turtle_build/infrastructure/file_system/

os.rs

use super::Metadata;
use crate::infrastructure::{FileError, FileSystem};
use async_trait::async_trait;
use std::{
    fs::{exists, metadata, read_to_string},
    io,
    path::Path,
};
use tokio::{
    fs::{create_dir_all, read, remove_file},
    sync::Semaphore,
};

/// A file system backed by an operating system.
#[derive(Debug)]
pub struct OsFileSystem {
    semaphore: Semaphore,
}

impl OsFileSystem {
    /// Creates a file system.
    pub fn new(open_file_limit: usize) -> Self {
        Self {
            semaphore: Semaphore::new(open_file_limit.min(Semaphore::MAX_PERMITS)),
        }
    }

    fn error(error: io::Error, path: &Path) -> FileError {
        FileError::new(format!("{}: {}", error, path.display()))
    }
}

#[async_trait]
impl FileSystem for OsFileSystem {
    async fn read_file(&self, path: &Path) -> Result<Vec<u8>, FileError> {
        let _permit = self.semaphore.acquire().await?;

        read(path).await.map_err(|error| Self::error(error, path))
    }

    // Text files are read inline because they are small enough for a read to be
    // cheaper than a round trip through the blocking thread pool.
    async fn read_file_to_string(&self, path: &Path) -> Result<String, FileError> {
        read_to_string(path).map_err(|error| Self::error(error, path))
    }

    // Existence checks run inline because a `stat` call is cheaper than a round
    // trip through the blocking thread pool.
    async fn exists(&self, path: &Path) -> Result<bool, FileError> {
        exists(path).map_err(|error| Self::error(error, path))
    }

    // Metadata queries run inline for the same reason as existence checks.
    async fn metadata(&self, path: &Path) -> Result<Option<Metadata>, FileError> {
        match metadata(path) {
            Ok(metadata) => Ok(Some(metadata.try_into()?)),
            Err(error) if error.kind() == io::ErrorKind::NotFound => Ok(None),
            Err(error) => Err(Self::error(error, path)),
        }
    }

    async fn create_directory(&self, path: &Path) -> Result<(), FileError> {
        create_dir_all(path)
            .await
            .map_err(|error| Self::error(error, path))?;

        Ok(())
    }

    async fn remove_file(&self, path: &Path) -> Result<(), FileError> {
        remove_file(path)
            .await
            .map_err(|error| Self::error(error, path))?;

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use pretty_assertions::assert_eq;
    use std::fs::{metadata, write};
    use tempfile::tempdir;

    #[test]
    fn limit_open_files() {
        assert_eq!(OsFileSystem::new(42).semaphore.available_permits(), 42);
    }

    #[test]
    fn limit_open_files_to_maximum_permits() {
        assert_eq!(
            OsFileSystem::new(usize::MAX).semaphore.available_permits(),
            Semaphore::MAX_PERMITS
        );
    }

    #[tokio::test]
    async fn read_file() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        write(&path, "bar").unwrap();

        assert_eq!(OsFileSystem::new(1).read_file(&path).await.unwrap(), b"bar");
    }

    #[tokio::test]
    async fn fail_to_read_missing_file() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        assert!(
            OsFileSystem::new(1)
                .read_file(&path)
                .await
                .unwrap_err()
                .to_string()
                .contains(&path.display().to_string())
        );
    }

    #[tokio::test]
    async fn read_file_to_string() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        write(&path, "bar").unwrap();

        assert_eq!(
            OsFileSystem::new(1)
                .read_file_to_string(&path)
                .await
                .unwrap(),
            "bar"
        );
    }

    #[tokio::test]
    async fn fail_to_read_missing_file_to_string() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        assert!(
            OsFileSystem::new(1)
                .read_file_to_string(&path)
                .await
                .unwrap_err()
                .to_string()
                .contains(&path.display().to_string())
        );
    }

    #[tokio::test]
    async fn check_file_existence() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");
        let file_system = OsFileSystem::new(1);

        assert!(!file_system.exists(&path).await.unwrap());

        write(&path, "").unwrap();

        assert!(file_system.exists(&path).await.unwrap());
    }

    #[tokio::test]
    async fn get_metadata_of_file() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        write(&path, "").unwrap();

        assert_eq!(
            OsFileSystem::new(1).metadata(&path).await.unwrap(),
            Some(Metadata::new(
                metadata(&path).unwrap().modified().unwrap(),
                false
            ))
        );
    }

    #[tokio::test]
    async fn get_metadata_of_directory() {
        let directory = tempdir().unwrap();

        assert_eq!(
            OsFileSystem::new(1)
                .metadata(directory.path())
                .await
                .unwrap(),
            Some(Metadata::new(
                metadata(directory.path()).unwrap().modified().unwrap(),
                true
            ))
        );
    }

    #[tokio::test]
    async fn get_metadata_of_missing_file() {
        let directory = tempdir().unwrap();

        assert_eq!(
            OsFileSystem::new(1)
                .metadata(&directory.path().join("foo"))
                .await,
            Ok(None)
        );
    }

    // Windows reports a path under a file as a missing file.
    #[cfg(unix)]
    #[tokio::test]
    async fn fail_to_get_metadata_under_file() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        write(&path, "").unwrap();

        assert!(
            OsFileSystem::new(1)
                .metadata(&path.join("bar"))
                .await
                .unwrap_err()
                .to_string()
                .contains(&path.join("bar").display().to_string())
        );
    }

    #[tokio::test]
    async fn create_directory() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo").join("bar");

        OsFileSystem::new(1).create_directory(&path).await.unwrap();

        assert!(metadata(&path).unwrap().is_dir());
    }

    #[tokio::test]
    async fn remove_file() {
        let directory = tempdir().unwrap();
        let path = directory.path().join("foo");

        write(&path, "").unwrap();

        OsFileSystem::new(1).remove_file(&path).await.unwrap();

        assert!(!path.try_exists().unwrap());
    }
}