f1-api 0.2.0

F1 API is a client library for the telemetry API of the F1 video games by Codemasters. It uses asynchronous networking to decode the incoming UDP packets, and turns them into strongly typed Rust structs.
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//! Decoder for telemetry packets sent by F1 2019
//!
//! The telemetry packets by F1 2018 and F1 2019 differ only in their packet headers, the rest of
//! the packet format is identical.

use std::io::{Cursor, Error, ErrorKind};

use bytes::{Buf, BytesMut};

use crate::nineteen::header::decode_header;
use crate::packet::ensure_packet_size;
use crate::packet::telemetry::{Button, Gear, Surface, Telemetry, TelemetryPacket};
use crate::types::CornerProperty;

/// Size of the telemetry packet in bytes
pub const PACKET_SIZE: usize = 1347;

/// Decode a telemetry packet sent by F1 2019
///
/// F1 2018 and F1 2019 publish the same data in their telemetry packets, but with different packet
/// headers.
pub fn decode_telemetry(cursor: &mut Cursor<&mut BytesMut>) -> Result<TelemetryPacket, Error> {
    ensure_packet_size(PACKET_SIZE, cursor)?;

    let header = decode_header(cursor)?;
    let mut telemetry = Vec::with_capacity(20);

    for _ in 0..20 {
        telemetry.push(Telemetry::new(
            cursor.get_u16_le(),
            cursor.get_f32_le(),
            cursor.get_f32_le(),
            cursor.get_f32_le(),
            cursor.get_u8(),
            decode_gear(cursor)?,
            cursor.get_u16_le(),
            cursor.get_u8() > 0,
            cursor.get_u8(),
            decode_brake_temperature(cursor),
            decode_tyre_surface_temperature(cursor),
            decode_tyre_inner_temperature(cursor),
            cursor.get_u16_le(),
            decode_tyre_pressure(cursor),
            decode_surface_type(cursor)?,
        ));
    }

    let button_status = match Button::from_bits(cursor.get_u32_le()) {
        Some(button) => button,
        None => Button::NONE,
    };

    Ok(TelemetryPacket::new(header, telemetry, button_status))
}

fn decode_gear(cursor: &mut Cursor<&mut BytesMut>) -> Result<Gear, Error> {
    let value = cursor.get_i8();

    match value {
        -1 => Ok(Gear::Reverse),
        0 => Ok(Gear::Neutral),
        1 => Ok(Gear::First),
        2 => Ok(Gear::Second),
        3 => Ok(Gear::Third),
        4 => Ok(Gear::Fourth),
        5 => Ok(Gear::Fifth),
        6 => Ok(Gear::Sixth),
        7 => Ok(Gear::Seventh),
        8 => Ok(Gear::Eighth),
        _ => Err(Error::new(ErrorKind::InvalidData, "Failed to decode gear.")),
    }
}

fn decode_brake_temperature(cursor: &mut Cursor<&mut BytesMut>) -> CornerProperty<u16> {
    CornerProperty::new(
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
    )
}

fn decode_tyre_surface_temperature(cursor: &mut Cursor<&mut BytesMut>) -> CornerProperty<u16> {
    CornerProperty::new(
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
    )
}

fn decode_tyre_inner_temperature(cursor: &mut Cursor<&mut BytesMut>) -> CornerProperty<u16> {
    CornerProperty::new(
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
        cursor.get_u16_le(),
    )
}

fn decode_tyre_pressure(cursor: &mut Cursor<&mut BytesMut>) -> CornerProperty<f32> {
    CornerProperty::new(
        cursor.get_f32_le(),
        cursor.get_f32_le(),
        cursor.get_f32_le(),
        cursor.get_f32_le(),
    )
}

fn decode_surface_type(
    cursor: &mut Cursor<&mut BytesMut>,
) -> Result<CornerProperty<Surface>, Error> {
    Ok(CornerProperty::new(
        decode_surface(cursor)?,
        decode_surface(cursor)?,
        decode_surface(cursor)?,
        decode_surface(cursor)?,
    ))
}

fn decode_surface(cursor: &mut Cursor<&mut BytesMut>) -> Result<Surface, Error> {
    let value = cursor.get_u8();

    match value {
        0 => Ok(Surface::Tarmac),
        1 => Ok(Surface::RumbleStrip),
        2 => Ok(Surface::Concrete),
        3 => Ok(Surface::Rock),
        4 => Ok(Surface::Gravel),
        5 => Ok(Surface::Mud),
        6 => Ok(Surface::Sand),
        7 => Ok(Surface::Grass),
        8 => Ok(Surface::Water),
        9 => Ok(Surface::Cobblestone),
        10 => Ok(Surface::Metal),
        11 => Ok(Surface::Ridged),
        _ => Err(Error::new(
            ErrorKind::InvalidData,
            "Failed to decode surface.",
        )),
    }
}

#[cfg(test)]
mod tests {
    use std::io::Cursor;

    use assert_approx_eq::assert_approx_eq;
    use bytes::{BufMut, BytesMut};

    use crate::nineteen::telemetry::{decode_telemetry, PACKET_SIZE};
    use crate::packet::telemetry::{Button, Gear, Surface};

    fn put_packet_header(mut bytes: BytesMut) -> BytesMut {
        bytes.put_u16_le(2019);
        bytes.put_u8(1);
        bytes.put_u8(2);
        bytes.put_u8(3);
        bytes.put_u8(0);
        bytes.put_u64_le(u64::max_value());
        bytes.put_f32_le(1.0);
        bytes.put_u32_le(u32::max_value());
        bytes.put_u8(0);

        bytes
    }

    #[test]
    fn decode_telemetry_with_error() {
        let mut bytes = BytesMut::with_capacity(0);
        let mut cursor = Cursor::new(&mut bytes);

        let packet = decode_telemetry(&mut cursor);
        assert!(packet.is_err());
    }

    #[test]
    fn decode_telemetry_with_success() {
        let mut bytes = BytesMut::with_capacity(PACKET_SIZE);
        bytes = put_packet_header(bytes);

        for _ in 0..20 {
            bytes.put_u16_le(1);
            bytes.put_f32_le(2.0);
            bytes.put_f32_le(3.0);
            bytes.put_f32_le(4.0);
            bytes.put_u8(5);
            bytes.put_u8(6);
            bytes.put_u16_le(7);
            bytes.put_u8(1);
            bytes.put_u8(9);
            bytes.put_u16_le(10);
            bytes.put_u16_le(11);
            bytes.put_u16_le(12);
            bytes.put_u16_le(13);
            bytes.put_u16_le(14);
            bytes.put_u16_le(15);
            bytes.put_u16_le(16);
            bytes.put_u16_le(17);
            bytes.put_u16_le(18);
            bytes.put_u16_le(19);
            bytes.put_u16_le(20);
            bytes.put_u16_le(21);
            bytes.put_u16_le(22);
            bytes.put_f32_le(23.0);
            bytes.put_f32_le(24.0);
            bytes.put_f32_le(25.0);
            bytes.put_f32_le(26.0);
            bytes.put_u8(5);
            bytes.put_u8(6);
            bytes.put_u8(7);
            bytes.put_u8(8);
        }

        bytes.put_u32_le(0x0001);

        let mut cursor = Cursor::new(&mut bytes);

        let packet = decode_telemetry(&mut cursor).unwrap();
        let telemetry = packet.telemetry()[0];

        assert_eq!(1, telemetry.speed());
        assert_approx_eq!(2.0, telemetry.throttle());
        assert_approx_eq!(3.0, telemetry.steering());
        assert_approx_eq!(4.0, telemetry.brake());
        assert_eq!(5, telemetry.clutch());
        assert_eq!(Gear::Sixth, telemetry.gear());
        assert_eq!(7, telemetry.engine_rpm());
        assert!(telemetry.drs());
        assert_eq!(9, telemetry.rev_lights());
        assert_eq!(10, telemetry.brake_temperature().front_left());
        assert_eq!(14, telemetry.tyre_surface_temperature().front_left());
        assert_eq!(18, telemetry.tyre_inner_temperature().front_left());
        assert_eq!(22, telemetry.engine_temperature());
        assert_approx_eq!(23.0, telemetry.tyre_pressure().front_left());
        assert_eq!(Surface::Mud, telemetry.surface_type().front_left());
        assert_eq!(Button::CROSS_OR_A, packet.button_status());
    }
}