use crate::Data;

pub mod class;
pub mod instruction;
pub use instruction::Instruction;

pub mod writer;
pub use writer::{BufferFull, Writer};

mod datasource;
pub use datasource::{DataSource, DataStream};

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Command<const S: usize> {
    class: class::Class,
    instruction: Instruction,

    pub p1: u8,
    pub p2: u8,

    /// The main reason this is modeled as Bytes and not
    /// a fixed array is for serde purposes.
    data: Data<S>,

    le: usize,
    pub extended: bool,
}

impl<const S: usize> Command<S> {
    pub fn try_from(apdu: &[u8]) -> Result<Self, FromSliceError> {
        apdu.try_into()
    }

    pub fn class(&self) -> class::Class {
        self.class
    }

    pub fn instruction(&self) -> Instruction {
        self.instruction
    }

    pub fn data(&self) -> &Data<S> {
        &self.data
    }

    pub fn data_mut(&mut self) -> &mut Data<S> {
        &mut self.data
    }

    pub fn expected(&self) -> usize {
        self.le
    }

    pub fn as_view(&self) -> CommandView {
        CommandView {
            class: self.class,
            instruction: self.instruction,
            p1: self.p1,
            p2: self.p2,
            data: self.data(),
            le: self.le,
            extended: self.extended,
        }
    }

    /// This can be use for APDU chaining to convert
    /// multiple APDU's into one.
    /// * Global Platform GPC_SPE_055 3.10
    #[allow(clippy::result_unit_err)]
    pub fn extend_from_command<const T: usize>(
        &mut self,
        command: &Command<T>,
    ) -> core::result::Result<(), ()> {
        self.extend_from_command_view(command.as_view())
    }

    /// This can be use for APDU chaining to convert
    /// multiple APDU's into one.
    /// * Global Platform GPC_SPE_055 3.10
    #[allow(clippy::result_unit_err)]
    pub fn extend_from_command_view(
        &mut self,
        command: CommandView,
    ) -> core::result::Result<(), ()> {
        // Always take the header from the last command;
        self.class = command.class();
        self.instruction = command.instruction();
        self.p1 = command.p1;
        self.p2 = command.p2;
        self.le = command.le;
        self.extended = true;

        // add the data to the end.
        self.data.extend_from_slice(command.data())
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
/// Memory-efficient unowned version of [`Command`]
pub struct CommandView<'a> {
    class: class::Class,
    instruction: Instruction,

    pub p1: u8,
    pub p2: u8,

    data: &'a [u8],

    le: usize,
    pub extended: bool,
}

impl<'a> CommandView<'a> {
    pub fn class(&self) -> class::Class {
        self.class
    }

    pub fn instruction(&self) -> Instruction {
        self.instruction
    }

    pub fn data(&self) -> &[u8] {
        self.data
    }

    pub fn expected(&self) -> usize {
        self.le
    }
}

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
enum ExtendedLen {
    Unsupported,
    Supported,
    Forced,
}

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct CommandBuilder<D> {
    class: class::Class,
    instruction: Instruction,

    pub p1: u8,
    pub p2: u8,

    data: D,

    le: ExpectedLen,
    extended_length: ExtendedLen,
}

#[derive(Debug)]
pub struct ChainedCommandIterator<'a> {
    command: Option<CommandBuilder<&'a [u8]>>,
    available_len: usize,
}

impl<'a> Iterator for ChainedCommandIterator<'a> {
    type Item = CommandBuilder<&'a [u8]>;

    fn next(&mut self) -> Option<CommandBuilder<&'a [u8]>> {
        let Some(next) = self.command.take() else {
            return None;
        };

        if let Some((cur, next)) = next.should_split(self.available_len) {
            self.command = Some(next);
            Some(cur)
        } else {
            Some(next)
        }
    }
}

const HEADER_LEN: usize = 4;

#[derive(Debug, PartialEq, Eq, Clone, PartialOrd, Ord, Copy)]
pub enum ExpectedLen {
    Ne(u16),
    Max,
}

impl From<u16> for ExpectedLen {
    fn from(value: u16) -> Self {
        Self::Ne(value)
    }
}

impl From<ExpectedLen> for usize {
    fn from(value: ExpectedLen) -> Self {
        (match value {
            ExpectedLen::Ne(l) => l,
            ExpectedLen::Max => u16::MAX,
        }) as _
    }
}

impl<D: DataSource> CommandBuilder<D> {
    /// Panics if data.len() > u16::MAX
    ///
    /// Assumes that extended length is supported
    ///
    pub fn new(
        class: class::Class,
        instruction: instruction::Instruction,
        p1: u8,
        p2: u8,
        data: D,
        le: impl Into<ExpectedLen>,
    ) -> Self {
        assert!(data.len() <= u16::MAX as usize);
        Self {
            class,
            instruction,
            p1,
            p2,
            data,
            le: le.into(),
            extended_length: ExtendedLen::Supported,
        }
    }

    /// Force the encoding of the APDU to be extended,
    /// even when the data and expected length are not neccessarily extended.
    pub fn force_extended(mut self) -> Self {
        assert!(!matches!(self.extended_length, ExtendedLen::Unsupported));
        self.extended_length = ExtendedLen::Forced;
        self
    }

    pub fn data(&self) -> D
    where
        D: Copy,
    {
        self.data
    }

    fn header_data(&self) -> BuildingHeaderData {
        /// Returns (data, len of data, and is_extended)
        fn serialize_data_len(
            len: u16,
            expected_len: ExpectedLen,
            extended: ExtendedLen,
        ) -> (heapless::Vec<u8, 3>, bool) {
            let expected_is_extended =
                matches!(expected_len, ExpectedLen::Ne(257..) | ExpectedLen::Max);
            match (len, expected_is_extended, extended) {
                (0, _, _) => (Default::default(), false),
                (1..=255, false, ExtendedLen::Unsupported | ExtendedLen::Supported) => {
                    ([len as u8].as_slice().try_into().unwrap(), false)
                }
                _ => {
                    let l = len.to_be_bytes();
                    ([0, l[0], l[1]].as_slice().try_into().unwrap(), true)
                }
            }
        }

        fn serialize_expected_len(
            len: ExpectedLen,
            lc_extended: bool,
            data_is_empty: bool,
            extended: ExtendedLen,
        ) -> heapless::Vec<u8, 3> {
            match (len, lc_extended, data_is_empty, extended) {
                (ExpectedLen::Ne(0), _, _, _) => Default::default(),
                (
                    ExpectedLen::Ne(len @ 1..=255),
                    false,
                    _,
                    ExtendedLen::Unsupported | ExtendedLen::Supported,
                ) => [len as u8].as_slice().try_into().unwrap(),
                (
                    ExpectedLen::Ne(256),
                    false,
                    _,
                    ExtendedLen::Unsupported | ExtendedLen::Supported,
                ) => [0].as_slice().try_into().unwrap(),
                (ExpectedLen::Ne(len), true, false, _) => {
                    let l = len.to_be_bytes();
                    [l[0], l[1]].as_slice().try_into().unwrap()
                }
                (ExpectedLen::Max, true, false, _) => [0, 0].as_slice().try_into().unwrap(),
                (ExpectedLen::Ne(len), false, true, _) => {
                    let l = len.to_be_bytes();
                    [0, l[0], l[1]].as_slice().try_into().unwrap()
                }
                (ExpectedLen::Max, false, true, _) => [0, 0, 0].as_slice().try_into().unwrap(),
                (ExpectedLen::Ne(257..) | ExpectedLen::Max, false, false, _)
                | (_, false, false, ExtendedLen::Forced) => {
                    unreachable!("Can't have non extended Lc and extended Le")
                }
                (_, true, true, _) => {
                    unreachable!("Can't have both no data and data extended length")
                }
            }
        }

        let le = if self.extended_length == ExtendedLen::Unsupported {
            self.le.min(256.into())
        } else {
            self.le
        };

        // Safe to unwrap because of check in `new`
        let (data_len, lc_extended) = serialize_data_len(
            self.data.len().try_into().unwrap(),
            le,
            self.extended_length,
        );

        let expected_data_len =
            serialize_expected_len(le, lc_extended, self.data.is_empty(), self.extended_length);
        BuildingHeaderData {
            le,
            data_len,
            expected_data_len,
        }
    }

    /// Required length for serialization in only one command.
    /// Assumes extended length support
    ///
    /// This can be useful to get the necessary dimension for the buffer to provide to [serialize_into](Self::serialize_into)
    pub fn required_len(&self) -> usize {
        let header_data = self.header_data();
        let header_len = 4;
        let length_len = header_data.data_len.len() + header_data.expected_data_len.len();
        header_len + length_len + self.data.len()
    }

    /// Serialize into one vector with assuming support for extended length information
    #[cfg(any(feature = "std", test))]
    pub fn serialize_to_vec(self) -> Vec<u8>
    where
        D: DataStream<Vec<u8>>,
    {
        let required_len = self.required_len();
        let mut buffer = Vec::with_capacity(required_len);
        self.serialize_into(&mut buffer).unwrap();
        debug_assert_eq!(required_len, buffer.len());
        buffer
    }

    /// This assumes that the writer has enough space to encode the APDU.
    /// If that might not be the case, first use [`should_split`](Self::should_split)
    pub fn serialize_into<W: Writer>(&self, writer: &mut W) -> Result<(), W::Error>
    where
        D: DataStream<W>,
    {
        let BuildingHeaderData {
            data_len,
            expected_data_len,
            ..
        } = self.header_data();

        writer.write_all(&[
            self.class.into_inner(),
            self.instruction.into(),
            self.p1,
            self.p2,
        ])?;

        writer.write_all(&data_len)?;
        self.data.to_writer(writer)?;
        writer.write_all(&expected_data_len)?;
        Ok(())
    }
}

struct BuildingHeaderData {
    le: ExpectedLen,
    data_len: heapless::Vec<u8, 3>,
    expected_data_len: heapless::Vec<u8, 3>,
}

impl<'a, D: PartialEq<&'a [u8]>> PartialEq<CommandView<'a>> for CommandBuilder<D> {
    fn eq(&self, other: &CommandView<'a>) -> bool {
        let Self {
            class,
            instruction,
            p1,
            p2,
            data,
            le,
            extended_length: _,
        } = self;
        let le: usize = (*le).into();
        class == &other.class
            && instruction == &other.instruction
            && p1 == &other.p1
            && p2 == &other.p2
            && data == &other.data
            && le == other.le
    }
}

impl<'a> CommandBuilder<&'a [u8]> {
    /// Panics if data.len() > u16::MAX
    ///
    /// Assumes that extended length is supported
    pub fn new_non_extended(
        class: class::Class,
        instruction: instruction::Instruction,
        p1: u8,
        p2: u8,
        data: &'a [u8],
        le: u16,
        buffer_len: Option<usize>,
    ) -> ChainedCommandIterator<'a> {
        assert!(data.len() <= u16::MAX as usize);
        ChainedCommandIterator {
            command: Some(Self {
                class,
                instruction,
                p1,
                p2,
                data,
                le: le.into(),
                extended_length: ExtendedLen::Unsupported,
            }),
            // default to u8::max for data, 5 bytes for the header, 1 for the trailer
            available_len: buffer_len.unwrap_or(255 + 5 + 1),
        }
    }

    /// Given the available length and the extended length support, split the command in 2 commands that use command chaining to be sent
    ///
    /// `None` means that the command can we serialized withinn `available_len` without needing Chaining
    /// `Some(command, rem)` means that `command` can be sent within `available_len` and that `rem` must then be sent (for command chaining). Note that `should_split` should also be called on `rem` as more than 2 commands might be required.
    ///
    /// In certain conditions can panic if `available_len <= 9` since 9 is the minimum length required to encode the header and trailer of a command.
    pub fn should_split(&self, available_len: usize) -> Option<(Self, Self)> {
        if available_len < HEADER_LEN {
            panic!("Commands cannot be encoded to fit in buffers smaller than 9 bytes");
        }

        let BuildingHeaderData {
            le,
            data_len,
            expected_data_len,
        } = self.header_data();

        let mut max_data_len = u16::MAX as usize;
        if self.extended_length == ExtendedLen::Unsupported {
            max_data_len = 255;
        }

        let available_data_len = (available_len - HEADER_LEN)
            .saturating_sub(data_len.len() + expected_data_len.len())
            .min(max_data_len);
        if available_data_len >= self.data.len() {
            // slitting not necessary
            return None;
        }

        if available_data_len == 0 {
            // Let's not support this case
            panic!("Commands cannot be encoded to fit in buffers smaller than 9 bytes");
        }

        let (send_now, send_later) = self.data.split_at(available_data_len);

        let send_now = Self {
            class: self.class.as_chained(),
            instruction: self.instruction,
            p1: self.p1,
            p2: self.p2,
            data: send_now,
            le: 0.into(),
            extended_length: self.extended_length,
        };
        let send_later = Self {
            class: self.class,
            instruction: self.instruction,
            p1: self.p1,
            p2: self.p2,
            data: send_later,
            le,
            extended_length: self.extended_length,
        };
        Some((send_now, send_later))
    }
}

impl<D: DataSource> DataSource for CommandBuilder<D> {
    fn len(&self) -> usize {
        self.required_len()
    }

    fn is_empty(&self) -> bool {
        false
    }
}

impl<W: Writer, D: DataStream<W>> DataStream<W> for CommandBuilder<D> {
    fn to_writer(&self, writer: &mut W) -> Result<(), <W as Writer>::Error> {
        self.serialize_into(writer)
    }
}

impl<'a, D: PartialEq<&'a [u8]>> PartialEq<CommandBuilder<D>> for CommandView<'a> {
    fn eq(&self, other: &CommandBuilder<D>) -> bool {
        other == self
    }
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum FromSliceError {
    TooShort,
    TooLong,
    InvalidClass,
    InvalidFirstBodyByteForExtended,
    InvalidSliceLength,
}

impl From<class::InvalidClass> for FromSliceError {
    fn from(_: class::InvalidClass) -> Self {
        Self::InvalidClass
    }
}

impl<'a> TryFrom<&'a [u8]> for CommandView<'a> {
    type Error = FromSliceError;
    fn try_from(apdu: &'a [u8]) -> core::result::Result<Self, Self::Error> {
        if apdu.len() < 4 {
            return Err(FromSliceError::TooShort);
        }
        #[cfg(test)]
        println!("{}", apdu.len());
        let (header, body) = apdu.split_at(4);
        let class = class::Class::try_from(header[0])?;
        let instruction = Instruction::from(header[1]);
        let p1 = header[2];
        let p2 = header[3];
        let parsed = parse_lengths(body)?;
        let data = &body[parsed.offset..][..parsed.lc];

        Ok(Self {
            // header
            class,
            instruction,
            p1,
            p2,
            // maximum expected response length
            le: parsed.le,
            // payload
            data,
            extended: parsed.extended,
        })
    }
}

impl<'a> CommandView<'a> {
    pub fn to_owned<const S: usize>(&self) -> Result<Command<S>, FromSliceError> {
        let &CommandView {
            class,
            instruction,
            p1,
            p2,
            le,
            data: data_slice,
            extended,
        } = self;
        // We use this way to construct the command instead of Data::from_slice as that would
        // triple stack usage on the lpc55.
        let mut command = Command {
            // header
            class,
            instruction,
            p1,
            p2,
            // maximum expected response length
            le,
            // payload
            data: Data::new(),
            extended,
        };
        command
            .data
            .extend_from_slice(data_slice)
            .map_err(|_| FromSliceError::TooLong)?;
        Ok(command)
    }
}

impl<const S: usize> TryFrom<&[u8]> for Command<S> {
    type Error = FromSliceError;
    fn try_from(apdu: &[u8]) -> core::result::Result<Self, Self::Error> {
        let view: CommandView = apdu.try_into()?;
        view.to_owned()
    }
}

// cf. ISO 7816-3, 12.1.3: Decoding conventions for command APDUs
// freely available version:
// http://www.ttfn.net/techno/smartcards/iso7816_4.html#table5

#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
struct ParsedLengths {
    lc: usize,
    le: usize,
    offset: usize,
    extended: bool,
}

#[inline(always)]
fn replace_zero(value: usize, replacement: usize) -> usize {
    if value == 0 {
        replacement
    } else {
        value
    }
}
#[inline]
fn parse_lengths(body: &[u8]) -> Result<ParsedLengths, FromSliceError> {
    // Encoding rules:
    // - Lc or Le = 0 => leave out
    // - short + extended length fields shall not be combined
    // - for extended, if Lc > 0, then Le has no leading zero byte

    let l = body.len();

    let mut parsed: ParsedLengths = Default::default();

    // Case 1
    if l == 0 {
        return Ok(parsed);
    }

    // the reference starts indexing at 1
    let b1 = body[0] as usize;

    #[cfg(test)]
    println!("l = {}, b1 = {}", l, b1);

    // Case 2S
    if l == 1 {
        parsed.lc = 0;
        parsed.le = replace_zero(b1, 256);
        return Ok(parsed);
    }

    // Case 3S
    if l == 1 + b1 && b1 != 0 {
        // B1 encodes Lc valued from 1 to 255
        parsed.lc = b1;
        parsed.le = 0;
        parsed.offset = 1;
        return Ok(parsed);
    }

    // Case 4S
    if l == 2 + b1 && b1 != 0 {
        // B1 encodes Lc valued from 1 to 255
        // Bl encodes Le from 1 to 256
        parsed.lc = b1;
        parsed.le = replace_zero(body[l - 1] as usize, 256);
        parsed.offset = 1;
        return Ok(parsed);
    }

    parsed.extended = true;

    // only extended cases left now
    if b1 != 0 {
        return Err(FromSliceError::InvalidFirstBodyByteForExtended);
    } else if l < 3 {
        return Err(FromSliceError::InvalidSliceLength);
    }

    // Case 2E (no data)
    if l == 3 && b1 == 0 {
        parsed.lc = 0;
        parsed.le = replace_zero(u16::from_be_bytes([body[1], body[2]]) as usize, 65_536);
        return Ok(parsed);
    }

    parsed.lc = u16::from_be_bytes([body[1], body[2]]) as usize;

    // Case 3E
    if l == 3 + parsed.lc {
        parsed.le = 0;
        parsed.offset = 3;
        return Ok(parsed);
    }

    // Case 4E
    if l == 5 + parsed.lc {
        parsed.le = replace_zero(
            u16::from_be_bytes([body[l - 2], body[l - 1]]) as usize,
            65_536,
        );
        parsed.offset = 3;
        return Ok(parsed);
    }

    // If we haven’t returned yet, the slice has an invalid length:  Either the encoded lc value is
    // wrong, or the lc and le lengths are not encoded properly (one byte per value for simple
    // APDU, two bytes per value for extended APDU).

    Err(FromSliceError::InvalidSliceLength)
}

#[cfg(test)]
mod test {
    use super::*;
    use hex_literal::hex;
    use quickcheck_macros::quickcheck;

    #[quickcheck]
    fn parse_no_panic(data: Vec<u8>) {
        let _ = parse_lengths(&data);
    }

    #[quickcheck]
    fn lengths(lc: u16, le: Option<u16>) {
        let extended =
            lc > u16::from(u8::MAX) || le.map(|val| val > u16::from(u8::MAX)).unwrap_or_default();
        let nc = usize::from(lc);
        let ne = le
            .map(usize::from)
            .map(|val| {
                if val == 0 {
                    (if extended {
                        usize::from(u16::MAX)
                    } else {
                        usize::from(u8::MAX)
                    }) + 1
                } else {
                    val
                }
            })
            .unwrap_or_default();

        let mut data = Vec::new();
        let mut offset = 0;

        if lc > 0 {
            if extended {
                data.push(0);
                data.extend_from_slice(&lc.to_be_bytes());
                offset = 3;
            } else {
                data.push(lc as u8);
                offset = 1;
            }
        }

        data.resize(data.len() + nc, 0);

        if let Some(le) = le {
            if extended {
                if lc == 0 {
                    data.push(0);
                }
                data.extend_from_slice(&le.to_be_bytes());
            } else {
                data.push(le as u8);
            }
        }

        let lengths = parse_lengths(&data).expect("failed to parse lengths");
        assert_eq!(extended, lengths.extended);
        assert_eq!(offset, lengths.offset);
        assert_eq!(nc, lengths.lc);
        assert_eq!(ne, lengths.le);
    }

    #[test]
    fn builder_forced_extended() {
        let cla = 0.try_into().unwrap();
        let ins = 1.into();
        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 0x04).force_extended();
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 00 00 04"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x05, 0x06], 0x04).force_extended();
        assert_eq!(
            command.serialize_to_vec(),
            &hex!("00 01 02 03 00 00 02 05 06 00 04")
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0x2AE], 0x100).force_extended();
        assert_eq!(
            command.serialize_to_vec(),
            [
                hex!("00 01 02 03 00 02AE").as_slice(),
                &[0x01; 0x2AE],
                &hex!("01 00"),
            ]
            .into_iter()
            .flatten()
            .copied()
            .collect::<Vec<u8>>()
        );
    }

    #[test]
    fn builder() {
        let cla = 0.try_into().unwrap();
        let ins = 1.into();
        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 0x04);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 04"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 0x00);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 256);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 00"));
        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 257);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 00 0101"));
        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 0xFFFF);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 00 FFFF"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x05, 0x06], 0x04);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 02 05 06 04"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x05, 0x06], 0x00);
        assert_eq!(command.serialize_to_vec(), &hex!("00 01 02 03 02 05 06"));

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x05, 0x06], 0x100);
        assert_eq!(
            command.serialize_to_vec(),
            // Large LE also forces the data length to be extended (can't mix extended/non-extended)
            &hex!("00 01 02 03 02 05 06 00")
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0x2AE], 0x100);
        assert_eq!(
            command.serialize_to_vec(),
            [
                hex!("00 01 02 03 00 02AE").as_slice(),
                &[0x01; 0x2AE],
                &hex!("01 00"),
            ]
            .into_iter()
            .flatten()
            .copied()
            .collect::<Vec<u8>>()
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0x2AE], 0x01);
        assert_eq!(
            command.serialize_to_vec(),
            [
                hex!("00 01 02 03 00 02AE").as_slice(),
                &[0x01; 0x2AE],
                &hex!("00 01"),
            ]
            .into_iter()
            .flatten()
            .copied()
            .collect::<Vec<u8>>()
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0x2AE], 0x00);
        assert_eq!(
            command.serialize_to_vec(),
            [hex!("00 01 02 03 00 02AE").as_slice(), &[0x01; 0x2AE],]
                .into_iter()
                .flatten()
                .copied()
                .collect::<Vec<u8>>()
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0x2AE], 0xFF);
        assert_eq!(
            command.serialize_to_vec(),
            [
                hex!("00 01 02 03 00 02AE").as_slice(),
                &[0x01; 0x2AE],
                &[0x00, 0xFF]
            ]
            .into_iter()
            .flatten()
            .copied()
            .collect::<Vec<u8>>()
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[0x01; 0xFFFF], 0xFFFF);
        assert_eq!(
            command.serialize_to_vec(),
            [
                hex!("00 01 02 03 00 FFFF").as_slice(),
                &[0x01; 0xFFFF],
                &[0xFF, 0xFF]
            ]
            .into_iter()
            .flatten()
            .copied()
            .collect::<Vec<u8>>()
        );

        let command = CommandBuilder::new(cla, ins, 2, 3, &[1, 2, 3, 4], 294);
        assert_eq!(
            command.serialize_to_vec(),
            &hex!("00 01 02 03 00 00 04 01020304 0126")
        );
    }

    #[test]
    fn building_chained() {
        let cla = 0x00.try_into().unwrap();
        let ins = 0x01.into();
        let mut buffer = heapless::Vec::<u8, 4096>::new();
        let command = CommandBuilder::new(cla, ins, 2, 3, &[], 0xFFFF);
        command.clone().serialize_into(&mut buffer).unwrap();
        assert_eq!(&*buffer, &command.clone().serialize_to_vec());

        buffer.clear();
        //  without extended length
        let command =
            CommandBuilder::new_non_extended(cla, ins, 2, 3, &[], 0xFFFF, Some(buffer.capacity()))
                .next()
                .unwrap();
        command.clone().serialize_into(&mut buffer).unwrap();
        assert_eq!(
            &*buffer,
            &CommandBuilder::new(cla, ins, 2, 3, &[], 0x0100).serialize_to_vec()
        );

        buffer.clear();
        //  without extended length
        let command =
            CommandBuilder::new_non_extended(cla, ins, 2, 3, &[], 0, Some(buffer.capacity()))
                .next()
                .unwrap();
        command.serialize_into(&mut buffer).unwrap();
        assert_eq!(
            &*buffer,
            &CommandBuilder::new(cla, ins, 2, 3, &[], 0).serialize_to_vec()
        );
        buffer.clear();

        let mut buffer = heapless::Vec::<u8, 105>::new();

        let mut command_iter =
            CommandBuilder::new_non_extended(cla, ins, 2, 3, &[5; 200], 0, Some(buffer.capacity()));
        let command = command_iter.next().unwrap();
        let mut rem = command_iter.next().unwrap();
        assert!(command_iter.next().is_none());
        command.serialize_into(&mut buffer).unwrap();
        assert_eq!(buffer.len(), 105);
        rem.extended_length = ExtendedLen::Supported;
        assert_eq!(
            rem,
            CommandBuilder::new(cla, ins, 2, 3, [5; 100].as_slice(), 0)
        );
        assert_eq!(
            &*buffer,
            &CommandBuilder::new(cla.as_chained(), ins, 2, 3, &[5; 100], 0).serialize_to_vec()
        );
    }

    #[test]
    fn nested_commands() {
        let cla = 0x00.try_into().unwrap();
        let ins = 0x01.into();
        let mut buffer = heapless::Vec::<u8, 4096>::new();
        let inner = CommandBuilder::new(cla, ins, 1, 2, &hex!("FFFEFDFCFBFA"), 0x10);
        let outer = CommandBuilder::new(cla, 0xAA.into(), 3, 4, &inner, 0x20);
        outer.serialize_into(&mut buffer).unwrap();
        #[rustfmt::skip]
        assert_eq!(
            &*buffer,
            hex!("
                00 AA 0304 0C
                   00 01 01 02 06  FFFEFDFCFBFA 10 
                20"
            )
        );
    }

    #[test]
    fn lengths_4s() {
        let data = &[0x02, 0xB6, 0x00, 0x00];
        let lengths = parse_lengths(data).expect("failed to parse lengths");
        assert_eq!(lengths.lc, 2);
        assert_eq!(lengths.le, 256);
        assert_eq!(lengths.offset, 1);
    }

    #[test]
    fn command_chaining() {
        let apdu = &[
            0x10, 0xdb, 0x3f, 0xff, 0xff, 0x5c, 0x03, 0x5f, 0xc1, 0x05, 0x53, 0x82, 0x01, 0x5b,
            0x70, 0x82, 0x01, 0x52, 0x30, 0x82, 0x01, 0x4e, 0x30, 0x81, 0xf5, 0xa0, 0x03, 0x02,
            0x01, 0x02, 0x02, 0x11, 0x00, 0x8b, 0xab, 0x31, 0xcf, 0x3e, 0xb9, 0xf5, 0x6a, 0x6f,
            0x38, 0xf0, 0x5a, 0x4d, 0x7f, 0x55, 0x62, 0x30, 0x0a, 0x06, 0x08, 0x2a, 0x86, 0x48,
            0xce, 0x3d, 0x04, 0x03, 0x02, 0x30, 0x2a, 0x31, 0x16, 0x30, 0x14, 0x06, 0x03, 0x55,
            0x04, 0x0a, 0x13, 0x0d, 0x79, 0x75, 0x62, 0x69, 0x6b, 0x65, 0x79, 0x2d, 0x61, 0x67,
            0x65, 0x6e, 0x74, 0x31, 0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x07,
            0x28, 0x64, 0x65, 0x76, 0x65, 0x6c, 0x29, 0x30, 0x20, 0x17, 0x0d, 0x32, 0x30, 0x30,
            0x35, 0x31, 0x36, 0x30, 0x31, 0x31, 0x37, 0x32, 0x36, 0x5a, 0x18, 0x0f, 0x32, 0x30,
            0x36, 0x32, 0x30, 0x35, 0x31, 0x36, 0x30, 0x32, 0x31, 0x37, 0x32, 0x36, 0x5a, 0x30,
            0x12, 0x31, 0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13, 0x07, 0x53, 0x53,
            0x48, 0x20, 0x6b, 0x65, 0x79, 0x30, 0x59, 0x30, 0x13, 0x06, 0x07, 0x2a, 0x86, 0x48,
            0xce, 0x3d, 0x02, 0x01, 0x06, 0x08, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07,
            0x03, 0x42, 0x00, 0x04, 0x4f, 0x98, 0x63, 0x2f, 0x53, 0xbd, 0xab, 0xee, 0xbf, 0x69,
            0x73, 0x3a, 0x84, 0x0f, 0xfd, 0x9f, 0x9d, 0xb3, 0xce, 0x5c, 0x1e, 0x1b, 0x84, 0x06,
            0x63, 0x32, 0xff, 0x9c, 0x44, 0x0b, 0xce, 0x56, 0x13, 0x94, 0x00, 0x98, 0xe3, 0x46,
            0xc2, 0xbc, 0x3d, 0xe6, 0x5e, 0xf2, 0x81, 0x4b, 0xbc, 0xea, 0x2b, 0x9d, 0x47, 0xcc,
            0x9b, 0x5e, 0xbe, 0x1e, 0x2c, 0x69, 0x1d, 0xc3, 0x53, 0x4c, 0x89, 0x14, 0xa3, 0x12,
            0x30, 0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x1d,
        ];

        let _command = Command::<256>::try_from(apdu).unwrap();
    }

    #[test]
    fn lc_oob() {
        let apdu = &hex!("00C00000 00FF");
        let _ = Command::<256>::try_from(apdu);
        let apdu = &hex!("00C00000 0000");
        let _ = Command::<256>::try_from(apdu);
    }
}