package healthcheck

import (
	"context"
	"net/http"
	"net/http/httptest"
	"net/url"
	"sync"
	"testing"
	"time"

	"github.com/containous/traefik/testhelpers"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"github.com/vulcand/oxy/roundrobin"
)

const healthCheckInterval = 200 * time.Millisecond
const healthCheckTimeout = 100 * time.Millisecond

type testHandler struct {
	done           func()
	healthSequence []int
}

func TestSetBackendsConfiguration(t *testing.T) {
	testCases := []struct {
		desc                       string
		startHealthy               bool
		healthSequence             []int
		expectedNumRemovedServers  int
		expectedNumUpsertedServers int
		expectedGaugeValue         float64
	}{
		{
			desc:                       "healthy server staying healthy",
			startHealthy:               true,
			healthSequence:             []int{http.StatusOK},
			expectedNumRemovedServers:  0,
			expectedNumUpsertedServers: 0,
			expectedGaugeValue:         1,
		},
		{
			desc:                       "healthy server staying healthy (StatusNoContent)",
			startHealthy:               true,
			healthSequence:             []int{http.StatusNoContent},
			expectedNumRemovedServers:  0,
			expectedNumUpsertedServers: 0,
			expectedGaugeValue:         1,
		},
		{
			desc:                       "healthy server staying healthy (StatusPermanentRedirect)",
			startHealthy:               true,
			healthSequence:             []int{http.StatusPermanentRedirect},
			expectedNumRemovedServers:  0,
			expectedNumUpsertedServers: 0,
			expectedGaugeValue:         1,
		},
		{
			desc:                       "healthy server becoming sick",
			startHealthy:               true,
			healthSequence:             []int{http.StatusServiceUnavailable},
			expectedNumRemovedServers:  1,
			expectedNumUpsertedServers: 0,
			expectedGaugeValue:         0,
		},
		{
			desc:                       "sick server becoming healthy",
			startHealthy:               false,
			healthSequence:             []int{http.StatusOK},
			expectedNumRemovedServers:  0,
			expectedNumUpsertedServers: 1,
			expectedGaugeValue:         1,
		},
		{
			desc:                       "sick server staying sick",
			startHealthy:               false,
			healthSequence:             []int{http.StatusServiceUnavailable},
			expectedNumRemovedServers:  0,
			expectedNumUpsertedServers: 0,
			expectedGaugeValue:         0,
		},
		{
			desc:                       "healthy server toggling to sick and back to healthy",
			startHealthy:               true,
			healthSequence:             []int{http.StatusServiceUnavailable, http.StatusOK},
			expectedNumRemovedServers:  1,
			expectedNumUpsertedServers: 1,
			expectedGaugeValue:         1,
		},
	}

	for _, test := range testCases {
		test := test
		t.Run(test.desc, func(t *testing.T) {
			t.Parallel()

			// The context is passed to the health check and canonically canceled by
			// the test server once all expected requests have been received.
			ctx, cancel := context.WithCancel(context.Background())
			defer cancel()
			ts := newTestServer(cancel, test.healthSequence)
			defer ts.Close()

			lb := &testLoadBalancer{RWMutex: &sync.RWMutex{}}
			backend := NewBackendConfig(Options{
				Path:     "/path",
				Interval: healthCheckInterval,
				Timeout:  healthCheckTimeout,
				LB:       lb,
			}, "backendName")

			serverURL := testhelpers.MustParseURL(ts.URL)
			if test.startHealthy {
				lb.servers = append(lb.servers, serverURL)
			} else {
				backend.disabledURLs = append(backend.disabledURLs, serverURL)
			}

			collectingMetrics := testhelpers.NewCollectingHealthCheckMetrics()
			check := HealthCheck{
				Backends: make(map[string]*BackendConfig),
				metrics:  collectingMetrics,
			}

			wg := sync.WaitGroup{}
			wg.Add(1)

			go func() {
				check.execute(ctx, backend)
				wg.Done()
			}()

			// Make test timeout dependent on number of expected requests, health
			// check interval, and a safety margin.
			timeout := time.Duration(len(test.healthSequence)*int(healthCheckInterval) + 500)
			select {
			case <-time.After(timeout):
				t.Fatal("test did not complete in time")
			case <-ctx.Done():
				wg.Wait()
			}

			lb.Lock()
			defer lb.Unlock()

			assert.Equal(t, test.expectedNumRemovedServers, lb.numRemovedServers, "removed servers")
			assert.Equal(t, test.expectedNumUpsertedServers, lb.numUpsertedServers, "upserted servers")
			// FIXME re add metrics
			//assert.Equal(t, test.expectedGaugeValue, collectingMetrics.Gauge.GaugeValue, "ServerUp Gauge")
		})
	}
}

func TestNewRequest(t *testing.T) {
	testCases := []struct {
		desc      string
		serverURL string
		options   Options
		expected  string
	}{
		{
			desc:      "no port override",
			serverURL: "http://backend1:80",
			options: Options{
				Path: "/test",
				Port: 0,
			},
			expected: "http://backend1:80/test",
		},
		{
			desc:      "port override",
			serverURL: "http://backend2:80",
			options: Options{
				Path: "/test",
				Port: 8080,
			},
			expected: "http://backend2:8080/test",
		},
		{
			desc:      "no port override with no port in server URL",
			serverURL: "http://backend1",
			options: Options{
				Path: "/health",
				Port: 0,
			},
			expected: "http://backend1/health",
		},
		{
			desc:      "port override with no port in server URL",
			serverURL: "http://backend2",
			options: Options{
				Path: "/health",
				Port: 8080,
			},
			expected: "http://backend2:8080/health",
		},
		{
			desc:      "scheme override",
			serverURL: "https://backend1:80",
			options: Options{
				Scheme: "http",
				Path:   "/test",
				Port:   0,
			},
			expected: "http://backend1:80/test",
		},
	}

	for _, test := range testCases {
		test := test
		t.Run(test.desc, func(t *testing.T) {
			t.Parallel()

			backend := NewBackendConfig(test.options, "backendName")

			u, err := url.Parse(test.serverURL)
			require.NoError(t, err)

			req, err := backend.newRequest(u)
			require.NoError(t, err, "failed to create new backend request")

			assert.Equal(t, test.expected, req.URL.String())
		})
	}
}

func TestAddHeadersAndHost(t *testing.T) {
	testCases := []struct {
		desc             string
		serverURL        string
		options          Options
		expectedHostname string
		expectedHeader   string
	}{
		{
			desc:      "override hostname",
			serverURL: "http://backend1:80",
			options: Options{
				Hostname: "myhost",
				Path:     "/",
			},
			expectedHostname: "myhost",
			expectedHeader:   "",
		},
		{
			desc:      "not override hostname",
			serverURL: "http://backend1:80",
			options: Options{
				Hostname: "",
				Path:     "/",
			},
			expectedHostname: "backend1:80",
			expectedHeader:   "",
		},
		{
			desc:      "custom header",
			serverURL: "http://backend1:80",
			options: Options{
				Headers:  map[string]string{"Custom-Header": "foo"},
				Hostname: "",
				Path:     "/",
			},
			expectedHostname: "backend1:80",
			expectedHeader:   "foo",
		},
		{
			desc:      "custom header with hostname override",
			serverURL: "http://backend1:80",
			options: Options{
				Headers:  map[string]string{"Custom-Header": "foo"},
				Hostname: "myhost",
				Path:     "/",
			},
			expectedHostname: "myhost",
			expectedHeader:   "foo",
		},
	}

	for _, test := range testCases {
		test := test
		t.Run(test.desc, func(t *testing.T) {
			t.Parallel()

			backend := NewBackendConfig(test.options, "backendName")

			u, err := url.Parse(test.serverURL)
			require.NoError(t, err)

			req, err := backend.newRequest(u)
			require.NoError(t, err, "failed to create new backend request")

			req = backend.addHeadersAndHost(req)

			assert.Equal(t, "http://backend1:80/", req.URL.String())
			assert.Equal(t, test.expectedHostname, req.Host)
			assert.Equal(t, test.expectedHeader, req.Header.Get("Custom-Header"))
		})
	}
}

type testLoadBalancer struct {
	// RWMutex needed due to parallel test execution: Both the system-under-test
	// and the test assertions reference the counters.
	*sync.RWMutex
	numRemovedServers  int
	numUpsertedServers int
	servers            []*url.URL
}

func (lb *testLoadBalancer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	// noop
}

func (lb *testLoadBalancer) RemoveServer(u *url.URL) error {
	lb.Lock()
	defer lb.Unlock()
	lb.numRemovedServers++
	lb.removeServer(u)
	return nil
}

func (lb *testLoadBalancer) UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error {
	lb.Lock()
	defer lb.Unlock()
	lb.numUpsertedServers++
	lb.servers = append(lb.servers, u)
	return nil
}

func (lb *testLoadBalancer) Servers() []*url.URL {
	return lb.servers
}

func (lb *testLoadBalancer) removeServer(u *url.URL) {
	var i int
	var serverURL *url.URL
	for i, serverURL = range lb.servers {
		if *serverURL == *u {
			break
		}
	}

	lb.servers = append(lb.servers[:i], lb.servers[i+1:]...)
}

func newTestServer(done func(), healthSequence []int) *httptest.Server {
	handler := &testHandler{
		done:           done,
		healthSequence: healthSequence,
	}
	return httptest.NewServer(handler)
}

// ServeHTTP returns HTTP response codes following a status sequences.
// It calls the given 'done' function once all request health indicators have been depleted.
func (th *testHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if len(th.healthSequence) == 0 {
		panic("received unexpected request")
	}

	w.WriteHeader(th.healthSequence[0])

	th.healthSequence = th.healthSequence[1:]
	if len(th.healthSequence) == 0 {
		th.done()
	}
}