dot15d4_frame/ie/

nested.rs

use super::{Error, Result};
use crate::time::Duration;
use bitflags::bitflags;

/// A reader/writer for the IEEE 802.15.4 Nested Information Elements.
///
/// ## Short format
/// ```notrust
/// +--------+--------+--------+--------------------------+
/// | Length | Sub-ID | Type=0 | Content (0-255 octets)...|
/// +--------+--------+--------+--------------------------+
/// ```
///
/// ## Long format
/// ```notrust
/// +--------+--------+--------+---------------------------+
/// | Length | Sub-ID | Type=1 | Content (0-2046 octets)...|
/// +--------+--------+--------+---------------------------+
/// ```
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub struct NestedInformationElement<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> NestedInformationElement<T> {
    /// Create a new [`NestedInformationElement`] reader/writer from a given
    /// buffer.
    ///
    /// # Errors
    ///
    /// Returns an error if the buffer is too short to contain the nested
    /// information element.
    pub fn new(data: T) -> Result<Self> {
        let nested = Self::new_unchecked(data);

        if !nested.check_len() {
            return Err(Error);
        }

        Ok(nested)
    }

    /// Returns `false` if the buffer is too short to contain the nested
    /// information element.
    fn check_len(&self) -> bool {
        if self.data.as_ref().len() < 2 {
            return false;
        }

        let len = self.length();

        self.data.as_ref().len() >= len + 2
    }

    /// Create a new [`NestedInformationElement`] reader/writer from a given
    /// buffer without length checking.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the length of the Nested Information Element in bytes.
    pub fn length(&self) -> usize {
        let b = &self.data.as_ref()[0..];
        if self.is_long() {
            (u16::from_le_bytes([b[0], b[1]]) & 0b1111111111) as usize
        } else {
            (u16::from_le_bytes([b[0], b[1]]) & 0b1111111) as usize
        }
    }

    /// Return the [`NestedSubId`].
    pub fn sub_id(&self) -> NestedSubId {
        let b = &self.data.as_ref()[0..];
        let id = u16::from_le_bytes([b[0], b[1]]);
        if self.is_long() {
            NestedSubId::Long(NestedSubIdLong::from(((id >> 11) & 0b1111) as u8))
        } else {
            NestedSubId::Short(NestedSubIdShort::from(((id >> 8) & 0b111111) as u8))
        }
    }

    /// Returns `true` when the Nested Information Element is a short type.
    pub fn is_short(&self) -> bool {
        !self.is_long()
    }

    /// Returns `true` when the Nested Information Element is a long type.
    pub fn is_long(&self) -> bool {
        let b = &self.data.as_ref()[0..];
        (u16::from_le_bytes([b[0], b[1]]) >> 15) & 0b1 == 0b1
    }

    /// Return the content of this Nested Information Element.
    pub fn content(&self) -> &[u8] {
        &self.data.as_ref()[2..][..self.length()]
    }
}

impl<T: AsRef<[u8]> + AsMut<[u8]>> NestedInformationElement<T> {
    /// Clear the content of this Nested Information Element.
    pub fn clear(&mut self) {
        self.data.as_mut().fill(0);
    }

    /// Set the length of the Nested Information Element.
    pub fn set_length(&mut self, len: u16, id: NestedSubId) {
        let mask: u16 = if id.is_short() {
            0b0000_1111_1111
        } else {
            0b0111_1111_1111
        };

        let b = &mut self.data.as_mut()[0..2];
        let value = u16::from_le_bytes([b[0], b[1]]) & !mask;
        let value = value | (len & mask);
        b[0..2].copy_from_slice(&value.to_le_bytes());
    }

    /// Set the [`NestedSubId`].
    pub fn set_sub_id(&mut self, id: NestedSubId) {
        let mask: u16 = if id.is_short() {
            0b0111_1111_0000_0000
        } else {
            0b0111_1000_0000_0000
        };

        let b = &mut self.data.as_mut()[0..2];
        let value = u16::from_le_bytes([b[0], b[1]]) & !mask;
        let value = value
            | match id {
                NestedSubId::Short(id) => (id as u16) << 8,
                NestedSubId::Long(id) => ((id as u16) << 11) | 0b1000_0000_0000_0000,
            };
        b[0..2].copy_from_slice(&value.to_le_bytes());
    }

    /// Return a mutable reference to the content of this Nested Information
    pub fn content_mut(&mut self) -> &mut [u8] {
        &mut self.data.as_mut()[2..]
    }
}

impl<T: AsRef<[u8]>> core::fmt::Display for NestedInformationElement<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self.sub_id() {
            NestedSubId::Short(id) => match id {
                NestedSubIdShort::TschSynchronization => {
                    let Ok(ts) = TschSynchronization::new(self.content()) else {
                        return write!(f, "  {id}");
                    };
                    write!(f, "  {id} {ts}")
                }
                NestedSubIdShort::TschTimeslot => {
                    let Ok(tt) = TschTimeslot::new(self.content()) else {
                        return write!(f, "  {id}");
                    };
                    write!(f, "  {id} {tt}")
                }
                NestedSubIdShort::TschSlotframeAndLink => {
                    let Ok(ts) = TschSlotframeAndLink::new(self.content()) else {
                        return write!(f, "  {id}");
                    };
                    write!(f, "  {id} {ts}")
                }
                _ => write!(f, "  {:?}({:0x?})", id, self.content()),
            },
            NestedSubId::Long(id) => match id {
                NestedSubIdLong::ChannelHopping => {
                    let Ok(ch) = ChannelHopping::new(self.content()) else {
                        return write!(f, "  {id}");
                    };
                    write!(f, "  {id} {ch}")
                }
                id => write!(f, "  {:?}({:0x?})", id, self.content()),
            },
        }
    }
}

/// Nested Information Element ID.
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum NestedSubId {
    /// Short Nested Information Element ID.
    Short(NestedSubIdShort),
    /// Long Nested Information Element ID.
    Long(NestedSubIdLong),
}

impl NestedSubId {
    /// Create a short [`NestedSubId`] from a `u8`.
    pub fn from_short(value: u8) -> Self {
        Self::Short(NestedSubIdShort::from(value))
    }

    /// Create a long [`NestedSubId`] from a `u8`.
    pub fn from_long(value: u8) -> Self {
        Self::Long(NestedSubIdLong::from(value))
    }

    /// Returns `true` when the Nested Information Element is a short type.
    pub fn is_short(&self) -> bool {
        matches!(self, Self::Short(_))
    }

    /// Returns `true` when the Nested Information Element is a long type.
    pub fn is_long(&self) -> bool {
        matches!(self, Self::Long(_))
    }
}

/// Short Nested Information Element ID.
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum NestedSubIdShort {
    /// TSCH Synchronization.
    TschSynchronization = 0x1a,
    /// TSCH Slotframe and Link.
    TschSlotframeAndLink = 0x1b,
    /// TSCH Timeslot.
    TschTimeslot = 0x1c,
    /// Hopping Timing.
    HoppingTiming = 0x1d,
    /// Enhanced Beacon Filter.
    EnhancedBeaconFilter = 0x1e,
    /// MAC Metrics.
    MacMetrics = 0x1f,
    /// All MAC Metrics.
    AllMacMetrics = 0x20,
    /// Coexistence Specification.
    CoexistenceSpecification = 0x21,
    /// Sun Device Capabilities.
    SunDeviceCapabilities = 0x22,
    /// Sun FSK Generic PHY.
    SunFskGenericPhy = 0x23,
    /// Mode Switch Parameter.
    ModeSwitchParameter = 0x24,
    /// PHY Parameter Change.
    PhyParameterChange = 0x25,
    /// O-QPSK PHY Mode.
    OQpskPhyMode = 0x26,
    /// PCA Allocation.
    PcaAllocation = 0x27,
    /// LECIM DSSS Operating Mode.
    LecimDsssOperatingMode = 0x28,
    /// LECIM FSK Operating Mode.
    LecimFskOperatingMode = 0x29,
    /// TVWS PHY Operating Mode.
    TvwsPhyOperatingMode = 0x2b,
    /// TVWS Device Capabilities.
    TvwsDeviceCapabilities = 0x2c,
    /// TVWS Device Category.
    TvwsDeviceCategory = 0x2d,
    /// TVWS Device Identification.
    TvwsDeviceIdentification = 0x2e,
    /// TVWS Device Location.
    TvwsDeviceLocation = 0x2f,
    /// TVWS Channel Information Query.
    TvwsChannelInformationQuery = 0x30,
    /// TVWS Channel Information Source.
    TvwsChannelInformationSource = 0x31,
    /// CTM.
    Ctm = 0x32,
    /// Timestamp.
    Timestamp = 0x33,
    /// Timestamp Difference.
    TimestampDifference = 0x34,
    /// TMCTP Specification.
    TmctpSpecification = 0x35,
    /// RCC PHY Operating Mode.
    RccPhyOperatingMode = 0x36,
    /// Link Margin.
    LinkMargin = 0x37,
    /// RS-GFSK Device Capabilities.
    RsGfskDeviceCapabilities = 0x38,
    /// Multi-PHY.
    MultiPhy = 0x39,
    /// Vendor Specific.
    VendorSpecific = 0x40,
    /// SRM.
    Srm = 0x46,
    /// Unknown.
    Unkown,
}

impl From<u8> for NestedSubIdShort {
    fn from(value: u8) -> Self {
        match value {
            0x1a => Self::TschSynchronization,
            0x1b => Self::TschSlotframeAndLink,
            0x1c => Self::TschTimeslot,
            0x1d => Self::HoppingTiming,
            0x1e => Self::EnhancedBeaconFilter,
            0x1f => Self::MacMetrics,
            0x20 => Self::AllMacMetrics,
            0x21 => Self::CoexistenceSpecification,
            0x22 => Self::SunDeviceCapabilities,
            0x23 => Self::SunFskGenericPhy,
            0x24 => Self::ModeSwitchParameter,
            0x25 => Self::PhyParameterChange,
            0x26 => Self::OQpskPhyMode,
            0x27 => Self::PcaAllocation,
            0x28 => Self::LecimDsssOperatingMode,
            0x29 => Self::LecimFskOperatingMode,
            0x2b => Self::TvwsPhyOperatingMode,
            0x2c => Self::TvwsDeviceCapabilities,
            0x2d => Self::TvwsDeviceCategory,
            0x2e => Self::TvwsDeviceIdentification,
            0x2f => Self::TvwsDeviceLocation,
            0x30 => Self::TvwsChannelInformationQuery,
            0x31 => Self::TvwsChannelInformationSource,
            0x32 => Self::Ctm,
            0x33 => Self::Timestamp,
            0x34 => Self::TimestampDifference,
            0x35 => Self::TmctpSpecification,
            0x36 => Self::RccPhyOperatingMode,
            0x37 => Self::LinkMargin,
            0x38 => Self::RsGfskDeviceCapabilities,
            0x39 => Self::MultiPhy,
            0x40 => Self::VendorSpecific,
            0x46 => Self::Srm,
            _ => Self::Unkown,
        }
    }
}

impl core::fmt::Display for NestedSubIdShort {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::TschTimeslot => write!(f, "TSCH Timeslot"),
            Self::TschSlotframeAndLink => write!(f, "TSCH Slotframe and Link"),
            Self::TschSynchronization => write!(f, "TSCH Synchronization"),
            _ => write!(f, "{:?}", self),
        }
    }
}

/// Long Nested Information Element ID.
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum NestedSubIdLong {
    /// Vendor Specific Nested Information Elements.
    VendorSpecificNested = 0x08,
    /// Channel Hopping.
    ChannelHopping = 0x09,
    /// Unnown.
    Unkown,
}

impl From<u8> for NestedSubIdLong {
    fn from(value: u8) -> Self {
        match value {
            0x08 => Self::VendorSpecificNested,
            0x09 => Self::ChannelHopping,
            _ => Self::Unkown,
        }
    }
}

impl core::fmt::Display for NestedSubIdLong {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::ChannelHopping => write!(f, "Channel Hopping"),
            _ => write!(f, "{:?}", self),
        }
    }
}

/// A reader/writer for the TSCH synchronization IE.
/// ```notrust
/// +-----+-------------+
/// | ASN | Join metric |
/// +-----+-------------+
/// 0     5             6
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TschSynchronization<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> TschSynchronization<T> {
    /// Create a new [`TschSynchronization`] reader/writer from a given buffer.
    pub fn new(data: T) -> Result<Self> {
        let ts = Self::new_unchecked(data);

        if !ts.check_len() {
            return Err(Error);
        }

        Ok(ts)
    }

    /// Returns `false` if the buffer is too short to contain a valid TSCH
    /// Synchronization IE.
    fn check_len(&self) -> bool {
        self.data.as_ref().len() >= 6
    }

    /// Create a new [`TschSynchronization`] reader/writer from a given buffer
    /// without length checking.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the absolute slot number field.
    pub fn absolute_slot_number(&self) -> u64 {
        let data = self.data.as_ref();
        let mut asn = data[0] as u64;
        asn += (data[1] as u64) << 8;
        asn += (data[2] as u64) << 16;
        asn += (data[3] as u64) << 24;
        asn += (data[4] as u64) << 32;
        asn
    }

    /// Return the join metric field.
    pub fn join_metric(&self) -> u8 {
        self.data.as_ref()[5]
    }
}

impl<T: AsRef<[u8]> + AsMut<[u8]>> TschSynchronization<T> {
    /// Set the absolute slot number field.
    pub fn set_absolute_slot_number(&mut self, asn: u64) {
        let data = self.data.as_mut();
        data[0] = (asn & 0xff) as u8;
        data[1] = ((asn >> 8) & 0xff) as u8;
        data[2] = ((asn >> 16) & 0xff) as u8;
        data[3] = ((asn >> 24) & 0xff) as u8;
        data[4] = ((asn >> 32) & 0xff) as u8;
    }

    /// Set the join metric field.
    pub fn set_join_metric(&mut self, join_metric: u8) {
        self.data.as_mut()[5] = join_metric;
    }
}

impl<T: AsRef<[u8]>> core::fmt::Display for TschSynchronization<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(
            f,
            "ASN: {}, join metric: {}",
            self.absolute_slot_number(),
            self.join_metric()
        )
    }
}

/// A reader/writer for the TSCH timeslot IE.
/// ```notrust
/// +----+--------------------------+
/// | ID | TSCH timeslot timings... |
/// +----+--------------------------+
/// 0    1
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TschTimeslot<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> TschTimeslot<T> {
    /// The default timeslot ID.
    pub const DEFAULT_ID: u8 = 0;

    /// Create a new [`TschTimeslot`] reader/writer from a given buffer.
    pub fn new(data: T) -> Result<Self> {
        let ts = Self::new_unchecked(data);

        if !ts.check_len() {
            return Err(Error);
        }

        Ok(ts)
    }

    /// Returns `false` if the buffer is too short to contain a valid TSCH
    /// Timeslot IE.
    fn check_len(&self) -> bool {
        let len = self.data.as_ref().len();

        if len < 1 {
            return false;
        }

        if self.id() == Self::DEFAULT_ID {
            return len >= 1;
        }

        len >= 25
    }

    /// Create a new [`TschTimeslot`] reader/writer from a given buffer without
    /// length checking.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the TSCH timeslot ID field.
    pub fn id(&self) -> u8 {
        self.data.as_ref()[0]
    }

    /// Return the TSCH timeslot timings.
    pub fn timeslot_timings(&self) -> TschTimeslotTimings {
        if self.id() == Self::DEFAULT_ID {
            TschTimeslotTimings::default()
        } else {
            TschTimeslotTimings {
                id: self.id(),
                cca_offset: Duration::from_us({
                    let b = &self.data.as_ref()[1..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                cca: Duration::from_us({
                    let b = &self.data.as_ref()[3..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                tx_offset: Duration::from_us({
                    let b = &self.data.as_ref()[5..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                rx_offset: Duration::from_us({
                    let b = &self.data.as_ref()[7..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                rx_ack_delay: Duration::from_us({
                    let b = &self.data.as_ref()[9..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                tx_ack_delay: Duration::from_us({
                    let b = &self.data.as_ref()[11..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                rx_wait: Duration::from_us({
                    let b = &self.data.as_ref()[13..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                ack_wait: Duration::from_us({
                    let b = &self.data.as_ref()[15..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                rx_tx: Duration::from_us({
                    let b = &self.data.as_ref()[17..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                max_ack: Duration::from_us({
                    let b = &self.data.as_ref()[19..][..2];
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                max_tx: Duration::from_us({
                    let len = if self.data.as_ref().len() == 25 { 2 } else { 3 };
                    let b = &self.data.as_ref()[21..][..len];
                    // TODO: handle the case where a 3 byte length is used.
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
                time_slot_length: Duration::from_us({
                    let offset = if self.data.as_ref().len() == 25 {
                        23
                    } else {
                        24
                    };
                    let len = if self.data.as_ref().len() == 25 { 2 } else { 3 };
                    let b = &self.data.as_ref()[offset..][..len];
                    // TODO: handle the case where a 3 byte length is used.
                    u16::from_le_bytes([b[0], b[1]]) as i64
                }),
            }
        }
    }
}

impl<T: AsRef<[u8]> + AsMut<[u8]>> TschTimeslot<T> {
    /// Set the TSCH timeslot ID field.
    pub fn set_time_slot_id(&mut self, id: u8) {
        self.data.as_mut()[0] = id;
    }
}

impl<T: AsRef<[u8]>> core::fmt::Display for TschTimeslot<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "slot ID: {}", self.id())
    }
}

/// A TSCH time slot timings (figure 6-30 in IEEE 802.15.4-2020).
///
/// If the time slot ID is 0, the default timings are used.
///
/// ```notrust
/// +----+------------+-----+-----------+-----------+--------------+--------------+---------+----------+-------+---------+--------+------------------+
/// | ID | CCA offset | CCA | TX offset | RX offset | RX ACK delay | TX ACK delay | RX wait | ACK wait | RX/TX | Max ACK | Max TX | Time slot length |
/// +----+------------+-----+-----------+-----------+--------------+--------------+---------+----------+-------+---------+--------+------------------+
/// ```
#[derive(Debug)]
pub struct TschTimeslotTimings {
    id: u8,
    /// Offset from the start of the time slot to the start of the CCA in
    /// microseconds.
    cca_offset: Duration,
    /// Duration of the CCA in microseconds.
    cca: Duration,
    /// Radio turnaround time in microseconds.
    rx_tx: Duration,

    /// Offset from the start of the time slot to the start of the TX in
    /// microseconds.
    tx_offset: Duration,
    /// Maximum transmission time for a frame in microseconds.
    max_tx: Duration,
    /// Wait time between the end of the TX and the start of the ACK RX in
    /// microseconds.
    rx_ack_delay: Duration,
    /// Maximum time to wait for receiving an ACK.
    ack_wait: Duration,

    /// Offset from the start of the time slot to the start of the RX in
    /// microseconds.
    rx_offset: Duration,
    /// Maximum time to wait for receiving a frame.
    rx_wait: Duration,
    /// Wait time between the end of the RX and the start of the ACK TX in
    /// microseconds.
    tx_ack_delay: Duration,
    /// Maximum transmission time for an ACK in microseconds.
    max_ack: Duration,

    /// Length of the time slot in microseconds.
    time_slot_length: Duration,
}

impl Default for TschTimeslotTimings {
    fn default() -> Self {
        Self::new(0, Self::DEFAULT_GUARD_TIME)
    }
}

impl TschTimeslotTimings {
    /// The default guard time (2200us) in microseconds.
    pub const DEFAULT_GUARD_TIME: Duration = Duration::from_us(2200);

    /// Create a new set of time slot timings.
    pub fn new(id: u8, guard_time: Duration) -> Self {
        Self {
            id,
            cca_offset: Duration::from_us(1800),
            cca: Duration::from_us(128),
            tx_offset: Duration::from_us(2120),
            rx_offset: Duration::from_us(2120) - (guard_time / 2),
            rx_ack_delay: Duration::from_us(800),
            tx_ack_delay: Duration::from_us(1000),
            rx_wait: guard_time,
            ack_wait: Duration::from_us(400),
            rx_tx: Duration::from_us(192),
            max_ack: Duration::from_us(2400),
            max_tx: Duration::from_us(4256),
            time_slot_length: Duration::from_us(10000),
        }
    }

    /// Return the CCA offset in microseconds.
    pub const fn cca_offset(&self) -> Duration {
        self.cca_offset
    }

    /// Set the CCA offset in microseconds.
    pub fn set_cca_offset(&mut self, cca_offset: Duration) {
        self.cca_offset = cca_offset;
    }

    /// Return the CCA duration in microseconds.
    pub const fn cca(&self) -> Duration {
        self.cca
    }

    /// Set the CCA duration in microseconds.
    pub fn set_cca(&mut self, cca: Duration) {
        self.cca = cca;
    }

    /// Return the TX offset in microseconds.
    pub const fn tx_offset(&self) -> Duration {
        self.tx_offset
    }

    /// Set the TX offset in microseconds.
    pub fn set_tx_offset(&mut self, tx_offset: Duration) {
        self.tx_offset = tx_offset;
    }

    /// Return the RX offset in microseconds.
    pub const fn rx_offset(&self) -> Duration {
        self.rx_offset
    }

    /// Set the RX offset in microseconds.
    pub fn set_rx_offset(&mut self, rx_offset: Duration) {
        self.rx_offset = rx_offset;
    }

    /// Return the RX ACK delay in microseconds.
    pub const fn rx_ack_delay(&self) -> Duration {
        self.rx_ack_delay
    }

    /// Set the RX ACK delay in microseconds.
    pub fn set_rx_ack_delay(&mut self, rx_ack_delay: Duration) {
        self.rx_ack_delay = rx_ack_delay;
    }

    /// Return the TX ACK delay in microseconds.
    pub const fn tx_ack_delay(&self) -> Duration {
        self.tx_ack_delay
    }

    /// Set the TX ACK delay in microseconds.
    pub fn set_tx_ack_delay(&mut self, tx_ack_delay: Duration) {
        self.tx_ack_delay = tx_ack_delay;
    }

    /// Return the RX wait in microseconds.
    pub const fn rx_wait(&self) -> Duration {
        self.rx_wait
    }

    /// Set the RX wait in microseconds.
    pub fn set_rx_wait(&mut self, rx_wait: Duration) {
        self.rx_wait = rx_wait;
    }

    /// Return the ACK wait in microseconds.
    pub const fn ack_wait(&self) -> Duration {
        self.ack_wait
    }

    /// Set the ACK wait in microseconds.
    pub fn set_ack_wait(&mut self, ack_wait: Duration) {
        self.ack_wait = ack_wait;
    }

    /// Return the RX/TX in microseconds.
    pub const fn rx_tx(&self) -> Duration {
        self.rx_tx
    }

    /// Set the RX/TX in microseconds.
    pub fn set_rx_tx(&mut self, rx_tx: Duration) {
        self.rx_tx = rx_tx;
    }

    /// Return the maximum ACK in microseconds.
    pub const fn max_ack(&self) -> Duration {
        self.max_ack
    }

    /// Set the maximum ACK in microseconds.
    pub fn set_max_ack(&mut self, max_ack: Duration) {
        self.max_ack = max_ack;
    }

    /// Return the maximum TX in microseconds.
    pub const fn max_tx(&self) -> Duration {
        self.max_tx
    }

    /// Set the maximum TX in microseconds.
    pub fn set_max_tx(&mut self, max_tx: Duration) {
        self.max_tx = max_tx;
    }

    /// Return the time slot length in microseconds.
    pub const fn time_slot_length(&self) -> Duration {
        self.time_slot_length
    }

    /// Set the time slot length in microseconds.
    pub fn set_time_slot_length(&mut self, time_slot_length: Duration) {
        self.time_slot_length = time_slot_length;
    }

    /// Emit the time slot timings into a buffer.
    pub fn emit(&self, buffer: &mut [u8]) {
        buffer[0] = self.id;
        buffer[1..][..2].copy_from_slice(&(self.cca_offset.as_us() as u16).to_le_bytes());
        buffer[3..][..2].copy_from_slice(&(self.cca.as_us() as u16).to_le_bytes());
        buffer[5..][..2].copy_from_slice(&(self.tx_offset.as_us() as u16).to_le_bytes());
        buffer[7..][..2].copy_from_slice(&(self.rx_offset.as_us() as u16).to_le_bytes());
        buffer[9..][..2].copy_from_slice(&(self.rx_ack_delay.as_us() as u16).to_le_bytes());
        buffer[11..][..2].copy_from_slice(&(self.tx_ack_delay.as_us() as u16).to_le_bytes());
        buffer[13..][..2].copy_from_slice(&(self.rx_wait.as_us() as u16).to_le_bytes());
        buffer[15..][..2].copy_from_slice(&(self.ack_wait.as_us() as u16).to_le_bytes());
        buffer[17..][..2].copy_from_slice(&(self.rx_tx.as_us() as u16).to_le_bytes());
        buffer[19..][..2].copy_from_slice(&(self.max_ack.as_us() as u16).to_le_bytes());

        // TODO: handle the case where the buffer is too small
        buffer[21..][..2].copy_from_slice(&(self.max_tx.as_us() as u16).to_le_bytes());
        // TODO: handle the case where the buffer is too small
        buffer[23..][..2].copy_from_slice(&(self.time_slot_length.as_us() as u16).to_le_bytes());
    }

    fn fmt(&self, indent: usize, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        writeln!(f, "{:indent$}cca_offset: {}", "", self.cca_offset(),)?;
        writeln!(f, "{:indent$}cca: {}", "", self.cca(), indent = indent)?;
        writeln!(f, "{:indent$}tx offset: {}", "", self.tx_offset(),)?;
        writeln!(f, "{:indent$}rx offset: {}", "", self.rx_offset(),)?;
        writeln!(
            f,
            "{:indent$}tx ack delay: {}",
            "",
            self.tx_ack_delay(),
            indent = indent
        )?;
        writeln!(f, "{:indent$}rx ack delay: {}", "", self.rx_ack_delay(),)?;
        writeln!(f, "{:indent$}rx wait: {}", "", self.rx_wait(),)?;
        writeln!(f, "{:indent$}ack wait: {}", "", self.ack_wait(),)?;
        writeln!(f, "{:indent$}rx/tx: {}", "", self.rx_tx(), indent = indent)?;
        writeln!(f, "{:indent$}max ack: {}", "", self.max_ack(),)?;
        writeln!(f, "{:indent$}max tx: {}", "", self.max_tx(),)?;
        writeln!(
            f,
            "{:indent$}time slot length: {}",
            "",
            self.time_slot_length(),
        )
    }
}

impl core::fmt::Display for TschTimeslotTimings {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        self.fmt(0, f)
    }
}

/// A reader/writer for the TSCH slotframe and link IE.
/// ```notrust
/// +----------------------+--------------------------+
/// | Number of slotframes | Slotframe descriptors... |
/// +----------------------+--------------------------+
/// 0                      1
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TschSlotframeAndLink<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> TschSlotframeAndLink<T> {
    /// Create a new [`TschSlotframeAndLink`] reader/writer from a given buffer.
    pub fn new(data: T) -> Result<Self> {
        let ts = Self::new_unchecked(data);

        if !ts.check_len() {
            return Err(Error);
        }

        Ok(ts)
    }

    /// Returns `false` if the buffer is too short to contain a valid TSCH
    /// Slotframe and Link IE.
    fn check_len(&self) -> bool {
        let len = self.data.as_ref().len();

        if len < 1 {
            return false;
        }

        let _number_of_slot_frames = self.number_of_slot_frames() as usize;
        let slotframe_descriptors_len =
            self.slotframe_descriptors().map(|d| d.len()).sum::<usize>();

        len > slotframe_descriptors_len
    }

    /// Create a new [`TschSlotframeAndLink`] reader/writer from a given buffer
    /// without length checking.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the number of slotframes field.
    pub fn number_of_slot_frames(&self) -> u8 {
        self.data.as_ref()[0]
    }

    /// Returns an [`Iterator`] over the [`SlotframeDescriptor`]s.
    pub fn slotframe_descriptors(&self) -> SlotframeDescriptorIterator {
        SlotframeDescriptorIterator::new(
            self.number_of_slot_frames() as usize,
            &self.data.as_ref()[1..],
        )
    }
}

impl<T: AsRef<[u8]> + AsMut<[u8]>> TschSlotframeAndLink<T> {
    /// Set the number of slotframes field.
    pub fn set_number_of_slot_frames(&mut self, number_of_slot_frames: u8) {
        self.data.as_mut()[0] = number_of_slot_frames;
    }
}

impl<T: AsRef<[u8]>> core::fmt::Display for TschSlotframeAndLink<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "#slot frames: {}", self.number_of_slot_frames())
    }
}

/// A reader/writer for the Slotframe Descriptor.
/// ```notrust
/// +--------+------+-------+---------------------+
/// | Handle | Size | Links | Link descriptors... |
/// +--------+------+-------+---------------------+
/// 0        1      3       4
/// ```
pub struct SlotframeDescriptor<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> SlotframeDescriptor<T> {
    /// Create a new [`SlotframeDescriptor`] reader/writer from a given buffer.
    pub fn new(data: T) -> Result<Self> {
        let descriptor = Self::new_unchecked(data);

        if !descriptor.check_len() {
            return Err(Error);
        }

        Ok(descriptor)
    }

    /// Returns `false` if the buffer is too short to contain a valid Slotframe
    /// Descriptor.
    fn check_len(&self) -> bool {
        let len = self.data.as_ref().len();

        if len < 4 {
            return false;
        }

        len > 4 + (self.links() as usize * LinkDescriptor::<&[u8]>::len())
    }

    /// Create a new [`SlotframeDescriptor`] reader/writer from a given buffer
    /// without length checking.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the length of the Slotframe Descriptor in bytes.
    #[allow(clippy::len_without_is_empty)]
    pub fn len(&self) -> usize {
        4 + (self.links() as usize) * 5
    }

    /// Return the handle field.
    pub fn handle(&self) -> u8 {
        self.data.as_ref()[0]
    }

    /// Return the size field.
    pub fn size(&self) -> u16 {
        let b = &self.data.as_ref()[1..][..2];
        u16::from_le_bytes([b[0], b[1]])
    }

    /// Return the links field.
    pub fn links(&self) -> u8 {
        self.data.as_ref()[3]
    }

    /// Return the link descriptors.
    pub fn link_descriptors(&self) -> LinkDescriptorIterator {
        LinkDescriptorIterator::new(
            &self.data.as_ref()[4..][..(self.links() as usize * LinkDescriptor::<&[u8]>::len())],
        )
    }
}

/// An [`Iterator`] over [`SlotframeDescriptor`].
pub struct SlotframeDescriptorIterator<'f> {
    data: &'f [u8],
    offset: usize,
    terminated: bool,
    slotframes: usize,
    slotframe_count: usize,
}

impl<'f> SlotframeDescriptorIterator<'f> {
    /// Create a new [`SlotframeDescriptorIterator`].
    pub fn new(slotframes: usize, data: &'f [u8]) -> Self {
        let terminated = slotframes == 0;

        Self {
            data,
            offset: 0,
            terminated,
            slotframes,
            slotframe_count: 0,
        }
    }
}

impl<'f> Iterator for SlotframeDescriptorIterator<'f> {
    type Item = SlotframeDescriptor<&'f [u8]>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.terminated {
            return None;
        }

        let Ok(descriptor) = SlotframeDescriptor::new(&self.data[self.offset..]) else {
            self.terminated = true;
            return None;
        };

        self.slotframe_count += 1;
        self.offset += descriptor.len();

        if self.offset >= self.data.as_ref().len() || self.slotframe_count >= self.slotframes {
            self.terminated = true;
        }

        Some(descriptor)
    }
}

/// A reader/writer for the Link Descriptor.
/// ```notrust
/// +----------+----------------+--------------+
/// | Timeslot | Channel offset | Link options |
/// +----------+----------------+--------------+
/// 0          2                4
/// ```
pub struct LinkDescriptor<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> LinkDescriptor<T> {
    /// Create a new [`LinkDescriptor`] reader/writer from a given buffer.
    pub fn new(data: T) -> Self {
        Self { data }
    }

    /// Return the length of the Link Descriptor in bytes.
    pub const fn len() -> usize {
        5
    }

    /// Return the timeslot field.
    pub fn timeslot(&self) -> u16 {
        let b = &self.data.as_ref()[0..][..2];
        u16::from_le_bytes([b[0], b[1]])
    }

    /// Return the channel offset field.
    pub fn channel_offset(&self) -> u16 {
        let b = &self.data.as_ref()[2..][..2];
        u16::from_le_bytes([b[0], b[1]])
    }

    /// Return the link options field.
    pub fn link_options(&self) -> TschLinkOption {
        TschLinkOption::from_bits_truncate(self.data.as_ref()[4])
    }
}

/// An [`Iterator`] over [`LinkDescriptor`].
pub struct LinkDescriptorIterator<'f> {
    data: &'f [u8],
    offset: usize,
    terminated: bool,
}

impl<'f> LinkDescriptorIterator<'f> {
    /// Create a new [`LinkDescriptorIterator`].
    pub fn new(data: &'f [u8]) -> Self {
        Self {
            data,
            offset: 0,
            terminated: false,
        }
    }
}

impl<'f> Iterator for LinkDescriptorIterator<'f> {
    type Item = LinkDescriptor<&'f [u8]>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.terminated {
            return None;
        }

        let descriptor = LinkDescriptor::new(&self.data[self.offset..]);

        self.offset += LinkDescriptor::<&[u8]>::len();
        self.terminated = self.offset >= self.data.as_ref().len();

        Some(descriptor)
    }
}

bitflags! {
    /// TSCH link options bitfield.
    /// ```notrust
    /// +----+----+--------+--------------+----------+----------+
    /// | Tx | Rx | Shared | Time keeping | Priority | Reserved |
    /// +----+----+--------+--------------+----------+----------+
    /// ```
    #[derive(Copy, Clone)]
    pub struct TschLinkOption: u8 {
        /// Transmit.
        const Tx = 0b0000_0001;
        /// Receive.
        const Rx = 0b0000_0010;
        /// Shared.
        const Shared = 0b0000_0100;
        /// Time keeping.
        const TimeKeeping = 0b0000_1000;
        /// Priority.
        const Priority = 0b0001_0000;
    }
}

impl core::fmt::Debug for TschLinkOption {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        bitflags::parser::to_writer(self, f)
    }
}

/// A reader/writer for the Channel Hopping IE.
/// ```notrust
/// +-------------+-----+
/// | Sequence ID | ... |
/// +-------------+-----+
/// 0             1
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ChannelHopping<T: AsRef<[u8]>> {
    data: T,
}

impl<T: AsRef<[u8]>> ChannelHopping<T> {
    /// Create a new [`ChannelHopping`] reader/writer from a given buffer.
    ///
    /// # Errors
    ///
    /// Returns an error if the buffer is too small.
    pub fn new(data: T) -> Result<Self> {
        let ts = Self::new_unchecked(data);

        if !ts.check_len() {
            return Err(Error);
        }

        Ok(ts)
    }

    /// Return `false` if the buffer is too small.
    fn check_len(&self) -> bool {
        !self.data.as_ref().is_empty()
    }

    /// Create a new [`ChannelHopping`] reader/writer from a given buffer
    /// without checking the length.
    pub fn new_unchecked(data: T) -> Self {
        Self { data }
    }

    /// Return the hopping sequence ID field.
    pub fn hopping_sequence_id(&self) -> u8 {
        self.data.as_ref()[0]
    }
}

impl<T: AsRef<[u8]> + AsMut<[u8]>> ChannelHopping<T> {
    /// Set the hopping sequence ID field.
    pub fn set_hopping_sequence_id(&mut self, id: u8) {
        self.data.as_mut()[0] = id;
    }
}

impl<T: AsRef<[u8]>> core::fmt::Display for ChannelHopping<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "sequence ID: {}", self.hopping_sequence_id())
    }
}

/// An [`Iterator`] over [`NestedInformationElement`].
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub struct NestedInformationElementsIterator<'f> {
    data: &'f [u8],
    offset: usize,
    terminated: bool,
}

impl<'f> NestedInformationElementsIterator<'f> {
    /// Create a new [`NestedInformationElementsIterator`].
    pub fn new(data: &'f [u8]) -> Self {
        Self {
            data,
            offset: 0,
            terminated: false,
        }
    }
}

impl<'f> Iterator for NestedInformationElementsIterator<'f> {
    type Item = NestedInformationElement<&'f [u8]>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.terminated {
            None
        } else {
            let Ok(nested) = NestedInformationElement::new(&self.data[self.offset..]) else {
                self.terminated = true;
                return None;
            };
            let len = nested.length() + 2;

            let nested = NestedInformationElement {
                data: &self.data[self.offset..][..len],
            };

            self.offset += len;

            if self.offset >= self.data.len() {
                self.terminated = true;
            }

            Some(nested)
        }
    }
}