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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150

use super::QoS;
use core::{
    ops::{BitAnd, Range},
    str::{from_utf8, Utf8Error},
};

#[derive(Debug)]
pub struct PublishBuilder<const N: usize> {
    buf: [u8; N],
}

impl<const N: usize> PublishBuilder<N> {
    const _PUBLISH_LEN_ASSERT: () = if N < 4 {
        ::core::panic!("Publish packet length is too short")
    };

    pub const fn new() -> Self {
        let mut p = Self { buf: [0; N] };
        p.buf[0] = (super::CtrlPkt::PUBLISH as u8) << 4;
        p.buf[1] = 2;
        p
    }

    pub const fn set_dup(mut self, dup: bool) -> Self {
        if dup {
            self.buf[0] |= 0b1000;
        } else {
            self.buf[0] &= !0b1000;
        }
        self
    }

    pub const fn set_qos(mut self, qos: QoS) -> Self {
        self.buf[0] &= !0b110;
        self.buf[0] |= (qos as u8) << 1;
        self
    }

    pub const fn set_retain(mut self, retain: bool) -> Self {
        if retain {
            self.buf[0] |= 0b1;
        } else {
            self.buf[0] &= !0b1;
        }
        self
    }

    const fn len(&self) -> usize {
        (self.buf[1] + 2) as usize
    }

    pub const fn set_topic(mut self, topic: &str) -> Self {
        let topic_len: u8 = topic.len() as u8;
        self.buf[1] += topic_len;
        self.buf[2] = 0;
        self.buf[3] = topic_len;
        let topic_bytes: &[u8] = topic.as_bytes();
        let len: usize = topic_bytes.len();
        let mut idx: usize = 0;
        loop {
            self.buf[idx + 4] = topic_bytes[idx];
            idx += 1;
            if idx >= len {
                break;
            }
        }
        self
    }

    pub const fn finalize(self) -> Publish<N> {
        Publish { bldr: self }
    }
}

impl<const N: usize> Default for PublishBuilder<N> {
    fn default() -> Self {
        Self::new()
    }
}

#[derive(Debug)]
pub struct Publish<const N: usize> {
    bldr: PublishBuilder<N>,
}

impl<const N: usize> Publish<N> {
    pub fn as_slice(&self) -> &[u8] {
        &self.bldr.buf[..self.bldr.len()]
    }
}

impl<const N: usize> core::fmt::Write for Publish<N> {
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        s.bytes().for_each(|byte| {
            self.bldr.buf[self.bldr.len()] = byte;
            self.bldr.buf[1] += 1;
        });
        Ok(())
    }
}

#[derive(Debug)]
pub struct PublishDe<'a> {
    pub dup_flag: bool,
    pub qos_level: Option<QoS>,
    pub retain: bool,
    pub topic: Result<&'a str, Utf8Error>,
    pub payload: &'a [u8],
}

impl<'a> PublishDe<'a> {
    pub fn new(buf: &'a [u8]) -> Option<Self> {
        let first_byte: u8 = *buf.first()?;
        if first_byte >> 4 & 0x0F == u8::from(super::CtrlPkt::PUBLISH) {
            let remain_len: u8 = *buf.get(1)?;
            let topic_len: u16 = u16::from_be_bytes(buf.get(2..4)?.try_into().unwrap());

            let topic_range: Range<usize> = Range {
                start: 4,
                end: 4_usize.saturating_add(topic_len as usize),
            };

            let payload_len: usize = remain_len
                .saturating_sub(u8::try_from(topic_len).unwrap_or(u8::MAX))
                .saturating_sub(2)
                .into();
            let payload_range: Range<usize> = Range {
                start: topic_range.end,
                end: topic_range.end.saturating_add(payload_len),
            };

            let topic_bytes: &[u8] = buf.get(topic_range)?;
            let payload_bytes: &[u8] = buf.get(payload_range)?;

            Some(Self {
                dup_flag: first_byte.bitand(0b1000).eq(&0b1000),
                qos_level: QoS::try_from(first_byte >> 1 & 0b11).ok(),
                retain: first_byte.bitand(0b1).eq(&0b1),
                topic: from_utf8(topic_bytes),
                payload: payload_bytes,
            })
        } else {
            None
        }
    }

    pub fn payload_utf8(&self) -> Result<&str, Utf8Error> {
        from_utf8(self.payload)
    }
}