feat: initial commit

1 files changed, 77 insertions, 0 deletions

diff --git a/src/http.rs b/src/http.rs
new file mode 100644
index 0000000..1b37d4c
--- /dev/null
+++ b/src/http.rs
@@ -0,0 +1,77 @@
+/// HTTP interfaces
+use crate::Error;
+
+use anyhow::Result;
+use reqwest::{Method, StatusCode};
+use tracing::{event, instrument, Level};
+
+// https://nix.dev/manual/nix/2.24/store/store-path
+const STORE_DIRECTORY: &str = "/nix/store";
+const DIGEST_SIZE: usize = 32;
+
+pub type Client = reqwest::Client;
+
+pub trait Ext {
+	fn default() -> Self;
+	async fn has_store_path(&self, binary_cache_url: &str, store_path: &str) -> Result<bool>;
+}
+
+impl Ext for Client {
+	/// Create a client with our user agent
+	fn default() -> Self {
+		Client::builder()
+			.user_agent(concat!(
+				env!("CARGO_PKG_NAME"),
+				"/",
+				env!("CARGO_PKG_VERSION")
+			))
+			.build()
+			.unwrap()
+	}
+
+	/// Check if a store path is available in the given binary cache
+	#[instrument(skip(self, binary_cache_url, store_path))]
+	async fn has_store_path(&self, binary_cache_url: &str, store_path: &str) -> Result<bool> {
+		let url = format!(
+			"{binary_cache_url}/{}.narinfo",
+			hash_from_store_path(store_path)
+		);
+
+		let request = self.request(Method::HEAD, url).build()?;
+		event!(
+			Level::TRACE,
+			"Checking for store path {store_path} in binary cache at {}",
+			request.url()
+		);
+		let response = self.execute(request).await?;
+
+		match response.status() {
+			StatusCode::OK => {
+				event!(
+					Level::TRACE,
+					"Found store path `{store_path}` in binary cache"
+				);
+				Ok(true)
+			}
+			StatusCode::NOT_FOUND => {
+				event!(
+					Level::TRACE,
+					"Did not find store path `{store_path}` in binary cache"
+				);
+				Ok(false)
+			}
+			status_code => Err(Error::HTTPFailed(status_code).into()),
+		}
+	}
+}
+
+/// Strip the <hash> from /nix/store/<hash>-<name>
+fn hash_from_store_path(store_path: &str) -> &str {
+	// Store paths will always start with the store directory, followed by a path separator. See
+	// the above link
+	let start_index = STORE_DIRECTORY.len() + 1;
+	// The next DIGEST_SIZE characters will then be the digest
+	let end_index = start_index + DIGEST_SIZE;
+
+	&store_path[start_index..end_index]
+}