package policy

import (
	"context"
	"path/filepath"
	"strings"
	"testing"
)

// loadRealPolicy compiles the committed policies/sinks/signing_service.rego
// so the tests fail if we rename the package or break the file.
func loadRealPolicy(t *testing.T) *OPAEvaluator {
	t.Helper()
	// From services/signing-service, walk up to repo root (two parents),
	// then into policies/sinks/signing_service.rego.
	p := filepath.Join("..", "..", "..", "..", "policies", "sinks", "signing_service.rego")
	opa, err := NewOPAEvaluator(context.Background(), p)
	if err != nil {
		t.Fatalf("load policy: %v", err)
	}
	return opa
}

func makeInput() Input {
	by := InputRegistryRow{
		AgentID:           "agent-approval-service",
		PocketIDClient:    "agent-approval-service",
		K8sNamespace:      "agent-trust",
		K8sServiceAccount: "approval-service",
		AllowedActions:    []string{"expense.submit"},
	}
	return Input{
		PocketIDClient: "agent-approval-service",
		K8s: InputK8s{
			Namespace:      "agent-trust",
			ServiceAccount: "approval-service",
		},
		KeyRef: "trust-api/approval-signer-2026-q4",
		Registry: InputRegistry{
			ByPocketID: &by,
			ByK8s:      &by,
		},
	}
}

func TestOPA_Allows_ApprovalService_HappyPath(t *testing.T) {
	opa := loadRealPolicy(t)
	dec, err := opa.Decide(context.Background(), makeInput())
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if !dec.Allow {
		t.Fatalf("expected allow, got deny: %q", dec.Reason)
	}
}

func TestOPA_Allows_TestAgentTransform_HappyPath(t *testing.T) {
	opa := loadRealPolicy(t)
	by := InputRegistryRow{
		AgentID:           "agent-testagent-transform",
		PocketIDClient:    "agent-testagent-transform",
		K8sNamespace:      "agent-trust",
		K8sServiceAccount: "testagent-transform",
	}
	in := Input{
		PocketIDClient: "agent-testagent-transform",
		K8s:            InputK8s{Namespace: "agent-trust", ServiceAccount: "testagent-transform"},
		KeyRef:         "trust-api/agent-testagent-transform-2026-q4",
		Registry:       InputRegistry{ByPocketID: &by, ByK8s: &by},
	}
	dec, err := opa.Decide(context.Background(), in)
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if !dec.Allow {
		t.Fatalf("expected allow, got deny: %q", dec.Reason)
	}
}

func TestOPA_Denies_RegistryMismatch(t *testing.T) {
	opa := loadRealPolicy(t)
	in := makeInput()
	// By-K8s returns a DIFFERENT agent row than By-PocketID — the double
	// identity check must deny.
	byK := InputRegistryRow{
		AgentID:           "agent-testagent-transform",
		PocketIDClient:    "agent-testagent-transform",
		K8sNamespace:      "agent-trust",
		K8sServiceAccount: "testagent-transform",
	}
	in.Registry.ByK8s = &byK
	dec, err := opa.Decide(context.Background(), in)
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if dec.Allow {
		t.Fatalf("expected deny on registry mismatch, got allow")
	}
	if !strings.Contains(dec.Reason, "do not resolve to the same registry agent") {
		t.Errorf("unexpected reason: %q", dec.Reason)
	}
}

func TestOPA_Denies_SubjectMismatchFromCaller(t *testing.T) {
	opa := loadRealPolicy(t)
	in := makeInput()
	// Caller presented a different Pocket-ID subject than the one stored
	// in the registry row — the policy must deny because the row no longer
	// matches the authenticated identity.
	in.PocketIDClient = "spoofed-client"
	dec, err := opa.Decide(context.Background(), in)
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if dec.Allow {
		t.Fatalf("expected deny when caller subject mismatches registry, got allow")
	}
}

func TestOPA_Denies_WrongKeyRefForRole(t *testing.T) {
	opa := loadRealPolicy(t)
	in := makeInput()
	in.KeyRef = "trust-api/agent-testagent-transform-2026-q4" // belongs to other agent
	dec, err := opa.Decide(context.Background(), in)
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if dec.Allow {
		t.Fatalf("expected deny on wrong key_ref, got allow")
	}
	if !strings.Contains(dec.Reason, "not permitted to sign") {
		t.Errorf("unexpected reason: %q", dec.Reason)
	}
}

func TestOPA_Denies_NilRegistryRow(t *testing.T) {
	opa := loadRealPolicy(t)
	in := makeInput()
	in.Registry.ByK8s = nil
	dec, err := opa.Decide(context.Background(), in)
	if err != nil {
		t.Fatalf("Decide: %v", err)
	}
	if dec.Allow {
		t.Fatalf("expected deny on missing registry row, got allow")
	}
}