// Package ipc defines the tiny control protocol shared by the daemon (server)
// and the CLI/TUI (clients). Messages are newline-delimited JSON over a unix
// socket, so switching layouts or reading status never requires restarting
// the video wall.
package ipc

import (
	"bufio"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"path/filepath"
	"strconv"
	"time"
)

// Request is a command sent to the daemon.
type Request struct {
	Cmd  string `json:"cmd"`            // "status" | "reload" | "set-layout"
	Name string `json:"name,omitempty"` // layout name for set-layout
}

// SlotStatus reports one grid cell's state.
type SlotStatus struct {
	Slot    int    `json:"slot"`
	Camera  string `json:"camera"`
	PID     int    `json:"pid"`
	Running bool   `json:"running"`
	Healthy bool   `json:"healthy"`
}

// Response is the daemon's reply.
type Response struct {
	OK           bool         `json:"ok"`
	Error        string       `json:"error,omitempty"`
	ActiveLayout string       `json:"active_layout,omitempty"`
	Slots        []SlotStatus `json:"slots,omitempty"`
}

// SocketPath returns the control socket path inside the runtime dir.
func SocketPath() string {
	return filepath.Join(RunDir(), "control.sock")
}

// RunDir is the per-user runtime directory for sockets, created on demand.
func RunDir() string {
	base := os.Getenv("XDG_RUNTIME_DIR")
	if base == "" {
		base = filepath.Join(os.TempDir(), "rtsp-streamer-"+strconv.Itoa(os.Getuid()))
	} else {
		base = filepath.Join(base, "rtsp-streamer")
	}
	return base
}

// Send dials the daemon, sends one request, and returns the reply.
func Send(req Request) (*Response, error) {
	conn, err := net.DialTimeout("unix", SocketPath(), 3*time.Second)
	if err != nil {
		return nil, fmt.Errorf("cannot reach daemon (is it running?): %w", err)
	}
	defer conn.Close()
	_ = conn.SetDeadline(time.Now().Add(5 * time.Second))

	enc := json.NewEncoder(conn)
	if err := enc.Encode(req); err != nil {
		return nil, err
	}
	var resp Response
	if err := json.NewDecoder(bufio.NewReader(conn)).Decode(&resp); err != nil {
		return nil, err
	}
	return &resp, nil
}