package intentgate

import (
	"context"
	"errors"
	"reflect"
	"testing"

	"agent-intent/intent"
	"agent-native/exec"
)

type stubBackend struct {
	name  string
	calls int
}

func (s *stubBackend) Name() string { return s.name }

func (s *stubBackend) Execute(ctx context.Context, req exec.Request) (*exec.Result, error) {
	s.calls++
	return &exec.Result{Success: true, Logs: "stub:" + req.Prompt}, nil
}

func emptySnapshot(t *testing.T) *intent.Snapshot {
	t.Helper()
	reg, err := intent.NewRegistryBuilder(intent.Options{}).Build()
	if err != nil {
		t.Fatal(err)
	}
	return reg.Snapshot()
}

// 带一个守卫 spec 与一个可路由 spec 的快照。
func loadedSnapshot(t *testing.T) *intent.Snapshot {
	t.Helper()
	b := intent.NewRegistryBuilder(intent.Options{
		GuardDomains:     []string{"guard"},
		ProtectedDomains: []string{"guard"},
	})
	if err := b.Register(intent.IntentSpec{
		ID: "guard.config_change", Domain: "guard", Version: 1,
		Matcher: intent.MatchSpec{IncludesAny: []string{"系统配置", "网关"}},
		Risk:    intent.RiskHigh,
		Handler: "refuse.and_guide",
		Metadata: map[string]string{
			"guidance": "系统配置请在管理界面修改",
		},
	}); err != nil {
		t.Fatal(err)
	}
	reg, err := b.Build()
	if err != nil {
		t.Fatal(err)
	}
	return reg.Snapshot()
}

func newRec() intent.Recognizer { return intent.NewRecognizer(intent.Options{}, nil, nil) }

func TestZeroSpecSnapshotPassthroughIdentical(t *testing.T) {
	// T0 行为解耦：零意图快照 + Wrap 后，与裸后端行为逐字节一致。
	bare := &stubBackend{name: "native"}
	gatedBe := Wrap(&stubBackend{name: "native"}, newRec(), emptySnapshot(t),
		func(ctx context.Context, req exec.Request, res intent.Result) (*exec.Result, error, bool) {
			t.Fatal("handler must not fire on empty snapshot")
			return nil, nil, false
		})
	req := exec.Request{Prompt: "帮我改一下系统网关地址"}
	want, werr := bare.Execute(context.Background(), req)
	got, gerr := gatedBe.Execute(context.Background(), req)
	if werr != nil || gerr != nil {
		t.Fatalf("execute errors: %v %v", werr, gerr)
	}
	if !reflect.DeepEqual(want, got) {
		t.Fatalf("results differ: %+v vs %+v", want, got)
	}
	if gatedBe.(*gated).next.(*stubBackend).calls != 1 {
		t.Fatal("next backend not invoked exactly once")
	}
}

func TestGuardHitInterceptsWithoutModel(t *testing.T) {
	next := &stubBackend{name: "native"}
	be := Wrap(next, newRec(), loadedSnapshot(t),
		func(ctx context.Context, req exec.Request, res intent.Result) (*exec.Result, error, bool) {
			if res.Branch != intent.BranchGuardHit || res.Top == nil || res.Top.ID != "guard.config_change" {
				t.Fatalf("unexpected result: %+v", res)
			}
			// 宿主解释守卫意图：拒绝 + 引导（合成结果语义由宿主定义）。
			return &exec.Result{Success: false, ErrorReason: "guard refused: " + res.Top.Metadata["guidance"]}, nil, true
		})
	out, err := be.Execute(context.Background(), exec.Request{Prompt: "帮我改一下系统网关地址"})
	if err != nil {
		t.Fatal(err)
	}
	if out.Success || out.ErrorReason == "" {
		t.Fatalf("expected guard refusal, got %+v", out)
	}
	if next.calls != 0 {
		t.Fatalf("model backend must not be called on guard hit, got %d calls", next.calls)
	}
}

func TestFallbackPassesThroughToBackend(t *testing.T) {
	next := &stubBackend{name: "native"}
	be := Wrap(next, newRec(), loadedSnapshot(t),
		func(ctx context.Context, req exec.Request, res intent.Result) (*exec.Result, error, bool) {
			t.Fatal("handler must not fire on fallback")
			return nil, nil, false
		})
	out, err := be.Execute(context.Background(), exec.Request{Prompt: "写一份周报"})
	if err != nil || out == nil || !out.Success {
		t.Fatalf("fallback must reach backend: %+v %v", out, err)
	}
	if next.calls != 1 {
		t.Fatalf("backend calls = %d", next.calls)
	}
}

func TestHandlerDeclineFallsBackToBackend(t *testing.T) {
	next := &stubBackend{name: "native"}
	be := Wrap(next, newRec(), loadedSnapshot(t),
		func(ctx context.Context, req exec.Request, res intent.Result) (*exec.Result, error, bool) {
			return nil, nil, false // 宿主放弃处理
		})
	out, err := be.Execute(context.Background(), exec.Request{Prompt: "帮我改一下系统网关地址"})
	if err != nil || out == nil || !out.Success {
		t.Fatalf("declined handling must pass through: %+v %v", out, err)
	}
	if next.calls != 1 {
		t.Fatalf("backend calls = %d", next.calls)
	}
}

func TestNilComponentsReturnNext(t *testing.T) {
	next := &stubBackend{name: "native"}
	if got := Wrap(next, nil, nil, nil); got != exec.Backend(next) {
		t.Fatal("nil components must return next unchanged")
	}
}

func TestRecognizeErrorFailsClosed(t *testing.T) {
	next := &stubBackend{name: "native"}
	b := intent.NewRegistryBuilder(intent.Options{MaxInputLen: 8})
	reg, err := b.Build()
	if err != nil {
		t.Fatal(err)
	}
	be := Wrap(next, newRec(), reg.Snapshot(),
		func(ctx context.Context, req exec.Request, res intent.Result) (*exec.Result, error, bool) {
			t.Fatal("handler must not fire on recognize error")
			return nil, nil, false
		})
	_, err = be.Execute(context.Background(), exec.Request{Prompt: "这一段输入明显超过八个字节"})
	if err == nil {
		t.Fatal("expected fail-closed error")
	}
	var ie *intent.Error
	if !errors.As(err, &ie) {
		t.Fatalf("expected *intent.Error, got %T", err)
	}
	if next.calls != 0 {
		t.Fatal("backend must not run on recognize error")
	}
}