package usb

import (
	"io"
	"sync"
)

// mockPort implements serialPort for testing without hardware.
// Reads block until Close() is called (simulating a hardware device that
// stays connected until explicitly disconnected).
type mockPort struct {
	mu     sync.Mutex
	closed bool
	closeCh chan struct{}
}

func newMockPort() *mockPort {
	return &mockPort{
		closeCh: make(chan struct{}),
	}
}

// Read blocks until the port is closed, then returns io.EOF.
// This mirrors the behaviour of a real serial port: Read blocks until data
// arrives or the port is closed.
func (p *mockPort) Read(buf []byte) (int, error) {
	<-p.closeCh
	return 0, io.EOF
}

// Write is a no-op for the mock (no hardware to write to).
func (p *mockPort) Write(data []byte) (int, error) {
	p.mu.Lock()
	defer p.mu.Unlock()
	if p.closed {
		return 0, io.ErrClosedPipe
	}
	return len(data), nil
}

// Close signals the mock port as closed, unblocking any pending Read.
func (p *mockPort) Close() error {
	p.mu.Lock()
	defer p.mu.Unlock()
	if !p.closed {
		p.closed = true
		close(p.closeCh)
	}
	return nil
}