// The v1c ethernet driver was ported to embassy from the awesome stm32-eth project (https://github.com/stm32-rs/stm32-eth).

use core::marker::PhantomData;
use core::sync::atomic::{fence, Ordering};
use core::task::Waker;

use embassy_cortex_m::peripheral::{PeripheralMutex, PeripheralState, StateStorage};
use embassy_hal_common::{into_ref, PeripheralRef};
use embassy_net::{Device, DeviceCapabilities, LinkState, PacketBuf, MTU};
use embassy_sync::waitqueue::AtomicWaker;

use crate::gpio::sealed::{AFType, Pin as __GpioPin};
use crate::gpio::{AnyPin, Speed};
#[cfg(eth_v1a)]
use crate::pac::AFIO;
#[cfg(any(eth_v1b, eth_v1c))]
use crate::pac::SYSCFG;
use crate::pac::{ETH, RCC};
use crate::Peripheral;

mod descriptors;
mod rx_desc;
mod tx_desc;

use descriptors::DescriptorRing;
use stm32_metapac::eth::vals::{Apcs, Cr, Dm, DmaomrSr, Fes, Ftf, Ifg, MbProgress, Mw, Pbl, Rsf, St, Tsf};

use super::*;

pub struct State<'d, T: Instance, const TX: usize, const RX: usize>(StateStorage<Inner<'d, T, TX, RX>>);
impl<'d, T: Instance, const TX: usize, const RX: usize> State<'d, T, TX, RX> {
    pub const fn new() -> Self {
        Self(StateStorage::new())
    }
}

pub struct Ethernet<'d, T: Instance, P: PHY, const TX: usize, const RX: usize> {
    state: PeripheralMutex<'d, Inner<'d, T, TX, RX>>,
    pins: [PeripheralRef<'d, AnyPin>; 9],
    _phy: P,
    clock_range: Cr,
    phy_addr: u8,
    mac_addr: [u8; 6],
}

#[cfg(eth_v1a)]
macro_rules! config_in_pins {
    ($($pin:ident),*) => {
        // NOTE(unsafe) Exclusive access to the registers
        critical_section::with(|_| {
            $(
                // TODO properly create a set_as_input function
                $pin.set_as_af($pin.af_num(), AFType::Input);
            )*
        })
    }
}

#[cfg(eth_v1a)]
macro_rules! config_af_pins {
    ($($pin:ident),*) => {
        // NOTE(unsafe) Exclusive access to the registers
        critical_section::with(|_| {
            $(
                // We are lucky here, this configures to max speed (50MHz)
                $pin.set_as_af($pin.af_num(), AFType::OutputPushPull);
            )*
        })
    };
}

#[cfg(any(eth_v1b, eth_v1c))]
macro_rules! config_pins {
    ($($pin:ident),*) => {
        // NOTE(unsafe) Exclusive access to the registers
        critical_section::with(|_| {
            $(
                $pin.set_as_af($pin.af_num(), AFType::OutputPushPull);
                $pin.set_speed(Speed::VeryHigh);
            )*
        })
    };
}

impl<'d, T: Instance, P: PHY, const TX: usize, const RX: usize> Ethernet<'d, T, P, TX, RX> {
    /// safety: the returned instance is not leak-safe
    pub unsafe fn new(
        state: &'d mut State<'d, T, TX, RX>,
        peri: impl Peripheral<P = T> + 'd,
        interrupt: impl Peripheral<P = crate::interrupt::ETH> + 'd,
        ref_clk: impl Peripheral<P = impl RefClkPin<T>> + 'd,
        mdio: impl Peripheral<P = impl MDIOPin<T>> + 'd,
        mdc: impl Peripheral<P = impl MDCPin<T>> + 'd,
        crs: impl Peripheral<P = impl CRSPin<T>> + 'd,
        rx_d0: impl Peripheral<P = impl RXD0Pin<T>> + 'd,
        rx_d1: impl Peripheral<P = impl RXD1Pin<T>> + 'd,
        tx_d0: impl Peripheral<P = impl TXD0Pin<T>> + 'd,
        tx_d1: impl Peripheral<P = impl TXD1Pin<T>> + 'd,
        tx_en: impl Peripheral<P = impl TXEnPin<T>> + 'd,
        phy: P,
        mac_addr: [u8; 6],
        phy_addr: u8,
    ) -> Self {
        into_ref!(interrupt, ref_clk, mdio, mdc, crs, rx_d0, rx_d1, tx_d0, tx_d1, tx_en);

        // Enable the necessary Clocks
        // NOTE(unsafe) We have exclusive access to the registers
        #[cfg(eth_v1a)]
        critical_section::with(|_| {
            RCC.apb2enr().modify(|w| w.set_afioen(true));

            // Select RMII (Reduced Media Independent Interface)
            // Must be done prior to enabling peripheral clock
            AFIO.mapr().modify(|w| w.set_mii_rmii_sel(true));

            RCC.ahbenr().modify(|w| {
                w.set_ethen(true);
                w.set_ethtxen(true);
                w.set_ethrxen(true);
            });
        });

        #[cfg(any(eth_v1b, eth_v1c))]
        critical_section::with(|_| {
            RCC.apb2enr().modify(|w| w.set_syscfgen(true));
            RCC.ahb1enr().modify(|w| {
                w.set_ethen(true);
                w.set_ethtxen(true);
                w.set_ethrxen(true);
            });

            // RMII (Reduced Media Independent Interface)
            SYSCFG.pmc().modify(|w| w.set_mii_rmii_sel(true));
        });

        #[cfg(eth_v1a)]
        {
            config_in_pins!(ref_clk, rx_d0, rx_d1);
            config_af_pins!(mdio, mdc, tx_d0, tx_d1, tx_en);
        }

        #[cfg(any(eth_v1b, eth_v1c))]
        config_pins!(ref_clk, mdio, mdc, crs, rx_d0, rx_d1, tx_d0, tx_d1, tx_en);

        // NOTE(unsafe) We are ourselves not leak-safe.
        let state = PeripheralMutex::new(interrupt, &mut state.0, || Inner::new(peri));

        // NOTE(unsafe) We have exclusive access to the registers
        let dma = ETH.ethernet_dma();
        let mac = ETH.ethernet_mac();

        // Reset and wait
        dma.dmabmr().modify(|w| w.set_sr(true));
        while dma.dmabmr().read().sr() {}

        mac.maccr().modify(|w| {
            w.set_ifg(Ifg::IFG96); // inter frame gap 96 bit times
            w.set_apcs(Apcs::STRIP); // automatic padding and crc stripping
            w.set_fes(Fes::FES100); // fast ethernet speed
            w.set_dm(Dm::FULLDUPLEX); // full duplex
                                      // TODO: Carrier sense ? ECRSFD
        });

        // Note: Writing to LR triggers synchronisation of both LR and HR into the MAC core,
        // so the LR write must happen after the HR write.
        mac.maca0hr()
            .modify(|w| w.set_maca0h(u16::from(mac_addr[4]) | (u16::from(mac_addr[5]) << 8)));
        mac.maca0lr().write(|w| {
            w.set_maca0l(
                u32::from(mac_addr[0])
                    | (u32::from(mac_addr[1]) << 8)
                    | (u32::from(mac_addr[2]) << 16)
                    | (u32::from(mac_addr[3]) << 24),
            )
        });

        // pause time
        mac.macfcr().modify(|w| w.set_pt(0x100));

        // Transfer and Forward, Receive and Forward
        dma.dmaomr().modify(|w| {
            w.set_tsf(Tsf::STOREFORWARD);
            w.set_rsf(Rsf::STOREFORWARD);
        });

        dma.dmabmr().modify(|w| {
            w.set_pbl(Pbl::PBL32) // programmable burst length - 32 ?
        });

        // TODO MTU size setting not found for v1 ethernet, check if correct

        // NOTE(unsafe) We got the peripheral singleton, which means that `rcc::init` was called
        let hclk = crate::rcc::get_freqs().ahb1;
        let hclk_mhz = hclk.0 / 1_000_000;

        // Set the MDC clock frequency in the range 1MHz - 2.5MHz
        let clock_range = match hclk_mhz {
            0..=24 => panic!("Invalid HCLK frequency - should be at least 25 MHz."),
            25..=34 => Cr::CR_20_35,     // Divide by 16
            35..=59 => Cr::CR_35_60,     // Divide by 26
            60..=99 => Cr::CR_60_100,    // Divide by 42
            100..=149 => Cr::CR_100_150, // Divide by 62
            150..=216 => Cr::CR_150_168, // Divide by 102
            _ => {
                panic!("HCLK results in MDC clock > 2.5MHz even for the highest CSR clock divider")
            }
        };

        let pins = [
            ref_clk.map_into(),
            mdio.map_into(),
            mdc.map_into(),
            crs.map_into(),
            rx_d0.map_into(),
            rx_d1.map_into(),
            tx_d0.map_into(),
            tx_d1.map_into(),
            tx_en.map_into(),
        ];

        let mut this = Self {
            state,
            pins,
            _phy: phy,
            clock_range,
            phy_addr,
            mac_addr,
        };

        this.state.with(|s| {
            s.desc_ring.init();

            fence(Ordering::SeqCst);

            let mac = ETH.ethernet_mac();
            let dma = ETH.ethernet_dma();

            mac.maccr().modify(|w| {
                w.set_re(true);
                w.set_te(true);
            });
            dma.dmaomr().modify(|w| {
                w.set_ftf(Ftf::FLUSH); // flush transmit fifo (queue)
                w.set_st(St::STARTED); // start transmitting channel
                w.set_sr(DmaomrSr::STARTED); // start receiving channel
            });

            // Enable interrupts
            dma.dmaier().modify(|w| {
                w.set_nise(true);
                w.set_rie(true);
                w.set_tie(true);
            });
        });
        P::phy_reset(&mut this);
        P::phy_init(&mut this);

        this
    }
}

unsafe impl<'d, T: Instance, P: PHY, const TX: usize, const RX: usize> StationManagement
    for Ethernet<'d, T, P, TX, RX>
{
    fn smi_read(&mut self, reg: u8) -> u16 {
        // NOTE(unsafe) These registers aren't used in the interrupt and we have `&mut self`
        unsafe {
            let mac = ETH.ethernet_mac();

            mac.macmiiar().modify(|w| {
                w.set_pa(self.phy_addr);
                w.set_mr(reg);
                w.set_mw(Mw::READ); // read operation
                w.set_cr(self.clock_range);
                w.set_mb(MbProgress::BUSY); // indicate that operation is in progress
            });
            while mac.macmiiar().read().mb() == MbProgress::BUSY {}
            mac.macmiidr().read().md()
        }
    }

    fn smi_write(&mut self, reg: u8, val: u16) {
        // NOTE(unsafe) These registers aren't used in the interrupt and we have `&mut self`
        unsafe {
            let mac = ETH.ethernet_mac();

            mac.macmiidr().write(|w| w.set_md(val));
            mac.macmiiar().modify(|w| {
                w.set_pa(self.phy_addr);
                w.set_mr(reg);
                w.set_mw(Mw::WRITE); // write
                w.set_cr(self.clock_range);
                w.set_mb(MbProgress::BUSY);
            });
            while mac.macmiiar().read().mb() == MbProgress::BUSY {}
        }
    }
}

impl<'d, T: Instance, P: PHY, const TX: usize, const RX: usize> Device for Ethernet<'d, T, P, TX, RX> {
    fn is_transmit_ready(&mut self) -> bool {
        self.state.with(|s| s.desc_ring.tx.available())
    }

    fn transmit(&mut self, pkt: PacketBuf) {
        self.state.with(|s| unwrap!(s.desc_ring.tx.transmit(pkt)));
    }

    fn receive(&mut self) -> Option<PacketBuf> {
        self.state.with(|s| s.desc_ring.rx.pop_packet())
    }

    fn register_waker(&mut self, waker: &Waker) {
        WAKER.register(waker);
    }

    fn capabilities(&self) -> DeviceCapabilities {
        let mut caps = DeviceCapabilities::default();
        caps.max_transmission_unit = MTU;
        caps.max_burst_size = Some(TX.min(RX));
        caps
    }

    fn link_state(&mut self) -> LinkState {
        if P::poll_link(self) {
            LinkState::Up
        } else {
            LinkState::Down
        }
    }

    fn ethernet_address(&self) -> [u8; 6] {
        self.mac_addr
    }
}

impl<'d, T: Instance, P: PHY, const TX: usize, const RX: usize> Drop for Ethernet<'d, T, P, TX, RX> {
    fn drop(&mut self) {
        // NOTE(unsafe) We have `&mut self` and the interrupt doesn't use this registers
        unsafe {
            let dma = ETH.ethernet_dma();
            let mac = ETH.ethernet_mac();

            // Disable the TX DMA and wait for any previous transmissions to be completed
            dma.dmaomr().modify(|w| w.set_st(St::STOPPED));

            // Disable MAC transmitter and receiver
            mac.maccr().modify(|w| {
                w.set_re(false);
                w.set_te(false);
            });

            dma.dmaomr().modify(|w| w.set_sr(DmaomrSr::STOPPED));
        }

        // NOTE(unsafe) Exclusive access to the regs
        critical_section::with(|_| unsafe {
            for pin in self.pins.iter_mut() {
                pin.set_as_disconnected();
            }
        })
    }
}

//----------------------------------------------------------------------

struct Inner<'d, T: Instance, const TX: usize, const RX: usize> {
    _peri: PhantomData<&'d mut T>,
    desc_ring: DescriptorRing<TX, RX>,
}

impl<'d, T: Instance, const TX: usize, const RX: usize> Inner<'d, T, TX, RX> {
    pub fn new(_peri: impl Peripheral<P = T> + 'd) -> Self {
        Self {
            _peri: PhantomData,
            desc_ring: DescriptorRing::new(),
        }
    }
}

impl<'d, T: Instance, const TX: usize, const RX: usize> PeripheralState for Inner<'d, T, TX, RX> {
    type Interrupt = crate::interrupt::ETH;

    fn on_interrupt(&mut self) {
        unwrap!(self.desc_ring.tx.on_interrupt());
        self.desc_ring.rx.on_interrupt();

        WAKER.wake();

        // TODO: Check and clear more flags
        unsafe {
            let dma = ETH.ethernet_dma();

            dma.dmasr().modify(|w| {
                w.set_ts(true);
                w.set_rs(true);
                w.set_nis(true);
            });
            // Delay two peripheral's clock
            dma.dmasr().read();
            dma.dmasr().read();
        }
    }
}

static WAKER: AtomicWaker = AtomicWaker::new();