use core::future::{poll_fn, Future};
use core::slice;
use core::task::Poll;

use embassy_cortex_m::interrupt::{Interrupt, InterruptExt};
use embassy_hal_common::atomic_ring_buffer::RingBuffer;
use embassy_sync::waitqueue::AtomicWaker;

use super::*;

pub struct State {
    tx_waker: AtomicWaker,
    tx_buf: RingBuffer,
    rx_waker: AtomicWaker,
    rx_buf: RingBuffer,
}

impl State {
    pub const fn new() -> Self {
        Self {
            rx_buf: RingBuffer::new(),
            tx_buf: RingBuffer::new(),
            rx_waker: AtomicWaker::new(),
            tx_waker: AtomicWaker::new(),
        }
    }
}

pub struct BufferedUart<'d, T: Instance> {
    phantom: PhantomData<&'d mut T>,
}

pub struct BufferedUartRx<'d, T: Instance> {
    phantom: PhantomData<&'d mut T>,
}

pub struct BufferedUartTx<'d, T: Instance> {
    phantom: PhantomData<&'d mut T>,
}

impl<'d, T: Instance> BufferedUart<'d, T> {
    pub fn new(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        tx: impl Peripheral<P = impl TxPin<T>> + 'd,
        rx: impl Peripheral<P = impl RxPin<T>> + 'd,
        tx_buffer: &'d mut [u8],
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(tx, rx);
        Self::new_inner(
            irq,
            tx.map_into(),
            rx.map_into(),
            None,
            None,
            tx_buffer,
            rx_buffer,
            config,
        )
    }

    pub fn new_with_rtscts(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        tx: impl Peripheral<P = impl TxPin<T>> + 'd,
        rx: impl Peripheral<P = impl RxPin<T>> + 'd,
        rts: impl Peripheral<P = impl RtsPin<T>> + 'd,
        cts: impl Peripheral<P = impl CtsPin<T>> + 'd,
        tx_buffer: &'d mut [u8],
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(tx, rx, cts, rts);
        Self::new_inner(
            irq,
            tx.map_into(),
            rx.map_into(),
            Some(rts.map_into()),
            Some(cts.map_into()),
            tx_buffer,
            rx_buffer,
            config,
        )
    }

    fn new_inner(
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        mut tx: PeripheralRef<'d, AnyPin>,
        mut rx: PeripheralRef<'d, AnyPin>,
        mut rts: Option<PeripheralRef<'d, AnyPin>>,
        mut cts: Option<PeripheralRef<'d, AnyPin>>,
        tx_buffer: &'d mut [u8],
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(irq);
        super::Uart::<'d, T, Async>::init(
            Some(tx.reborrow()),
            Some(rx.reborrow()),
            rts.as_mut().map(|x| x.reborrow()),
            cts.as_mut().map(|x| x.reborrow()),
            config,
        );

        let state = T::state();
        let regs = T::regs();

        let len = tx_buffer.len();
        unsafe { state.tx_buf.init(tx_buffer.as_mut_ptr(), len) };
        let len = rx_buffer.len();
        unsafe { state.rx_buf.init(rx_buffer.as_mut_ptr(), len) };

        unsafe {
            regs.uartimsc().modify(|w| {
                w.set_rxim(true);
                w.set_rtim(true);
                w.set_txim(true);
            });
        }

        irq.set_handler(on_interrupt::<T>);
        irq.unpend();
        irq.enable();

        Self { phantom: PhantomData }
    }

    pub fn split(&mut self) -> (BufferedUartRx<'d, T>, BufferedUartTx<'d, T>) {
        (
            BufferedUartRx { phantom: PhantomData },
            BufferedUartTx { phantom: PhantomData },
        )
    }
}

impl<'d, T: Instance> BufferedUartRx<'d, T> {
    pub fn new(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        rx: impl Peripheral<P = impl RxPin<T>> + 'd,
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(rx);
        Self::new_inner(irq, rx.map_into(), None, rx_buffer, config)
    }

    pub fn new_with_rts(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        rx: impl Peripheral<P = impl RxPin<T>> + 'd,
        rts: impl Peripheral<P = impl RtsPin<T>> + 'd,
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(rx, rts);
        Self::new_inner(irq, rx.map_into(), Some(rts.map_into()), rx_buffer, config)
    }

    fn new_inner(
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        mut rx: PeripheralRef<'d, AnyPin>,
        mut rts: Option<PeripheralRef<'d, AnyPin>>,
        rx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(irq);
        super::Uart::<'d, T, Async>::init(
            None,
            Some(rx.reborrow()),
            rts.as_mut().map(|x| x.reborrow()),
            None,
            config,
        );

        let state = T::state();
        let regs = T::regs();

        let len = rx_buffer.len();
        unsafe { state.rx_buf.init(rx_buffer.as_mut_ptr(), len) };

        unsafe {
            regs.uartimsc().modify(|w| {
                w.set_rxim(true);
                w.set_rtim(true);
            });
        }

        irq.set_handler(on_interrupt::<T>);
        irq.unpend();
        irq.enable();

        Self { phantom: PhantomData }
    }

    fn read<'a>(buf: &'a mut [u8]) -> impl Future<Output = Result<usize, Error>> + 'a {
        poll_fn(move |cx| {
            let state = T::state();
            let mut rx_reader = unsafe { state.rx_buf.reader() };
            let n = rx_reader.pop(|data| {
                let n = data.len().min(buf.len());
                buf[..n].copy_from_slice(&data[..n]);
                n
            });
            if n == 0 {
                state.rx_waker.register(cx.waker());
                return Poll::Pending;
            }

            Poll::Ready(Ok(n))
        })
    }

    fn fill_buf<'a>() -> impl Future<Output = Result<&'a [u8], Error>> {
        poll_fn(move |cx| {
            let state = T::state();
            let mut rx_reader = unsafe { state.rx_buf.reader() };
            let (p, n) = rx_reader.pop_buf();
            if n == 0 {
                state.rx_waker.register(cx.waker());
                return Poll::Pending;
            }

            let buf = unsafe { slice::from_raw_parts(p, n) };
            Poll::Ready(Ok(buf))
        })
    }

    fn consume(amt: usize) {
        let state = T::state();
        let mut rx_reader = unsafe { state.rx_buf.reader() };
        rx_reader.pop_done(amt)
    }
}

impl<'d, T: Instance> BufferedUartTx<'d, T> {
    pub fn new(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        tx: impl Peripheral<P = impl TxPin<T>> + 'd,
        tx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(tx);
        Self::new_inner(irq, tx.map_into(), None, tx_buffer, config)
    }

    pub fn new_with_cts(
        _uart: impl Peripheral<P = T> + 'd,
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        tx: impl Peripheral<P = impl TxPin<T>> + 'd,
        cts: impl Peripheral<P = impl CtsPin<T>> + 'd,
        tx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(tx, cts);
        Self::new_inner(irq, tx.map_into(), Some(cts.map_into()), tx_buffer, config)
    }

    fn new_inner(
        irq: impl Peripheral<P = T::Interrupt> + 'd,
        mut tx: PeripheralRef<'d, AnyPin>,
        mut cts: Option<PeripheralRef<'d, AnyPin>>,
        tx_buffer: &'d mut [u8],
        config: Config,
    ) -> Self {
        into_ref!(irq);
        super::Uart::<'d, T, Async>::init(
            Some(tx.reborrow()),
            None,
            None,
            cts.as_mut().map(|x| x.reborrow()),
            config,
        );

        let state = T::state();
        let regs = T::regs();

        let len = tx_buffer.len();
        unsafe { state.tx_buf.init(tx_buffer.as_mut_ptr(), len) };

        unsafe {
            regs.uartimsc().modify(|w| {
                w.set_txim(true);
            });
        }

        irq.set_handler(on_interrupt::<T>);
        irq.unpend();
        irq.enable();

        Self { phantom: PhantomData }
    }

    fn write<'a>(buf: &'a [u8]) -> impl Future<Output = Result<usize, Error>> + 'a {
        poll_fn(move |cx| {
            let state = T::state();
            let mut tx_writer = unsafe { state.tx_buf.writer() };
            let n = tx_writer.push(|data| {
                let n = data.len().min(buf.len());
                data[..n].copy_from_slice(&buf[..n]);
                n
            });
            if n == 0 {
                state.tx_waker.register(cx.waker());
                return Poll::Pending;
            } else {
                unsafe { T::Interrupt::steal() }.pend();
            }

            Poll::Ready(Ok(n))
        })
    }

    fn flush() -> impl Future<Output = Result<(), Error>> {
        poll_fn(move |cx| {
            let state = T::state();
            if !state.tx_buf.is_empty() {
                state.tx_waker.register(cx.waker());
                return Poll::Pending;
            }

            Poll::Ready(Ok(()))
        })
    }
}

impl<'d, T: Instance> Drop for BufferedUart<'d, T> {
    fn drop(&mut self) {
        unsafe {
            T::Interrupt::steal().disable();
            let state = T::state();
            state.tx_buf.deinit();
            state.rx_buf.deinit();
        }
    }
}

impl<'d, T: Instance> Drop for BufferedUartRx<'d, T> {
    fn drop(&mut self) {
        unsafe {
            T::Interrupt::steal().disable();
            let state = T::state();
            state.tx_buf.deinit();
            state.rx_buf.deinit();
        }
    }
}

impl<'d, T: Instance> Drop for BufferedUartTx<'d, T> {
    fn drop(&mut self) {
        unsafe {
            T::Interrupt::steal().disable();
            let state = T::state();
            state.tx_buf.deinit();
            state.rx_buf.deinit();
        }
    }
}

pub(crate) unsafe fn on_interrupt<T: Instance>(_: *mut ()) {
    trace!("on_interrupt");

    let r = T::regs();
    let s = T::state();

    unsafe {
        // RX

        let ris = r.uartris().read();
        // Clear interrupt flags
        r.uarticr().write(|w| {
            w.set_rxic(true);
            w.set_rtic(true);
        });

        if ris.peris() {
            warn!("Parity error");
            r.uarticr().write(|w| {
                w.set_peic(true);
            });
        }
        if ris.feris() {
            warn!("Framing error");
            r.uarticr().write(|w| {
                w.set_feic(true);
            });
        }
        if ris.beris() {
            warn!("Break error");
            r.uarticr().write(|w| {
                w.set_beic(true);
            });
        }
        if ris.oeris() {
            warn!("Overrun error");
            r.uarticr().write(|w| {
                w.set_oeic(true);
            });
        }

        let mut rx_writer = s.rx_buf.writer();
        let rx_buf = rx_writer.push_slice();
        let mut n_read = 0;
        for rx_byte in rx_buf {
            if r.uartfr().read().rxfe() {
                break;
            }
            *rx_byte = r.uartdr().read().data();
            n_read += 1;
        }
        if n_read > 0 {
            rx_writer.push_done(n_read);
            s.rx_waker.wake();
        }

        // TX
        let mut tx_reader = s.tx_buf.reader();
        let tx_buf = tx_reader.pop_slice();
        if tx_buf.len() == 0 {
            // Disable interrupt until we have something to transmit again
            r.uartimsc().modify(|w| {
                w.set_txim(false);
            });
        } else {
            r.uartimsc().modify(|w| {
                w.set_txim(true);
            });

            let mut n_written = 0;
            for tx_byte in tx_buf.iter_mut() {
                if r.uartfr().read().txff() {
                    break;
                }
                r.uartdr().write(|w| w.set_data(*tx_byte));
                n_written += 1;
            }
            if n_written > 0 {
                tx_reader.pop_done(n_written);
                s.tx_waker.wake();
            }
        }
    }
}

impl embedded_io::Error for Error {
    fn kind(&self) -> embedded_io::ErrorKind {
        embedded_io::ErrorKind::Other
    }
}

impl<'d, T: Instance> embedded_io::Io for BufferedUart<'d, T> {
    type Error = Error;
}

impl<'d, T: Instance> embedded_io::Io for BufferedUartRx<'d, T> {
    type Error = Error;
}

impl<'d, T: Instance> embedded_io::Io for BufferedUartTx<'d, T> {
    type Error = Error;
}

impl<'d, T: Instance + 'd> embedded_io::asynch::Read for BufferedUart<'d, T> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        BufferedUartRx::<'d, T>::read(buf).await
    }
}

impl<'d, T: Instance + 'd> embedded_io::asynch::Read for BufferedUartRx<'d, T> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        Self::read(buf).await
    }
}

impl<'d, T: Instance + 'd> embedded_io::asynch::BufRead for BufferedUart<'d, T> {
    async fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
        BufferedUartRx::<'d, T>::fill_buf().await
    }

    fn consume(&mut self, amt: usize) {
        BufferedUartRx::<'d, T>::consume(amt)
    }
}

impl<'d, T: Instance + 'd> embedded_io::asynch::BufRead for BufferedUartRx<'d, T> {
    async fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
        Self::fill_buf().await
    }

    fn consume(&mut self, amt: usize) {
        Self::consume(amt)
    }
}

impl<'d, T: Instance + 'd> embedded_io::asynch::Write for BufferedUart<'d, T> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        BufferedUartTx::<'d, T>::write(buf).await
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        BufferedUartTx::<'d, T>::flush().await
    }
}

impl<'d, T: Instance + 'd> embedded_io::asynch::Write for BufferedUartTx<'d, T> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        Self::write(buf).await
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        Self::flush().await
    }
}