pub mod addr;
pub mod ctrl_pipe;
pub mod ext_reg;
pub mod pck_size;
pub mod status_bk;
pub mod status_pipe;

use addr::Addr;
use ctrl_pipe::CtrlPipe;
use ext_reg::ExtReg;
use pck_size::PckSize;
use status_bk::StatusBk;
use status_pipe::StatusPipe;

use core::convert::TryInto;
use log::info;

use atsamd_hal::target_device::usb::{
    self,
    host::{BINTERVAL, PCFG, PINTFLAG, PSTATUS, PSTATUSCLR, PSTATUSSET},
};

// TODO: verify this timeout against §9.2.6.1 of USB 2.0 spec.
const USB_TIMEOUT: usize = 5 * 1024; // 5 Seconds

// samd21 only supports 8 pipes.
const MAX_PIPES: usize = 8;

#[derive(Copy, Clone, Debug, PartialEq)]
pub(crate) enum PipeErr {
    InvalidPipe,
    InvalidToken,
    Stall,
    TransferFail,
    Flow,
    HWTimeout,
    DataToggle,
    SWTimeout,
    Other,
}
pub(crate) struct PipeTable {
    tbl: [PipeDesc; MAX_PIPES],
}

impl PipeTable {
    pub(crate) fn new() -> Self {
        Self {
            tbl: [PipeDesc::new(); MAX_PIPES],
        }
    }

    pub(crate) fn pipe_for<'a, 'b>(
        &'a mut self,
        host: &'b mut usb::HOST,
        addr: u8,
        ep: u8,
    ) -> Pipe<'a, 'b> {
        // Just use two pipes for now. 0 is always for control
        // endpoints, 1 for everything else.
        //
        // TODO: cache in-use pipes and return them without init if
        // possible.
        let i = if ep == 0 { 0 } else { 1 };

        let pregs = PipeRegs::from(host, i);
        let pdesc = &mut self.tbl[i];

        info!("setting paddr of pipe {} to {}:{}", i, addr, ep);
        info!("cpipe0: {:x}", pdesc.bank0.ctrl_pipe.read().bits());
        pdesc.bank0.ctrl_pipe.write(|w| {
            w.pdaddr().set_addr(addr);
            w.pepnum().set_epnum(ep)
        });
        info!("cpipe1: {:x}", pdesc.bank0.ctrl_pipe.read().bits());
        Pipe {
            num: i,
            regs: pregs,
            desc: pdesc,
        }
    }
}

// TODO: hide regs/desc fields. Needed right now for init_pipe0.
pub(crate) struct Pipe<'a, 'b> {
    num: usize,
    pub(crate) regs: PipeRegs<'b>,
    pub(crate) desc: &'a mut PipeDesc,
}
impl Pipe<'_, '_> {
    pub(crate) fn send(
        &mut self,
        token: USBToken,
        buf: &DataBuf,
        nak_limit: usize,
        millis: &dyn Fn() -> usize,
    ) -> Result<(), PipeErr> {
        // Data needs to be word aligned.
        assert!((buf.ptr as u32) & 0x3 == 0);
        // byte_count section of register is 14 bits.
        assert!(buf.len < 16_384);

        info!("p{}: sending {:?}", self.num, buf);

        self.desc
            .bank0
            .addr
            .write(|w| unsafe { w.addr().bits(buf.ptr as u32) });
        // configure packet size PCKSIZE.SIZE
        self.desc.bank0.pcksize.write(|w| {
            unsafe { w.byte_count().bits(buf.len as u16) };
            unsafe { w.multi_packet_size().bits(0) }
        });

        self.dispatch_retries(token, nak_limit, millis)
    }

    pub(crate) fn in_transfer(
        &mut self,
        buf: &DataBuf,
        nak_limit: usize,
        millis: &dyn Fn() -> usize,
    ) -> Result<(), PipeErr> {
        // Data needs to be word aligned.
        assert!((buf.ptr as u32) & 0x3 == 0);
        // byte_count section of register is 14 bits.
        assert!(buf.len < 16_384);

        info!("p{}: Should IN for {}b.", self.num, buf.len);
        self.desc.bank0.pcksize.write(|w| {
            unsafe { w.byte_count().bits(buf.len as u16) };
            unsafe { w.multi_packet_size().bits(0) }
        });

        let mut bytes_received = 0;
        while bytes_received < buf.len {
            // Update buffer pointer.
            //
            // FIXME: This only works when the packet size is a word
            // multiple, since `addr` requires word-aligned pointers.
            self.desc
                .bank0
                .addr
                .write(|w| unsafe { w.addr().bits(buf.ptr as u32 + bytes_received as u32) });
            self.regs.statusclr.write(|w| w.bk0rdy().set_bit());

            self.dispatch_retries(USBToken::In, nak_limit, millis)?;
            bytes_received += self.desc.bank0.pcksize.read().byte_count().bits() as usize;
            assert!(bytes_received <= buf.len);
            info!("!! read {} of {}", bytes_received, buf.len);
        }
        self.regs.statusset.write(|w| w.pfreeze().set_bit());

        if self.regs.status.read().dtgl().bit_is_set() {
            self.regs.statusset.write(|w| w.dtgl().set_bit());
        } else {
            self.regs.statusclr.write(|w| unsafe {
                // No function for this. FIXME: need to patch the SVD for PSTATUSCLR.DTGL at bit0
                w.bits(1)
            });
        }
        Ok(())
    }

    pub(crate) fn dispatch_retries(
        &mut self,
        token: USBToken,
        retries: usize,
        millis: &dyn Fn() -> usize,
    ) -> Result<(), PipeErr> {
        assert!(retries > 0);

        info!("initial regs");
        self.log_regs();

        let until = millis() + USB_TIMEOUT;
        let mut last_result: Result<(), PipeErr> = Err(PipeErr::SWTimeout);
        let mut naks = 0;
        while naks <= retries {
            info!("p{}: dispatch {:?} retry {}", self.num, token, naks);

            self.dispatch_packet(token);
            last_result = self.dispatch_result(token, until, millis);
            match last_result {
                Ok(_) => return Ok(()),
                // FIXME: handle datatoggle
                Err(PipeErr::DataToggle) => {
                    if self.regs.status.read().dtgl().bit_is_set() {
                        self.regs.statusset.write(|w| w.dtgl().set_bit());
                    } else {
                        self.regs.statusclr.write(|w| unsafe {
                            // No function for this. FIXME: need to patch the SVD for PSTATUSCLR.DTGL at bit0
                            w.bits(1)
                        });
                    }
                }
                Err(PipeErr::SWTimeout) => break,
                Err(PipeErr::Stall) => break,
                Err(_) => naks += 1,
            }
        }

        last_result
    }

    fn log_regs(&self) {
        // Pipe regs
        let cfg = self.regs.cfg.read().bits();
        let bin = self.regs.binterval.read().bits();
        let sts = self.regs.status.read().bits();
        let ifl = self.regs.intflag.read().bits();
        info!(
            "p{}: cfg: {:x}, bin: {:x}, sts: {:x}, ifl: {:x}",
            self.num, cfg, bin, sts, ifl
        );

        // Pipe RAM regs
        let adr = self.desc.bank0.addr.read().bits();
        let pks = self.desc.bank0.pcksize.read().bits();
        let ext = self.desc.bank0.extreg.read().bits();
        let sbk = self.desc.bank0.status_bk.read().bits();
        let hcp = self.desc.bank0.ctrl_pipe.read().bits();
        let spi = self.desc.bank0.status_pipe.read().bits();
        info!(
            "p{}: adr: {:x}, pks: {:x}, ext: {:x}, sbk: {:x}, hcp: {:x}, spi: {:x}",
            self.num, adr, pks, ext, sbk, hcp, spi
        );
    }

    fn dispatch_packet(&mut self, token: USBToken) {
        self.regs
            .cfg
            .modify(|_, w| unsafe { w.ptoken().bits(token as u8) });
        match token {
            USBToken::Setup => {
                self.regs.intflag.write(|w| w.txstp().set_bit());
                self.regs.statusset.write(|w| w.bk0rdy().set_bit());
            }
            USBToken::In => self.regs.statusclr.write(|w| w.bk0rdy().set_bit()),
            USBToken::Out => {
                self.regs.intflag.write(|w| w.trcpt0().set_bit());
                self.regs.statusset.write(|w| w.bk0rdy().set_bit());
            }
            _ => {}
        }
        self.regs.statusclr.write(|w| w.pfreeze().set_bit());
    }

    fn dispatch_result(
        &mut self,
        token: USBToken,
        until: usize,
        millis: &dyn Fn() -> usize,
    ) -> Result<(), PipeErr> {
        while millis() <= until {
            if self.is_transfer_complete(token)? {
                return Ok(());
            } else if self.regs.intflag.read().stall().bit_is_set() {
                info!("stall");
                self.log_regs();
                self.regs.intflag.write(|w| w.stall().set_bit());
                return Err(PipeErr::Stall);
            } else if self.regs.intflag.read().trfail().bit_is_set() {
                info!("trfail");
                self.log_regs();
                self.regs.intflag.write(|w| w.trfail().set_bit());
                return Err(PipeErr::TransferFail);
            } else if self.desc.bank0.status_bk.read().errorflow().bit_is_set() {
                info!("errorflow");
                self.log_regs();
                self.desc
                    .bank0
                    .status_bk
                    .write(|w| w.errorflow().clear_bit());
                return Err(PipeErr::Flow);
            } else if self.desc.bank0.status_pipe.read().touter().bit_is_set() {
                info!("touter");
                self.log_regs();
                self.desc
                    .bank0
                    .status_pipe
                    .write(|w| w.touter().clear_bit());
                return Err(PipeErr::HWTimeout);
            } else if self.desc.bank0.status_pipe.read().dtgler().bit_is_set() {
                info!("dtgler");
                self.log_regs();
                self.desc
                    .bank0
                    .status_pipe
                    .write(|w| w.dtgler().clear_bit());
                return Err(PipeErr::DataToggle);
            }
        }
        info!("swtimeout");
        self.log_regs();
        Err(PipeErr::SWTimeout)
    }

    fn is_transfer_complete(&mut self, token: USBToken) -> Result<bool, PipeErr> {
        match token {
            USBToken::Setup => {
                if self.regs.intflag.read().txstp().bit_is_set() {
                    self.regs.intflag.write(|w| w.txstp().set_bit());
                    self.regs.statusset.write(|w| w.pfreeze().set_bit());
                    Ok(true)
                } else {
                    Ok(false)
                }
            }
            USBToken::In => {
                if self.regs.intflag.read().trcpt0().bit_is_set() {
                    self.regs.intflag.write(|w| w.trcpt0().set_bit());
                    self.regs.statusset.write(|w| w.pfreeze().set_bit());
                    Ok(true)
                } else {
                    Ok(false)
                }
            }
            USBToken::Out => {
                if self.regs.intflag.read().trcpt0().bit_is_set() {
                    self.regs.intflag.write(|w| w.trcpt0().set_bit());
                    self.regs.statusset.write(|w| w.pfreeze().set_bit());
                    Ok(true)
                } else {
                    Ok(false)
                }
            }
            _ => Err(PipeErr::InvalidToken),
        }
    }
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub(crate) enum USBToken {
    Setup = 0,
    In = 1,
    Out = 2,
    Reserved = 3,
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub(crate) enum USBPipeType {
    Disabled = 0x0,
    Control = 0x1,
    ISO = 0x2,
    Bulk = 0x3,
    Interrupt = 0x4,
    Extended = 0x5,
    _Reserved0 = 0x06,
    _Reserved1 = 0x07,
}

pub(crate) struct DataBuf<'a> {
    pub(crate) ptr: *mut u8,
    pub(crate) len: usize,
    _marker: core::marker::PhantomData<&'a ()>,
}
impl DataBuf<'_> {}

impl core::fmt::Debug for DataBuf<'_> {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        write!(f, "DataBuf {{ len: {}, ptr: [", self.len)?;
        for i in 0..self.len {
            write!(f, " {:x}", unsafe {
                *self.ptr.offset(i.try_into().unwrap())
            })?;
        }
        write!(f, " ] }}")
    }
}

impl<'a, T> From<&'a mut T> for DataBuf<'a> {
    fn from(v: &'a mut T) -> Self {
        Self {
            ptr: v as *mut T as *mut u8,
            len: core::mem::size_of::<T>(),
            _marker: core::marker::PhantomData,
        }
    }
}

pub(crate) struct PipeRegs<'a> {
    pub(crate) cfg: &'a mut PCFG,
    pub(crate) binterval: &'a mut BINTERVAL,
    pub(crate) statusclr: &'a mut PSTATUSCLR,
    pub(crate) statusset: &'a mut PSTATUSSET,
    pub(crate) status: &'a mut PSTATUS,
    pub(crate) intflag: &'a mut PINTFLAG,
}
impl<'a> PipeRegs<'a> {
    pub(crate) fn from(host: &'a mut usb::HOST, i: usize) -> PipeRegs {
        assert!(i < MAX_PIPES);
        match i {
            0 => Self {
                cfg: &mut host.pcfg0,
                binterval: &mut host.binterval0,
                statusclr: &mut host.pstatusclr0,
                statusset: &mut host.pstatusset0,
                status: &mut host.pstatus0,
                intflag: &mut host.pintflag0,
            },
            1 => Self {
                cfg: &mut host.pcfg1,
                binterval: &mut host.binterval1,
                statusclr: &mut host.pstatusclr1,
                statusset: &mut host.pstatusset1,
                status: &mut host.pstatus1,
                intflag: &mut host.pintflag1,
            },
            2 => Self {
                cfg: &mut host.pcfg2,
                binterval: &mut host.binterval2,
                statusclr: &mut host.pstatusclr2,
                statusset: &mut host.pstatusset2,
                status: &mut host.pstatus2,
                intflag: &mut host.pintflag2,
            },
            3 => Self {
                cfg: &mut host.pcfg3,
                binterval: &mut host.binterval3,
                statusclr: &mut host.pstatusclr3,
                statusset: &mut host.pstatusset3,
                status: &mut host.pstatus3,
                intflag: &mut host.pintflag3,
            },
            4 => Self {
                cfg: &mut host.pcfg4,
                binterval: &mut host.binterval4,
                statusclr: &mut host.pstatusclr4,
                statusset: &mut host.pstatusset4,
                status: &mut host.pstatus4,
                intflag: &mut host.pintflag4,
            },
            5 => Self {
                cfg: &mut host.pcfg5,
                binterval: &mut host.binterval5,
                statusclr: &mut host.pstatusclr5,
                statusset: &mut host.pstatusset5,
                status: &mut host.pstatus5,
                intflag: &mut host.pintflag5,
            },
            6 => Self {
                cfg: &mut host.pcfg6,
                binterval: &mut host.binterval6,
                statusclr: &mut host.pstatusclr6,
                statusset: &mut host.pstatusset6,
                status: &mut host.pstatus6,
                intflag: &mut host.pintflag6,
            },
            7 => Self {
                cfg: &mut host.pcfg7,
                binterval: &mut host.binterval7,
                statusclr: &mut host.pstatusclr7,
                statusset: &mut host.pstatusset7,
                status: &mut host.pstatus7,
                intflag: &mut host.pintflag7,
            },
            _ => unreachable!(),
        }
    }
}

// §32.8.7.1
#[derive(Clone, Copy, Debug)]
pub(crate) struct PipeDesc {
    pub bank0: BankDesc,
    pub bank1: BankDesc,
}

// 2 banks: 32 bytes per pipe.
impl PipeDesc {
    pub fn new() -> Self {
        Self {
            bank0: BankDesc::new(),
            bank1: BankDesc::new(),
        }
    }
}

#[derive(Clone, Copy, Debug)]
#[repr(C)]
// 16 bytes per bank.
pub(crate) struct BankDesc {
    pub addr: Addr,
    pub pcksize: PckSize,
    pub extreg: ExtReg,
    pub status_bk: StatusBk,
    pub ctrl_pipe: CtrlPipe,
    pub status_pipe: StatusPipe,

    _reserved: u8,
}

impl BankDesc {
    fn new() -> Self {
        Self {
            addr: Addr::from(0),
            pcksize: PckSize::from(0),
            extreg: ExtReg::from(0),
            status_bk: StatusBk::from(0),
            ctrl_pipe: CtrlPipe::from(0),
            status_pipe: StatusPipe::from(0),
            _reserved: 0,
        }
    }
}