package wal

// WriteResult is sent to the caller when the write completes or fails.
type WriteResult struct {
	Sequence uint64
	Err      error
}

// CommitRequest represents a single write request submitted by a caller.
type CommitRequest struct {
	Entries []*WalEntry
	Result  chan WriteResult
}

// CommitQueue is a bounded buffered channel for write requests.
type CommitQueue struct {
	ch chan *CommitRequest
}

// NewCommitQueue creates a bounded queue for commit requests.
func NewCommitQueue(capacity int) *CommitQueue {
	if capacity < 1 {
		capacity = 1
	}
	return &CommitQueue{ch: make(chan *CommitRequest, capacity)}
}

// Submit creates a commit request, submits it to the queue, and returns it.
// The send blocks when the queue is full, preserving backpressure.
func (cq *CommitQueue) Submit(entries []*WalEntry) *CommitRequest {
	req := &CommitRequest{
		Entries: entries,
		Result:  make(chan WriteResult, 1),
	}
	cq.ch <- req
	return req
}

// Collect drains all currently pending requests from the queue.
func (cq *CommitQueue) Collect() []*CommitRequest {
	var requests []*CommitRequest
	for {
		select {
		case req, ok := <-cq.ch:
			if !ok {
				return requests
			}
			requests = append(requests, req)
		default:
			return requests
		}
	}
}

// Close closes the queue. Callers must stop submitting before Close.
func (cq *CommitQueue) Close() {
	close(cq.ch)
}