cachet 0.2.0 

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
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

use std::fmt::Debug;

use crate::{CacheEntry, CacheTier, Codec, Encoder, Error, SizeError};

type EncodeFn<A, B> = Box<dyn Fn(&A) -> Result<B, Error> + Send + Sync>;

/// A boxed-closure encoder for custom one-directional transforms (keys).
pub struct TransformEncoder<A, B> {
    encode_fn: EncodeFn<A, B>,
}

impl<A, B> TransformEncoder<A, B> {
    /// Creates a new `TransformEncoder` from a fallible closure.
    pub fn new<EncodeError>(encode_fn: impl Fn(&A) -> Result<B, EncodeError> + Send + Sync + 'static) -> Self
    where
        EncodeError: std::error::Error + Send + Sync + 'static,
    {
        Self {
            encode_fn: Box::new(move |a| encode_fn(a).map_err(|e| Error::from_source(e))),
        }
    }

    /// Creates a new `TransformEncoder` from an infallible closure.
    pub fn infallible(encode_fn: impl Fn(&A) -> B + Send + Sync + 'static) -> Self {
        Self {
            encode_fn: Box::new(move |a| Ok(encode_fn(a))),
        }
    }
}

impl<A, B> Encoder<A, B> for TransformEncoder<A, B> {
    fn encode(&self, value: &A) -> Result<B, Error> {
        (self.encode_fn)(value)
    }
}

impl<A, B> Debug for TransformEncoder<A, B> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TransformEncoder")
            .field("A", &std::any::type_name::<A>())
            .field("B", &std::any::type_name::<B>())
            .finish()
    }
}

/// A boxed-closure codec for custom bidirectional transforms (values).
pub struct TransformCodec<A, B> {
    encode_fn: EncodeFn<A, B>,
    decode_fn: EncodeFn<B, A>,
}

impl<A, B> TransformCodec<A, B> {
    /// Creates a new `TransformCodec` from a pair of fallible closures.
    pub fn new<EncodeError, DecodeError>(
        encode_fn: impl Fn(&A) -> Result<B, EncodeError> + Send + Sync + 'static,
        decode_fn: impl Fn(&B) -> Result<A, DecodeError> + Send + Sync + 'static,
    ) -> Self
    where
        EncodeError: std::error::Error + Send + Sync + 'static,
        DecodeError: std::error::Error + Send + Sync + 'static,
    {
        Self {
            encode_fn: Box::new(move |a| encode_fn(a).map_err(|e| Error::from_source(e))),
            decode_fn: Box::new(move |b| decode_fn(b).map_err(|e| Error::from_source(e))),
        }
    }
}

impl<A, B> Encoder<A, B> for TransformCodec<A, B> {
    fn encode(&self, value: &A) -> Result<B, Error> {
        (self.encode_fn)(value)
    }
}

impl<A, B> Codec<A, B> for TransformCodec<A, B> {
    fn decode(&self, value: &B) -> Result<A, Error> {
        (self.decode_fn)(value)
    }
}

impl<A, B> Debug for TransformCodec<A, B> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TransformCodec")
            .field("A", &std::any::type_name::<A>())
            .field("B", &std::any::type_name::<B>())
            .finish()
    }
}

/// Adapter that transforms keys and values between user types and storage types.
///
/// `TransformAdapter<K, KT, V, VT, S>`:
/// - `K, V` are the user-facing types (the types the adapter exposes via `CacheTier<K, V>`)
/// - `KT, VT` are the storage types (the types used by the inner `S: CacheTier<KT, VT>`)
/// - `key_encoder: K->KT` (one-directional), `value_codec: V<->VT` (bidirectional)
///
/// Implements `CacheTier<K, V>` by encoding keys/values to `KT, VT` for the inner tier.
pub(crate) struct TransformAdapter<K, KT, V, VT, S>
where
    S: CacheTier<KT, VT>,
{
    inner: S,
    key_encoder: Box<dyn Encoder<K, KT>>,
    value_codec: Box<dyn Codec<V, VT>>,
}

impl<K, KT, V, VT, S> TransformAdapter<K, KT, V, VT, S>
where
    S: CacheTier<KT, VT>,
{
    /// Creates a new `TransformAdapter` from pre-boxed codecs.
    pub(crate) fn from_boxed(inner: S, key_encoder: Box<dyn Encoder<K, KT>>, value_codec: Box<dyn Codec<V, VT>>) -> Self {
        Self {
            inner,
            key_encoder,
            value_codec,
        }
    }
}

impl<K, KT, V, VT, S> CacheTier<K, V> for TransformAdapter<K, KT, V, VT, S>
where
    K: Send + Sync,
    V: Send + Sync,
    KT: Send + Sync,
    VT: Send + Sync,
    S: CacheTier<KT, VT> + Send + Sync,
{
    async fn get(&self, key: &K) -> Result<Option<CacheEntry<V>>, Error> {
        let mapped_key = self.key_encoder.encode(key)?;
        let entry_option = self.inner.get(&mapped_key).await?;
        if let Some(entry) = entry_option {
            entry.try_map_value(|v| self.value_codec.decode(&v)).map(Some)
        } else {
            Ok(None)
        }
    }

    async fn insert(&self, key: K, entry: CacheEntry<V>) -> Result<(), Error> {
        let mapped_key = self.key_encoder.encode(&key)?;
        let mapped_entry = entry.try_map_value(|v| self.value_codec.encode(&v))?;
        self.inner.insert(mapped_key, mapped_entry).await
    }

    async fn invalidate(&self, key: &K) -> Result<(), Error> {
        let mapped_key = self.key_encoder.encode(key)?;
        self.inner.invalidate(&mapped_key).await
    }

    async fn clear(&self) -> Result<(), Error> {
        self.inner.clear().await
    }

    async fn len(&self) -> Result<u64, SizeError> {
        self.inner.len().await
    }
}

impl<K, KT, V, VT, S> Debug for TransformAdapter<K, KT, V, VT, S>
where
    S: CacheTier<KT, VT> + Debug,
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TransformAdapter")
            .field("inner", &self.inner)
            .field("K", &std::any::type_name::<K>())
            .field("KT", &std::any::type_name::<KT>())
            .field("V", &std::any::type_name::<V>())
            .field("VT", &std::any::type_name::<VT>())
            .finish_non_exhaustive()
    }
}

#[cfg(test)]
mod tests {
    use cachet_tier::MockCache;

    use super::*;

    #[test]
    fn transform_adapter_debug() {
        let codec = TransformCodec::new(
            |v: &String| v.parse::<i32>(),
            |v: &i32| Ok::<_, std::convert::Infallible>(v.to_string()),
        );
        // Exercise both directions so closure bodies are covered.
        assert_eq!(codec.encode(&"42".to_string()).unwrap(), 42);
        assert_eq!(codec.decode(&42).unwrap(), "42");

        let key_encoder = TransformEncoder::new(|k: &String| k.parse::<i32>());
        // Exercise the encoder so the wrapping closure is covered.
        assert_eq!(key_encoder.encode(&"7".to_string()).unwrap(), 7);

        let inner = MockCache::<i32, i32>::new();
        let adapter = TransformAdapter::from_boxed(inner, Box::new(key_encoder), Box::new(codec));
        let debug = format!("{adapter:?}");
        assert!(debug.contains("TransformAdapter"));
    }

    #[test]
    fn infallible_encoder_closure_is_covered() {
        let encoder = TransformEncoder::infallible(|k: &i32| k.to_string());
        assert_eq!(encoder.encode(&42).unwrap(), "42");
    }

    #[cfg_attr(miri, ignore)]
    #[tokio::test]
    async fn len_delegates_to_inner() {
        use crate::infallible;

        let data = vec![(1, CacheEntry::new(10)), (2, CacheEntry::new(20))];
        let inner = MockCache::with_data(data.into_iter().collect());
        let adapter = TransformAdapter::from_boxed(
            inner,
            Box::new(TransformEncoder::new(|k: &String| k.parse::<i32>())),
            Box::new(TransformCodec::new(infallible(|v: &i32| *v), infallible(|v: &i32| *v))),
        );
        assert_eq!(adapter.len().await.expect("MockCache::len returns Ok"), 2);
    }
}