feat: add cas pruning command

Removes unused files from the CAS. Still needs to
remove individual package index entries to be
complete.

Cargo.lock

@@ -2502,7 +2502,7 @@ checksum = "f9c7c7c8ac16c798734b8a24560c1362120597c40d5e1459f09498f8f6c8f2ba"
 dependencies = [
  "cfg-if",
  "libc",
- "windows",
+ "windows 0.52.0",
 ]
 
 [[package]]
@@ -2652,7 +2652,7 @@ dependencies = [
  "iana-time-zone-haiku",
  "js-sys",
  "wasm-bindgen",
- "windows-core",
+ "windows-core 0.52.0",
 ]
 
 [[package]]
@@ -3656,6 +3656,7 @@ dependencies = [
  "url",
  "urlencoding",
  "wax",
+ "windows 0.59.0",
  "windows-registry 0.4.0",
 ]
 
@@ -5669,10 +5670,20 @@ version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e48a53791691ab099e5e2ad123536d0fff50652600abaf43bbf952894110d0be"
 dependencies = [
- "windows-core",
+ "windows-core 0.52.0",
  "windows-targets 0.52.6",
 ]
 
+[[package]]
+name = "windows"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f919aee0a93304be7f62e8e5027811bbba96bcb1de84d6618be56e43f8a32a1"
+dependencies = [
+ "windows-core 0.59.0",
+ "windows-targets 0.53.0",
+]
+
 [[package]]
 name = "windows-core"
 version = "0.52.0"
@@ -5682,6 +5693,41 @@ dependencies = [
  "windows-targets 0.52.6",
 ]
 
+[[package]]
+name = "windows-core"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "810ce18ed2112484b0d4e15d022e5f598113e220c53e373fb31e67e21670c1ce"
+dependencies = [
+ "windows-implement",
+ "windows-interface",
+ "windows-result 0.3.0",
+ "windows-strings 0.3.0",
+ "windows-targets 0.53.0",
+]
+
+[[package]]
+name = "windows-implement"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "83577b051e2f49a058c308f17f273b570a6a758386fc291b5f6a934dd84e48c1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]
+
+[[package]]
+name = "windows-interface"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb26fd936d991781ea39e87c3a27285081e3c0da5ca0fcbc02d368cc6f52ff01"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]
+
 [[package]]
 name = "windows-registry"
 version = "0.2.0"

Cargo.toml

@@ -24,6 +24,7 @@ bin = [
     "dep:paste",
     "dep:serde_json",
     "dep:windows-registry",
+    "dep:windows",
     "gix/worktree-mutation",
     "fs-err/expose_original_error",
     "tokio/rt",
@@ -91,6 +92,7 @@ paste = { version = "1.0.15", optional = true }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows-registry = { version = "0.4.0", optional = true }
+windows = { version = "0.59.0", features = ["Win32_Storage", "Win32_Storage_FileSystem", "Win32_Security"], optional = true }
 
 [workspace]
 resolver = "2"

src/cli/commands/cas/mod.rs

@@ -0,0 +1,18 @@
+use clap::Subcommand;
+use pesde::Project;
+
+mod prune;
+
+#[derive(Debug, Subcommand)]
+pub enum CasCommands {
+	/// Removes unused files from the CAS
+	Prune(prune::PruneCommand),
+}
+
+impl CasCommands {
+	pub async fn run(self, project: Project) -> anyhow::Result<()> {
+		match self {
+			CasCommands::Prune(prune) => prune.run(project).await,
+		}
+	}
+}

src/cli/commands/cas/prune.rs

@@ -0,0 +1,161 @@
+use anyhow::Context;
+use clap::Args;
+use fs_err::tokio as fs;
+use pesde::Project;
+use std::{collections::HashSet, path::Path};
+use tokio::task::{spawn_blocking, JoinSet};
+
+#[derive(Debug, Args)]
+pub struct PruneCommand {}
+
+#[allow(unreachable_code)]
+async fn get_nlinks(path: &Path) -> anyhow::Result<u64> {
+	#[cfg(unix)]
+	{
+		use std::os::unix::fs::MetadataExt;
+		let metadata = fs::metadata(path).await?;
+		return Ok(metadata.nlink());
+	}
+	// life if rust stabilized the nightly feature from 2019
+	#[cfg(windows)]
+	{
+		use std::os::windows::ffi::OsStrExt;
+		use windows::{
+			core::PWSTR,
+			Win32::{
+				Foundation::CloseHandle,
+				Storage::FileSystem::{
+					CreateFileW, GetFileInformationByHandle, FILE_ATTRIBUTE_NORMAL,
+					FILE_GENERIC_READ, FILE_SHARE_READ, OPEN_EXISTING,
+				},
+			},
+		};
+
+		let path = path.to_path_buf();
+		return spawn_blocking(move || unsafe {
+			let handle = CreateFileW(
+				PWSTR(
+					path.as_os_str()
+						.encode_wide()
+						.chain(std::iter::once(0))
+						.collect::<Vec<_>>()
+						.as_mut_ptr(),
+				),
+				FILE_GENERIC_READ.0,
+				FILE_SHARE_READ,
+				None,
+				OPEN_EXISTING,
+				FILE_ATTRIBUTE_NORMAL,
+				None,
+			)?;
+
+			let mut info =
+				windows::Win32::Storage::FileSystem::BY_HANDLE_FILE_INFORMATION::default();
+			let res = GetFileInformationByHandle(handle, &mut info);
+			CloseHandle(handle)?;
+			res?;
+
+			Ok(info.nNumberOfLinks as u64)
+		})
+		.await
+		.unwrap();
+	}
+	#[cfg(not(any(unix, windows)))]
+	{
+		compile_error!("unsupported platform");
+	}
+	anyhow::bail!("unsupported platform")
+}
+
+async fn remove_hashes(cas_dir: &Path) -> anyhow::Result<HashSet<String>> {
+	let mut tasks = JoinSet::new();
+
+	let mut cas_entries = fs::read_dir(cas_dir)
+		.await
+		.context("failed to read directory")?;
+
+	while let Some(cas_entry) = cas_entries
+		.next_entry()
+		.await
+		.context("failed to read dir entry")?
+	{
+		let prefix = cas_entry.file_name();
+		let Some(prefix) = prefix.to_str() else {
+			continue;
+		};
+		// we only want hash directories
+		if prefix.len() != 2 {
+			continue;
+		}
+
+		let prefix = prefix.to_string();
+
+		tasks.spawn(async move {
+			let mut hash_entries = fs::read_dir(cas_entry.path())
+				.await
+				.context("failed to read hash directory")?;
+
+			let mut tasks = JoinSet::new();
+
+			while let Some(hash_entry) = hash_entries
+				.next_entry()
+				.await
+				.context("failed to read hash dir entry")?
+			{
+				let hash = hash_entry.file_name();
+				let hash = hash.to_str().expect("non-UTF-8 hash").to_string();
+				let hash = format!("{prefix}{hash}");
+
+				let path = hash_entry.path();
+				tasks.spawn(async move {
+					let nlinks = get_nlinks(&path)
+						.await
+						.context("failed to count file usage")?;
+					if nlinks != 1 {
+						return Ok::<_, anyhow::Error>(None);
+					}
+
+					fs::remove_file(path)
+						.await
+						.context("failed to remove unused file")?;
+
+					Ok::<_, anyhow::Error>(Some(hash))
+				});
+			}
+
+			let mut removed_hashes = HashSet::new();
+
+			while let Some(removed_hash) = tasks.join_next().await {
+				let Some(hash) = removed_hash.unwrap()? else {
+					continue;
+				};
+
+				removed_hashes.insert(hash);
+			}
+
+			Ok::<_, anyhow::Error>(removed_hashes)
+		});
+	}
+
+	let mut res = HashSet::new();
+
+	while let Some(removed_hashes) = tasks.join_next().await {
+		res.extend(removed_hashes.unwrap()?);
+	}
+
+	Ok(res)
+}
+
+impl PruneCommand {
+	pub async fn run(self, project: Project) -> anyhow::Result<()> {
+		// CAS structure:
+		// /2 first chars of hash/rest of hash
+		// /index/hash/name/version/target
+		// /wally_index/hash/name/version
+		// /git_index/hash/hash
+		// the last thing in the path is the serialized PackageFs
+		let _ = remove_hashes(project.cas_dir()).await?;
+
+		todo!("remove unused index entries");
+	}
+}

src/cli/commands/mod.rs

@@ -2,6 +2,7 @@ use pesde::Project;
 
 mod add;
 mod auth;
+mod cas;
 mod config;
 mod deprecate;
 mod execute;
@@ -30,6 +31,10 @@ pub enum Subcommand {
 	#[command(subcommand)]
 	Config(config::ConfigCommands),
 
+	/// CAS-related commands
+	#[command(subcommand)]
+	Cas(cas::CasCommands),
+
 	/// Initializes a manifest file in the current directory
 	Init(init::InitCommand),
 
@@ -83,6 +88,7 @@ impl Subcommand {
 		match self {
 			Subcommand::Auth(auth) => auth.run(project, reqwest).await,
 			Subcommand::Config(config) => config.run().await,
+			Subcommand::Cas(cas) => cas.run(project).await,
 			Subcommand::Init(init) => init.run(project).await,
 			Subcommand::Run(run) => run.run(project).await,
 			Subcommand::Install(install) => install.run(project, reqwest).await,

src/cli/mod.rs

@@ -297,7 +297,7 @@ pub fn display_err(result: anyhow::Result<()>, prefix: &str) {
 		if !cause.is_empty() {
 			eprintln!("{}:", ERROR_STYLE.apply_to("caused by"));
 			for err in cause {
-				eprintln!("\t- {}", ERROR_STYLE.apply_to(err));
+				eprintln!("\t- {err}");
 			}
 		}