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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
//! Support for deferring inspection requests.
use super::InspectMut;
use super::InternalNode;
use super::Request;
use super::RequestRoot;
use super::Response;
use super::SensitivityLevel;
use super::UpdateRequest;
use super::Value;
use alloc::borrow::ToOwned;
use alloc::string::String;
use mesh::MeshPayload;
impl Request<'_> {
/// Defers the inspection request, producing a value that can be sent to
/// another thread or context to continue the inspection asynchronously.
pub fn defer(self) -> Deferred {
let (send, recv) = mesh::oneshot();
*self.node = InternalNode::Deferred(recv);
Deferred {
path: self.path.to_owned(),
value: self.value.map(|x| x.to_owned()),
depth: self.depth,
node: send,
sensitivity: self.sensitivity,
}
}
}
impl UpdateRequest<'_> {
/// Defers this update request, returning an object that can be sent across
/// threads or processes and then used to report the update result at a
/// later time.
pub fn defer(self) -> DeferredUpdate {
let (send, recv) = mesh::oneshot();
*self.node = InternalNode::Deferred(recv);
DeferredUpdate {
value: self.value.to_owned(),
node: send,
}
}
}
/// A deferred inspection, which can provide inspection results asynchronously
/// from a call to [`inspect`](crate::Inspect::inspect).
#[derive(Debug, MeshPayload)]
pub struct Deferred {
path: String,
value: Option<String>,
depth: usize,
node: mesh::OneshotSender<InternalNode>,
sensitivity: SensitivityLevel,
}
impl Deferred {
/// Inspect an object as part of a deferred inspection.
pub fn inspect(self, mut obj: impl InspectMut) {
let mut root = self.root();
obj.inspect_mut(root.request());
let node = root.node;
self.node.send(node);
}
/// Responds to the deferred inspection, calling `f` with a [`Response`].
pub fn respond<F: FnOnce(&mut Response<'_>)>(self, f: F) {
let mut root = self.root();
f(&mut root.request().respond());
let node = root.node;
self.node.send(node);
}
/// Responds to the deferred request with a value.
pub fn value(self, value: Value) {
let mut root = self.root();
root.request().value(value);
let node = root.node;
self.node.send(node);
}
/// Returns an object used for handling an update request.
///
/// If this is not an update request, returns `Err(self)`.
pub fn update(self) -> Result<DeferredUpdate, Self> {
if self.value.is_some() && self.path.is_empty() {
Ok(DeferredUpdate {
value: self.value.unwrap(),
node: self.node,
})
} else {
Err(self)
}
}
fn root(&self) -> RequestRoot<'_> {
RequestRoot::new(
&self.path,
self.depth,
self.value.as_deref(),
self.sensitivity,
)
}
/// Removes this node from the inspection output.
pub fn ignore(self) {
self.node.send(InternalNode::Ignored);
}
/// Gets the request information for sending to a remote node via a non-mesh
/// communication mechanism, for use with [`complete_external`][].
///
/// You don't need this if you are communicating with the remote object via
/// mesh. In that case, just send this object to the remote object over a
/// mesh channel, and then use [`respond`][] or similar methods to
/// handle the request.
///
/// Use this when the remote object is across some other communication
/// boundary, such as gRPC. In that case, you will be responsible for using
/// [`inspect`][] on the remote node to handle the request, and to serializing
/// and deserializing the [`Node`][] structure across the communications
/// boundary.
///
/// [`inspect`]: crate::inspect
/// [`Node`]: crate::Node
/// [`respond`]: Self::respond
/// [`complete_external`]: Self::complete_external
#[cfg(feature = "initiate")]
pub fn external_request(&self) -> ExternalRequest<'_> {
ExternalRequest {
path: &self.path,
sensitivity: self.sensitivity,
request_type: match &self.value {
None => ExternalRequestType::Inspect { depth: self.depth },
Some(value) => ExternalRequestType::Update { value },
},
}
}
/// Complete the request with a [`Node`][] and a [`SensitivityLevel`].
///
/// See [`external_request`][] for details on how to use this.
///
/// [`Node`]: crate::Node
/// [`external_request`]: Self::external_request
#[cfg(feature = "initiate")]
pub fn complete_external(self, node: super::Node, sensitivity: SensitivityLevel) {
// If the returned sensitivity level is not allowed for this request, drop it.
if sensitivity > self.sensitivity {
return;
}
if let Some(node) = InternalNode::from_node(node, self.sensitivity) {
// Add the prefixed path back on as a sequence of directory nodes. This
// is necessary so that they can be skipped in post-processing.
let node =
self.path
.split('/')
.filter(|s| !s.is_empty())
.rev()
.fold(node, |node, name| {
InternalNode::DirResolved(alloc::vec![crate::InternalEntry {
name: name.to_owned(),
node,
sensitivity: Some(sensitivity),
}])
});
self.node.send(node);
}
}
/// Gets the sensitivity level for this request.
pub fn sensitivity(&self) -> SensitivityLevel {
self.sensitivity
}
}
impl InternalNode {
#[cfg(feature = "initiate")]
pub(crate) fn from_node(
value: crate::Node,
request_sensitivity: SensitivityLevel,
) -> Option<Self> {
use crate::Error;
use crate::InternalError;
use crate::Node;
let node = match value {
Node::Unevaluated => Self::Unevaluated,
Node::Failed(err) => Self::Failed(match err {
Error::NotFound => return None,
Error::Unresolved => InternalError::Unresolved,
Error::Mesh(err) => InternalError::Mesh(err),
Error::Immutable => InternalError::Immutable,
Error::Update(err) => InternalError::Update(err),
Error::NotADirectory => InternalError::NotADirectory,
Error::Internal => return None,
}),
Node::Value(v) => Self::Value(v),
Node::Dir(children) => Self::DirResolved(
children
.into_iter()
.filter_map(|e| {
// If the returned sensitivity level is not allowed for this request, drop it.
if e.sensitivity.unwrap_or_default() > request_sensitivity {
return None;
}
InternalNode::from_node(e.node, request_sensitivity).map(|v| {
crate::InternalEntry {
name: e.name,
node: v,
sensitivity: e.sensitivity,
}
})
})
.collect(),
),
};
Some(node)
}
}
/// Return value from [`Deferred::external_request`], specifying parameters for
/// a remote inspection.
#[cfg(feature = "initiate")]
pub struct ExternalRequest<'a> {
/// The remaining path of the request.
pub path: &'a str,
/// The request type and associated data.
pub request_type: ExternalRequestType<'a>,
/// The sensitivity level of the request.
pub sensitivity: SensitivityLevel,
}
/// The request type associated with [`ExternalRequest`].
#[cfg(feature = "initiate")]
pub enum ExternalRequestType<'a> {
/// An inspection request.
Inspect {
/// The depth to which to recurse.
depth: usize,
},
/// An update request.
Update {
/// The value to update to.
value: &'a str,
},
}
/// A deferred inspection, which can provide inspection results asynchronously
/// from a call to [`inspect`](crate::Inspect::inspect).
#[derive(Debug, MeshPayload)]
pub struct DeferredUpdate {
value: String,
node: mesh::OneshotSender<InternalNode>,
}
impl DeferredUpdate {
/// Gets the requested new value.
pub fn new_value(&self) -> &str {
&self.value
}
/// Report that the update succeeded, with a new value of `value`.
pub fn succeed(self, value: Value) {
self.node.send(InternalNode::Value(value));
}
/// Report that the update failed, with the reason in `err`.
pub fn fail<E: Into<alloc::boxed::Box<dyn core::error::Error + Send + Sync>>>(self, err: E) {
self.node.send(InternalNode::failed(err.into()));
}
}