use super::pipe::{PipeErr, PipeTable, NO_DATA_STAGE};
use super::usbproto::*;

use core::convert::TryInto;
use log::{debug, error, info, trace};

// TODO: impl Drop for Device/Endpoint cleanup if any ends up being
// required.

// FIXME: once again, this doesn't belong here. The issue is that
// we're using `pipe_for`, which requires it.
use atsamd_hal::target_device::usb;

const MAX_DEVICES: usize = 16;

// TODO:
// This may be wrong. It may be 15 additional input + 15 additional
// output! cf §5.3.1.2 of USB 2.0.
const MAX_ENDPOINTS: usize = 16;

// How long to wait before talking to the device again after setting
// its address. cf §9.2.6.3 of USB 2.0
const SETTLE_DELAY: usize = 2;

#[derive(Copy, Clone, Debug, PartialEq)]
pub(crate) enum Error {
    PipeErr(PipeErr),
}
impl From<PipeErr> for Error {
    fn from(e: PipeErr) -> Self {
        Self::PipeErr(e)
    }
}

enum FSM {
    AddressSet,
    WaitForSettle(usize),
    GetConfigDescriptor,
    SetConfig,
    GetReport(usize),
    Steady,
}

pub(crate) struct DeviceTable {
    devices: [Option<Device>; MAX_DEVICES],
}
// TODO: Untie device address from table index. Right now it's wasting
// a table slot because addr 0 isn't used here. And rather than just
// putting in an offset, which can be forgotten, it's better to let
// something else handle address assignment.
impl DeviceTable {
    pub(crate) fn new<F>(millis: &'static F) -> Self
    where
        F: Fn() -> usize + 'static,
    {
        let mut devices: [Option<Device>; MAX_DEVICES] = {
            let mut devs: [core::mem::MaybeUninit<Option<Device>>; MAX_DEVICES] =
                unsafe { core::mem::MaybeUninit::uninit().assume_init() };
            for d in &mut devs[..] {
                unsafe { core::ptr::write(d.as_mut_ptr(), None) }
            }
            unsafe { core::mem::transmute(devs) }
        };
        devices[0] = Some(Device::new(0, 8, millis));
        Self { devices: devices }
    }

    /// Return the device at address `addr`.
    pub(crate) fn device_for(&mut self, addr: u8) -> Option<&mut Device> {
        if let Some(ref mut d) = self.devices[addr as usize] {
            Some(d)
        } else {
            None
        }
    }

    /// Allocate a device with the next available address.
    // TODO: get rid of the millis argument somehow, but the device
    // does need a way of tracking time for Settle reasons.
    pub(crate) fn next(
        &mut self,
        max_packet_size: u8,
        millis: &'static dyn Fn() -> usize,
    ) -> Option<&mut Device> {
        for i in 1..self.devices.len() {
            if self.devices[i].is_none() {
                let a = i.try_into().unwrap();
                let d = Device::new(a, max_packet_size, millis);
                self.devices[i] = Some(d);
                return self.device_for(a);
            }
        }
        None
    }

    /// Remove the device at address `addr`.
    pub(crate) fn remove(&mut self, addr: u8) -> Option<Device> {
        let v = core::mem::replace(&mut self.devices[addr as usize], None);
        v
    }

    pub(crate) fn run(&mut self, pipe_table: &mut PipeTable, host: &mut usb::HOST) {
        for i in 1..self.devices.len() {
            // TODO: Woof, this is ugly, but I'm not sure of a better
            // way to avoid mutably borrowing self twice.
            let mut remove_addr: Option<u8> = None;
            if let Some(ref mut d) = self.devices[i] {
                if let Err(e) = d.fsm(pipe_table, host) {
                    error!("Removing device {}: {:?}", d.addr, e);
                    remove_addr = Some(d.addr);
                } else {
                    remove_addr = None;
                }
            }

            if let Some(addr) = remove_addr {
                self.remove(addr);
            }
        }
    }
}

pub struct Device {
    pub addr: u8,
    pub max_packet_size: u8,
    pub endpoints: [Option<Endpoint>; MAX_ENDPOINTS],
    pub ep0: Endpoint,

    state: FSM,
    millis: &'static dyn Fn() -> usize,
}
impl Device {
    // TODO: get max packet size from device descriptor.
    pub fn new(addr: u8, max_packet_size: u8, millis: &'static dyn Fn() -> usize) -> Self {
        // Set up endpoints array with 0 as default control endpoint.
        let endpoints: [Option<Endpoint>; MAX_ENDPOINTS] = {
            let mut eps: [core::mem::MaybeUninit<Option<Endpoint>>; MAX_ENDPOINTS] =
                unsafe { core::mem::MaybeUninit::uninit().assume_init() };
            for ep in &mut eps[..] {
                unsafe { core::ptr::write(ep.as_mut_ptr(), None) }
            }
            unsafe { core::mem::transmute(eps) }
        };

        Self {
            addr: addr,
            max_packet_size: max_packet_size,
            endpoints: endpoints,
            ep0: Endpoint::new(
                addr,
                0,
                TransferType::Control,
                TransferDirection::In,
                max_packet_size,
            ),

            state: FSM::AddressSet,

            // TODO: This doesn't belong here. Ideally the current
            // time is passed in to the FSM routine.
            millis: millis,
        }
    }
}

impl Device {
    pub(crate) fn fsm(
        &mut self,
        pipe_table: &mut PipeTable,
        host: &mut usb::HOST,
    ) -> Result<(), Error> {
        match self.state {
            FSM::AddressSet => self.state = FSM::WaitForSettle((self.millis)() + SETTLE_DELAY),

            FSM::WaitForSettle(until) => {
                if (self.millis)() >= until {
                    // Dunno why we get the device descriptor a second time.
                    let mut pipe = pipe_table.pipe_for(host, &self.ep0);

                    let mut vol_descr =
                        ::vcell::VolatileCell::<DeviceDescriptor>::new(Default::default());
                    pipe.control_transfer(
                        &mut self.ep0,
                        RequestType::get_descr(),
                        RequestCode::GetDescriptor,
                        WValue::from((0, DescriptorType::Device as u8)),
                        0,
                        Some(&mut vol_descr),
                        self.millis,
                    )?;

                    let desc = vol_descr.get();
                    trace!(" -- devDesc: {:?}", desc);

                    self.state = FSM::GetConfigDescriptor
                }
            }

            FSM::GetConfigDescriptor => {
                // Get config descriptor with minimal data, to see how much we need to allocate for the full descriptor.
                let mut pipe = pipe_table.pipe_for(host, &self.ep0);

                let mut vol_descr =
                    ::vcell::VolatileCell::<ConfigurationDescriptor>::new(Default::default());
                pipe.control_transfer(
                    &mut self.ep0,
                    RequestType::get_descr(),
                    RequestCode::GetDescriptor,
                    WValue::from((0, DescriptorType::Configuration as u8)),
                    0,
                    Some(&mut vol_descr),
                    self.millis,
                )?;
                let desc = vol_descr.get();
                debug!("config: {:?}", desc);

                // TODO: do real allocation later.
                assert!(desc.w_total_length < 64);
                let buf: [u8; 64] = [0; 64];
                let mut tmp = &buf[..desc.w_total_length as usize];
                pipe.control_transfer(
                    &mut self.ep0,
                    RequestType::get_descr(),
                    RequestCode::GetDescriptor,
                    WValue::from((0, DescriptorType::Configuration as u8)),
                    0,
                    Some(&mut tmp),
                    self.millis,
                )?;

                self.state = FSM::SetConfig
            }

            FSM::SetConfig => {
                let mut pipe = pipe_table.pipe_for(host, &self.ep0);

                debug!("+++ setting configuration");
                let conf: u8 = 1;
                pipe.control_transfer(
                    &mut self.ep0,
                    RequestType::set(),
                    RequestCode::SetConfiguration,
                    WValue::from((conf, 0)),
                    0,
                    NO_DATA_STAGE,
                    self.millis,
                )?;
                debug!(" -- configuration set");

                debug!("+++ setting idle");
                pipe.control_transfer(
                    &mut self.ep0,
                    RequestType::from((
                        RequestDirection::HostToDevice,
                        RequestKind::Class,
                        RequestRecipient::Interface,
                    )),
                    RequestCode::GetInterface, // This is also idle, but can't have two enums with the same value.
                    WValue::from((0, 0)),
                    0,
                    NO_DATA_STAGE,
                    self.millis,
                )?;
                debug!(" -- idle set");

                debug!("+++ setting report");
                let mut report: u8 = 0;
                pipe.control_transfer(
                    &mut self.ep0,
                    RequestType::from((
                        RequestDirection::HostToDevice,
                        RequestKind::Class,
                        RequestRecipient::Interface,
                    )),
                    RequestCode::SetConfiguration,
                    WValue::from((0, 2)),
                    0,
                    Some(&mut report),
                    self.millis,
                )?;
                debug!(" -- report set");

                // Stub in some endpoints until we can parse the
                // configuration descriptor.
                self.endpoints[1] = Some(Endpoint::new(
                    self.addr,
                    1,
                    TransferType::Interrupt,
                    TransferDirection::In,
                    8,
                ));
                self.endpoints[2] = Some(Endpoint::new(
                    self.addr,
                    2,
                    TransferType::Interrupt,
                    TransferDirection::In,
                    8,
                ));
                self.state = FSM::GetReport(2)
            }

            FSM::GetReport(0) => self.state = FSM::Steady,

            FSM::GetReport(count) => {
                debug!("+++ getting report {}", count);

                // For now, just do an IN transfer to see if we can
                // get some keyboard reports without further setup.

                // EP 1 is boot proto keyboard.
                self.read_report(pipe_table, host, 1);

                // EP 2 is consumer control keys.
                self.read_report(pipe_table, host, 2);

                self.state = FSM::GetReport(count)
            }

            FSM::Steady => {}
        }
        Ok(())
    }

    fn read_report(&mut self, pipe_table: &mut PipeTable, host: &mut usb::HOST, id: u8) {
        if let Some(ref mut ep) = self.endpoints[id as usize] {
            let mut pipe = pipe_table.pipe_for(host, ep);
            let mut buf: [u8; 8] = [0; 8];
            match pipe.in_transfer(ep, &mut buf, 15, self.millis) {
                Ok(bytes_received) => info!("report {}: {} - {:?}", id, bytes_received, buf),

                Err(PipeErr::Flow) => return,

                Err(e) => trace!("error {}: {:?}", id, e),
            }
        } else {
            error!("endpoint {} doesn't exist!", id)
        }
    }
}

// TransferType (INTERRUPT)
// Direction (IN)
pub struct Endpoint {
    // This just points back to the address because we need to know it
    // for all endpoint operations, but we don't want to pass the
    // address struct (which contains all endpoints) around.
    pub addr: u8,
    pub num: u8,
    pub transfer_type: TransferType,
    pub direction: TransferDirection,
    pub in_toggle: bool,
    pub out_toggle: bool,
    pub max_packet_size: u8,
}

// cf §9.6.6 of USB 2.0
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum TransferDirection {
    Out,
    In,
}

// ibid
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum TransferType {
    Control = 0,
    Isochronous = 1,
    Bulk = 2,
    Interrupt = 3,
}

impl Endpoint {
    // TODO: direction is ignored on control endpoints. Try to remove
    // it from the API in those cases as well.
    pub fn new(
        addr: u8,
        num: u8,
        transfer_type: TransferType,
        direction: TransferDirection,
        max_packet_size: u8,
    ) -> Self {
        Self {
            addr: addr,
            num: num,
            transfer_type: transfer_type,
            direction: direction,
            in_toggle: false,
            out_toggle: false,
            max_packet_size: max_packet_size,
        }
    }
}