From fb025fa4cc0b8f311805f6308b04f0250252609b Mon Sep 17 00:00:00 2001
From: Nico Fricke <nfricke@eos-uptrade.de>
Date: Fri, 17 Jan 2025 13:56:56 +0100
Subject: [PATCH] implement file downloads

---
 Cargo.lock                           | 10 +++--
 casket-backend/Cargo.toml            |  2 +-
 casket-backend/src/files/download.rs | 67 ++++++++++++++++++++++++++++
 casket-backend/src/files/mod.rs      |  5 ++-
 casket-backend/src/routes.rs         | 12 +++--
 5 files changed, 85 insertions(+), 11 deletions(-)
 create mode 100644 casket-backend/src/files/download.rs

diff --git a/Cargo.lock b/Cargo.lock
index 4a4ac9c..7a37cd6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -143,7 +143,7 @@ dependencies = [
  "problem_details",
  "serde",
  "tokio",
- "tokio-stream",
+ "tokio-util",
  "tracing",
  "tracing-log",
  "tracing-subscriber",
@@ -837,12 +837,14 @@ dependencies = [
 ]
 
 [[package]]
-name = "tokio-stream"
-version = "0.1.17"
+name = "tokio-util"
+version = "0.7.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eca58d7bba4a75707817a2c44174253f9236b2d5fbd055602e9d5c07c139a047"
+checksum = "d7fcaa8d55a2bdd6b83ace262b016eca0d79ee02818c5c1bcdf0305114081078"
 dependencies = [
+ "bytes",
  "futures-core",
+ "futures-sink",
  "pin-project-lite",
  "tokio",
 ]
diff --git a/casket-backend/Cargo.toml b/casket-backend/Cargo.toml
index a84789d..f6a9628 100644
--- a/casket-backend/Cargo.toml
+++ b/casket-backend/Cargo.toml
@@ -8,7 +8,7 @@ repository = "https://git.nifni.eu/nif/casket"
 [dependencies]
 axum = { version = "0.8.1", features = ["multipart", "macros"] }
 tokio = { version = "1.42.0", features = ["full"] }
-tokio-stream = "0.1.17"
+tokio-util = { version = "0.7.13", features = ["io"] }
 futures = "0.3"
 futures-util = "0.3"
 figment = { version = "0.10.19", features = ["toml", "env"] }
diff --git a/casket-backend/src/files/download.rs b/casket-backend/src/files/download.rs
new file mode 100644
index 0000000..41d506d
--- /dev/null
+++ b/casket-backend/src/files/download.rs
@@ -0,0 +1,67 @@
+use crate::errors::to_internal_error;
+use crate::extractor_helper::WithProblemDetails;
+use crate::files::build_system_path;
+use crate::AppState;
+use axum::body::Body;
+use axum::extract::{Query, State};
+use axum::http::{header, StatusCode};
+use axum::response::IntoResponse;
+use problem_details::ProblemDetails;
+use serde::Deserialize;
+use std::borrow::Cow;
+use std::ffi::OsStr;
+use std::path::{Path, PathBuf};
+use tokio::fs::File;
+use tokio_util::io::ReaderStream;
+use tracing::error;
+
+pub async fn handler(
+    State(state): State<AppState>,
+    axum::extract::Path(user_id): axum::extract::Path<String>,
+    WithProblemDetails(Query(query)): WithProblemDetails<Query<SingleFileQuery>>,
+) -> Result<impl IntoResponse, ProblemDetails> {
+    let filesystem_path = build_system_path(&state.config.files.directory, &user_id, &query.path)?;
+
+    let file_name = get_file_name(&filesystem_path)?;
+    let file = open_file(&filesystem_path).await?;
+
+    let metadata = file.metadata().await.map_err(to_internal_error)?;
+    if !metadata.is_file() {
+        return Err(ProblemDetails::from_status_code(StatusCode::BAD_REQUEST)
+            .with_detail(format!("Path {:?} is not a file", query.path)));
+    }
+
+    let stream = ReaderStream::new(file);
+    let body = Body::from_stream(stream);
+    Ok((
+        [(
+            header::CONTENT_DISPOSITION,
+            format!("attachment; filename=\"{file_name}\""),
+        )],
+        body,
+    ))
+}
+
+async fn open_file(filesystem_path: &Path) -> Result<File, ProblemDetails> {
+    File::open(filesystem_path).await.map_err(|err| {
+        ProblemDetails::from_status_code(StatusCode::NOT_FOUND)
+            .with_detail(format!("Failed to open file: {err}"))
+    })
+}
+
+fn get_file_name(filesystem_path: &PathBuf) -> Result<Cow<str>, ProblemDetails> {
+    filesystem_path
+        .file_name()
+        .ok_or_else(|| {
+            error!("Failed to get file name for {:?}", filesystem_path);
+            ProblemDetails::from_status_code(StatusCode::INTERNAL_SERVER_ERROR)
+        })
+        .map(OsStr::to_string_lossy)
+}
+
+/// Query to download a file
+#[derive(Deserialize)]
+pub struct SingleFileQuery {
+    /// Path which is used as base path to query the tree.
+    path: PathBuf,
+}
diff --git a/casket-backend/src/files/mod.rs b/casket-backend/src/files/mod.rs
index d7f5d84..5b88616 100644
--- a/casket-backend/src/files/mod.rs
+++ b/casket-backend/src/files/mod.rs
@@ -3,10 +3,11 @@ use axum::http::StatusCode;
 use problem_details::ProblemDetails;
 use std::path::{Component, Path, PathBuf};
 
+pub mod download;
 pub mod list;
 pub mod upload;
 
-fn build_system_path(
+pub fn build_system_path(
     base_directory: &Path,
     user_id: &str,
     user_path: &PathBuf,
@@ -23,7 +24,7 @@ fn build_system_path(
     }
 }
 
-pub fn sanitize_path(path: &Path) -> Result<PathBuf, ProblemDetails> {
+fn sanitize_path(path: &Path) -> Result<PathBuf, ProblemDetails> {
     let mut ret = PathBuf::new();
     for component in path.components().peekable() {
         match component {
diff --git a/casket-backend/src/routes.rs b/casket-backend/src/routes.rs
index d2a8a89..2ed73fa 100644
--- a/casket-backend/src/routes.rs
+++ b/casket-backend/src/routes.rs
@@ -1,14 +1,18 @@
 use crate::files;
+use crate::files::download;
 use crate::AppState;
 use axum::routing::post;
 use axum::{response::Html, routing::get, Router};
 use files::list::query_file_tree;
 
 pub fn routes() -> Router<AppState> {
-    Router::new().route("/", get(handler)).route(
-        "/api/v1/user/{:user_id}/files",
-        post(files::upload::handle_file_uploads).get(query_file_tree),
-    )
+    Router::new()
+        .route("/", get(handler))
+        .route(
+            "/api/v1/user/{:user_id}/files",
+            post(files::upload::handle_file_uploads).get(query_file_tree),
+        )
+        .route("/api/v1/user/{:user_id}/download", get(download::handler))
 }
 
 async fn handler() -> Html<&'static str> {