package main

// White-box tests for the signal plumbing. Unlike the game package's test
// files this one carries no //nolint:testpackage directive: testpackage
// exempts package main, so nolintlint rejects the directive as unused.

import (
	"os"
	"os/signal"
	"slices"
	"strings"
	"sync"
	"syscall"
	"testing"
)

// signalRecorder stands in for the game and the terminal in the signal
// handler, recording the order of the steps the handler takes. The mutex
// matters: the handler runs on its own goroutine, so an unguarded slice
// would be a data race under -race, which is exactly what these tests
// are meant to rule out.
type signalRecorder struct {
	mu    sync.Mutex
	steps []string
	code  int
	done  chan struct{}
}

func newSignalRecorder() *signalRecorder {
	return &signalRecorder{done: make(chan struct{})}
}

// AutoSave records a save attempt (the saver half).
func (r *signalRecorder) AutoSave() {
	r.record("save")
}

// Fini records a terminal restore (the finisher half).
func (r *signalRecorder) Fini() {
	r.record("fini")
}

// exit records the process exit that ends the handler and releases any
// waiter. It stands in for os.Exit, which cannot be called in a test.
func (r *signalRecorder) exit(code int) {
	r.mu.Lock()
	r.code = code
	r.steps = append(r.steps, "exit")
	r.mu.Unlock()

	close(r.done)
}

// record appends one step.
func (r *signalRecorder) record(step string) {
	r.mu.Lock()
	defer r.mu.Unlock()

	r.steps = append(r.steps, step)
}

// taken returns the recorded steps and the exit code.
func (r *signalRecorder) taken() ([]string, int) {
	r.mu.Lock()
	defer r.mu.Unlock()

	return slices.Clone(r.steps), r.code
}

// TestLeaveOnSignalRestoresTerminalBeforeExit is the core of issue #12:
// whatever the signal, the terminal is restored before the process ends,
// so the player is never dropped into a shell with the tty still in raw
// mode.
func TestLeaveOnSignalRestoresTerminalBeforeExit(t *testing.T) {
	t.Parallel()

	for _, sig := range handledSignals() {
		rec := newSignalRecorder()

		ch := make(chan os.Signal, 1)
		ch <- sig

		leaveOnSignal(ch, rec, rec, rec.exit)

		steps, code := rec.taken()

		fini := slices.Index(steps, "fini")
		exit := slices.Index(steps, "exit")

		if fini < 0 || exit < 0 || fini > exit {
			t.Errorf("%v: want the terminal restored before exit, got %v",
				sig, steps)
		}

		if code != 0 {
			t.Errorf("%v: exit code = %d, want 0", sig, code)
		}
	}
}

// TestLeaveOnSignalSaveSplit pins the decision recorded on savesOnSignal:
// SIGHUP/SIGTERM (involuntary teardown) save on the way out, SIGINT and
// SIGQUIT (a deliberate "stop now" from the player) do not, matching C,
// where auto_save is reserved for HUP/TERM and neither leave() nor quit()
// nor endit() writes a save file.
func TestLeaveOnSignalSaveSplit(t *testing.T) {
	t.Parallel()

	want := map[os.Signal][]string{
		syscall.SIGHUP:  {"save", "fini", "exit"},
		syscall.SIGTERM: {"save", "fini", "exit"},
		syscall.SIGINT:  {"fini", "exit"},
		syscall.SIGQUIT: {"fini", "exit"},
	}

	for _, sig := range handledSignals() {
		rec := newSignalRecorder()

		ch := make(chan os.Signal, 1)
		ch <- sig

		leaveOnSignal(ch, rec, rec, rec.exit)

		steps, _ := rec.taken()
		if !slices.Equal(steps, want[sig]) {
			t.Errorf("%v: steps = %v, want %v", sig, steps, want[sig])
		}

		if saved := slices.Contains(steps, "save"); saved != savesOnSignal(sig) {
			t.Errorf("%v: saved = %v, savesOnSignal = %v",
				sig, saved, savesOnSignal(sig))
		}
	}
}

// TestLeaveOnSignalIgnoresLaterSignals covers the ordering guarantee in
// leaveOnSignal's comment: only the first signal is read, so a second one
// arriving mid-save cannot exit out from under the save and truncate the
// player's file. The saver here blocks until a second signal has been
// queued, reproducing that window.
func TestLeaveOnSignalIgnoresLaterSignals(t *testing.T) {
	t.Parallel()

	rec := newSignalRecorder()

	ch := make(chan os.Signal, 2)
	ch <- syscall.SIGHUP

	blocker := &blockingSaver{rec: rec, queue: ch, extra: syscall.SIGINT}

	leaveOnSignal(ch, blocker, rec, rec.exit)

	steps, _ := rec.taken()
	if !slices.Equal(steps, []string{"save", "fini", "exit"}) {
		t.Errorf("steps = %v, want one save, one fini, one exit", steps)
	}

	if len(ch) != 1 {
		t.Errorf("queued signals left unread = %d, want 1", len(ch))
	}
}

// blockingSaver queues another signal while the save is in flight, the
// race window leaveOnSignal is built to close.
type blockingSaver struct {
	rec   *signalRecorder
	queue chan os.Signal
	extra os.Signal
}

// AutoSave delivers the extra signal mid-save, then records the save.
func (b *blockingSaver) AutoSave() {
	b.queue <- b.extra

	b.rec.AutoSave()
}

// TestLeaveOnRealSignal is the deepest headless check available: it
// delivers real SIGINT/SIGQUIT/SIGHUP/SIGTERM to this process through
// os/signal, exactly as notifySignals wires them in the game, and
// verifies each one reaches the handler and restores the terminal before
// exiting.
//
// What cannot be checked here is the tty itself coming back out of raw
// mode: that needs a controlling terminal and a live tcell screen, which
// a headless test run does not have. This test covers everything up to
// the Terminal.Fini call; term.Tcell.Fini is a direct pass-through to
// tcell's Screen.Fini, which is the same call myExit already relies on.
func TestLeaveOnRealSignal(t *testing.T) {
	t.Parallel()

	ch := notifySignals()
	defer signal.Stop(ch)

	for _, sig := range handledSignals() {
		rec := newSignalRecorder()

		go leaveOnSignal(ch, rec, rec, rec.exit)

		unix, ok := sig.(syscall.Signal)
		if !ok {
			t.Fatalf("%v is not a unix signal", sig)
		}

		err := syscall.Kill(os.Getpid(), unix)
		if err != nil {
			t.Fatalf("kill(%v): %v", sig, err)
		}

		<-rec.done

		steps, code := rec.taken()
		if !strings.HasSuffix(strings.Join(steps, ","), "fini,exit") {
			t.Errorf("%v: steps = %v, want the terminal restored before exit",
				sig, steps)
		}

		if code != 0 {
			t.Errorf("%v: exit code = %d, want 0", sig, code)
		}
	}
}