Struct DownloadQueue 

pub struct DownloadQueue { /* private fields */ }

Synchronous download queue that tracks tasks and enforces concurrency limits.

This is a pure data structure — it does not perform I/O. The caller is responsible for taking tasks via take_next, spawning async downloads, and updating task state when downloads progress or complete.

Implementations

impl DownloadQueue

pub fn new(max_concurrent: usize) -> Self

Create a new queue with the given concurrency limit.

pub fn enqueue( &mut self, url: String, dest: PathBuf, expected_hash: Option<u64>, meta: DownloadMeta, ) -> usize

Add a task to the queue. Returns the assigned task ID.

pub fn load_from_sidecars( download_dir: &Path, max_concurrent: usize, ) -> Result<Self>

Rebuild a queue from persisted .meta sidecars in a download directory.

Active downloads are restored as paused because no transport is running after process startup. Complete entries are restored only when the downloaded file still exists.

pub fn save_sidecars(&mut self) -> Result<()>

Persist every task’s .meta sidecar beside its destination file.

pub fn pause(&mut self, id: usize)

Pause an active download. No-op if the task is not Active.

pub fn resume(&mut self, id: usize)

Resume a paused download by moving it back to Queued.

pub fn cancel(&mut self, id: usize)

Remove a task from the queue entirely.

pub fn active_count(&self) -> usize

Number of currently active downloads.

pub fn pending(&self) -> Vec<&DownloadTask>

All tasks in the Queued state, ready to be started.

pub fn take_next(&mut self) -> Option<&mut DownloadTask>

Get the next Queued task if the concurrency limit has not been reached.

Transitions the task to Active and returns a mutable reference so the caller can spawn the download.

pub fn get(&self, id: usize) -> Option<&DownloadTask>

Look up a task by ID.

pub fn get_mut(&mut self, id: usize) -> Option<&mut DownloadTask>

Look up a task by ID (mutable).

pub fn all(&self) -> &[DownloadTask]

View all tracked tasks in insertion order.

pub fn len(&self) -> usize

Total number of tasks in the queue (all states).

pub fn is_empty(&self) -> bool

Whether the queue is empty.