package watcher_test

import (
	"context"
	"log/slog"
	"slices"
	"testing"

	"sneak.berlin/go/dnswatcher/internal/livednstest"
	"sneak.berlin/go/dnswatcher/internal/resolver"
	"sneak.berlin/go/dnswatcher/internal/state"
	"sneak.berlin/go/dnswatcher/internal/watcher"
)

// cnameHost is a CNAME into another zone: its nameservers answer with
// the CNAME and no address.
const cnameHost = "www.python.org"

// TestCNAMEIntoAnotherZonePortAndTLSChecks checks cnameHost against
// live DNS. Its port and TLS checks must use the addresses at the end
// of its CNAME chain.
func TestCNAMEIntoAnotherZonePortAndTLSChecks(t *testing.T) {
	t.Parallel()

	cfg := defaultTestConfig(t)
	cfg.Hostnames = []string{cnameHost}

	deps := runChecks(t, cfg, nil, nil)

	snap := deps.state.GetSnapshot()
	hs := snap.Hostnames[cnameHost]

	if len(hs.CNAMEAddresses) == 0 {
		t.Fatalf(
			"%s: no addresses saved from following its CNAME; if it "+
				"is no longer a CNAME into another zone, this test "+
				"needs another name",
			cnameHost,
		)
	}

	for _, ip := range hs.CNAMEAddresses {
		ps, ok := snap.Ports[ip+":443"]
		if !ok || !slices.Contains(ps.Hostnames, cnameHost) {
			t.Errorf("no port state for %s at %s:443", cnameHost, ip)
		}

		certKey := ip + ":443:" + cnameHost
		if _, ok := snap.Certificates[certKey]; !ok {
			t.Errorf("no certificate state %s", certKey)
		}
	}
}

// TestCNAMEThatCannotBeFollowedKeepsPrevious gives a name a CNAME to a
// target under .invalid, whose lookup fails. The addresses the previous
// check saved from following its CNAME are kept.
func TestCNAMEThatCannotBeFollowedKeepsPrevious(t *testing.T) {
	t.Parallel()

	w := watcher.NewForTest(
		nil, nil, resolver.NewFromLogger(slog.Default()), nil, nil, nil,
	)

	current := hostnameState(map[string]map[string][]string{
		nsA: {"CNAME": {"target.example.invalid."}},
	})
	prev := &state.HostnameState{CNAMEAddresses: []string{oldIP}}

	// The result is the same whether or not live DNS answers, so the
	// lookup is not retried.
	_ = livednstest.Run(func(ctx context.Context) error {
		w.ResolveCNAMEAddresses(ctx, host, current, prev)

		return nil
	})

	if !slices.Equal(current.CNAMEAddresses, prev.CNAMEAddresses) {
		t.Errorf(
			"saved %v, want %v",
			current.CNAMEAddresses, prev.CNAMEAddresses,
		)
	}
}

// followLive follows in live DNS the CNAMEs in a name's records, built
// from records, and returns the addresses saved for the name. The
// previous check saved oldIP, which is kept when a target cannot be
// followed; that is retried.
func followLive(
	t *testing.T,
	records map[string]map[string][]string,
) []string {
	t.Helper()

	w := watcher.NewForTest(
		nil, nil, resolver.NewFromLogger(slog.Default()), nil, nil, nil,
	)
	prev := cnameState(oldIP)

	var current *state.HostnameState

	livednstest.Retry(t, "following CNAMEs", func(ctx context.Context) error {
		current = hostnameState(records)

		w.ResolveCNAMEAddresses(ctx, host, current, prev)

		if slices.Equal(current.CNAMEAddresses, prev.CNAMEAddresses) {
			return livednstest.ErrNoAnswer
		}

		return nil
	})

	return current.CNAMEAddresses
}

// TestCNAMEAddressesOfEveryTarget gives a name's two nameservers
// different CNAME targets, as when a secondary still serves an old one.
// The addresses at the end of both are saved, whichever answer is read
// first: one.one.one.one has 1.1.1.1, and dns.google has 8.8.8.8.
func TestCNAMEAddressesOfEveryTarget(t *testing.T) {
	t.Parallel()

	found := followLive(t, map[string]map[string][]string{
		nsA: {"CNAME": {"one.one.one.one."}},
		nsB: {"CNAME": {"dns.google."}},
	})

	for _, ip := range []string{"1.1.1.1", "8.8.8.8"} {
		if !slices.Contains(found, ip) {
			t.Errorf("saved %v, want %s among them", found, ip)
		}
	}
}

// TestCNAMEChainEndingInNoAddressSavesEmptyList follows a CNAME to a
// name live DNS answers with NXDOMAIN. An empty list is saved, not nil,
// which would mean the addresses are not known.
func TestCNAMEChainEndingInNoAddressSavesEmptyList(t *testing.T) {
	t.Parallel()

	found := followLive(t, map[string]map[string][]string{
		nsA: {"CNAME": {"this-surely-does-not-exist-xyz.google.com."}},
	})

	if found == nil || len(found) != 0 {
		t.Errorf("saved %#v, want an empty list", found)
	}
}

// TestCNAMEBesideAnAddressNotFollowed gives one nameserver of a name an
// address and another a CNAME. The CNAME is not followed: an empty list
// is saved, not nil, and nothing is looked up, the watcher having no
// resolver.
func TestCNAMEBesideAnAddressNotFollowed(t *testing.T) {
	t.Parallel()

	w := watcher.NewForTest(nil, nil, nil, nil, nil, nil)

	current := hostnameState(map[string]map[string][]string{
		nsA: {"A": {ip1}},
		nsB: {"CNAME": {"target.example.org."}},
	})

	w.ResolveCNAMEAddresses(t.Context(), host, current, nil)

	if current.CNAMEAddresses == nil || len(current.CNAMEAddresses) != 0 {
		t.Errorf("saved %#v, want an empty list", current.CNAMEAddresses)
	}
}

// TestCNAMEWhoseNameserversAllFailedKeepsPrevious checks a name none of
// whose nameservers answered. The addresses the previous check saved
// from following its CNAME are kept, and nothing is looked up: the
// watcher has no resolver.
func TestCNAMEWhoseNameserversAllFailedKeepsPrevious(t *testing.T) {
	t.Parallel()

	w := watcher.NewForTest(nil, nil, nil, nil, nil, nil)

	current := saved(map[string]*state.NameserverRecordState{
		nsA: failed(), nsB: failed(),
	})
	prev := cnameState(oldIP)

	w.ResolveCNAMEAddresses(t.Context(), host, current, prev)

	if !slices.Equal(current.CNAMEAddresses, prev.CNAMEAddresses) {
		t.Errorf(
			"saved %v, want %v",
			current.CNAMEAddresses, prev.CNAMEAddresses,
		)
	}
}

// cnameState builds the state a check leaves behind for a name whose
// nameserver answered with a CNAME and no address, when following the
// CNAME found these addresses, which may be none.
func cnameState(addresses ...string) *state.HostnameState {
	hs := hostnameState(map[string]map[string][]string{
		nsA: {"CNAME": {"target.example.org."}},
	})

	hs.CNAMEAddresses = append([]string{}, addresses...)

	return hs
}

func TestCNAMEAddressChangeAlerts(t *testing.T) {
	t.Parallel()

	// A state file written before the addresses were saved loads with
	// them nil.
	olderStateFile := cnameState()
	olderStateFile.CNAMEAddresses = nil

	// Each case is the state saved by the previous check and by the
	// current one. The name's records are the same in both.
	tests := []struct {
		name          string
		prev, current *state.HostnameState
		want          int
	}{
		{
			"same addresses",
			cnameState(ip1, ip2), cnameState(ip1, ip2), 0,
		},
		{
			"same addresses in another order",
			cnameState(ip2, ip1), cnameState(ip1, ip2), 0,
		},
		{
			"address replaced",
			cnameState(ip1), cnameState(ip2), 1,
		},
		{
			"address added",
			cnameState(ip1), cnameState(ip1, ip2), 1,
		},
		{
			"no address at the end of the chain now",
			cnameState(ip1), cnameState(), 1,
		},
		{
			"addresses at the end of the chain again",
			cnameState(), cnameState(ip1), 1,
		},
		{
			"state file from before addresses were saved",
			olderStateFile, cnameState(ip1), 0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			notifier := &mockNotifier{}
			w := watcher.NewForTest(nil, nil, nil, nil, nil, notifier)

			w.DetectHostnameChanges(t.Context(), host, tt.prev, tt.current)

			got := len(notifier.getNotifications())
			if got != tt.want {
				t.Errorf("sent %d notifications, want %d", got, tt.want)
			}
		})
	}
}

func TestCNAMEAddressChangeAlertNamesHostnameAndAddresses(t *testing.T) {
	t.Parallel()

	notifier := &mockNotifier{}
	w := watcher.NewForTest(nil, nil, nil, nil, nil, notifier)

	w.DetectHostnameChanges(
		t.Context(), host, cnameState(ip1), cnameState(ip2, ip3),
	)

	want := notification{
		Title: "CNAME Address Change: " + host,
		Message: "Hostname: " + host +
			"\nOld: " + ip1 + "\nNew: " + ip2 + ", " + ip3,
		Priority: "warning",
	}

	got := notifier.getNotifications()
	if len(got) != 1 || got[0] != want {
		t.Errorf("sent %v, want %v", got, want)
	}
}

// TestNameMovedFromARecordsToCNAMEAlerts checks a name that answers
// with an A record and then with a CNAME whose chain ends in ip2. The
// second check is notified as a CNAME address change from no addresses,
// beside the record change. Nothing is looked up: the watcher has no
// resolver.
func TestNameMovedFromARecordsToCNAMEAlerts(t *testing.T) {
	t.Parallel()

	notifier := &mockNotifier{}
	w := watcher.NewForTest(nil, nil, nil, nil, nil, notifier)

	prev := hostnameState(map[string]map[string][]string{
		nsA: {"A": {ip1}},
	})
	w.ResolveCNAMEAddresses(t.Context(), host, prev, nil)

	w.DetectHostnameChanges(t.Context(), host, prev, cnameState(ip2))

	title := "CNAME Address Change: " + host
	message := "Hostname: " + host + "\nOld: \nNew: " + ip2

	got := notifier.getNotifications()
	if !slices.ContainsFunc(got, func(n notification) bool {
		return n.Title == title && n.Message == message
	}) {
		t.Errorf("sent %v, want %q with %q among them", got, title, message)
	}
}