//! Independent per-link scheduling, encoding, framing and bounded transmission.
use super::{
    peripherals::{self, F722UsbMavlink, OwnedUart, ReceiveInterrupt},
    serial::{ReceiveEvent, RxChunk, SerialDevice, SerialIo},
};
use crate::SerialInventory;
use kaptan_data_channel::{DataChannel, DataChannelRates};
use kaptan_mavlink::{
    MavlinkFrame,
    receiver::{IntegrityCheckedFrame, IntegrityMavlinkReceiver},
};
use kaptan_ports::PortId;
use kaptan_tx::PendingFrame;

pub(crate) const SERVICE_HZ: usize = 100;

pub(crate) struct Link {
    pub(crate) channel: DataChannel<SERVICE_HZ>,
    pub(crate) receiver: IntegrityMavlinkReceiver<2>,
}
impl Link {
    pub(crate) fn new(
        system: u8,
        component: u8,
        rates: DataChannelRates,
    ) -> Result<Self, crate::BoardError> {
        Ok(Self {
            channel: DataChannel::new(system, component, rates, 100_000)
                .map_err(|_| crate::BoardError::Initialization)?,
            receiver: IntegrityMavlinkReceiver::new(),
        })
    }
}

impl SerialDevice for OwnedUart {
    fn receive(&mut self) -> ReceiveEvent {
        match OwnedUart::receive(self) {
            ReceiveInterrupt::Byte(byte) => ReceiveEvent::Byte(byte),
            ReceiveInterrupt::Fault => ReceiveEvent::Fault,
            ReceiveInterrupt::NotPending => ReceiveEvent::Idle,
        }
    }
}

/// Bounded data exchanged between the worker and I/O owners. Decoding,
/// scheduling and persistence cannot borrow the physical owners through this API.
#[derive(Default)]
pub struct IoBatch {
    pub(crate) serial: RxChunk,
    pub(crate) usb: Option<IntegrityCheckedFrame>,
    pub(crate) accepted: bool,
    pub(crate) pending: bool,
}
impl<I: SerialDevice> SerialIo<I> {
    pub fn exchange(&mut self, frame: Option<PendingFrame<MavlinkFrame>>) -> IoBatch {
        match frame {
            Some(frame) => IoBatch {
                accepted: self.send(frame),
                ..IoBatch::default()
            },
            None => {
                let serial = self.take_chunk();
                IoBatch {
                    pending: serial.pending,
                    serial,
                    ..IoBatch::default()
                }
            }
        }
    }
}

/// One short-lock RTIC resource for the board's declared UARTs. All UART IRQs
/// have priority 14. Protocol work stays outside this bounded I/O handoff.
pub struct PortIo<const N: usize> {
    inventory: SerialInventory,
    pub(crate) ports: [SerialIo<OwnedUart>; N],
}
impl<const N: usize> PortIo<N> {
    pub(crate) fn new(inventory: SerialInventory) -> Self {
        assert_eq!(inventory.len(), N, "validated board port count");
        Self {
            inventory,
            ports: core::array::from_fn(|_| SerialIo::new(None, false)),
        }
    }
    pub fn on_interrupt(&mut self, id: PortId, now: kaptan_time::Timestamp) -> bool {
        self.inventory
            .index(id)
            .is_some_and(|index| self.ports[index].on_interrupt(now))
    }
    pub fn exchange(&mut self, id: PortId, frame: Option<PendingFrame<MavlinkFrame>>) -> IoBatch {
        self.inventory
            .index(id)
            .map_or_else(IoBatch::default, |index| self.ports[index].exchange(frame))
    }
}

pub struct UsbIo {
    usb: F722UsbMavlink,
    rx_interrupt: RxFifoInterruptGate,
}
impl UsbIo {
    pub(crate) fn new(usb: F722UsbMavlink, rx_interrupt: RxFifoInterruptGate) -> Self {
        Self { usb, rx_interrupt }
    }
    pub fn on_interrupt(&mut self) -> bool {
        self.usb.with_rx_interrupt_gate(
            |usb| usb.poll(),
            |enabled| self.rx_interrupt.set_enabled(enabled),
        )
    }
    pub fn exchange(&mut self, frame: Option<PendingFrame<MavlinkFrame>>) -> IoBatch {
        exchange_usb(&mut self.usb, frame, |enabled| {
            self.rx_interrupt.set_enabled(enabled)
        })
    }
}

/// Private F722 capability delegated alongside the UsbPeripheral in its factory.
/// The USB I/O owner retains it at runtime. No register-block reference is made.
pub(crate) struct RxFifoInterruptGate {
    _private: (),
}
impl RxFifoInterruptGate {
    pub(crate) fn new(_global: &stm32f7::stm32f722::OTG_FS_GLOBAL) -> Self {
        Self { _private: () }
    }

    /// Call after bus enable in init, or inside the USB RTIC resource lock.
    /// Defers RXFLVL only. IN, reset and suspend can still interrupt. EP0 shares
    /// the RX FIFO and cannot bypass a bulk packet blocked at its head.
    pub(crate) fn set_enabled(&mut self, enabled: bool) {
        // RM0431: OTG_FS_GINTMSK is an aligned, 32-bit RW register at +0x18.
        // Form only its raw address, without borrowing the driver's register block.
        let gintmsk = (stm32f7::stm32f722::OTG_FS_GLOBAL::ptr() as usize + 0x18) as *mut u32;
        // SAFETY: the factory consumes the PAC tokens and enables the bus before
        // use. This single-core device keeps its USB clock on. UsbIo's RTIC lock
        // excludes every runtime USB caller through this RMW. The pinned 0.4.0
        // driver writes GINTMSK only in enable(), before this capability is used.
        unsafe { set_rx_fifo_interrupt_enabled(gintmsk, enabled) };
        // Complete the device write before unlocking or returning from the IRQ.
        cortex_m::asm::dsb();
    }
}

/// # Safety
/// `gintmsk` must permit aligned 32-bit volatile reads/writes, with no concurrent
/// writer. The caller must complete the device write before releasing exclusion.
unsafe fn set_rx_fifo_interrupt_enabled(gintmsk: *mut u32, enabled: bool) {
    const RXFLVLM: u32 = 1 << 4;
    // SAFETY: the caller provides exclusive access to this RW register. GINTMSK
    // has no read/clear or write-one-to-clear fields. Preserve all other bits.
    unsafe {
        let mask = gintmsk.read_volatile();
        gintmsk.write_volatile(if enabled {
            mask | RXFLVLM
        } else {
            mask & !RXFLVLM
        });
    }
}

pub(crate) fn exchange_usb<B: super::usb::UsbBusHealth>(
    usb: &mut super::usb::UsbMavlink<'_, B>,
    frame: Option<PendingFrame<MavlinkFrame>>,
    set_rx_interrupt_enabled: impl FnOnce(bool),
) -> IoBatch {
    usb.with_rx_interrupt_gate(
        |usb| match frame {
            Some(frame) => IoBatch {
                accepted: usb.send(frame),
                ..IoBatch::default()
            },
            None => {
                usb.poll();
                // The existing USB adapter consumes at most one 64-byte packet
                // here, including bounded framing. Message decode/dispatch stays
                // worker-local. Bus polling has separate hardware wait constraints.
                let frame = usb.take_received();
                let pending = usb.poll();
                IoBatch {
                    usb: frame,
                    pending,
                    ..IoBatch::default()
                }
            }
        },
        set_rx_interrupt_enabled,
    )
}

pub(crate) enum F722StatusLed {
    Pd2(peripherals::ActiveLowLedPd2),
    Pa13(GeprcStatusLed),
}
impl F722StatusLed {
    pub(crate) fn toggle(&mut self) {
        match self {
            Self::Pd2(led) => led.toggle(),
            Self::Pa13(led) => led.toggle(),
        }
    }
}

pub(crate) struct GeprcStatusLed {
    port: stm32f7::stm32f722::GPIOA,
    is_high: bool,
}
impl GeprcStatusLed {
    pub(crate) fn new(rcc: &stm32f7::stm32f722::RCC, port: stm32f7::stm32f722::GPIOA) -> Self {
        rcc.ahb1enr().modify(|_, write| write.gpioaen().set_bit());
        port.moder().modify(|_, write| write.moder13().output());
        port.otyper().modify(|_, write| write.ot13().push_pull());
        port.ospeedr()
            .modify(|_, write| write.ospeedr13().low_speed());
        port.pupdr().modify(|_, write| write.pupdr13().floating());
        port.bsrr().write(|write| write.br13().set_bit());
        Self {
            port,
            is_high: false,
        }
    }
    fn toggle(&mut self) {
        self.is_high = !self.is_high;
        self.port.bsrr().write(|write| {
            if self.is_high {
                write.bs13().set_bit()
            } else {
                write.br13().set_bit()
            }
        });
    }
}

#[cfg(test)]
#[path = "../../tests/support/usb_irq.rs"]
mod usb_irq;