Program {
    code: dynasmrt::ExecutableBuffer,
    start: dynasmrt::AssemblyOffset,
}

/// The type of function that we will assemble and then call.
///
/// # Parameters
///
/// `<'a>` – the lifetime of the channel references in the run-time system state.
///
/// `memory` – the address of the beginning of memory (also where the pointer starts).
///
/// `memory_size` – the amount of memory allocated, defaults to 30,000 bytes.
///
/// `rts_state` – the state that the run-time system needs to do I/O.
type EntryFunction<'a> = extern "win64" fn(memory: *mut u8,
                                           memory_size: u64,
                                           rts_state: *mut RtsState<'a>) -> u64;

impl Interpretable for Program {
    fn interpret_state<R: Read, W: Write>(&self, mut state: State,
                                          mut input: R, mut output: W)
                                          -> BfResult<()>
    {
        let mut rts = RtsState::new(&mut input, &mut output);

        let f: EntryFunction = unsafe { mem::transmute(self.code.ptr(self.start)) };

        let result = f(state.as_mut_ptr(), state.capacity() as u64, &mut rts);;

        match result {
            rts::OKAY      => Ok(()),
            rts::UNDERFLOW => Err(Error::PointerUnderflow),
            rts::OVERFLOW  => Err(Error::PointerOverflow),
            _ => panic!(format!("Unknown result code: {}", result)),
        }
    }
}

#[cfg(test)]
mod tests {
    use test_helpers::*;
    use common::{BfResult, Error};

    #[test]
    fn move_right_once() {
        assert_parse_interpret(b">", "", Ok(""));
    }

    #[test]
    fn move_left_once() {
        assert_parse_interpret(b"<", "", Err(Error::PointerUnderflow));
    }

    #[test]
    fn move_right_forever() {
        assert_parse_interpret(b"+[>+]", "", Err(Error::PointerOverflow));
    }

    #[test]
    fn echo_one_byte() {
        assert_parse_interpret(b",.", "A", Ok("A"));
    }

    #[test]
    fn inc_echo_one_byte() {
        assert_parse_interpret(b",+.", "A", Ok("B"));
    }

    #[test]
    fn hello_world() {
        assert_parse_interpret(HELLO_WORLD_SRC, "", Ok("Hello, World!"));
    }

    #[test]
    fn factoring() {
        assert_parse_interpret(FACTOR_SRC, "2\n", Ok("2: 2\n"));
        assert_parse_interpret(FACTOR_SRC, "3\n", Ok("3: 3\n"));
        assert_parse_interpret(FACTOR_SRC, "6\n", Ok("6: 2 3\n"));
        assert_parse_interpret(FACTOR_SRC, "100\n", Ok("100: 2 2 5 5\n"));
    }

    fn assert_parse_interpret(program: &[u8], input: &str, output: BfResult<&str>) {
        let program = ::ast::parse_program(program).unwrap();
        let program = ::rle::compile(&program);
        let program = ::peephole::compile(&program);
        let program = ::jit::compile(&program, true);
        assert_interpret_result(&program, input.as_bytes(), output.map(|s| s.as_bytes()));
    }
}