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
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
use std::{
    clone::Clone,
    fmt::{self, Debug},
    marker::PhantomData,
    mem,
};

use serde::{
    de::{self, Deserialize, DeserializeSeed, Deserializer, IgnoredAny, MapAccess, Visitor},
    ser::{Serialize, Serializer},
};
use serde_json::value::{to_raw_value as to_raw_json_value, RawValue as RawJsonValue};

/// A wrapper around `Box<RawValue>` with a generic parameter for the expected Rust type.
///
/// Ruma offers the `Raw` wrapper to enable passing around JSON text that is only partially
/// validated. This is useful when a client receives events that do not follow the spec perfectly
/// or a server needs to generate reference hashes with the original canonical JSON string.
/// All event structs and enums implement `Serialize` / `Deserialize`, `Raw` should be used
/// to pass around events in a lossless way.
///
/// ```no_run
/// # use serde::Deserialize;
/// # use ruma_common::serde::Raw;
/// # #[derive(Deserialize)]
/// # struct AnyTimelineEvent;
///
/// let json = r#"{ "type": "imagine a full event", "content": {...} }"#;
///
/// let deser = serde_json::from_str::<Raw<AnyTimelineEvent>>(json)
///     .unwrap() // the first Result from serde_json::from_str, will not fail
///     .deserialize() // deserialize to the inner type
///     .unwrap(); // finally get to the AnyTimelineEvent
/// ```
#[repr(transparent)]
pub struct Raw<T> {
    json: Box<RawJsonValue>,
    _ev: PhantomData<T>,
}

impl<T> Raw<T> {
    /// Create a `Raw` by serializing the given `T`.
    ///
    /// Shorthand for `serde_json::value::to_raw_value(val).map(Raw::from_json)`, but specialized to
    /// `T`.
    ///
    /// # Errors
    ///
    /// Fails if `T`s [`Serialize`] implementation fails.
    pub fn new(val: &T) -> serde_json::Result<Self>
    where
        T: Serialize,
    {
        to_raw_json_value(val).map(Self::from_json)
    }

    /// Create a `Raw` from a boxed `RawValue`.
    pub fn from_json(json: Box<RawJsonValue>) -> Self {
        Self { json, _ev: PhantomData }
    }

    /// Convert an owned `String` of JSON data to `Raw<T>`.
    ///
    /// This function is equivalent to `serde_json::from_str::<Raw<T>>` except that an allocation
    /// and copy is avoided if both of the following are true:
    ///
    /// * the input has no leading or trailing whitespace, and
    /// * the input has capacity equal to its length.
    pub fn from_json_string(json: String) -> serde_json::Result<Self> {
        RawJsonValue::from_string(json).map(Self::from_json)
    }

    /// Access the underlying json value.
    pub fn json(&self) -> &RawJsonValue {
        &self.json
    }

    /// Convert `self` into the underlying json value.
    pub fn into_json(self) -> Box<RawJsonValue> {
        self.json
    }

    /// Try to access a given field inside this `Raw`, assuming it contains an object.
    ///
    /// Returns `Err(_)` when the contained value is not an object, or the field exists but is fails
    /// to deserialize to the expected type.
    ///
    /// Returns `Ok(None)` when the field doesn't exist or is `null`.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # type CustomMatrixEvent = ();
    /// # fn foo() -> serde_json::Result<()> {
    /// # let raw_event: ruma_common::serde::Raw<()> = todo!();
    /// if raw_event.get_field::<String>("type")?.as_deref() == Some("org.custom.matrix.event") {
    ///     let event = raw_event.deserialize_as::<CustomMatrixEvent>()?;
    ///     // ...
    /// }
    /// # Ok(())
    /// # }
    /// ```
    pub fn get_field<'a, U>(&'a self, field_name: &str) -> serde_json::Result<Option<U>>
    where
        U: Deserialize<'a>,
    {
        struct FieldVisitor<'b>(&'b str);

        impl<'b, 'de> Visitor<'de> for FieldVisitor<'b> {
            type Value = bool;

            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                write!(formatter, "`{}`", self.0)
            }

            fn visit_str<E>(self, value: &str) -> Result<bool, E>
            where
                E: de::Error,
            {
                Ok(value == self.0)
            }
        }

        struct Field<'b>(&'b str);

        impl<'b, 'de> DeserializeSeed<'de> for Field<'b> {
            type Value = bool;

            fn deserialize<D>(self, deserializer: D) -> Result<bool, D::Error>
            where
                D: Deserializer<'de>,
            {
                deserializer.deserialize_identifier(FieldVisitor(self.0))
            }
        }

        struct SingleFieldVisitor<'b, T> {
            field_name: &'b str,
            _phantom: PhantomData<T>,
        }

        impl<'b, T> SingleFieldVisitor<'b, T> {
            fn new(field_name: &'b str) -> Self {
                Self { field_name, _phantom: PhantomData }
            }
        }

        impl<'b, 'de, T> Visitor<'de> for SingleFieldVisitor<'b, T>
        where
            T: Deserialize<'de>,
        {
            type Value = Option<T>;

            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                formatter.write_str("a string")
            }

            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
            where
                A: MapAccess<'de>,
            {
                let mut res = None;
                while let Some(is_right_field) = map.next_key_seed(Field(self.field_name))? {
                    if is_right_field {
                        res = Some(map.next_value()?);
                    } else {
                        map.next_value::<IgnoredAny>()?;
                    }
                }

                Ok(res)
            }
        }

        let mut deserializer = serde_json::Deserializer::from_str(self.json().get());
        deserializer.deserialize_map(SingleFieldVisitor::new(field_name))
    }

    /// Try to deserialize the JSON as the expected type.
    pub fn deserialize<'a>(&'a self) -> serde_json::Result<T>
    where
        T: Deserialize<'a>,
    {
        serde_json::from_str(self.json.get())
    }

    /// Try to deserialize the JSON as a custom type.
    pub fn deserialize_as<'a, U>(&'a self) -> serde_json::Result<U>
    where
        U: Deserialize<'a>,
    {
        serde_json::from_str(self.json.get())
    }

    /// Turns `Raw<T>` into `Raw<U>` without changing the underlying JSON.
    ///
    /// This is useful for turning raw specific event types into raw event enum types.
    pub fn cast<U>(self) -> Raw<U> {
        Raw::from_json(self.into_json())
    }

    /// Turns `&Raw<T>` into `&Raw<U>` without changing the underlying JSON.
    ///
    /// This is useful for turning raw specific event types into raw event enum types.
    pub fn cast_ref<U>(&self) -> &Raw<U> {
        unsafe { mem::transmute(self) }
    }
}

impl<T> Clone for Raw<T> {
    fn clone(&self) -> Self {
        Self::from_json(self.json.clone())
    }
}

impl<T> Debug for Raw<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use std::any::type_name;
        f.debug_struct(&format!("Raw::<{}>", type_name::<T>())).field("json", &self.json).finish()
    }
}

impl<'de, T> Deserialize<'de> for Raw<T> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        Box::<RawJsonValue>::deserialize(deserializer).map(Self::from_json)
    }
}

impl<T> Serialize for Raw<T> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        self.json.serialize(serializer)
    }
}

#[cfg(test)]
mod tests {
    use serde::Deserialize;
    use serde_json::{from_str as from_json_str, value::RawValue as RawJsonValue};

    use super::Raw;

    #[test]
    fn get_field() -> serde_json::Result<()> {
        #[derive(Debug, PartialEq, Deserialize)]
        struct A<'a> {
            #[serde(borrow)]
            b: Vec<&'a str>,
        }

        const OBJ: &str = r#"{ "a": { "b": [  "c"] }, "z": 5 }"#;
        let raw: Raw<()> = from_json_str(OBJ)?;

        assert_eq!(raw.get_field::<u8>("z")?, Some(5));
        assert_eq!(raw.get_field::<&RawJsonValue>("a")?.unwrap().get(), r#"{ "b": [  "c"] }"#);
        assert_eq!(raw.get_field::<A<'_>>("a")?, Some(A { b: vec!["c"] }));

        assert_eq!(raw.get_field::<u8>("b")?, None);
        raw.get_field::<u8>("a").unwrap_err();

        Ok(())
    }
}