// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package control

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"syscall"
	"testing"
	"time"
	"unsafe"
)

// The caller lives inside a private, real Screen session. A separate test
// socket coordinates requests without typing into any terminal.
func TestScreenCallerProcess(t *testing.T) {
	path := os.Getenv("FENRIR_SCREEN_TEST_COORDINATOR")
	if path == "" {
		return
	}
	listener, err := net.Listen("unix", path)
	if err != nil {
		os.Exit(1)
	}
	defer listener.Close()
	for {
		connection, err := listener.Accept()
		if err != nil {
			os.Exit(1)
		}
		var request processCommand
		if json.NewDecoder(connection).Decode(&request) != nil {
			connection.Close()
			continue
		}
		reply := processReply{PID: os.Getpid()}
		target, err := net.DialTimeout("unix", request.Path, time.Second)
		if err == nil {
			target.SetDeadline(time.Now().Add(2 * time.Second))
			_, err = io.WriteString(target, request.Text+"\n")
			if err == nil {
				var data []byte
				data, err = io.ReadAll(target)
				reply.Response = string(data)
			}
			target.Close()
		}
		if err != nil {
			reply.Error = err.Error()
		}
		json.NewEncoder(connection).Encode(reply)
		connection.Close()
	}
}

func TestNativeScreenReattachmentRoutesSayAndNotify(t *testing.T) {
	screen, err := exec.LookPath("screen")
	if err != nil {
		t.Skip("GNU Screen not installed")
	}
	options := private_options(t)
	// The shared owner and an unrelated old-window reader must never receive
	// messages intended for the terminal displaying the reattached session.
	t.Setenv("DISPLAY", ":fixture")
	t.Setenv("WINDOWID", "old")
	start_reader_process(t, options.Directory, "tty")
	start_reader_process(t, options.Directory, "terminal")
	options.TerminalMode, options.WindowID = true, "current"
	server, err := Open(context.Background(), options)
	if err != nil {
		t.Fatal(err)
	}
	defer server.Close()
	go func() {
		for {
			select {
			case request := <-server.Requests():
				data, _ := json.Marshal(requestReceipt{os.Getpid(), request.PID, request.UID, request.Text})
				request.Reply <- string(data)
			case <-server.ctx.Done():
				return
			}
		}
	}()
	screenDirectory := filepath.Join(options.Directory, "screen")
	if err := os.Mkdir(screenDirectory, 0700); err != nil {
		t.Fatal(err)
	}
	coordinator := filepath.Join(options.Directory, "caller.sock")
	session := fmt.Sprintf("fenrir-test-%d", os.Getpid())
	environment := append(os.Environ(), "SCREENDIR="+screenDirectory, "TERM=xterm", "STY=", "FENRIR_SCREEN_TEST_COORDINATOR="+coordinator)
	start := exec.Command(screen, "-dmS", session, "-c", "/dev/null", os.Args[0], "-test.run=^TestScreenCallerProcess$")
	start.Env = environment
	if output, err := start.CombinedOutput(); err != nil {
		t.Fatal(string(output), err)
	}
	t.Cleanup(func() {
		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		defer cancel()
		stop := exec.CommandContext(ctx, screen, "-S", session, "-X", "quit")
		stop.Env = environment
		_ = stop.Run()
	})
	send := func(text string) processReply {
		t.Helper()
		connection, err := net.DialTimeout("unix", coordinator, time.Second)
		if err != nil {
			t.Fatal(err)
		}
		defer connection.Close()
		connection.SetDeadline(time.Now().Add(3 * time.Second))
		if err := json.NewEncoder(connection).Encode(processCommand{Path: server.main_path(), Text: text}); err != nil {
			t.Fatal(err)
		}
		var reply processReply
		if err := json.NewDecoder(connection).Decode(&reply); err != nil || reply.Error != "" {
			t.Fatal(reply, err)
		}
		return reply
	}
	deadline := time.Now().Add(3 * time.Second)
	for {
		if _, err := os.Stat(coordinator); err == nil {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("private Screen caller did not start")
		}
		time.Sleep(10 * time.Millisecond)
	}
	if reply := send("COMMAND SAY detached"); !strings.Contains(reply.Response, "unique attached reader") {
		for pid := reply.PID; pid > 1; pid = parent_pid(pid) {
			command, _ := os.ReadFile(fmt.Sprintf("/proc/%d/cmdline", pid))
			executable, _ := os.Readlink(fmt.Sprintf("/proc/%d/exe", pid))
			t.Logf("ancestor %d command %q executable %q", pid, command, executable)
		}
		t.Fatal("detached Screen used the old window", reply)
	}
	fd, err := syscall.Open("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK|syscall.O_CLOEXEC, 0)
	if err != nil {
		t.Fatal(err)
	}
	master := os.NewFile(uintptr(fd), "private Screen display")
	defer master.Close()
	var unlock int32
	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.TIOCSPTLCK, uintptr(unsafe.Pointer(&unlock))); err != 0 {
		t.Fatal(err)
	}
	var number uint32
	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.TIOCGPTN, uintptr(unsafe.Pointer(&number))); err != 0 {
		t.Fatal(err)
	}
	slave, err := os.OpenFile(fmt.Sprintf("/dev/pts/%d", number), os.O_RDWR|syscall.O_NOCTTY, 0)
	if err != nil {
		t.Fatal(err)
	}
	defer slave.Close()
	attach := exec.Command(screen, "-r", session)
	attach.Env = append(environment, "WINDOWID=current")
	attach.Stdin, attach.Stdout, attach.Stderr = slave, slave, slave
	attach.SysProcAttr = &syscall.SysProcAttr{Setsid: true, Setctty: true, Ctty: 0}
	if err := attach.Start(); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = attach.Process.Kill(); _ = attach.Wait() })
	deadline = time.Now().Add(3 * time.Second)
	for {
		reply := send("COMMAND SAY attached")
		if !strings.HasPrefix(reply.Response, "Remote routing failed:") {
			check_receipt(t, reply, os.Getpid(), "COMMAND SAY attached")
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("reattached Screen did not find its reader", reply)
		}
		time.Sleep(10 * time.Millisecond)
	}
	check_receipt(t, send("COMMAND NOTIFY notification"), os.Getpid(), "COMMAND NOTIFY notification")
}