mq-bridge 0.3.6

An asynchronous message bridging library connecting Kafka, MQTT, AMQP, NATS, MongoDB, HTTP, and more.
Documentation 
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

//  mq-bridge
//  © Copyright 2026, by Marco Mengelkoch
//  Licensed under MIT License, see License file for more details
//  git clone https://github.com/marcomq/mq-bridge

use super::error::{ErrorKind, TransformError};
use serde_json::Value;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(super) enum Ty {
    String,
    Integer,
    Number,
    Boolean,
    Object,
    Array,
    Null,
}

impl Ty {
    pub(super) fn parse(s: &str) -> Option<Ty> {
        Some(match s {
            "string" => Ty::String,
            "integer" => Ty::Integer,
            "number" => Ty::Number,
            "boolean" => Ty::Boolean,
            "object" => Ty::Object,
            "array" => Ty::Array,
            "null" => Ty::Null,
            _ => return None,
        })
    }

    pub(super) fn name(self) -> &'static str {
        match self {
            Ty::String => "string",
            Ty::Integer => "integer",
            Ty::Number => "number",
            Ty::Boolean => "boolean",
            Ty::Object => "object",
            Ty::Array => "array",
            Ty::Null => "null",
        }
    }

    pub(super) fn matches(self, v: &Value) -> bool {
        match (self, v) {
            (Ty::String, Value::String(_)) => true,
            (Ty::Integer, Value::Number(n)) => n.is_i64() || n.is_u64(),
            (Ty::Number, Value::Number(_)) => true,
            (Ty::Boolean, Value::Bool(_)) => true,
            (Ty::Object, Value::Object(_)) => true,
            (Ty::Array, Value::Array(_)) => true,
            (Ty::Null, Value::Null) => true,
            _ => false,
        }
    }
}

pub(super) fn type_name(v: &Value) -> &'static str {
    match v {
        Value::Null => "null",
        Value::Bool(_) => "boolean",
        Value::Number(n) => {
            if n.is_i64() || n.is_u64() {
                "integer"
            } else {
                "number"
            }
        }
        Value::String(_) => "string",
        Value::Array(_) => "array",
        Value::Object(_) => "object",
    }
}

/// Applies the one safe coercion for `ty`, or fails. Never best-effort: a value that
/// cannot be converted losslessly is an error, not a silent substitution.
pub(super) fn coerce(
    value: &mut Value,
    ty: Ty,
    crumbs: &[Crumb<'_>],
) -> Result<(), TransformError> {
    let coerced = match (ty, &*value) {
        (Ty::Integer, Value::String(s)) => {
            let t = s.trim();
            t.parse::<i64>()
                .ok()
                .map(Value::from)
                .or_else(|| t.parse::<u64>().ok().map(Value::from))
        }
        (Ty::Number, Value::String(s)) => s
            .trim()
            .parse::<f64>()
            .ok()
            .and_then(serde_json::Number::from_f64)
            .map(Value::Number),
        (Ty::Boolean, Value::String(s)) => match s.trim() {
            "true" | "1" => Some(Value::Bool(true)),
            "false" | "0" => Some(Value::Bool(false)),
            _ => None,
        },
        (Ty::String, Value::Number(n)) => Some(Value::String(n.to_string())),
        _ => None,
    };

    match coerced {
        Some(new_value) => {
            *value = new_value;
            Ok(())
        }
        None => Err(TransformError::new(
            render_path(crumbs),
            ErrorKind::Coercion,
            format!(
                "cannot coerce {} {} to {}",
                type_name(value),
                value,
                ty.name()
            ),
        )),
    }
}

#[derive(Debug, Clone, Copy)]
pub(super) enum Crumb<'a> {
    Key(&'a str),
    Index(usize),
}

pub(super) fn render_path(crumbs: &[Crumb<'_>]) -> String {
    let mut out = String::from("$");
    for crumb in crumbs {
        match crumb {
            Crumb::Key(k) => {
                out.push('.');
                out.push_str(k);
            }
            Crumb::Index(i) => {
                out.push('[');
                out.push_str(&i.to_string());
                out.push(']');
            }
        }
    }
    out
}