Scaffold utility and library (#3)

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Signed-off-by: xermicus <bigcyrill@hotmail.com>

crates/solc-binaries/src/cache.rs

@@ -0,0 +1,71 @@
+//! Helper for caching the solc binaries.
+
+use std::{
+    collections::HashSet,
+    fs::{File, create_dir_all},
+    io::{BufWriter, Write},
+    os::unix::fs::PermissionsExt,
+    path::{Path, PathBuf},
+    sync::{LazyLock, Mutex},
+};
+
+use crate::download::GHDownloader;
+
+pub const SOLC_CACHE_DIRECTORY: &str = "solc";
+pub(crate) static SOLC_CACHER: LazyLock<Mutex<HashSet<PathBuf>>> = LazyLock::new(Default::default);
+
+pub(crate) fn get_or_download(
+    working_directory: &Path,
+    downloader: &GHDownloader,
+) -> anyhow::Result<PathBuf> {
+    let target_directory = working_directory
+        .join(SOLC_CACHE_DIRECTORY)
+        .join(downloader.version.to_string());
+    let target_file = target_directory.join(downloader.target);
+
+    let mut cache = SOLC_CACHER.lock().unwrap();
+    if cache.contains(&target_file) {
+        log::debug!("using cached solc: {}", target_file.display());
+        return Ok(target_file);
+    }
+
+    create_dir_all(target_directory)?;
+    download_to_file(&target_file, downloader)?;
+    cache.insert(target_file.clone());
+
+    Ok(target_file)
+}
+
+fn download_to_file(path: &Path, downloader: &GHDownloader) -> anyhow::Result<()> {
+    log::info!("caching file: {}", path.display());
+
+    let Ok(file) = File::create_new(path) else {
+        log::debug!("cache file already exists: {}", path.display());
+        return Ok(());
+    };
+
+    #[cfg(unix)]
+    {
+        let mut permissions = file.metadata()?.permissions();
+        permissions.set_mode(permissions.mode() | 0o111);
+        file.set_permissions(permissions)?;
+    }
+
+    let mut file = BufWriter::new(file);
+    file.write_all(&downloader.download()?)?;
+    file.flush()?;
+    drop(file);
+
+    #[cfg(target_os = "macos")]
+    std::process::Command::new("xattr")
+        .arg("-d")
+        .arg("com.apple.quarantine")
+        .arg(&path)
+        .stderr(std::process::Stdio::null())
+        .stdout(std::process::Stdio::null())
+        .stdout(std::process::Stdio::null())
+        .spawn()?
+        .wait()?;
+
+    Ok(())
+}