// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

//! Typesafe wrappers around an open package directory.

use crate::{
    MetaContents, MetaContentsError, MetaPackage, MetaPackageError, MetaSubpackages,
    MetaSubpackagesError,
};
use fidl::endpoints::ServerEnd;
use fuchsia_hash::{Hash, ParseHashError};
use thiserror::Error;
use version_history::AbiRevision;
use {fidl_fuchsia_io as fio, zx_status};

// re-export wrapped fuchsia_fs errors.
pub use fuchsia_fs::file::ReadError;
pub use fuchsia_fs::node::{CloneError, CloseError, OpenError};

/// An error encountered while reading/parsing the package's hash
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum ReadHashError {
    #[error("while reading 'meta/'")]
    Read(#[source] ReadError),

    #[error("while parsing 'meta/'")]
    Parse(#[source] ParseHashError),
}

/// An error encountered while reading/parsing the package's meta/package file
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum LoadMetaPackageError {
    #[error("while reading 'meta/package'")]
    Read(#[source] ReadError),

    #[error("while parsing 'meta/package'")]
    Parse(#[source] MetaPackageError),
}

/// An error encountered while reading/parsing the package's
/// meta/fuchsia.pkg/subpackages file
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum LoadMetaSubpackagesError {
    #[error("while reading '{}'", MetaSubpackages::PATH)]
    Read(#[source] ReadError),

    #[error("while parsing '{}'", MetaSubpackages::PATH)]
    Parse(#[source] MetaSubpackagesError),
}

/// An error encountered while reading/parsing the package's meta/contents file
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum LoadMetaContentsError {
    #[error("while reading 'meta/contents'")]
    Read(#[source] ReadError),

    #[error("while parsing 'meta/contents'")]
    Parse(#[source] MetaContentsError),
}

/// An error encountered while reading/parsing the package's `AbiRevision`.
#[derive(Debug, Error)]
#[allow(missing_docs)]
pub enum LoadAbiRevisionError {
    #[error("while opening '{}'", AbiRevision::PATH)]
    Open(#[from] OpenError),

    #[error("while reading '{}'", AbiRevision::PATH)]
    Read(#[from] ReadError),

    #[error("while parsing '{}'", AbiRevision::PATH)]
    Parse(#[from] std::array::TryFromSliceError),
}

/// An open package directory
#[derive(Debug, Clone)]
pub struct PackageDirectory {
    proxy: fio::DirectoryProxy,
}

impl PackageDirectory {
    /// Interprets the provided directory proxy as a package dir.
    pub fn from_proxy(proxy: fio::DirectoryProxy) -> Self {
        Self { proxy }
    }

    /// Creates a new channel pair, returning the client end as Self and the
    /// server end as a channel.
    pub fn create_request() -> Result<(Self, ServerEnd<fio::DirectoryMarker>), fidl::Error> {
        let (proxy, request) = fidl::endpoints::create_proxy::<fio::DirectoryMarker>()?;
        Ok((Self::from_proxy(proxy), request))
    }

    /// Returns the current component's package directory.
    #[cfg(target_os = "fuchsia")]
    pub fn open_from_namespace() -> Result<Self, OpenError> {
        let dir = fuchsia_fs::directory::open_in_namespace("/pkg", fio::PERM_READABLE)?;
        Ok(Self::from_proxy(dir))
    }

    /// Cleanly close the package directory, consuming self.
    pub async fn close(self) -> Result<(), CloseError> {
        fuchsia_fs::directory::close(self.proxy).await
    }

    /// Send request to also serve this package directory on the given directory request.
    pub fn reopen(&self, dir_request: ServerEnd<fio::DirectoryMarker>) -> Result<(), CloneError> {
        fuchsia_fs::directory::clone_onto_no_describe(&self.proxy, None, dir_request)
    }

    /// Unwraps the inner DirectoryProxy, consuming self.
    pub fn into_proxy(self) -> fio::DirectoryProxy {
        self.proxy
    }

    /// Read the file in the package given by `path`, and return its contents as
    /// a UTF-8 decoded string.
    async fn read_file_to_string(&self, path: &str) -> Result<String, ReadError> {
        fuchsia_fs::directory::read_file_to_string(&self.proxy, path).await
    }

    /// Read the file in the package given by `path`, and return its contents.
    pub async fn read_file(&self, path: &str) -> Result<Vec<u8>, ReadError> {
        fuchsia_fs::directory::read_file(&self.proxy, path).await
    }

    /// Reads the merkle root of the package.
    pub async fn merkle_root(&self) -> Result<Hash, ReadHashError> {
        let merkle = self.read_file_to_string("meta").await.map_err(ReadHashError::Read)?;
        merkle.parse().map_err(ReadHashError::Parse)
    }

    /// Reads and parses the package's meta/contents file.
    pub async fn meta_contents(&self) -> Result<MetaContents, LoadMetaContentsError> {
        let meta_contents =
            self.read_file("meta/contents").await.map_err(LoadMetaContentsError::Read)?;
        let meta_contents = MetaContents::deserialize(meta_contents.as_slice())
            .map_err(LoadMetaContentsError::Parse)?;
        Ok(meta_contents)
    }

    /// Reads and parses the package's meta/package file.
    pub async fn meta_package(&self) -> Result<MetaPackage, LoadMetaPackageError> {
        let meta_package =
            self.read_file("meta/package").await.map_err(LoadMetaPackageError::Read)?;
        let meta_package = MetaPackage::deserialize(meta_package.as_slice())
            .map_err(LoadMetaPackageError::Parse)?;
        Ok(meta_package)
    }

    /// Reads and parses the package's meta/fuchsia.pkg/subpackages file. If the file
    /// doesn't exist, an empty `MetaSubpackages` is returned.
    pub async fn meta_subpackages(&self) -> Result<MetaSubpackages, LoadMetaSubpackagesError> {
        match self.read_file(MetaSubpackages::PATH).await {
            Ok(file) => Ok(MetaSubpackages::deserialize(file.as_slice())
                .map_err(LoadMetaSubpackagesError::Parse)?),
            Err(ReadError::Open(OpenError::OpenError(zx_status::Status::NOT_FOUND))) => {
                Ok(MetaSubpackages::default())
            }
            Err(err) => Err(LoadMetaSubpackagesError::Read(err)),
        }
    }

    /// Reads and parses the package's meta/fuchsia.abi/abi-revision file.
    pub async fn abi_revision(&self) -> Result<AbiRevision, LoadAbiRevisionError> {
        let abi_revision_bytes = self.read_file(AbiRevision::PATH).await?;
        Ok(AbiRevision::try_from(abi_revision_bytes.as_slice())?)
    }

    /// Returns an iterator of blobs needed by this package, does not include meta.far blob itself.
    /// Hashes may appear more than once.
    pub async fn blobs(&self) -> Result<impl Iterator<Item = Hash>, LoadMetaContentsError> {
        Ok(self.meta_contents().await?.into_hashes_undeduplicated())
    }
}

#[cfg(test)]
#[cfg(target_os = "fuchsia")]
mod tests {
    use super::*;
    use assert_matches::assert_matches;
    use fidl::endpoints::Proxy;

    #[fuchsia_async::run_singlethreaded(test)]
    async fn open_close() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();
        let () = pkg.close().await.unwrap();
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn reopen_is_new_connection() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        let (proxy, server_end) = fidl::endpoints::create_proxy().unwrap();
        assert_matches!(pkg.reopen(server_end), Ok(()));
        assert_matches!(PackageDirectory::from_proxy(proxy).close().await, Ok(()));

        pkg.into_proxy().into_channel().expect("no other users of the wrapped channel");
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn merkle_root_is_pkg_meta() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        let merkle: Hash = std::fs::read_to_string("/pkg/meta").unwrap().parse().unwrap();

        assert_eq!(pkg.merkle_root().await.unwrap(), merkle);
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn list_blobs() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        // listing blobs succeeds, and this package has some blobs.
        let blobs = pkg.blobs().await.unwrap().collect::<Vec<_>>();
        assert!(!blobs.is_empty());

        // the test duplicate blob appears twice
        let duplicate_blob_merkle = fuchsia_merkle::from_slice("Hello World!".as_bytes()).root();
        assert_eq!(blobs.iter().filter(|hash| *hash == &duplicate_blob_merkle).count(), 2);
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn package_name_is_test_package_name() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        assert_eq!(
            pkg.meta_package().await.unwrap().into_path().to_string(),
            "fuchsia-pkg-tests/0"
        );
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn missing_subpackages_file_is_empty_subpackages() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        assert_eq!(pkg.meta_subpackages().await.unwrap(), MetaSubpackages::default(),);
    }

    #[fuchsia_async::run_singlethreaded(test)]
    async fn abi_revision_succeeds() {
        let pkg = PackageDirectory::open_from_namespace().unwrap();

        let _: AbiRevision = pkg.abi_revision().await.unwrap();
    }
}