sway/subscribe.go

package sway

import (
	"context"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"net"

	"git.milar.in/milarin/slices"
)

// Subscribe subscribes to the given event types
// and returns a channel in which all events get written into.
// A new socket connection will be established
// so other requests can still be used during a subscription.
// The subscription connection will be closed as soon as ctx is closed.
func (c *Client) Subscribe(ctx context.Context, events ...EventType) (<-chan Event, error) {
	conn, err := net.Dial("unix", c.socket)
	if err != nil {
		return nil, err
	}

	if _, err := fmt.Fprint(conn, "i3-ipc"); err != nil {
		return nil, err
	}

	payload, err := json.Marshal(slices.Map(events, EventType.String))
	if err != nil {
		return nil, err
	}

	if err := binary.Write(conn, binary.LittleEndian, uint32(len(payload))); err != nil {
		return nil, err
	}

	if err := binary.Write(conn, binary.LittleEndian, uint32(2)); err != nil {
		return nil, err
	}

	if _, err := conn.Write(payload); err != nil {
		return nil, err
	}

	if _, err := conn.Read(make([]byte, 6)); err != nil {
		return nil, err
	}

	var length uint32
	if err := binary.Read(conn, binary.LittleEndian, &length); err != nil {
		return nil, err
	}

	var messageType uint32
	if err := binary.Read(conn, binary.LittleEndian, &messageType); err != nil {
		return nil, err
	}

	result := commandResult{}
	if err := json.NewDecoder(io.LimitReader(conn, int64(length))).Decode(&result); err != nil {
		return nil, err
	}

	if result.HasError() {
		return nil, result.GetError()
	}

	return parseEvents(ctx, conn)
}

func parseEvents(ctx context.Context, conn net.Conn) (<-chan Event, error) {
	out := make(chan Event, 10)

	go func() {
		defer conn.Close()
		<-ctx.Done()
	}()

	go func() {
		defer close(out)

		for ctx.Err() == nil {
			if _, err := conn.Read(make([]byte, 6)); err != nil {
				return
			}

			var length uint32
			if err := binary.Read(conn, binary.LittleEndian, &length); err != nil {
				return
			}

			var messageType EventType
			if err := binary.Read(conn, binary.LittleEndian, &messageType); err != nil {
				return
			}

			event, err := parseEvent(conn, length, messageType)
			if err != nil {
				return
			}

			out <- event
		}
	}()

	return out, nil
}

func parseEvent(conn net.Conn, length uint32, messageType EventType) (Event, error) {
	var event Event
	switch messageType {
	case EventTypeWorkspace:
		event = &WorkspaceEvent{}
	case EventTypeMode:
		event = &ModeEvent{}
	case EventTypeWindow:
		event = &WindowEvent{}
	case EventTypeBinding:
		event = &BindingEvent{}
	case EventTypeShutdown:
		event = &ShutdownEvent{}
	case EventTypeTick:
		event = &TickEvent{}
	case EventTypeBarStateUpdate:
		event = &BarStateUpdateEvent{}
	case EventTypeInput:
		event = &InputEvent{}
	default:
		return nil, fmt.Errorf("invalid event type: %x", messageType)
	}

	if err := json.NewDecoder(io.LimitReader(conn, int64(length))).Decode(event); err != nil {
		return nil, err
	}

	return event, nil
}