//! API for the UART peripheral
use core::{convert::Infallible, ptr};
use core::{marker::PhantomData, ops::Deref};
use libm::floorf;

use crate::clock::enable_peripheral_clock;
use crate::{
    clock,
    gpio::pins::{
        Alternate, Funsel1, Funsel2, Funsel3, Pin, PA16, PA17, PA18, PA19, PA2, PA26, PA27, PA3,
        PA30, PA31, PA8, PA9, PB18, PB19, PB20, PB21, PB22, PB23, PB6, PB7, PB8, PB9,
    },
    pac::{uarta as uart_base, SYSCONFIG, UARTA, UARTB},
    prelude::*,
    time::{Bps, Hertz},
};

use embedded_hal::{blocking, serial};

pub trait Pins<UART> {}

impl Pins<UARTA> for (Pin<PA9, Alternate<Funsel2>>, Pin<PA8, Alternate<Funsel2>>) {}
impl Pins<UARTA> for (Pin<PA17, Alternate<Funsel3>>, Pin<PA16, Alternate<Funsel3>>) {}
impl Pins<UARTA> for (Pin<PA31, Alternate<Funsel3>>, Pin<PA30, Alternate<Funsel3>>) {}

impl Pins<UARTA> for (Pin<PB9, Alternate<Funsel1>>, Pin<PB8, Alternate<Funsel1>>) {}
impl Pins<UARTA> for (Pin<PB23, Alternate<Funsel1>>, Pin<PB22, Alternate<Funsel1>>) {}

impl Pins<UARTB> for (Pin<PA3, Alternate<Funsel2>>, Pin<PA2, Alternate<Funsel2>>) {}
impl Pins<UARTB> for (Pin<PA19, Alternate<Funsel3>>, Pin<PA18, Alternate<Funsel3>>) {}
impl Pins<UARTB> for (Pin<PA27, Alternate<Funsel3>>, Pin<PA26, Alternate<Funsel3>>) {}

impl Pins<UARTB> for (Pin<PB7, Alternate<Funsel1>>, Pin<PB6, Alternate<Funsel1>>) {}
impl Pins<UARTB> for (Pin<PB19, Alternate<Funsel2>>, Pin<PB18, Alternate<Funsel2>>) {}
impl Pins<UARTB> for (Pin<PB21, Alternate<Funsel1>>, Pin<PB20, Alternate<Funsel1>>) {}

#[derive(Debug)]
pub enum Error {
    Overrun,
    FramingError,
    ParityError,
    BreakCondition,
}

#[derive(Copy, Clone, PartialEq)]
pub enum Event {
    // Receiver FIFO interrupt enable. Generates interrupt
    // when FIFO is at least half full. Half full is defined as FIFO
    // count >= RXFIFOIRQTRG
    RxFifoHalfFull,
    // Framing error, Overrun error, Parity Error and Break error
    RxError,
    // Event for timeout condition: Data in the FIFO and no receiver
    // FIFO activity for 4 character times
    RxTimeout,

    // Transmitter FIFO interrupt enable. Generates interrupt
    // when FIFO is at least half full. Half full is defined as FIFO
    // count >= TXFIFOIRQTRG
    TxFifoHalfFull,
    // FIFO overflow error
    TxError,
    // Generate interrupt when transmit FIFO is empty and TXBUSY is 0
    TxEmpty,
    // Interrupt when CTSn changes value
    TxCts,
}

#[derive(Copy, Clone, PartialEq)]
pub enum Parity {
    None,
    Odd,
    Even,
}

#[derive(Copy, Clone, PartialEq)]
pub enum StopBits {
    One = 0,
    Two = 1,
}

#[derive(Copy, Clone, PartialEq)]
pub enum WordSize {
    Five = 0,
    Six = 1,
    Seven = 2,
    Eight = 3,
}

pub struct Config {
    pub baudrate: Bps,
    pub parity: Parity,
    pub stopbits: StopBits,
    // When false, use standard 16x baud clock, other 8x baud clock
    pub baud8: bool,
    pub wordsize: WordSize,
    pub enable_tx: bool,
    pub enable_rx: bool,
}

impl Config {
    pub fn baudrate(mut self, baudrate: Bps) -> Self {
        self.baudrate = baudrate;
        self
    }

    pub fn parity_none(mut self) -> Self {
        self.parity = Parity::None;
        self
    }

    pub fn parity_even(mut self) -> Self {
        self.parity = Parity::Even;
        self
    }

    pub fn parity_odd(mut self) -> Self {
        self.parity = Parity::Odd;
        self
    }

    pub fn stopbits(mut self, stopbits: StopBits) -> Self {
        self.stopbits = stopbits;
        self
    }

    pub fn wordsize(mut self, wordsize: WordSize) -> Self {
        self.wordsize = wordsize;
        self
    }

    pub fn baud8(mut self, baud: bool) -> Self {
        self.baud8 = baud;
        self
    }
}

impl Default for Config {
    fn default() -> Config {
        let baudrate = 115_200_u32.bps();
        Config {
            baudrate,
            parity: Parity::None,
            stopbits: StopBits::One,
            baud8: false,
            wordsize: WordSize::Eight,
            enable_tx: true,
            enable_rx: true,
        }
    }
}

impl From<Bps> for Config {
    fn from(baud: Bps) -> Self {
        Config::default().baudrate(baud)
    }
}

/// Serial abstraction
pub struct Uart<UART, PINS> {
    uart: UART,
    pins: PINS,
    tx: Tx<UART>,
    rx: Rx<UART>,
}

/// Serial receiver
pub struct Rx<UART> {
    _usart: PhantomData<UART>,
}

/// Serial transmitter
pub struct Tx<UART> {
    _usart: PhantomData<UART>,
}

impl<UART> Rx<UART> {
    fn new() -> Self {
        Self {
            _usart: PhantomData,
        }
    }
}

impl<UART> Tx<UART> {
    fn new() -> Self {
        Self {
            _usart: PhantomData,
        }
    }
}

pub trait Instance: Deref<Target = uart_base::RegisterBlock> {
    fn ptr() -> *const uart_base::RegisterBlock;
}

impl<UART, PINS> Uart<UART, PINS>
where
    UART: Instance,
{
    /// This function assumes that the peripheral clock was alredy enabled
    /// in the SYSCONFIG register
    fn init(self, config: Config, sys_clk: Hertz) -> Self {
        let baud_multiplier = match config.baud8 {
            false => 16,
            true => 8,
        };
        let x = sys_clk.0 as f32 / (config.baudrate.0 * baud_multiplier) as f32;
        let integer_part = floorf(x) as u32;
        let frac = floorf((64.0 * (x - integer_part as f32) + 0.5) as f32) as u32;
        self.uart
            .clkscale
            .write(|w| unsafe { w.bits(integer_part * 64 + frac) });

        let (paren, pareven) = match config.parity {
            Parity::None => (false, false),
            Parity::Odd => (true, false),
            Parity::Even => (true, true),
        };
        let stopbits = match config.stopbits {
            StopBits::One => false,
            StopBits::Two => true,
        };
        let wordsize = config.wordsize as u8;
        let baud8 = config.baud8;
        self.uart.ctrl.write(|w| {
            w.paren().bit(paren);
            w.pareven().bit(pareven);
            w.stopbits().bit(stopbits);
            w.baud8().bit(baud8);
            unsafe { w.wordsize().bits(wordsize) }
        });
        let (txenb, rxenb) = (config.enable_tx, config.enable_rx);
        // Clear the FIFO
        self.uart.fifo_clr.write(|w| {
            w.rxfifo().set_bit();
            w.txfifo().set_bit()
        });
        self.uart.enable.write(|w| {
            w.rxenable().bit(rxenb);
            w.txenable().bit(txenb)
        });
        self
    }

    pub fn listen(self, event: Event) -> Self {
        self.uart.irq_enb.modify(|_, w| match event {
            Event::RxError => w.irq_rx_status().set_bit(),
            Event::RxFifoHalfFull => w.irq_rx().set_bit(),
            Event::RxTimeout => w.irq_rx_to().set_bit(),
            Event::TxEmpty => w.irq_tx_empty().set_bit(),
            Event::TxError => w.irq_tx_status().set_bit(),
            Event::TxFifoHalfFull => w.irq_tx().set_bit(),
            Event::TxCts => w.irq_tx_cts().set_bit(),
        });
        self
    }

    pub fn unlisten(self, event: Event) -> Self {
        self.uart.irq_enb.modify(|_, w| match event {
            Event::RxError => w.irq_rx_status().clear_bit(),
            Event::RxFifoHalfFull => w.irq_rx().clear_bit(),
            Event::RxTimeout => w.irq_rx_to().clear_bit(),
            Event::TxEmpty => w.irq_tx_empty().clear_bit(),
            Event::TxError => w.irq_tx_status().clear_bit(),
            Event::TxFifoHalfFull => w.irq_tx().clear_bit(),
            Event::TxCts => w.irq_tx_cts().clear_bit(),
        });
        self
    }

    pub fn release(self) -> (UART, PINS) {
        // Clear the FIFO
        self.uart.fifo_clr.write(|w| {
            w.rxfifo().set_bit();
            w.txfifo().set_bit()
        });
        self.uart.enable.write(|w| {
            w.rxenable().clear_bit();
            w.txenable().clear_bit()
        });
        (self.uart, self.pins)
    }

    pub fn split(self) -> (Tx<UART>, Rx<UART>) {
        (self.tx, self.rx)
    }
}

macro_rules! uart_impl {
    ($($UARTX:ident: ($uartx:ident, $clk_enb_enum:path),)+) => {
        $(
            impl Instance for $UARTX {
                fn ptr() -> *const uart_base::RegisterBlock {
                    $UARTX::ptr() as *const _
                }
            }

            impl<PINS: Pins<$UARTX>> Uart<$UARTX, PINS> {
                pub fn $uartx(
                    uart: $UARTX,
                    pins: PINS,
                    config: impl Into<Config>,
                    syscfg: &mut SYSCONFIG,
                    sys_clk: Hertz
                ) -> Self
                {
                    enable_peripheral_clock(syscfg, $clk_enb_enum);
                    Uart { uart, pins, tx: Tx::new(), rx: Rx::new() }.init(
                        config.into(), sys_clk
                    )
                }
            }
        )+
    }
}

uart_impl! {
    UARTA: (uarta, clock::PeripheralClocks::Uart0),
    UARTB: (uartb, clock::PeripheralClocks::Uart1),
}

impl<UART> Tx<UART> where UART: Instance {}

impl<UART, PINS> serial::Write<u8> for Uart<UART, PINS>
where
    UART: Instance,
{
    type Error = Infallible;
    fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
        self.tx.write(word)
    }
    fn flush(&mut self) -> nb::Result<(), Self::Error> {
        self.tx.flush()
    }
}

impl<UART: Instance, PINS> blocking::serial::write::Default<u8> for Uart<UART, PINS> {}

impl<UART: Instance> serial::Write<u8> for Tx<UART> {
    type Error = Infallible;

    fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
        let reader = unsafe { &(*UART::ptr()) }.txstatus.read();
        if reader.wrrdy().bit_is_clear() {
            return Err(nb::Error::WouldBlock);
        } else {
            // DPARITY bit not supported yet
            unsafe {
                // NOTE(unsafe) atomic write to data register
                // NOTE(write_volatile) 8-bit write that's not
                // possible through the svd2rust API
                ptr::write_volatile(&(*UART::ptr()).data as *const _ as *mut _, word);
            }
        }
        Ok(())
    }

    fn flush(&mut self) -> nb::Result<(), Self::Error> {
        let reader = unsafe { &(*UART::ptr()) }.txstatus.read();
        if reader.wrbusy().bit_is_clear() {
            Ok(())
        } else {
            Err(nb::Error::WouldBlock)
        }
    }
}

impl<UART: Instance, PINS> serial::Read<u8> for Uart<UART, PINS> {
    type Error = Error;

    fn read(&mut self) -> nb::Result<u8, Error> {
        self.rx.read()
    }
}

impl<UART: Instance> serial::Read<u8> for Rx<UART> {
    type Error = Error;

    fn read(&mut self) -> nb::Result<u8, Error> {
        let uart = unsafe { &(*UART::ptr()) };
        let status_reader = uart.rxstatus.read();
        let err = if status_reader.rxovr().bit_is_set() {
            Some(Error::Overrun)
        } else if status_reader.rxfrm().bit_is_set() {
            Some(Error::FramingError)
        } else if status_reader.rxpar().bit_is_set() {
            Some(Error::ParityError)
        } else {
            None
        };
        if let Some(err) = err {
            // The status code is always related to the next bit for the framing
            // and parity status bits. We have to read the DATA register
            // so that the next status reflects the next DATA word
            // For overrun error, we read as well to clear the peripheral
            uart.data.read().bits();
            Err(err.into())
        } else if status_reader.rdavl().bit_is_set() {
            let data = uart.data.read().bits();
            Ok((data & 0xff) as u8)
        } else {
            Err(nb::Error::WouldBlock)
        }
    }
}

impl<UART> core::fmt::Write for Tx<UART>
where
    Tx<UART>: embedded_hal::serial::Write<u8>,
{
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        s.as_bytes()
            .iter()
            .try_for_each(|c| nb::block!(self.write(*c)))
            .map_err(|_| core::fmt::Error)
    }
}