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
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178

use core::mem;
use std::{fs, io, path::PathBuf};

use serde::{Deserialize, Serialize};

use crate::{Context, ContextUnit, Element, Preamble};

/// Empty config set for atomic serialization that is not parametrizable
pub struct AtomicConfig;

impl Default for AtomicConfig {
    fn default() -> Self {
        AtomicConfig
    }
}

impl From<&Config> for AtomicConfig {
    fn from(_config: &Config) -> Self {
        AtomicConfig
    }
}

impl From<&Config> for Config {
    fn from(config: &Config) -> Self {
        *config
    }
}

/// Base configuration schema
pub trait BaseConfig: Sized + Default + Serialize + for<'a> Deserialize<'a> {
    /// Package name (e.g. `CARGO_PKG_NAME`)
    const PACKAGE: &'static str;

    /// Path of the serialized configuration
    fn path() -> Option<PathBuf> {
        dirs::config_dir()
            .map(|p| p.join(Self::PACKAGE))
            .map(|p| p.join("config.toml"))
    }

    /// Load a config instance from the config dir
    fn load() -> io::Result<Self> {
        let path = Self::path().ok_or_else(|| {
            io::Error::new(io::ErrorKind::Other, "unable to define configuration path")
        })?;

        if !path.exists() {
            let config = Self::default();

            // config serialization is optional
            path.parent()
                .ok_or_else(|| {
                    io::Error::new(
                        io::ErrorKind::Other,
                        "unable to fetch parent dir of config file",
                    )
                })
                .and_then(fs::create_dir_all)
                .and_then(|_| {
                    toml::to_string_pretty(&config)
                        .map_err(|e| io::Error::new(io::ErrorKind::Other, e))
                })
                .and_then(|contents| fs::write(path, contents))
                .unwrap_or_else(|e| eprintln!("failed to serialize config file: {}", e));

            return Ok(config);
        }

        let contents = fs::read_to_string(path)?;

        toml::from_str(&contents).map_err(|e| io::Error::new(io::ErrorKind::Other, e))
    }
}

/// Configuration parameters for encoding and decoding
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub struct Config {
    /// Flag to zero skip scalar values during encoding, and zero them during decoding
    pub zeroed_scalar_values: bool,
}

impl Default for Config {
    fn default() -> Self {
        Self::DEFAULT
    }
}

impl Config {
    /// Serialized length
    pub const LEN: usize = mem::size_of::<bool>();

    /// Default value as constant
    pub const DEFAULT: Self = Self {
        zeroed_scalar_values: false,
    };

    /// Set the flag to cache the source path
    pub fn with_zeroed_scalar_values(&mut self, zeroed_scalar_values: bool) -> &mut Self {
        self.zeroed_scalar_values = zeroed_scalar_values;
        self
    }
}

impl BaseConfig for Config {
    const PACKAGE: &'static str = env!("CARGO_PKG_NAME");
}

impl Element for Config {
    type Config = AtomicConfig;

    fn zeroed() -> Self {
        Self::DEFAULT
    }

    fn len(_config: &Self::Config) -> usize {
        Self::LEN
    }

    fn to_buffer(&self, _config: &Self::Config, context: &mut ContextUnit, buf: &mut [u8]) {
        let _ = self
            .zeroed_scalar_values
            .encode(&AtomicConfig, context, buf);
    }

    fn try_from_buffer_in_place<S>(
        &mut self,
        config: &Self::Config,
        context: &mut Context<S>,
        buf: &[u8],
    ) -> io::Result<()>
    where
        S: io::Read + io::Seek,
    {
        Self::validate_buffer_len(config, buf.len())?;

        let _ = self
            .zeroed_scalar_values
            .try_decode_in_place(&AtomicConfig, context, buf)?;

        Ok(())
    }

    fn validate(&self, _preamble: &Preamble) -> io::Result<()> {
        Ok(())
    }
}

#[test]
fn builder_functions_works() {
    assert!(
        Config::default()
            .with_zeroed_scalar_values(true)
            .zeroed_scalar_values
    );

    assert!(
        !Config::default()
            .with_zeroed_scalar_values(false)
            .zeroed_scalar_values
    );
}

#[test]
fn zeroed_works() {
    assert_eq!(Config::zeroed(), Config::DEFAULT)
}

#[test]
fn atomic_config_has_default() {
    AtomicConfig::default();
}

#[test]
fn validate_works() {
    Config::default()
        .validate(&Default::default())
        .expect("default config validate should pass");
}