package auth

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/containous/alice"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"github.com/traefik/traefik/v3/pkg/config/dynamic"
	"github.com/traefik/traefik/v3/pkg/config/static"
	tracingMiddleware "github.com/traefik/traefik/v3/pkg/middlewares/tracing"
	"github.com/traefik/traefik/v3/pkg/testhelpers"
	"github.com/traefik/traefik/v3/pkg/tracing"
	"github.com/traefik/traefik/v3/pkg/tracing/opentelemetry"
	"github.com/traefik/traefik/v3/pkg/version"
	"github.com/vulcand/oxy/v2/forward"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
)

func TestForwardAuthFail(t *testing.T) {
	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, "traefik")
	})

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set(forward.ProxyAuthenticate, "test")
		http.Error(w, "Forbidden", http.StatusForbidden)
	}))
	t.Cleanup(server.Close)

	middleware, err := NewForward(context.Background(), next, dynamic.ForwardAuth{
		Address: server.URL,
	}, "authTest")
	require.NoError(t, err)

	ts := httptest.NewServer(middleware)
	t.Cleanup(ts.Close)

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
	res, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	assert.Equal(t, http.StatusForbidden, res.StatusCode)

	body, err := io.ReadAll(res.Body)
	require.NoError(t, err)
	err = res.Body.Close()
	require.NoError(t, err)

	assert.Equal(t, "test", res.Header.Get(forward.ProxyAuthenticate))
	assert.Equal(t, "Forbidden\n", string(body))
}

func TestForwardAuthSuccess(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Auth-User", "user@example.com")
		w.Header().Set("X-Auth-Secret", "secret")
		w.Header().Add("X-Auth-Group", "group1")
		w.Header().Add("X-Auth-Group", "group2")
		w.Header().Add("Foo-Bar", "auth-value")
		fmt.Fprintln(w, "Success")
	}))
	t.Cleanup(server.Close)

	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		assert.Equal(t, "user@example.com", r.Header.Get("X-Auth-User"))
		assert.Empty(t, r.Header.Get("X-Auth-Secret"))
		assert.Equal(t, []string{"group1", "group2"}, r.Header["X-Auth-Group"])
		assert.Equal(t, "auth-value", r.Header.Get("Foo-Bar"))
		assert.Empty(t, r.Header.Get("Foo-Baz"))
		fmt.Fprintln(w, "traefik")
	})

	auth := dynamic.ForwardAuth{
		Address:                  server.URL,
		AuthResponseHeaders:      []string{"X-Auth-User", "X-Auth-Group"},
		AuthResponseHeadersRegex: "^Foo-",
	}
	middleware, err := NewForward(context.Background(), next, auth, "authTest")
	require.NoError(t, err)

	ts := httptest.NewServer(middleware)
	t.Cleanup(ts.Close)

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
	req.Header.Set("X-Auth-Group", "admin_group")
	req.Header.Set("Foo-Bar", "client-value")
	req.Header.Set("Foo-Baz", "client-value")
	res, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	assert.Equal(t, http.StatusOK, res.StatusCode)

	body, err := io.ReadAll(res.Body)
	require.NoError(t, err)
	err = res.Body.Close()
	require.NoError(t, err)
	assert.Equal(t, "traefik\n", string(body))
}

func TestForwardAuthRedirect(t *testing.T) {
	authTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, "http://example.com/redirect-test", http.StatusFound)
	}))
	t.Cleanup(authTs.Close)

	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, "traefik")
	})

	auth := dynamic.ForwardAuth{Address: authTs.URL}

	authMiddleware, err := NewForward(context.Background(), next, auth, "authTest")
	require.NoError(t, err)

	ts := httptest.NewServer(authMiddleware)
	t.Cleanup(ts.Close)

	client := &http.Client{
		CheckRedirect: func(r *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)

	res, err := client.Do(req)
	require.NoError(t, err)

	assert.Equal(t, http.StatusFound, res.StatusCode)

	location, err := res.Location()
	require.NoError(t, err)
	assert.Equal(t, "http://example.com/redirect-test", location.String())

	body, err := io.ReadAll(res.Body)
	require.NoError(t, err)
	err = res.Body.Close()
	require.NoError(t, err)
	assert.NotEmpty(t, string(body))
}

func TestForwardAuthRemoveHopByHopHeaders(t *testing.T) {
	authTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		headers := w.Header()
		for _, header := range hopHeaders {
			if header == forward.TransferEncoding {
				headers.Set(header, "chunked")
			} else {
				headers.Add(header, "test")
			}
		}

		http.Redirect(w, r, "http://example.com/redirect-test", http.StatusFound)
	}))
	t.Cleanup(authTs.Close)

	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, "traefik")
	})

	auth := dynamic.ForwardAuth{Address: authTs.URL}

	authMiddleware, err := NewForward(context.Background(), next, auth, "authTest")
	require.NoError(t, err)

	ts := httptest.NewServer(authMiddleware)
	t.Cleanup(ts.Close)

	client := &http.Client{
		CheckRedirect: func(r *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
	res, err := client.Do(req)
	require.NoError(t, err)
	assert.Equal(t, http.StatusFound, res.StatusCode, "they should be equal")

	for _, header := range forward.HopHeaders {
		assert.Equal(t, "", res.Header.Get(header), "hop-by-hop header '%s' mustn't be set", header)
	}

	location, err := res.Location()
	require.NoError(t, err)
	assert.Equal(t, "http://example.com/redirect-test", location.String(), "they should be equal")

	body, err := io.ReadAll(res.Body)
	require.NoError(t, err)
	assert.NotEmpty(t, string(body), "there should be something in the body")
}

func TestForwardAuthFailResponseHeaders(t *testing.T) {
	authTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		cookie := &http.Cookie{Name: "example", Value: "testing", Path: "/"}
		http.SetCookie(w, cookie)
		w.Header().Add("X-Foo", "bar")
		http.Error(w, "Forbidden", http.StatusForbidden)
	}))
	t.Cleanup(authTs.Close)

	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, "traefik")
	})

	auth := dynamic.ForwardAuth{
		Address: authTs.URL,
	}
	authMiddleware, err := NewForward(context.Background(), next, auth, "authTest")
	require.NoError(t, err)

	ts := httptest.NewServer(authMiddleware)
	t.Cleanup(ts.Close)

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)

	res, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	assert.Equal(t, http.StatusForbidden, res.StatusCode)

	require.Len(t, res.Cookies(), 1)
	for _, cookie := range res.Cookies() {
		assert.Equal(t, "testing", cookie.Value)
	}

	expectedHeaders := http.Header{
		"Content-Length":         []string{"10"},
		"Content-Type":           []string{"text/plain; charset=utf-8"},
		"X-Foo":                  []string{"bar"},
		"Set-Cookie":             []string{"example=testing; Path=/"},
		"X-Content-Type-Options": []string{"nosniff"},
	}

	assert.Len(t, res.Header, 6)
	for key, value := range expectedHeaders {
		assert.Equal(t, value, res.Header[key])
	}

	body, err := io.ReadAll(res.Body)
	require.NoError(t, err)
	err = res.Body.Close()
	require.NoError(t, err)

	assert.Equal(t, "Forbidden\n", string(body))
}

func Test_writeHeader(t *testing.T) {
	testCases := []struct {
		name                      string
		headers                   map[string]string
		authRequestHeaders        []string
		trustForwardHeader        bool
		emptyHost                 bool
		expectedHeaders           map[string]string
		checkForUnexpectedHeaders bool
	}{
		{
			name: "trust Forward Header",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
			trustForwardHeader: true,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
		},
		{
			name: "not trust Forward Header",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "foo.bar",
			},
		},
		{
			name: "trust Forward Header with empty Host",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
			trustForwardHeader: true,
			emptyHost:          true,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
		},
		{
			name: "not trust Forward Header with empty Host",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
			},
			trustForwardHeader: false,
			emptyHost:          true,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "",
			},
		},
		{
			name: "trust Forward Header with forwarded URI",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
				"X-Forwarded-Uri":  "/forward?q=1",
			},
			trustForwardHeader: true,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
				"X-Forwarded-Uri":  "/forward?q=1",
			},
		},
		{
			name: "not trust Forward Header with forward requested URI",
			headers: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "fii.bir",
				"X-Forwarded-Uri":  "/forward?q=1",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"Accept":           "application/json",
				"X-Forwarded-Host": "foo.bar",
				"X-Forwarded-Uri":  "/path?q=1",
			},
		},
		{
			name: "trust Forward Header with forwarded request Method",
			headers: map[string]string{
				"X-Forwarded-Method": "OPTIONS",
			},
			trustForwardHeader: true,
			expectedHeaders: map[string]string{
				"X-Forwarded-Method": "OPTIONS",
			},
		},
		{
			name: "not trust Forward Header with forward request Method",
			headers: map[string]string{
				"X-Forwarded-Method": "OPTIONS",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"X-Forwarded-Method": "GET",
			},
		},
		{
			name: "remove hop-by-hop headers",
			headers: map[string]string{
				forward.Connection:         "Connection",
				forward.KeepAlive:          "KeepAlive",
				forward.ProxyAuthenticate:  "ProxyAuthenticate",
				forward.ProxyAuthorization: "ProxyAuthorization",
				forward.Te:                 "Te",
				forward.Trailers:           "Trailers",
				forward.TransferEncoding:   "TransferEncoding",
				forward.Upgrade:            "Upgrade",
				"X-CustomHeader":           "CustomHeader",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"X-CustomHeader":           "CustomHeader",
				"X-Forwarded-Proto":        "http",
				"X-Forwarded-Host":         "foo.bar",
				"X-Forwarded-Uri":          "/path?q=1",
				"X-Forwarded-Method":       "GET",
				forward.ProxyAuthenticate:  "ProxyAuthenticate",
				forward.ProxyAuthorization: "ProxyAuthorization",
			},
			checkForUnexpectedHeaders: true,
		},
		{
			name: "filter forward request headers",
			headers: map[string]string{
				"X-CustomHeader": "CustomHeader",
				"Content-Type":   "multipart/form-data; boundary=---123456",
			},
			authRequestHeaders: []string{
				"X-CustomHeader",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"x-customHeader":     "CustomHeader",
				"X-Forwarded-Proto":  "http",
				"X-Forwarded-Host":   "foo.bar",
				"X-Forwarded-Uri":    "/path?q=1",
				"X-Forwarded-Method": "GET",
			},
			checkForUnexpectedHeaders: true,
		},
		{
			name: "filter forward request headers doesn't add new headers",
			headers: map[string]string{
				"X-CustomHeader": "CustomHeader",
				"Content-Type":   "multipart/form-data; boundary=---123456",
			},
			authRequestHeaders: []string{
				"X-CustomHeader",
				"X-Non-Exists-Header",
			},
			trustForwardHeader: false,
			expectedHeaders: map[string]string{
				"X-CustomHeader":     "CustomHeader",
				"X-Forwarded-Proto":  "http",
				"X-Forwarded-Host":   "foo.bar",
				"X-Forwarded-Uri":    "/path?q=1",
				"X-Forwarded-Method": "GET",
			},
			checkForUnexpectedHeaders: true,
		},
	}

	for _, test := range testCases {
		t.Run(test.name, func(t *testing.T) {
			req := testhelpers.MustNewRequest(http.MethodGet, "http://foo.bar/path?q=1", nil)
			for key, value := range test.headers {
				req.Header.Set(key, value)
			}

			if test.emptyHost {
				req.Host = ""
			}

			forwardReq := testhelpers.MustNewRequest(http.MethodGet, "http://foo.bar/path?q=1", nil)

			writeHeader(req, forwardReq, test.trustForwardHeader, test.authRequestHeaders)

			actualHeaders := forwardReq.Header

			expectedHeaders := test.expectedHeaders
			for key, value := range expectedHeaders {
				assert.Equal(t, value, actualHeaders.Get(key))
				actualHeaders.Del(key)
			}
			if test.checkForUnexpectedHeaders {
				for key := range actualHeaders {
					assert.Fail(t, "Unexpected header found", key)
				}
			}
		})
	}
}

func TestForwardAuthUsesTracing(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("Traceparent") == "" {
			t.Errorf("expected Traceparent header to be present in request")
		}
	}))
	t.Cleanup(server.Close)

	next := http.Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))

	auth := dynamic.ForwardAuth{
		Address: server.URL,
	}

	exporter := tracetest.NewInMemoryExporter()

	tres, err := resource.New(context.Background(),
		resource.WithAttributes(semconv.ServiceNameKey.String("traefik")),
		resource.WithAttributes(semconv.ServiceVersionKey.String(version.Version)),
		resource.WithFromEnv(),
		resource.WithTelemetrySDK(),
	)
	require.NoError(t, err)

	tracerProvider := sdktrace.NewTracerProvider(
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
		sdktrace.WithResource(tres),
		sdktrace.WithBatcher(exporter),
	)
	otel.SetTracerProvider(tracerProvider)

	config := &static.Tracing{
		ServiceName: "testApp",
		SampleRate:  1,
		OTLP: &opentelemetry.Config{
			HTTP: &opentelemetry.HTTP{
				Endpoint: "http://127.0.0.1:8080",
			},
		},
	}
	tr, closer, err := tracing.NewTracing(config)
	require.NoError(t, err)
	t.Cleanup(func() {
		_ = closer.Close()
	})

	next, err = NewForward(context.Background(), next, auth, "authTest")
	require.NoError(t, err)

	chain := alice.New(tracingMiddleware.WrapEntryPointHandler(context.Background(), tr, "tracingTest"))
	next, err = chain.Then(next)
	require.NoError(t, err)

	ts := httptest.NewServer(next)
	t.Cleanup(ts.Close)

	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
	res, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	assert.Equal(t, http.StatusOK, res.StatusCode)
}