meta-language 0.27.0

A self-describing links-network core for lossless language representation
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

use std::sync::Arc;

use crate::link_network::LinkNetwork;

/// Immutable versioned view of a links network.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct NetworkSnapshot {
    version: u64,
    parent_version: Option<u64>,
    provenance: String,
    network: Arc<LinkNetwork>,
}

impl NetworkSnapshot {
    /// Creates an immutable snapshot from a network value.
    #[must_use]
    pub fn new(version: u64, network: LinkNetwork, provenance: impl Into<String>) -> Self {
        Self {
            version,
            parent_version: None,
            provenance: provenance.into(),
            network: Arc::new(network),
        }
    }

    /// Snapshot version.
    #[must_use]
    pub const fn version(&self) -> u64 {
        self.version
    }

    /// Parent version when this snapshot was committed from a mutable snapshot.
    #[must_use]
    pub const fn parent_version(&self) -> Option<u64> {
        self.parent_version
    }

    /// Human-readable change provenance for this snapshot.
    #[must_use]
    pub fn provenance(&self) -> &str {
        &self.provenance
    }

    /// Immutable network data held by this snapshot.
    #[must_use]
    pub fn network(&self) -> &LinkNetwork {
        self.network.as_ref()
    }

    /// Number of immutable snapshot handles sharing the same network value.
    #[must_use]
    pub fn shared_snapshot_count(&self) -> usize {
        Arc::strong_count(&self.network)
    }

    /// Creates an editable snapshot fork from this immutable snapshot.
    #[must_use]
    pub fn to_mutable(&self, provenance: impl Into<String>) -> MutableNetworkSnapshot {
        MutableNetworkSnapshot {
            base_version: self.version,
            network: self.network().clone(),
            provenance: provenance.into(),
        }
    }

    fn committed(
        version: u64,
        parent_version: u64,
        network: LinkNetwork,
        provenance: String,
    ) -> Self {
        Self {
            version,
            parent_version: Some(parent_version),
            provenance,
            network: Arc::new(network),
        }
    }
}

/// Editable fork of an immutable network snapshot.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct MutableNetworkSnapshot {
    base_version: u64,
    network: LinkNetwork,
    provenance: String,
}

impl MutableNetworkSnapshot {
    /// Version this mutable snapshot was forked from.
    #[must_use]
    pub const fn base_version(&self) -> u64 {
        self.base_version
    }

    /// Human-readable provenance that will be attached when committed.
    #[must_use]
    pub fn provenance(&self) -> &str {
        &self.provenance
    }

    /// Immutable view of the editable network.
    #[must_use]
    pub const fn network(&self) -> &LinkNetwork {
        &self.network
    }

    /// Mutable view of the editable network.
    pub fn network_mut(&mut self) -> &mut LinkNetwork {
        &mut self.network
    }

    /// Commits this mutable snapshot as the next sequential version.
    #[must_use]
    pub fn commit(self) -> NetworkSnapshot {
        let next_version = self
            .base_version
            .checked_add(1)
            .expect("snapshot version overflow");
        self.commit_as(next_version)
    }

    /// Commits this mutable snapshot with an explicit forward version.
    #[must_use]
    pub fn commit_as(self, version: u64) -> NetworkSnapshot {
        assert!(
            version > self.base_version,
            "snapshot version must move forward"
        );
        NetworkSnapshot::committed(version, self.base_version, self.network, self.provenance)
    }
}

impl LinkNetwork {
    /// Captures the current network as an immutable versioned snapshot.
    #[must_use]
    pub fn snapshot(&self, version: u64, provenance: impl Into<String>) -> NetworkSnapshot {
        NetworkSnapshot::new(version, self.clone(), provenance)
    }
}