package main

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

	"github.com/go-logr/logr"
	"github.com/stretchr/testify/require"
	discov1 "k8s.io/api/discovery/v1"

	"github.com/kedacore/http-add-on/pkg/k8s"
	kedanet "github.com/kedacore/http-add-on/pkg/net"
	"github.com/kedacore/http-add-on/pkg/queue"
)

func TestCounts(t *testing.T) {
	r := require.New(t)
	ctx := context.Background()
	const (
		ns           = "testns"
		svcName      = "testsvc"
		deplName     = "testdepl"
		tickDur      = 10 * time.Millisecond
		numEndpoints = 3
	)

	// assemble an in-memory queue and start up a fake server that serves it.
	// we'll configure the queue pinger to use that server below
	counts := map[string]queue.Count{
		"host1": {
			Concurrency: 123,
			RPS:         123,
		},
		"host2": {
			Concurrency: 234,
			RPS:         234,
		},
		"host3": {
			Concurrency: 345,
			RPS:         345,
		},
		"host4": {
			Concurrency: 456,
			RPS:         456,
		},
	}

	q := queue.NewMemory()
	for host, count := range counts {
		q.EnsureKey(host, time.Minute, time.Second)
		r.NoError(q.Increase(host, count.Concurrency))
	}

	srv, srvURL, endpoints, err := startFakeQueueEndpointServer(svcName, q, 3)
	r.NoError(err)
	defer srv.Close()
	pinger := newQueuePinger(
		logr.Discard(),
		func(context.Context, string, string) (k8s.Endpoints, error) {
			return extractAddresses(endpoints), nil
		},
		ns,
		svcName,
		deplName,
		srvURL.Port(),
	)

	ticker := time.NewTicker(tickDur)
	fakeCache := k8s.NewFakeEndpointsCache()
	go func() {
		_ = pinger.start(ctx, ticker, fakeCache)
	}()
	// sleep to ensure we ticked and finished calling
	// fetchAndSaveCounts
	time.Sleep(tickDur * 2)

	// now ensure that all the counts in the pinger
	// are the same as in the queue, which has been updated
	retCounts := pinger.counts()
	expectedCounts, err := q.Current()
	r.NoError(err)
	r.Equal(len(expectedCounts.Counts), len(retCounts))
	for host, count := range expectedCounts.Counts {
		retCount, ok := retCounts[host]
		r.True(ok, "returned count not found for host %s", host)

		// note that the returned value should be:
		// (queue_count * num_endpoints)
		r.Equal(count.Concurrency*3, retCount.Concurrency)
		r.Equal(count.RPS*3, retCount.RPS)
	}
}

func TestFetchAndSaveCounts(t *testing.T) {
	r := require.New(t)
	ctx, done := context.WithCancel(context.Background())
	defer done()
	const (
		ns           = "testns"
		svcName      = "testsvc"
		deplName     = "testdepl"
		adminPort    = "8081"
		numEndpoints = 3
	)
	counts := queue.NewCounts()
	counts.Counts = map[string]queue.Count{
		"host1": {
			Concurrency: 123,
			RPS:         123,
		},
		"host2": {
			Concurrency: 234,
			RPS:         234,
		},
		"host3": {
			Concurrency: 345,
			RPS:         345,
		},
		"host4": {
			Concurrency: 456,
			RPS:         456,
		},
	}
	q := queue.NewMemory()
	for host, count := range counts.Counts {
		q.EnsureKey(host, time.Minute, time.Second)
		r.NoError(q.Increase(host, count.Concurrency))
	}
	srv, srvURL, endpoints, err := startFakeQueueEndpointServer(svcName, q, numEndpoints)
	r.NoError(err)
	defer srv.Close()
	endpointsFn := func(ctx context.Context, ns, svcName string) (k8s.Endpoints, error) {
		return extractAddresses(endpoints), nil
	}

	pinger := newQueuePinger(
		logr.Discard(),
		endpointsFn,
		ns,
		svcName,
		deplName,
		srvURL.Port(),
	)

	r.NoError(pinger.fetchAndSaveCounts(ctx))

	// since all endpoints serve the same counts,
	// the hosts will be the same as the original counts,
	// but the value is (individual count * # endpoints)
	expectedCounts := counts.Counts
	for host, val := range expectedCounts {
		val.Concurrency *= 3
		val.RPS *= 3
		expectedCounts[host] = val
	}
	r.Equal(expectedCounts, pinger.allCounts)
}

func TestFetchCounts(t *testing.T) {
	r := require.New(t)
	ctx, done := context.WithCancel(context.Background())
	defer done()
	const (
		ns           = "testns"
		svcName      = "testsvc"
		adminPort    = "8081"
		numEndpoints = 3
	)
	counts := queue.NewCounts()
	counts.Counts = map[string]queue.Count{
		"host1": {
			Concurrency: 123,
			RPS:         123,
		},
		"host2": {
			Concurrency: 234,
			RPS:         234,
		},
		"host3": {
			Concurrency: 345,
			RPS:         345,
		},
		"host4": {
			Concurrency: 456,
			RPS:         456,
		},
	}
	q := queue.NewMemory()
	for host, count := range counts.Counts {
		q.EnsureKey(host, time.Minute, time.Second)
		r.NoError(q.Increase(host, count.Concurrency))
	}
	srv, srvURL, endpoints, err := startFakeQueueEndpointServer(svcName, q, numEndpoints)
	r.NoError(err)

	defer srv.Close()
	endpointsFn := func(context.Context, string, string) (k8s.Endpoints, error) {
		return extractAddresses(endpoints), nil
	}

	cts, err := fetchCounts(
		ctx,
		logr.Discard(),
		endpointsFn,
		ns,
		svcName,
		fmt.Sprintf("%v", srvURL.Port()),
	)
	r.NoError(err)

	// since all endpoints serve the same counts,
	// the hosts will be the same as the original counts,
	// but the value is (individual count * # endpoints)
	expectedCounts := counts.Counts
	for host, val := range expectedCounts {
		val.Concurrency *= 3
		val.RPS *= 3
		expectedCounts[host] = val
	}
	r.Equal(expectedCounts, cts)
}

// startFakeQueuePinger starts a fake server that simulates
// an interceptor with its /queue endpoint, then returns a
// *v1.Endpoints object that contains the URL of the new fake
// server. also returns the *httptest.Server that runs the
// endpoint along with its URL. the caller is responsible for
// calling testServer.Close() when done.
//
// returns nil for the first 3 return value and a non-nil error in
// case of a failure.
func startFakeQueueEndpointServer(svcName string, q queue.CountReader, numEndpoints int) (*httptest.Server, *url.URL, *discov1.EndpointSliceList, error) {
	hdl := http.NewServeMux()
	queue.AddCountsRoute(logr.Discard(), hdl, q)
	srv, srvURL, err := kedanet.StartTestServer(hdl)
	if err != nil {
		return nil, nil, nil, err
	}
	endpoints, err := k8s.FakeEndpointsForURL(srvURL, "testns", svcName, numEndpoints)
	if err != nil {
		return nil, nil, nil, err
	}
	return srv, srvURL, endpoints, nil
}

type fakeQueuePingerOpts struct {
	endpoints *discov1.EndpointSliceList
	tickDur   time.Duration
	port      string
}

type optsFunc func(*fakeQueuePingerOpts)

// newFakeQueuePinger creates the machinery required for a fake
// queuePinger implementation, including a time.Ticker, then returns
// the ticker and the pinger. it is the caller's responsibility to
// call ticker.Stop() on the returned ticker.
func newFakeQueuePinger(lggr logr.Logger, optsFuncs ...optsFunc) (*time.Ticker, *queuePinger, error) {
	opts := &fakeQueuePingerOpts{
		endpoints: &discov1.EndpointSliceList{},
		tickDur:   time.Second,
		port:      "8080",
	}
	for _, optsFunc := range optsFuncs {
		optsFunc(opts)
	}
	ticker := time.NewTicker(opts.tickDur)

	pinger := newQueuePinger(
		lggr,
		func(context.Context, string, string) (k8s.Endpoints, error) {
			return extractAddresses(opts.endpoints), nil
		},
		"testns",
		"testsvc",
		"testdepl",
		opts.port,
	)
	return ticker, pinger, nil
}

// extractAddresses extracts all addresses from a list of EndpointSlice
// doesn't perform deduplication because of the way the tests are designed, they "run" multiple fake queue endpoints on the same host:port
func extractAddresses(eps *discov1.EndpointSliceList) k8s.Endpoints {
	ret := []string{}
	for _, ep := range eps.Items {
		for _, addr := range ep.Endpoints {
			ret = append(ret, addr.Addresses...)
		}
	}
	return k8s.Endpoints{ReadyAddresses: ret}
}