use core::ptr::{read_volatile, write_volatile};
use cslice::CSlice;
use log::error;

use crate::pl::csr;

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;

#[repr(C)]
pub struct TimestampedData {
    timestamp: i64,
    data: i32,
}

pub extern fn init() {
    unsafe {
        csr::rtio_core::reset_write(1);
    }
}

pub extern fn get_destination_status(destination: i32) -> bool {
    // TODO
    destination == 0
}

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 {
        error!("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 {
        error!("RTIO destination unreachable, output, at {0} mu, channel {1}",
               timestamp, channel as i64);
    }
}

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()).rev() {
            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) -> i64 {
    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);
            error!("RTIO input overflow on channel {0}",
                   channel as i64);
        }
        if status & RTIO_I_STATUS_WAIT_EVENT != 0 {
            return -1
        }
        if status & RTIO_I_STATUS_DESTINATION_UNREACHABLE != 0 {
            error!("RTIO destination unreachable, input, on channel {0}",
                   channel as i64);
        }

        csr::rtio::i_timestamp_read() as i64
    }
}

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);
            error!("RTIO input overflow on channel {0}",
                   channel as i64);
        }
        if status & RTIO_I_STATUS_DESTINATION_UNREACHABLE != 0 {
            error!("RTIO destination unreachable, input, on channel {0}",
                   channel as i64);
        }

        rtio_i_data_read(0) as i32
    }
}

pub extern fn input_timestamped_data(timeout: i64, channel: i32) -> TimestampedData {
    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);
            error!("RTIO input overflow on channel {0}",
                   channel as i64);
        }
        if status & RTIO_I_STATUS_WAIT_EVENT != 0 {
            return TimestampedData { timestamp: -1, data: 0 }
        }
        if status & RTIO_I_STATUS_DESTINATION_UNREACHABLE != 0 {
            error!("RTIO destination unreachable, input, on channel {0}",
                   channel as i64);
        }

        TimestampedData {
            timestamp: csr::rtio::i_timestamp_read() as i64,
            data: rtio_i_data_read(0) as i32
        }
    }
}