#![no_std]
#![allow(dead_code)]

mod pipe;
mod usbproto;

use pipe::{DataBuf, PipeErr, PipeTable, USBPipeType, USBToken};
use rb::{Reader, RingBuffer, Writer};
use usbproto::*;

use atsamd_hal::{
    calibration::{usb_transn_cal, usb_transp_cal, usb_trim_cal},
    clock::{ClockGenId, ClockSource, GenericClockController},
    gpio::{self, Floating, Input, OpenDrain, Output},
    target_device::{PM, USB},
};
use embedded_hal::digital::v2::OutputPin;
use log::{debug, error, trace, warn};

#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Event {
    Error,
    Detached,
    Attached,
}
type Events = RingBuffer<Event>;
type EventReader = Reader<'static, Event>;
type EventWriter = Writer<'static, Event>;

#[derive(Clone, Copy, Debug, PartialEq)]
enum DetachedState {
    Initialize,
    WaitForDevice,
    Illegal,
}

#[derive(Clone, Copy, Debug, PartialEq)]
enum AttachedState {
    WaitForSettle,
    WaitResetComplete,
    WaitSOF,
}

#[derive(Clone, Copy, Debug, PartialEq)]
enum SteadyState {
    Configuring,
    Running,
    Error,
}

#[derive(Clone, Copy, Debug, PartialEq)]
enum TaskState {
    Detached(DetachedState),
    Attached(AttachedState),
    Steady(SteadyState),
}

const MAX_DEVICES: usize = 16;
const SETTLE_DELAY: usize = 205; // Delay in sec/1024
const NAK_LIMIT: usize = 15;

static mut EVENTS: Events = Events::new(Event::Error);
// FIXME: this is just for testing. The enum needs to be
// thread-safe if this is the way we're going.
static mut LATEST_EVENT: Event = Event::Detached;

pub struct USBHost<F>
where
    F: Fn() -> usize + 'static,
{
    usb: USB,

    events: EventReader,
    task_state: TaskState,
    delay: usize,

    // Need chunk of RAM for USB pipes, which gets used with DESCADD
    // register.
    pipe_table: PipeTable,

    // need sof 1kHz pad?
    _sof_pad: gpio::Pa23<gpio::PfG>,
    _dm_pad: gpio::Pa24<gpio::PfG>,
    _dp_pad: gpio::Pa25<gpio::PfG>,
    host_enable_pin: Option<gpio::Pa28<Output<OpenDrain>>>,

    // To get current milliseconds.
    millis: &'static F,
}

impl<F> USBHost<F>
where
    F: Fn() -> usize + 'static,
{
    pub fn new(
        usb: USB,
        sof_pin: gpio::Pa23<Input<Floating>>,
        dm_pin: gpio::Pa24<Input<Floating>>,
        dp_pin: gpio::Pa25<Input<Floating>>,
        host_enable_pin: Option<gpio::Pa28<Input<Floating>>>,
        port: &mut gpio::Port,
        clocks: &mut GenericClockController,
        pm: &mut PM,
        millis: &'static F,
    ) -> (Self, impl FnMut()) {
        let (eventr, mut eventw) = unsafe { EVENTS.split() };
        let mut rc = Self {
            usb: usb,
            events: eventr,
            task_state: TaskState::Detached(DetachedState::Initialize),
            delay: 0,
            pipe_table: PipeTable::new(),

            _sof_pad: sof_pin.into_function_g(port),
            _dm_pad: dm_pin.into_function_g(port),
            _dp_pad: dp_pin.into_function_g(port),
            host_enable_pin: None,

            millis: millis,
        };

        if let Some(he_pin) = host_enable_pin {
            rc.host_enable_pin = Some(he_pin.into_open_drain_output(port));
        }

        pm.apbbmask.modify(|_, w| w.usb_().set_bit());

        // Set up USB clock from 48MHz source on generic clock 6.
        clocks.configure_gclk_divider_and_source(ClockGenId::GCLK6, 1, ClockSource::DFLL48M, false);
        let gclk6 = clocks
            .get_gclk(ClockGenId::GCLK6)
            .expect("Could not get clock 6");
        clocks.usb(&gclk6);

        let usbp = &rc.usb as *const _ as usize;
        (rc, move || handler(usbp, &mut eventw))
    }

    pub fn reset_periph(&mut self) {
        debug!("resetting usb");
        // Reset the USB peripheral and wait for sync.
        self.usb.host().ctrla.write(|w| w.swrst().set_bit());
        while self.usb.host().syncbusy.read().swrst().bit_is_set() {}

        // Specify host mode.
        self.usb.host().ctrla.modify(|_, w| w.mode().host());

        // Unsafe due to use of raw bits method.
        unsafe {
            self.usb.host().padcal.write(|w| {
                w.transn().bits(usb_transn_cal());
                w.transp().bits(usb_transp_cal());
                w.trim().bits(usb_trim_cal())
            });
        }

        // Use normal, which is 0 and apparently means low-and-full capable
        self.usb.host().ctrlb.modify(|_, w| w.spdconf().normal());
        // According to docs, 1,2,3 are reserved, but .fs returns 3
        //self.usb.host().ctrlb.modify(|_, w| w.spdconf().fs());

        self.usb.host().ctrla.modify(|_, w| w.runstdby().set_bit()); // keep usb clock running in standby.

        // Set address of USB SRAM.
        // Unsafe due to use of raw bits method.
        unsafe {
            self.usb
                .host()
                .descadd
                .write(|w| w.bits(&self.pipe_table as *const _ as u32));
        }

        if let Some(he_pin) = &mut self.host_enable_pin {
            he_pin.set_high().expect("turning on usb host enable pin");
        }

        self.usb.host().intenset.write(|w| {
            w.wakeup().set_bit();
            w.dconn().set_bit();
            w.ddisc().set_bit()
        });

        self.usb.host().ctrla.modify(|_, w| w.enable().set_bit());
        while self.usb.host().syncbusy.read().enable().bit_is_set() {}

        // Set VBUS OK to allow host operation.
        self.usb.host().ctrlb.modify(|_, w| w.vbusok().set_bit());
        debug!("...done");
    }

    pub fn task(&mut self) {
        static mut LAST_EVENT: Event = Event::Error;
        unsafe {
            if LAST_EVENT != LATEST_EVENT {
                trace!("new event: {:?}", LATEST_EVENT);
            }
        }

        static mut LAST_TASK_STATE: TaskState = TaskState::Detached(DetachedState::Illegal);
        self.task_state = match unsafe { LATEST_EVENT } {
            Event::Error => TaskState::Detached(DetachedState::Illegal),
            Event::Detached => {
                if let TaskState::Detached(_) = self.task_state {
                    self.task_state
                } else {
                    TaskState::Detached(DetachedState::Initialize)
                }
            }
            Event::Attached => {
                if let TaskState::Detached(_) = self.task_state {
                    self.delay = (self.millis)() + SETTLE_DELAY;
                    TaskState::Attached(AttachedState::WaitForSettle)
                } else {
                    self.task_state
                }
            }
        };

        static mut LAST_CBITS: u16 = 0;
        static mut LAST_FLAGS: u16 = 0;
        let cbits = self.usb.host().ctrlb.read().bits();
        let bits = self.usb.host().intflag.read().bits();
        unsafe {
            if LAST_CBITS != cbits || LAST_FLAGS != bits || LAST_TASK_STATE != self.task_state {
                trace!(
                    "cb: {:x}, f: {:x} changing state {:?} -> {:?}",
                    cbits,
                    bits,
                    LAST_TASK_STATE,
                    self.task_state,
                );
            }
            LAST_CBITS = cbits;
            LAST_FLAGS = bits;
            LAST_TASK_STATE = self.task_state
        };

        if let Some(_event) = self.events.shift() {
            // trace!("Found event: {:?}", event);
            // self.task_state = match event {
            //     Event::None => TaskState::Detached(DetachedState::Illegal),
            //     Event::Detached => {
            //         if let TaskState::Detached(_) = self.task_state {
            //             self.task_state
            //         } else {
            //             TaskState::Detached(DetachedState::Initialize)
            //         }
            //     }
            //     Event::Attached => {
            //         if let TaskState::Detached(_) = self.task_state {
            //             self.delay = self.millis() + SETTLE_DELAY;
            //             TaskState::Attached(AttachedState::WaitForSettle)
            //         } else {
            //             self.task_state
            //         }
            //     }
            // };
        }

        self.poll_devices();
        self.fsm();

        unsafe {
            LAST_EVENT = LATEST_EVENT;
        }
    }

    fn poll_devices(&mut self) {
        for _ in 0..MAX_DEVICES {}
    }

    fn fsm(&mut self) {
        // respond to events from interrupt.
        match self.task_state {
            TaskState::Detached(s) => self.detached_fsm(s),
            TaskState::Attached(s) => self.attached_fsm(s),
            TaskState::Steady(s) => self.steady_fsm(s),
        };
    }

    fn detached_fsm(&mut self, s: DetachedState) {
        match s {
            DetachedState::Initialize => {
                self.reset_periph();
                // TODO: Free resources.

                self.task_state = TaskState::Detached(DetachedState::WaitForDevice);
            }

            // Do nothing state. Just wait for an interrupt to come in
            // saying we have a device attached.
            DetachedState::WaitForDevice => {}

            // TODO: should probably reset everything if we end up here somehow.
            DetachedState::Illegal => {}
        }
    }

    fn attached_fsm(&mut self, s: AttachedState) {
        match s {
            AttachedState::WaitForSettle => {
                if (self.millis)() >= self.delay {
                    self.usb.host().ctrlb.modify(|_, w| w.busreset().set_bit());
                    self.task_state = TaskState::Attached(AttachedState::WaitResetComplete);
                }
            }

            AttachedState::WaitResetComplete => {
                if self.usb.host().intflag.read().rst().bit_is_set() {
                    trace!("reset was sent");
                    self.usb.host().intflag.write(|w| w.rst().set_bit());

                    // Make sure we always have a control pipe set up.
                    self.init_pipe0();

                    // Seems unneccesary, since SOFE will be set
                    // immediately after reset according to §32.6.3.3.
                    self.usb.host().ctrlb.modify(|_, w| w.sofe().set_bit());
                    // USB spec requires 20ms of SOF after bus reset.
                    self.delay = (self.millis)() + 20;
                    self.task_state = TaskState::Attached(AttachedState::WaitSOF);
                }
            }

            AttachedState::WaitSOF => {
                if self.usb.host().intflag.read().hsof().bit_is_set() {
                    self.usb.host().intflag.write(|w| w.hsof().set_bit());
                    if (self.millis)() >= self.delay {
                        self.task_state = TaskState::Steady(SteadyState::Configuring);
                    }
                }
            }
        }
    }

    fn steady_fsm(&mut self, s: SteadyState) {
        match s {
            SteadyState::Configuring => {
                let low_speed = 0;
                self.task_state = match self.configure_dev(0, 0, low_speed) {
                    Ok(_) => TaskState::Steady(SteadyState::Running),
                    Err(e) => {
                        warn!("Enumeration error: {:?}", e);
                        TaskState::Steady(SteadyState::Error)
                    }
                }
            }

            SteadyState::Running => {}

            SteadyState::Error => {}
        }
    }

    fn configure_dev(&mut self, _parent: u32, _port: u32, _low_speed: u32) -> Result<(), PipeErr> {
        // addr: 0x20007774
        let tmp: USBDeviceDescriptor = Default::default();
        // addr: 0x20007788
        let mut vol_descr = ::vcell::VolatileCell::new(tmp);
        self.control_req(
            0,
            0,
            BMRequestType::get_descr(),
            USBRequest::GetDescriptor,
            WValue::from((0, USBDescriptor::Device as u8)),
            0,
            Some(DataBuf::from(&mut vol_descr)),
        )?;

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

        // Assign address to this device and:
        //  - Stash bMaxPacketSize
        // Then SET_ADDRESS(newAddr)
        let new_address: u8 = 1;
        debug!("Setting address to {}.", new_address);
        self.control_req(
            0,
            0,
            BMRequestType::set(),
            USBRequest::SetAddress,
            WValue::from((new_address, 0)),
            0,
            None,
        )?;
        // Delay according to §9.2.6.3 of USB 2.0
        let until = (self.millis)() + 300;
        while (self.millis)() < until {}

        debug!("getting config with array");
        //let tmp: USBConfigurationDescriptor = Default::default();
        let mut tmp: [u8; 9] = [0; 9];
        //let vol_descr = ::vcell::VolatileCell::new(tmp);
        self.control_req(
            new_address,
            0,
            BMRequestType::get_descr(),
            USBRequest::GetConfiguration,
            WValue::from((0, 0)),
            0,
            Some(DataBuf::from(&mut tmp)),
        )?;

        //let desc = vol_descr.get();
        debug!("cdesc.len: {}, type: {}", tmp[0], tmp[1]);

        // Once addressed, SET_CONFIGURATION(0)
        debug!("+++ setting configuration");
        let conf: u8 = 0;
        self.control_req(
            new_address,
            0,
            BMRequestType::set(),
            USBRequest::SetConfiguration,
            WValue::from((conf, 0)),
            0,
            None,
        )?;
        debug!(" -- configuration set");

        // Now we should be able to access it normally.

        Ok(())
    }

    fn control_req(
        &mut self,
        addr: u8,
        ep: u8,
        bm_request_type: BMRequestType,
        b_request: USBRequest,
        w_value: WValue,
        w_index: u16,
        buf: Option<DataBuf>,
    ) -> Result<(), PipeErr> {
        if let Some(ref b) = buf {
            assert!(b.ptr as usize & 0x3 == 0);
            assert!(b.len <= 65_535);
        }

        /*
         * Setup stage.
         */
        let mut setup_packet = USBSetupPacket {
            bm_request_type: bm_request_type,
            b_request: b_request,
            w_value: w_value,
            w_index: w_index,
            w_length: match buf {
                None => 0,
                Some(ref b) => b.len as u16,
            },
        };
        let mut pipe = self.pipe_table.pipe_for(self.usb.host_mut(), addr, ep);
        pipe.send(
            USBToken::Setup,
            &DataBuf::from(&mut setup_packet),
            NAK_LIMIT,
            self.millis,
        )?;

        /*
         * Data stage.
         */
        if let Some(b) = buf {
            match bm_request_type.direction() {
                USBSetupDirection::DeviceToHost => {
                    trace!("buf0: {:?}", &b);
                    pipe.in_transfer(&b, NAK_LIMIT, self.millis)?;
                    trace!("buf1: {:?}", &b);
                }

                USBSetupDirection::HostToDevice => {
                    debug!("Should OUT for {}b", b.len);
                }
            }
        }

        /*
         * Status stage.
         */
        pipe.desc.bank0.pcksize.write(|w| {
            // FIXME: see note in `Pipe.send`.
            unsafe { w.bits(0) }
        });

        // PSTATUSSET.DTGL set -- TODO: figure out if this is
        // necessary.
        pipe.regs.statusset.write(|w| w.dtgl().set_bit());

        let token = match bm_request_type.direction() {
            USBSetupDirection::DeviceToHost => USBToken::Out,
            USBSetupDirection::HostToDevice => USBToken::In,
        };

        // TODO: should probably make `pipe.send` have optional
        // `DataBuf`, rather than exposing `dispatch_retries`.
        trace!("dispatching status stage");
        pipe.dispatch_retries(token, NAK_LIMIT, self.millis)?;
        Ok(())
    }

    // Set up a default pipe for the control endpoint 0 on pipe 0.
    fn init_pipe0(&mut self) {
        let speed = self.usb.host().status.read().speed().bits();
        let pipe = self.pipe_table.pipe_for(self.usb.host_mut(), 0, 0);
        pipe.regs.cfg.write(|w| {
            unsafe { w.ptype().bits(USBPipeType::Control as u8) };
            w.bk().clear_bit()
        });
        pipe.desc.bank0.pcksize.write(|w| match speed {
            0 => w.size().bytes64(),
            _ => w.size().bytes8(),
        });
    }
}

pub fn handler(usbp: usize, events: &mut EventWriter) {
    let usb: &mut USB = unsafe { core::mem::transmute(usbp) };
    let flags = usb.host().intflag.read();

    trace!("USB - {:x}", flags.bits());

    let mut unshift_event = |e: Event| {
        unsafe { LATEST_EVENT = e };
        if let Err(_) = events.unshift(e) {
            error!("Couldn't write USB event to queue.");
        }
    };

    if flags.hsof().bit_is_set() {
        trace!(" +hsof");
        usb.host().intflag.write(|w| w.hsof().set_bit());
        unshift_event(Event::Attached);
    }

    if flags.rst().bit_is_set() {
        // We seem to get this whenever a device attaches/detaches.
        trace!(" +rst");
        usb.host().intflag.write(|w| w.rst().set_bit());
        unshift_event(Event::Detached);
    }

    if flags.uprsm().bit_is_set() {
        trace!(" +uprsm");
        usb.host().intflag.write(|w| w.uprsm().set_bit());
        unshift_event(Event::Detached);
    }

    if flags.dnrsm().bit_is_set() {
        trace!(" +dnrsm");
        usb.host().intflag.write(|w| w.dnrsm().set_bit());
        unshift_event(Event::Detached);
    }

    if flags.wakeup().bit_is_set() {
        // §32.8.5.8 - since VBUSOK is set, then this happens when a
        // device is connected.
        trace!(" +wakeup");
        usb.host().intflag.write(|w| w.wakeup().set_bit());
        unshift_event(Event::Attached);
    }

    if flags.ramacer().bit_is_set() {
        trace!(" +ramacer");
        usb.host().intflag.write(|w| w.ramacer().set_bit());
        unshift_event(Event::Detached);
    }

    if flags.dconn().bit_is_set() {
        trace!(" +dconn");
        usb.host().intflag.write(|w| w.dconn().set_bit());
        usb.host().intenclr.write(|w| w.dconn().set_bit());
        usb.host().intflag.write(|w| w.ddisc().set_bit());
        usb.host().intenset.write(|w| w.ddisc().set_bit());
        usb.host().intflag.write(|w| w.dconn().set_bit());
        unshift_event(Event::Attached);
    }

    if flags.ddisc().bit_is_set() {
        trace!(" +ddisc");
        usb.host().intflag.write(|w| w.ddisc().set_bit());
        usb.host().intenclr.write(|w| w.ddisc().set_bit());
        //			// Stop reset signal, in case of disconnection during reset
        //			uhd_stop_reset(); // nothing on samd21
        usb.host().intflag.write(|w| w.dconn().set_bit());
        usb.host().intenset.write(|w| w.dconn().set_bit());
        usb.host().intflag.write(|w| w.ddisc().set_bit());
        unshift_event(Event::Detached);
    }
}