hyphae 1.0.5

Reactive cells and runtime primitives for rship
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

//! Project plan node implementing [`MapQuery`].
//!
//! `project` builds an uncompiled plan node that composes with other
//! [`MapQuery`] operators. Call [`MapQuery::materialize`] to compile a plan
//! into a subscribable [`CellMap`](crate::CellMap).

use std::{hash::Hash, marker::PhantomData, sync::Arc};

use crate::{
    map_query::{MapDiffSink, MapQuery, MapQueryInstall},
    subscription::SubscriptionGuard,
    traits::{CellValue, collections::internal::map_runtime::install_map_runtime_via_query},
};

/// Plan node for [`ProjectMapExt::project`].
///
/// Each source row maps to at most one output row. The closure returns
/// `Some((output_key, output_value))` to include/update a row, or `None` to
/// exclude that source row from the output.
///
/// Not [`Clone`]: cloning a plan would silently duplicate projection work;
/// share by materializing once.
pub struct ProjectPlan<S, SK, SV, OK, OV, F>
where
    S: MapQuery<SK, SV>,
    SK: Hash + Eq + CellValue,
    SV: CellValue,
    OK: Hash + Eq + CellValue,
    OV: CellValue,
    F: Fn(&SK, &SV) -> Option<(OK, OV)> + Send + Sync + 'static,
{
    pub(crate) source: S,
    pub(crate) f: Arc<F>,
    #[allow(clippy::type_complexity)]
    pub(crate) _types: PhantomData<fn() -> (SK, SV, OK, OV)>,
}

impl<S, SK, SV, OK, OV, F> MapQueryInstall<OK, OV> for ProjectPlan<S, SK, SV, OK, OV, F>
where
    S: MapQuery<SK, SV>,
    SK: Hash + Eq + CellValue,
    SV: CellValue,
    OK: Hash + Eq + CellValue,
    OV: CellValue,
    F: Fn(&SK, &SV) -> Option<(OK, OV)> + Send + Sync + 'static,
{
    fn install(self, sink: MapDiffSink<OK, OV>) -> Vec<SubscriptionGuard> {
        let f = self.f;
        install_map_runtime_via_query::<SK, SV, OK, OV, S, _>(
            self.source,
            move |k, v| f(k, v).into_iter().collect(),
            sink,
        )
    }
}

#[allow(private_bounds)]
impl<S, SK, SV, OK, OV, F> MapQuery<OK, OV> for ProjectPlan<S, SK, SV, OK, OV, F>
where
    S: MapQuery<SK, SV>,
    SK: Hash + Eq + CellValue,
    SV: CellValue,
    OK: Hash + Eq + CellValue,
    OV: CellValue,
    F: Fn(&SK, &SV) -> Option<(OK, OV)> + Send + Sync + 'static,
{
}

/// Project operator returning a [`MapQuery`] plan node.
///
/// `project` consumes `self` and returns an uncompiled plan node; call
/// [`MapQuery::materialize`] on the result to obtain a subscribable
/// [`CellMap`](crate::CellMap).
pub trait ProjectMapExt<K, V>: MapQuery<K, V>
where
    K: Hash + Eq + CellValue,
    V: CellValue,
{
    /// Projects each source row to at most one output row.
    ///
    /// `f(&source_key, &source_value)` returns:
    /// - `Some((output_key, output_value))` to include/update a row
    /// - `None` to remove/exclude that source row from output
    #[track_caller]
    fn project<K2, V2, F>(self, f: F) -> ProjectPlan<Self, K, V, K2, V2, F>
    where
        K2: Hash + Eq + CellValue,
        V2: CellValue,
        F: Fn(&K, &V) -> Option<(K2, V2)> + Send + Sync + 'static,
    {
        ProjectPlan {
            source: self,
            f: Arc::new(f),
            _types: PhantomData,
        }
    }
}

impl<K, V, M> ProjectMapExt<K, V> for M
where
    K: Hash + Eq + CellValue,
    V: CellValue,
    M: MapQuery<K, V>,
{
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::CellMap;

    #[test]
    fn project_handles_projection_disappearance_without_extra_rows() {
        let source = CellMap::<String, i32>::new();
        let projected = source
            .clone()
            .project(|key, value| {
                if *value > 0 {
                    Some((format!("p:{key}"), value * 10))
                } else {
                    None
                }
            })
            .materialize();

        source.insert("a".to_string(), 1);
        assert_eq!(projected.get_value(&"p:a".to_string()), Some(10));
        source.insert("a".to_string(), -1);
        assert_eq!(projected.get_value(&"p:a".to_string()), None);
    }
}