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use std::collections::HashMap;
use bstr::{BStr, BString};
use crate::{
driver,
driver::{process, process::client::invoke, Operation, Process, State},
Driver,
};
/// What to do if delay is supported by a process filter.
#[derive(Default, Debug, Copy, Clone)]
pub enum Delay {
/// Use delayed processing for this entry.
///
/// Note that it's up to the filter to determine whether or not the processing should be delayed.
#[default]
Allow,
/// Do not delay the processing, and force it to happen immediately. In this case, no delayed processing will occur
/// even if the filter supports it.
///
/// This is the default as it requires no special precautions to be taken by the caller as
/// outputs will be produced immediately.
Forbid,
}
/// The error returned by [State::apply()][super::State::apply()].
#[derive(Debug, thiserror::Error)]
#[allow(missing_docs)]
pub enum Error {
#[error(transparent)]
Init(#[from] driver::init::Error),
#[error("Could not write entire object to driver")]
WriteSource(#[from] std::io::Error),
#[error("Filter process delayed an entry even though that was not requested")]
DelayNotAllowed,
#[error("Failed to invoke '{command}' command")]
ProcessInvoke {
source: process::client::invoke::Error,
command: String,
},
#[error("The invoked command '{command}' in process indicated an error: {status:?}")]
ProcessStatus {
status: driver::process::Status,
command: String,
},
}
/// Additional information for use in the [`State::apply()`] method.
#[derive(Debug, Copy, Clone)]
pub struct Context<'a, 'b> {
/// The repo-relative using slashes as separator of the entry currently being processed.
pub rela_path: &'a BStr,
/// The name of the reference that `HEAD` is pointing to. It's passed to `process` filters if present.
pub ref_name: Option<&'b BStr>,
/// The root-level tree that contains the current entry directly or indirectly, or the commit owning the tree (if available).
///
/// This is passed to `process` filters if present.
pub treeish: Option<gix_hash::ObjectId>,
/// The actual blob-hash of the data we are processing. It's passed to `process` filters if present.
///
/// Note that this hash might be different from the `$Id$` of the respective `ident` filter, as the latter generates the hash itself.
pub blob: Option<gix_hash::ObjectId>,
}
/// Apply operations to filter programs.
impl State {
/// Apply `operation` of `driver` to the bytes read from `src` and return a reader to immediately consume the output
/// produced by the filter. `rela_path` is the repo-relative path of the entry to handle.
/// It's possible that the filter stays inactive, in which case the `src` isn't consumed and has to be used by the caller.
///
/// Each call to this method will cause the corresponding filter to be invoked unless `driver` indicates a `process` filter,
/// which is only launched once and maintained using this state.
///
/// Note that it's not an error if there is no filter process for `operation` or if a long-running process doesn't supported
/// the desired capability.
///
/// ### Deviation
///
/// If a long running process returns the 'abort' status after receiving the data, it will be removed similar to how `git` does it.
/// However, it delivers an unsuccessful error status later, it will not be removed, but reports the error only.
/// If any other non-'error' status is received, the process will be stopped. But that doesn't happen if if such a status is received
/// after reading the filtered result.
pub fn apply<'a>(
&'a mut self,
driver: &Driver,
src: &mut impl std::io::Read,
operation: Operation,
ctx: Context<'_, '_>,
) -> Result<Option<Box<dyn std::io::Read + 'a>>, Error> {
match self.apply_delayed(driver, src, operation, Delay::Forbid, ctx)? {
Some(MaybeDelayed::Delayed(_)) => {
unreachable!("we forbid delaying the entry")
}
Some(MaybeDelayed::Immediate(read)) => Ok(Some(read)),
None => Ok(None),
}
}
/// Like [`apply()]`[Self::apply()], but use `delay` to determine if the filter result may be delayed or not.
///
/// Poll [`list_delayed_paths()`][Self::list_delayed_paths()] until it is empty and query the available paths again.
/// Note that even though it's possible, the API assumes that commands aren't mixed when delays are allowed.
pub fn apply_delayed<'a>(
&'a mut self,
driver: &Driver,
src: &mut impl std::io::Read,
operation: Operation,
delay: Delay,
ctx: Context<'_, '_>,
) -> Result<Option<MaybeDelayed<'a>>, Error> {
match self.maybe_launch_process(driver, operation, ctx.rela_path)? {
Some(Process::SingleFile { mut child, command }) => {
std::io::copy(src, &mut child.stdin.take().expect("configured"))?;
Ok(Some(MaybeDelayed::Immediate(Box::new(ReadFilterOutput {
inner: child.stdout.take(),
child: driver.required.then_some((child, command)),
}))))
}
Some(Process::MultiFile { client, key }) => {
let command = operation.as_str();
if !client.capabilities().contains(command) {
return Ok(None);
}
let invoke_result = client.invoke(
command,
&mut [
("pathname", Some(ctx.rela_path.to_owned())),
("ref", ctx.ref_name.map(ToOwned::to_owned)),
("treeish", ctx.treeish.map(|id| id.to_hex().to_string().into())),
("blob", ctx.blob.map(|id| id.to_hex().to_string().into())),
(
"can-delay",
match delay {
Delay::Allow if client.capabilities().contains("delay") => Some("1".into()),
Delay::Forbid | Delay::Allow => None,
},
),
]
.into_iter()
.filter_map(|(key, value)| value.map(|v| (key, v))),
src,
);
let status = match invoke_result {
Ok(status) => status,
Err(err) => {
let invoke::Error::Io(io_err) = &err;
handle_io_err(io_err, &mut self.running, key.0.as_ref());
return Err(Error::ProcessInvoke {
command: command.into(),
source: err,
});
}
};
if status.is_delayed() {
if matches!(delay, Delay::Forbid) {
return Err(Error::DelayNotAllowed);
}
Ok(Some(MaybeDelayed::Delayed(key)))
} else if status.is_success() {
// TODO: find a way to not have to do the 'borrow-dance'.
let client = self.running.remove(&key.0).expect("present for borrowcheck dance");
self.running.insert(key.0.clone(), client);
let client = self.running.get_mut(&key.0).expect("just inserted");
Ok(Some(MaybeDelayed::Immediate(Box::new(client.as_read()))))
} else {
let message = status.message().unwrap_or_default();
match message {
"abort" => {
client.capabilities_mut().remove(command);
}
"error" => {}
_strange => {
let client = self.running.remove(&key.0).expect("we definitely have it");
client.into_child().kill().ok();
}
}
Err(Error::ProcessStatus {
command: command.into(),
status,
})
}
}
None => Ok(None),
}
}
}
/// A type to represent delayed or immediate apply-filter results.
pub enum MaybeDelayed<'a> {
/// Using the delayed protocol, this entry has been sent to a long-running process and needs to be
/// checked for again, later, using the [`driver::Key`] to refer to the filter who owes a response.
///
/// Note that the path to the entry is also needed to obtain the filtered result later.
Delayed(driver::Key),
/// The filtered result can be read from the contained reader right away.
///
/// Note that it must be consumed in full or till a read error occurs.
Immediate(Box<dyn std::io::Read + 'a>),
}
/// A utility type to facilitate streaming the output of a filter process.
struct ReadFilterOutput {
inner: Option<std::process::ChildStdout>,
/// The child is present if we need its exit code to be positive.
child: Option<(std::process::Child, std::process::Command)>,
}
pub(crate) fn handle_io_err(err: &std::io::Error, running: &mut HashMap<BString, process::Client>, process: &BStr) {
if matches!(
err.kind(),
std::io::ErrorKind::BrokenPipe | std::io::ErrorKind::UnexpectedEof
) {
running.remove(process).expect("present or we wouldn't be here");
}
}
impl std::io::Read for ReadFilterOutput {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
match self.inner.as_mut() {
Some(inner) => {
let num_read = inner.read(buf)?;
if num_read == 0 {
self.inner.take();
if let Some((mut child, cmd)) = self.child.take() {
let status = child.wait()?;
if !status.success() {
return Err(std::io::Error::new(
std::io::ErrorKind::Other,
format!("Driver process {cmd:?} failed"),
));
}
}
}
Ok(num_read)
}
None => Ok(0),
}
}
}