#[cfg(has_rtio)]
mod imp {
    use core::ptr::{read_volatile, write_volatile};
    use cslice::CSlice;

    use board_misoc::csr;
    use ::send;
    use ::recv;
    use kernel_proto::*;

    pub const RTIO_O_STATUS_WAIT:                      u8 = 1;
    pub const RTIO_O_STATUS_UNDERFLOW:                 u8 = 2;
    pub const RTIO_O_STATUS_DESTINATION_UNREACHABLE:   u8 = 4;
    pub const RTIO_I_STATUS_WAIT_EVENT:                u8 = 1;
    pub const RTIO_I_STATUS_OVERFLOW:                  u8 = 2;
    pub const RTIO_I_STATUS_WAIT_STATUS:               u8 = 4;
    pub const RTIO_I_STATUS_DESTINATION_UNREACHABLE:   u8 = 8;

    pub extern fn init() {
        send(&RtioInitRequest);
    }

    pub extern fn get_destination_status(destination: i32) -> bool {
        if 0 <= destination && destination <= 255 {
            send(&RtioDestinationStatusRequest { destination: destination as u8 });
            recv!(&RtioDestinationStatusReply { up } => up)
        } else {
            false
        }
    }

    pub extern fn get_counter() -> i64 {
        unsafe {
            csr::rtio::counter_update_write(1);
            csr::rtio::counter_read() as i64
        }
    }

    // writing the LSB of o_data (offset=0) triggers the RTIO write
    #[inline(always)]
    pub unsafe fn rtio_o_data_write(offset: usize, data: u32) {
        write_volatile(
            csr::rtio::O_DATA_ADDR.offset((csr::rtio::O_DATA_SIZE - 1 - offset) as isize),
            data);
    }

    #[inline(always)]
    pub unsafe fn rtio_i_data_read(offset: usize) -> u32 {
        read_volatile(
            csr::rtio::I_DATA_ADDR.offset((csr::rtio::I_DATA_SIZE - 1 - offset) as isize))
    }

    #[inline(never)]
    unsafe fn process_exceptional_status(channel: i32, status: u8) {
        let timestamp = *(csr::rtio::NOW_HI_ADDR as *const i64);
        if status & RTIO_O_STATUS_WAIT != 0 {
            while csr::rtio::o_status_read() & RTIO_O_STATUS_WAIT != 0 {}
        }
        if status & RTIO_O_STATUS_UNDERFLOW != 0 {
            raise!("RTIOUnderflow",
                "RTIO underflow at {0} mu, channel {1}, slack {2} mu",
                timestamp, channel as i64, timestamp - get_counter());
        }
        if status & RTIO_O_STATUS_DESTINATION_UNREACHABLE != 0 {
            raise!("RTIODestinationUnreachable",
                "RTIO destination unreachable, output, at {0} mu, channel {1}",
                timestamp, channel as i64, 0);
        }
    }

    pub extern fn output(target: i32, data: i32) {
        unsafe {
            csr::rtio::target_write(target as u32);
            // writing target clears o_data
            rtio_o_data_write(0, data as _);
            let status = csr::rtio::o_status_read();
            if status != 0 {
                process_exceptional_status(target >> 8, status);
            }
        }
    }

    pub extern fn output_wide(target: i32, data: CSlice<i32>) {
        unsafe {
            csr::rtio::target_write(target as u32);
            // writing target clears o_data
            for i in 0..data.len() {
                rtio_o_data_write(i, data[i] as _)
            }
            let status = csr::rtio::o_status_read();
            if status != 0 {
                process_exceptional_status(target >> 8, status);
            }
        }
    }

    pub extern fn input_timestamp(timeout: i64, channel: i32) -> u64 {
        unsafe {
            csr::rtio::target_write((channel as u32) << 8);
            csr::rtio::i_timeout_write(timeout as u64);

            let mut status = RTIO_I_STATUS_WAIT_STATUS;
            while status & RTIO_I_STATUS_WAIT_STATUS != 0 {
                status = csr::rtio::i_status_read();
            }

            if status & RTIO_I_STATUS_OVERFLOW != 0 {
                csr::rtio::i_overflow_reset_write(1);
                raise!("RTIOOverflow",
                    "RTIO input overflow on channel {0}",
                    channel as i64, 0, 0);
            }
            if status & RTIO_I_STATUS_WAIT_EVENT != 0 {
                return !0
            }
            if status & RTIO_I_STATUS_DESTINATION_UNREACHABLE != 0 {
                raise!("RTIODestinationUnreachable",
                    "RTIO destination unreachable, input, on channel {0}",
                    channel as i64, 0, 0);
            }

            csr::rtio::i_timestamp_read()
        }
    }

    pub extern fn input_data(channel: i32) -> i32 {
        unsafe {
            csr::rtio::target_write((channel as u32) << 8);
            csr::rtio::i_timeout_write(0xffffffff_ffffffff);

            let mut status = RTIO_I_STATUS_WAIT_STATUS;
            while status & RTIO_I_STATUS_WAIT_STATUS != 0 {
                status = csr::rtio::i_status_read();
            }

            if status & RTIO_I_STATUS_OVERFLOW != 0 {
                csr::rtio::i_overflow_reset_write(1);
                raise!("RTIOOverflow",
                    "RTIO input overflow on channel {0}",
                    channel as i64, 0, 0);
            }
            if status & RTIO_I_STATUS_DESTINATION_UNREACHABLE != 0 {
                raise!("RTIODestinationUnreachable",
                    "RTIO destination unreachable, input, on channel {0}",
                    channel as i64, 0, 0);
            }

            rtio_i_data_read(0) as i32
        }
    }

    #[cfg(has_rtio_log)]
    pub fn log(data: &[u8]) {
        unsafe {
            csr::rtio::target_write(csr::CONFIG_RTIO_LOG_CHANNEL << 8);

            let mut word: u32 = 0;
            for i in 0..data.len() {
                word <<= 8;
                word |= data[i] as u32;
                if i % 4 == 3 {
                    rtio_o_data_write(0, word);
                    word = 0;
                }
            }

            if word != 0 {
                rtio_o_data_write(0, word);
            }
        }
    }

    #[cfg(not(has_rtio_log))]
    pub fn log(_data: &[u8]) {
        unimplemented!("not(has_rtio_log)")
    }
}

#[cfg(not(has_rtio))]
mod imp {
    use cslice::CSlice;

    pub extern fn init() {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn get_destination_status(_destination: i32) -> bool {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn get_counter() -> i64 {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn output(_target: i32, _data: i32) {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn output_wide(_target: i32, _data: CSlice<i32>) {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn input_timestamp(_timeout: i64, _channel: i32) -> u64 {
        unimplemented!("not(has_rtio)")
    }

    pub extern fn input_data(_channel: i32) -> i32 {
        unimplemented!("not(has_rtio)")
    }

    pub fn log(_data: &[u8]) {
        unimplemented!("not(has_rtio)")
    }
}

pub use self::imp::*;