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"
	"sync"
	"syscall"
	"testing"
	"time"
)

// The steps the signal handler can take, in the order signalRecorder
// records them.
const (
	stepSave = "save"
	stepFini = "fini"
	stepExit = "exit"
)

// wantHandledSignals is the exact set of signals the game must leave on.
// This is the subject of issue #12: SIGHUP and SIGTERM were handled and
// SIGINT and SIGQUIT were not, so the latter two killed the process with
// the tty still raw. Every other test here iterates handledSignals(), so
// without this one the whole file would pass against a set that had
// silently lost SIGINT and SIGQUIT again.
func wantHandledSignals() []os.Signal {
	return []os.Signal{
		syscall.SIGHUP, syscall.SIGTERM, syscall.SIGINT, syscall.SIGQUIT,
	}
}

// wantSteps is the expected handler step sequence for each handled
// signal, and the single source of truth for the tests that check the
// save/no-save split.
func wantSteps() map[os.Signal][]string {
	return map[os.Signal][]string{
		syscall.SIGHUP:  {stepSave, stepFini, stepExit},
		syscall.SIGTERM: {stepSave, stepFini, stepExit},
		syscall.SIGINT:  {stepFini, stepExit},
		syscall.SIGQUIT: {stepFini, stepExit},
	}
}

// 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{})}
}

// AutoSaveOnSignal records a save attempt (the saver half). The real one
// hands the work to the game goroutine and waits; the recorder stands in
// for a game that takes it immediately.
func (r *signalRecorder) AutoSaveOnSignal(time.Duration) bool {
	r.record(stepSave)

	return true
}

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

// 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, stepExit)
	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
}

// TestHandledSignalsSet pins the membership of handledSignals() itself.
// The regression issue #12 exists to prevent is a signal dropping out of
// that set — SIGINT and SIGQUIT reaching the process at SIG_DFL and
// killing it with the tty raw — and every other test in this file is
// driven by the set, so only this test can fail on it.
func TestHandledSignalsSet(t *testing.T) {
	t.Parallel()

	got := handledSignals()
	want := wantHandledSignals()

	if len(got) != len(want) {
		t.Errorf("handledSignals() = %v, want exactly %v", got, want)
	}

	for _, sig := range want {
		if !slices.Contains(got, sig) {
			t.Errorf("handledSignals() = %v, missing %v", got, sig)
		}
	}

	for _, sig := range got {
		if !slices.Contains(want, sig) {
			t.Errorf("handledSignals() = %v, unexpected %v", got, sig)
		}
	}
}

// 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, stepFini)
		exit := slices.Index(steps, stepExit)

		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.
//
// It is driven by the expectation table rather than by
// handledSignals(), so that every entry — including the SIGINT and
// SIGQUIT ones — is actually read, and a signal dropped from the handled
// set fails here as well as in TestHandledSignalsSet.
func TestLeaveOnSignalSaveSplit(t *testing.T) {
	t.Parallel()

	for sig, want := range wantSteps() {
		if !slices.Contains(handledSignals(), sig) {
			t.Errorf("%v is not handled at all, so it cannot exit cleanly", sig)

			continue
		}

		rec := newSignalRecorder()

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

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

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

		if saved := slices.Contains(steps, stepSave); 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{stepSave, stepFini, stepExit}) {
		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
}

// AutoSaveOnSignal delivers the extra signal mid-save, then records the
// save.
func (b *blockingSaver) AutoSaveOnSignal(timeout time.Duration) bool {
	b.queue <- b.extra

	return b.rec.AutoSaveOnSignal(timeout)
}

// 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 produces the full expected
// step sequence — including the save/no-save split, which this test is
// the best placed to check end to end.
//
// 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 want := wantSteps()[sig]; !slices.Equal(steps, want) {
			t.Errorf("%v: steps = %v, want %v", sig, steps, want)
		}

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

// TestPendingSaverArmsBeforeTheGameExists covers what lets the handlers
// be installed the instant the terminal goes raw rather than after the
// game is built: a signal arriving before there is a game must still
// reach Fini, and must not save anything, while one arriving after the
// game is handed over saves it.
func TestPendingSaverArmsBeforeTheGameExists(t *testing.T) {
	t.Parallel()

	pending := &pendingSaver{}
	rec := newSignalRecorder()

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

	// No game yet: the SIGHUP still restores the terminal and exits, it
	// just has nothing to write.
	leaveOnSignal(ch, pending, rec, rec.exit)

	steps, code := rec.taken()
	if want := []string{stepFini, stepExit}; !slices.Equal(steps, want) {
		t.Errorf("before the game exists: steps = %v, want %v", steps, want)
	}

	if code != 0 {
		t.Errorf("before the game exists: exit code = %d, want 0", code)
	}

	// Once the game is handed over, the same saver writes it.
	started := newSignalRecorder()
	pending.set(started)

	if !pending.AutoSaveOnSignal(signalSaveTimeout) {
		t.Error("after set: the save was not reported as taken")
	}

	saved, _ := started.taken()
	if want := []string{stepSave}; !slices.Equal(saved, want) {
		t.Errorf("after set: steps = %v, want %v", saved, want)
	}
}

// TestPendingSaverDoesNotHoldItsLockAcrossTheSave pins the reason
// pendingSaver reads the game out from under the mutex instead of
// delegating with it held: since issue #24 the delegated save blocks
// until the game goroutine takes it or the deadline expires, so a mutex
// held across it would stall whoever calls set. Nothing calls set twice
// today, which is why the PR #23 review recorded this as a future-proof
// note rather than a bug — this test is what stops it becoming one.
func TestPendingSaverDoesNotHoldItsLockAcrossTheSave(t *testing.T) {
	t.Parallel()

	pending := &pendingSaver{}
	stuck := &stuckSaver{entered: make(chan struct{}), release: make(chan struct{})}
	pending.set(stuck)

	go pending.AutoSaveOnSignal(signalSaveTimeout)

	<-stuck.entered // the delegated save is in flight

	done := make(chan struct{})

	go func() {
		defer close(done)

		pending.set(newSignalRecorder()) // must not block on the save
	}()

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Error("set blocked while a save was in flight: the lock is held across it")
	}

	close(stuck.release)
}

// stuckSaver blocks inside the delegated save until it is released,
// standing in for a game goroutine that is slow to answer.
type stuckSaver struct {
	entered chan struct{}
	release chan struct{}
}

// AutoSaveOnSignal blocks until the test releases it.
func (s *stuckSaver) AutoSaveOnSignal(time.Duration) bool {
	close(s.entered)
	<-s.release

	return true
}

// TestDigsNewDungeon pins which invocations reach C's greeting. In main.c
// the printf is the last statement before initscr(), so -s and -d, which
// exit earlier, never see it, and neither does a restored game, because
// restore() does not return. The saved-game case is the one worth having
// a test for: resuming a dungeon must not announce that one is being dug.
func TestDigsNewDungeon(t *testing.T) {
	t.Parallel()

	cases := []struct {
		name      string
		deathDemo bool
		args      []string
		want      bool
	}{
		{name: "new game", args: nil, want: true},
		{name: "restore a save", args: []string{"rogue.save"}, want: false},
		{name: "death demo", deathDemo: true, want: false},
		{
			name:      "death demo wins over a save argument",
			deathDemo: true,
			args:      []string{"rogue.save"},
			want:      false,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			if got := digsNewDungeon(tc.deathDemo, tc.args); got != tc.want {
				t.Errorf("digsNewDungeon(%v, %v) = %v, want %v",
					tc.deathDemo, tc.args, got, tc.want)
			}
		})
	}
}