package hopp

import "io"
import "net"
// import "time"

const defaultSizeLimit int64 = 1024 * 1024 // 1 megabyte

// Conn is a HOPP connection.
type Conn interface {
	// Close closes the connection. Any blocked operations on the connection
	// or its transactions will be unblocked and return errors.
	Close() error
	
	// See documentation for [net.Conn]
	LocalAddr() net.Addr
	RemoteAddr() net.Addr
	
	// OpenTrans opens a transaction. The other party will not know about
	// this until the first message is sent.
	OpenTrans() (Trans, error)
	// AcceptTrans accepts a transaction from the other party. This must
	// be called in a loop to avoid the connection locking up.
	AcceptTrans() (Trans, error)

	// SetSizeLimit sets a limit (in bytes) for how large messages can be.
	// By default, this limit is 1 megabyte.
	SetSizeLimit(limit int64)
}

// Trans is a HOPP transaction. Methods of this interface are not safe for
// concurrent use with the exception of the Close and ID methods. The
// recommended use case is one goroutine per transaction.
type Trans interface {
	// Close closes the transaction. Any blocked operations will be
	// unblocked and return errors. This method is safe for concurrent use.
	Close() error

	// ID returns the transaction ID. This must not change, and it must be
	// unique within the connection. This method is safe for concurrent use.
	ID() int64

	// TODO: add methods for setting send and receive deadlines
		
	// Send sends a message. This method is not safe for concurrent use.
	Send(method uint16, data []byte) error
	// SendWriter sends data written to an [io.Writer]. The writer must be
	// closed after use. Closing the writer flushes any data that hasn't
	// been written yet. Any writer previously opened through this function
	// will be discarded. This method is not safe for concurrent use, and
	// neither is its result.
	SendWriter(method uint16) (io.WriteCloser, error)
	// Receive receives a message. This method is not safe for concurrent
	// use.
	Receive() (method uint16, data []byte, err error)
	// ReceiveReader receives a message as an [io.Reader]. Any reader
	// previously opened through this function will be discarded. This
	// method is not safe for concurrent use, and neither is its result.
	ReceiveReader() (method uint16, data io.Reader, err error)
}