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>`, to be used in place of any type in the Matrix endpoint
/// definition to allow request and response types to contain that said type represented by
/// the generic argument `Ev`.
///
/// 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<'_>) -> std::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(())
}
}