package backthink

import (
	"context"
	"errors"
	"testing"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/bus"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/iot"
)

// newBackthink builds a Backthink with a fresh in-memory DB and the given deps,
// returning the zeroed deps filled with the DB handle so tests can inspect deps.
func newBackthink(t *testing.T, cfg Config, deps Deps) (*Backthink, Deps) {
	t.Helper()
	deps.DB = newTestDB(t)
	b, err := New(cfg, deps)
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	t.Cleanup(func() { _ = b.Stop(context.Background()) })
	return b, deps
}

func TestNew_Validation(t *testing.T) {
	t.Parallel()
	if _, err := New(Config{}, Deps{DB: newTestDB(t)}); !errors.Is(err, ErrNoThinker) {
		t.Fatalf("missing thinker: err = %v, want ErrNoThinker", err)
	}
	if _, err := New(Config{}, Deps{Thinker: &mockThinker{}}); !errors.Is(err, ErrNilDB) {
		t.Fatalf("missing db: err = %v, want ErrNilDB", err)
	}
}

func TestBackthink_Heartbeat_TriggersThink(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "nothing to report"}
	b, _ := newBackthink(t, Config{Interval: 20 * time.Millisecond}, Deps{Thinker: thinker})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	eventually(t, 2*time.Second, func() bool { return thinker.count() >= 1 })
	eventually(t, 2*time.Second, func() bool {
		recs, _ := b.List(context.Background(), 10)
		return len(recs) >= 1
	})
	recs, err := b.List(context.Background(), 10)
	if err != nil {
		t.Fatalf("List: %v", err)
	}
	if recs[0].Trigger != "heartbeat" {
		t.Fatalf("Trigger = %q, want heartbeat", recs[0].Trigger)
	}
}

func TestBackthink_EventTrigger_Push(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "washing finished, clothes ready"}
	pusher := &mockPusher{result: PushResult{Pushed: true, Route: RouteActiveClient}}
	bs := bus.New()
	b, _ := newBackthink(t, Config{}, Deps{
		Bus:     bs,
		Thinker: thinker,
		State:   &mockState{state: UserState{}},
		Pusher:  pusher,
		Now:     func() time.Time { return dayAt() },
	})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	if err := bs.Publish(context.Background(), SubjectReminderTrigger, "reminder due"); err != nil {
		t.Fatalf("Publish: %v", err)
	}

	eventually(t, 2*time.Second, func() bool {
		recs, _ := b.List(context.Background(), 10)
		return len(recs) >= 1
	})
	if got := thinker.count(); got != 1 {
		t.Fatalf("thinker calls = %d, want 1", got)
	}
	if got := pusher.count(); got != 1 {
		t.Fatalf("pusher calls = %d, want 1 (important + daytime)", got)
	}
	recs, _ := b.List(context.Background(), 10)
	if !recs[0].ShouldPush {
		t.Fatalf("ShouldPush = false, want true")
	}
	if !recs[0].PushResult.Pushed || recs[0].PushResult.Route != RouteActiveClient {
		t.Fatalf("PushResult = %+v, want pushed active_client", recs[0].PushResult)
	}
}

func TestBackthink_EventTrigger_NoPush(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "washing finished, clothes ready"}
	pusher := &mockPusher{result: PushResult{Pushed: true, Route: RouteActiveClient}}
	bs := bus.New()
	b, _ := newBackthink(t, Config{}, Deps{
		Bus:     bs,
		Thinker: thinker,
		State:   &mockState{state: UserState{Sleeping: true}},
		Pusher:  pusher,
		Now:     func() time.Time { return nightAt() },
	})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	if err := bs.Publish(context.Background(), iot.DeviceUpdateSubject, iot.DeviceUpdate{
		Device: iot.Device{ID: "washer", Type: "sensor"},
		Action: "finished",
	}); err != nil {
		t.Fatalf("Publish: %v", err)
	}

	eventually(t, 2*time.Second, func() bool {
		recs, _ := b.List(context.Background(), 10)
		return len(recs) >= 1
	})
	if got := pusher.count(); got != 0 {
		t.Fatalf("pusher calls = %d, want 0 (asleep + night)", got)
	}
	recs, _ := b.List(context.Background(), 10)
	if recs[0].ShouldPush {
		t.Fatalf("ShouldPush = true, want false")
	}
	if recs[0].PushResult.Route != RouteNone {
		t.Fatalf("PushResult.Route = %q, want %q", recs[0].PushResult.Route, RouteNone)
	}
	if recs[0].Trigger != "iot.device_update" {
		t.Fatalf("Trigger = %q, want iot.device_update", recs[0].Trigger)
	}
}

func TestBackthink_SystemEventLowValueDowngraded(t *testing.T) {
	t.Parallel()
	// design/12 §6 策略一: a low-value system event on a public platform does not
	// wake a full thinking pass — it is downgraded to a registration-only record.
	thinker := &mockThinker{text: "should not be called"}
	bs := bus.New()
	b, _ := newBackthink(t, Config{}, Deps{
		Bus:     bs,
		Thinker: thinker,
		Now:     func() time.Time { return dayAt() },
	})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	if err := bs.Publish(context.Background(), SubjectSystemEvent, SystemEvent{Summary: "member joined"}); err != nil {
		t.Fatalf("Publish: %v", err)
	}

	eventually(t, 2*time.Second, func() bool {
		recs, _ := b.List(context.Background(), 10)
		return len(recs) >= 1 && recs[0].Trigger == SubjectSystemEvent
	})
	if got := thinker.count(); got != 0 {
		t.Fatalf("thinker calls = %d, want 0 (low-value system event downgraded)", got)
	}
	recs, _ := b.List(context.Background(), 10)
	if recs[0].ShouldPush {
		t.Fatalf("ShouldPush = true for a downgraded system event")
	}
	if recs[0].PushResult.Route != RouteNone {
		t.Fatalf("PushResult.Route = %q, want %q", recs[0].PushResult.Route, RouteNone)
	}
}

func TestBackthink_SystemEventHighValueThinks(t *testing.T) {
	t.Parallel()
	// A high-importance (owner-relevant) system event still wakes a thinking pass —
	// the denoise gate only downgrades low-value noise (design/12 §6 策略一).
	thinker := &mockThinker{text: "important notice"}
	bs := bus.New()
	b, _ := newBackthink(t, Config{}, Deps{
		Bus:     bs,
		Thinker: thinker,
		Now:     func() time.Time { return dayAt() },
	})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	if err := bs.Publish(context.Background(), SubjectSystemEvent, SystemEvent{Summary: "owner tagged", Import: ImportanceHigh}); err != nil {
		t.Fatalf("Publish: %v", err)
	}

	eventually(t, 2*time.Second, func() bool { return thinker.count() >= 1 })
}

func TestBackthink_List_NewestFirst(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "nothing to report"}
	b, _ := newBackthink(t, Config{Interval: 15 * time.Millisecond}, Deps{Thinker: thinker})

	b.Start(context.Background())
	defer func() { _ = b.Stop(context.Background()) }()

	eventually(t, 2*time.Second, func() bool {
		recs, _ := b.List(context.Background(), 10)
		return len(recs) >= 2
	})
	top, err := b.List(context.Background(), 1)
	if err != nil {
		t.Fatalf("List: %v", err)
	}
	if len(top) != 1 {
		t.Fatalf("len = %d, want 1", len(top))
	}
	all, err := b.List(context.Background(), 10)
	if err != nil {
		t.Fatalf("List: %v", err)
	}
	// The single-row listing must be the same newest record as the head of the
	// full listing, and the full listing must be strictly newest-first.
	if top[0].ID != all[0].ID {
		t.Fatalf("List(1)[0].ID = %d, want %d (== newest)", top[0].ID, all[0].ID)
	}
	for i := 1; i < len(all); i++ {
		if all[i].ID >= all[i-1].ID {
			t.Fatalf("records not newest-first: %d before %d", all[i-1].ID, all[i].ID)
		}
	}
}

func TestBackthink_Stop_NoLeak(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "nothing to report"}
	b, _ := newBackthink(t, Config{Interval: 10 * time.Millisecond}, Deps{Thinker: thinker})

	b.Start(context.Background())
	eventually(t, 2*time.Second, func() bool { return thinker.count() >= 1 })

	if err := b.Stop(context.Background()); err != nil {
		t.Fatalf("Stop: %v", err)
	}
	// Idempotent.
	if err := b.Stop(context.Background()); err != nil {
		t.Fatalf("second Stop: %v", err)
	}

	before := thinker.count()
	time.Sleep(40 * time.Millisecond)
	if got := thinker.count(); got != before {
		t.Fatalf("thinker calls grew after stop: %d -> %d", before, got)
	}
}

func TestBackthink_Stop_UnsubscribesBus(t *testing.T) {
	t.Parallel()
	thinker := &mockThinker{text: "nothing to report"}
	bs := bus.New()
	b, _ := newBackthink(t, Config{Interval: 25 * time.Millisecond}, Deps{Bus: bs, Thinker: thinker})

	b.Start(context.Background())
	// Confirm the subscription is live by triggering one think.
	if err := bs.Publish(context.Background(), SubjectReminderTrigger, "first"); err != nil {
		t.Fatalf("Publish: %v", err)
	}
	eventually(t, 2*time.Second, func() bool { return thinker.count() >= 1 })

	if err := b.Stop(context.Background()); err != nil {
		t.Fatalf("Stop: %v", err)
	}

	before := thinker.count()
	if err := bs.Publish(context.Background(), iot.DeviceUpdateSubject, iot.DeviceUpdate{
		Device: iot.Device{ID: "washer", Type: "sensor"}, Action: "finished",
	}); err != nil {
		t.Fatalf("Publish after stop: %v", err)
	}
	time.Sleep(40 * time.Millisecond)
	if got := thinker.count(); got != before {
		t.Fatalf("thinker calls grew after stop (bus not unsubscribed): %d -> %d", before, got)
	}
}