package ucp

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
)

func TestSigningConfig_FromPEM(t *testing.T) {
	// PEM from the generated key pair (openssl ecparam -genkey -name prime256v1)
	pemData := `-----BEGIN EC PRIVATE KEY-----
MHcCAQEEIDTssEctnrEqym80fx2jEVolTW+tWrHyo8fmbi8hMFWmoAoGCCqGSM49
AwEHoUQDQgAEpnPksDSSMcNgUYT4++Z6XuS0V2p6TNMSjWBsgXOu7mo5Esoux+Cm
y+C84ty5VUAdEpoDyNfWMeaAlHKGo+FjiQ==
-----END EC PRIVATE KEY-----`

	cfg, err := NewSigningConfigFromPEM([]byte(pemData), "k6n-ecdsa-2026")
	if err != nil {
		t.Fatalf("NewSigningConfigFromPEM failed: %v", err)
	}
	if cfg.KeyID != "k6n-ecdsa-2026" {
		t.Fatalf("expected key ID 'k6n-ecdsa-2026', got %q", cfg.KeyID)
	}
	if cfg.PrivateKey == nil {
		t.Fatal("expected non-nil private key")
	}
	if cfg.PrivateKey.Curve.Params().Name != "P-256" {
		t.Fatalf("expected P-256 curve, got %s", cfg.PrivateKey.Curve.Params().Name)
	}
}

func TestSigningConfig_InvalidPEM(t *testing.T) {
	_, err := NewSigningConfigFromPEM([]byte("not a pem"), "test")
	if err == nil {
		t.Fatal("expected error for invalid PEM")
	}
}

func TestWithSigning_AddsHeaders(t *testing.T) {
	// Load the test key.
	cfg := mustLoadTestKey(t)

	// A simple handler that returns a JSON response.
	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	})

	wrapped := WithSigning(handler, cfg)
	req := httptest.NewRequest("GET", "/test", nil)
	rec := httptest.NewRecorder()
	wrapped.ServeHTTP(rec, req)

	// Check the response body.
	if rec.Code != http.StatusOK {
		t.Fatalf("expected 200, got %d", rec.Code)
	}

	// Check that signature headers are present.
	sigInput := rec.Header().Get("Signature-Input")
	sig := rec.Header().Get("Signature")
	ts := rec.Header().Get("x-ucp-timestamp")
	digest := rec.Header().Get("Content-Digest")

	if sigInput == "" {
		t.Fatal("expected Signature-Input header")
	}
	if sig == "" {
		t.Fatal("expected Signature header")
	}
	if ts == "" {
		t.Fatal("expected x-ucp-timestamp header")
	}
	if digest == "" {
		t.Fatal("expected Content-Digest header")
	}

	// Verify the signature input format.
	if !strings.HasPrefix(sigInput, `sig1=(@status "content-type" "x-ucp-timestamp" "content-digest");`) {
		t.Fatalf("unexpected Signature-Input format: %q", sigInput)
	}
	if !strings.Contains(sigInput, `keyid="k6n-ecdsa-2026"`) {
		t.Fatalf("Signature-Input missing keyid: %q", sigInput)
	}
	if !strings.Contains(sigInput, `alg="ecdsa-p256"`) {
		t.Fatalf("Signature-Input missing alg: %q", sigInput)
	}

	// Verify the signature format.
	if !strings.HasPrefix(sig, "sig1=:") || !strings.HasSuffix(sig, ":") {
		t.Fatalf("unexpected Signature format: %q", sig)
	}
}

func TestWithSigning_NilConfig(t *testing.T) {
	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("ok"))
	})

	wrapped := WithSigning(handler, nil)
	req := httptest.NewRequest("GET", "/test", nil)
	rec := httptest.NewRecorder()
	wrapped.ServeHTTP(rec, req)

	if rec.Code != http.StatusOK {
		t.Fatalf("expected 200, got %d", rec.Code)
	}
	if rec.Header().Get("Signature-Input") != "" {
		t.Fatal("expected no Signature-Input when signing is nil")
	}
}

func TestWithSigning_DifferentStatuses(t *testing.T) {
	cfg := mustLoadTestKey(t)

	for _, status := range []int{200, 201, 400, 404, 500} {
		handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.WriteHeader(status)
			w.Write([]byte(`{}`))
		})

		wrapped := WithSigning(handler, cfg)
		req := httptest.NewRequest("GET", "/test", nil)
		rec := httptest.NewRecorder()
		wrapped.ServeHTTP(rec, req)

		if rec.Code != status {
			t.Fatalf("expected status %d, got %d", status, rec.Code)
		}
		if rec.Header().Get("Signature-Input") == "" {
			t.Fatalf("expected Signature-Input for status %d", status)
		}
	}
}

func TestWithSigning_WithUCPCartHandler(t *testing.T) {
	cfg := mustLoadTestKey(t)
	applier := newTestApplier()
	handler := CartHandler(applier)
	wrapped := WithSigning(handler, cfg)

	// Create a cart through the wrapped handler.
	req := httptest.NewRequest("POST", "/", nil)
	rec := httptest.NewRecorder()
	wrapped.ServeHTTP(rec, req)

	if rec.Code != http.StatusCreated {
		t.Fatalf("expected 201, got %d", rec.Code)
	}

	// Verify signed.
	if rec.Header().Get("Signature-Input") == "" {
		t.Fatal("expected Signature-Input on UCP cart response")
	}
	if rec.Header().Get("x-ucp-timestamp") == "" {
		t.Fatal("expected x-ucp-timestamp on UCP cart response")
	}
	if rec.Header().Get("Content-Digest") == "" {
		t.Fatal("expected Content-Digest on UCP cart response")
	}
}

// mustLoadTestKey loads the test PEM for signing tests.
func mustLoadTestKey(t testing.TB) *SigningConfig {
	t.Helper()
	pemData := `-----BEGIN EC PRIVATE KEY-----
MHcCAQEEIDTssEctnrEqym80fx2jEVolTW+tWrHyo8fmbi8hMFWmoAoGCCqGSM49
AwEHoUQDQgAEpnPksDSSMcNgUYT4++Z6XuS0V2p6TNMSjWBsgXOu7mo5Esoux+Cm
y+C84ty5VUAdEpoDyNfWMeaAlHKGo+FjiQ==
-----END EC PRIVATE KEY-----`
	cfg, err := NewSigningConfigFromPEM([]byte(pemData), "k6n-ecdsa-2026")
	if err != nil {
		t.Fatalf("mustLoadTestKey: %v", err)
	}
	return cfg
}