package udp

import (
	"bytes"
	"encoding/binary"

	"hamlog/internal/applog"
)

// WSJT-X Configure (message 15) — change the decoder's settings remotely. Used
// for ONE thing here: clicking an FT4 spot while the decoder sits in FT8
// switches its mode too, so the operator lands ready to decode instead of
// staring at a band of gibberish. Every other field is sent as "no change"
// (empty strings, max-quint32), per the protocol.
const wsjtMsgConfigure = 15

// EncodeConfigureMode builds a Configure datagram that changes only the mode.
func EncodeConfigureMode(programID, mode string) []byte {
	const noChange32 = ^uint32(0)
	var b bytes.Buffer
	_ = binary.Write(&b, binary.BigEndian, uint32(wsjtMagic))
	_ = binary.Write(&b, binary.BigEndian, uint32(2))
	_ = binary.Write(&b, binary.BigEndian, uint32(wsjtMsgConfigure))
	writeQString(&b, programID)
	writeQString(&b, mode)                             // Mode
	_ = binary.Write(&b, binary.BigEndian, noChange32) // Frequency Tolerance — no change
	writeQString(&b, "")                               // Submode — no change
	_ = binary.Write(&b, binary.BigEndian, uint8(0))   // Fast Mode — off (right for every HF mode)
	_ = binary.Write(&b, binary.BigEndian, noChange32) // T/R Period — no change
	_ = binary.Write(&b, binary.BigEndian, noChange32) // Rx DF — no change
	writeQString(&b, "")                               // DX Call — no change
	writeQString(&b, "")                               // DX Grid — no change
	_ = binary.Write(&b, binary.BigEndian, uint8(0))   // Generate Messages — no
	return b.Bytes()
}

// SendConfigureMode asks every decoder heard this session to switch mode.
// Sent to all instances rather than one: the spot click does not say which
// decoder the operator is looking at, and a second instance already in the
// right mode treats the message as a no-op.
func (m *Manager) SendConfigureMode(mode string) {
	for _, inst := range m.Instances() {
		if err := m.sendToInstance(inst, EncodeConfigureMode(inst, mode), "configure-mode"); err == nil {
			applog.Printf("udp: asked %q to switch to %s", inst, mode)
		}
	}
}