1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use std::convert::{TryFrom, TryInto};
use std::string::FromUtf8Error;

use crate::header::{Header, HeaderOctets, HEADER_LENGTH};
use crate::{Octet, Octets};

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Too short packet found.")]
    PacketTooShort,
}

#[derive(Debug, PartialEq)]
pub struct Packet {
    header: Header,
    message: Vec<Octet>,
}

impl Packet {
    pub fn new(message: Vec<Octet>) -> Self {
        Self {
            header: Header::default(),
            message,
        }
    }

    pub fn from_raw_parts(header: &HeaderOctets, message: &Octets) -> Self {
        Self {
            header: Header::from(header),
            message: message.to_vec(),
        }
    }

    pub fn to_octets_vec(&self) -> Vec<Octet> {
        let mut vec: Vec<u8> = self.header.to_octets_vec();

        vec.extend_from_slice(&(self.message.len() as u64).to_le_bytes());
        vec.extend_from_slice(self.message.as_slice());

        vec
    }

    pub fn message(&self) -> &[Octet] {
        &self.message
    }
}

impl Default for Packet {
    fn default() -> Self {
        Self::new(Vec::new())
    }
}

impl TryFrom<&Octets> for Packet {
    type Error = Error;

    fn try_from(value: &Octets) -> Result<Self, Self::Error> {
        if value.len() < HEADER_LENGTH + 8 {
            Err(Error::PacketTooShort)
        } else {
            let mut header = HeaderOctets::default();
            header.copy_from_slice(&value[0..HEADER_LENGTH]);

            let offset = HEADER_LENGTH + 8;
            let mut length: [Octet; 8] = [0; 8];
            length.copy_from_slice(&value[HEADER_LENGTH..offset]);

            let length = u64::from_le_bytes(length);
            let rest = &value[offset..];

            // TODO: Support Fragmentation
            assert_eq!(length as usize, rest.len());

            Ok(Packet::from_raw_parts(&header, rest))
        }
    }
}

impl TryInto<String> for Packet {
    type Error = FromUtf8Error;

    fn try_into(self) -> Result<String, Self::Error> {
        String::from_utf8(self.message)
    }
}

#[cfg(test)]
mod tests {
    use crate::packet::Packet;
    use crate::Octets;
    use std::convert::TryFrom;

    #[test]
    fn default() {
        let packet = Packet::default();
        let header_bytes = packet.header.to_octets_vec();
        let header_len = header_bytes.len();
        let bytes = packet.to_octets_vec();

        assert_eq!(header_len + 8, bytes.len());
        assert_eq!(&header_bytes, &bytes[..header_len])
    }

    #[test]
    fn with_message() {
        let message = vec![b'f', b'o', b'o'];
        let packet = Packet::new(message.clone());
        let header_bytes = packet.header.to_octets_vec();
        let header_len = header_bytes.len();
        let bytes = packet.to_octets_vec();

        assert_eq!(header_len + 8 + message.len(), bytes.len());
        assert_eq!(&header_bytes, &bytes[..header_len]);
        assert_eq!(&message, &bytes[header_len + 8..]);
    }

    #[test]
    fn try_from_header_only() {
        let octets = vec![
            b'Y', b'M', b'M', b'P', b'v', b'0', b'.', b'1', 0, 0, 0, 0, 0, 0, 0, 0,
        ];

        let octets: &Octets = octets.as_slice();
        let packet = Packet::try_from(octets).expect("failed");

        assert_eq!(0, packet.message.len())
    }
}