package reputation_test

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/netip"
	"net/url"
	"reflect"
	"slices"
	"strings"
	"sync"
	"testing"
	"testing/synctest"
	"time"

	"sneak.berlin/go/smallwebwaf/internal/alerts"
	"sneak.berlin/go/smallwebwaf/internal/reputation"
)

// The tests run in a synctest bubble, where the time package runs on a
// clock of the test's own: time.Sleep moves it on at once, and
// synctest.Wait returns once Run waits for the next list to be due, so
// that every fetch due by then has been made. The stand-in for the
// servers the lists are fetched from answers without the network, since a
// fetch waiting on the network would keep that clock from moving on.

const (
	// dropURL and torURL are the blocklists, and asnURL the file of
	// AS:percent lines.
	dropURL = "https://lists.example/drop.txt"
	torURL  = "https://lists.example/tor.txt"
	asnURL  = "https://lists.example/asn.txt"
	// refresh is the tests' SWWAF_BLOCKLIST_REFRESH, and cooldown their
	// SWWAF_ALERT_COOLDOWN, longer than it.
	refresh  = 24 * time.Hour
	cooldown = 48 * time.Hour
	// drop is a blocklist as the Spamhaus DROP list is written, with an
	// address and a netblock in each of its comments, which list nothing.
	drop = "; Spamhaus DROP List 2026/10/07 - (c) 2026 The Spamhaus Project SLL\n" +
		"; Last-Modified: Wed, 07 Oct 2026 00:00:00 GMT ; 192.0.2.1\n" +
		"# 198.51.100.0/24\n" +
		"\n" +
		"203.0.113.0/24 ; SBL1\n" +
		"  192.0.2.9  # one address\n" +
		"2001:db8:1::/48 ; SBL2\n"
)

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{dropURL: drop}}
		lists := start(t, servers, params(dropURL))

		for addr, want := range map[string][]string{
			"203.0.113.0":   {dropURL},
			"203.0.113.255": {dropURL},
			"192.0.2.9":     {dropURL},
			"2001:db8:1::7": {dropURL},
			"203.0.114.0":   nil,
			"192.0.2.8":     nil,
			"192.0.2.1":     nil,
			"198.51.100.7":  nil,
			"2001:db8:2::7": nil,
		} {
			wantListedBy(t, lists, addr, want...)
		}
	})
}

func TestIPv4MappedLineListsTheIPv4AddressOrNetblockItStandsFor(t *testing.T) {
	t.Parallel()

	now := time.Now()
	lists := reputation.New(params(dropURL))

	err := lists.Load([]reputation.List{{
		URL: dropURL, Tried: now, Fetched: now,
		Lines: []string{"::ffff:192.0.2.9", "::ffff:203.0.113.0/120"},
	}})
	if err != nil {
		t.Fatalf("load: %v", err)
	}

	for addr, want := range map[string][]string{
		"192.0.2.9":     {dropURL},
		"203.0.113.255": {dropURL},
		"192.0.2.8":     nil,
		"203.0.114.0":   nil,
	} {
		wantListedBy(t, lists, addr, want...)
	}

	// A mapped netblock shorter than /96 stands for no IPv4 one.
	err = lists.Load([]reputation.List{{
		URL: dropURL, Tried: now, Fetched: now, Lines: []string{"::ffff:198.51.100.0/88"},
	}})

	const want = "the copy of " + dropURL +
		": line 1 is not an address or a netblock, such as 192.0.2.0/24"
	if err == nil || err.Error() != want {
		t.Errorf("error %v, want %s", err, want)
	}
}

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{
			dropURL: "203.0.113.0/24\n", torURL: "203.0.113.9\n",
		}}
		lists := start(t, servers, params(torURL, dropURL))

		// In the order SWWAF_BLOCKLIST_URLS names them.
		wantListedBy(t, lists, "203.0.113.9", torURL, dropURL)
		wantListedBy(t, lists, "203.0.113.8", dropURL)
	})
}

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{dropURL: "203.0.113.9\n"}}
		lists := start(t, servers, params(dropURL))
		began := time.Now()

		wantFetches(t, servers, 1)

		servers.set(dropURL, "203.0.113.10\n")
		time.Sleep(refresh - time.Nanosecond)
		wantFetches(t, servers, 1)
		wantListedBy(t, lists, "203.0.113.9", dropURL)

		time.Sleep(time.Nanosecond)
		wantFetches(t, servers, 2)
		wantListedBy(t, lists, "203.0.113.9")
		wantListedBy(t, lists, "203.0.113.10", dropURL)

		if fetched := lists.Fetched(dropURL); !fetched.Equal(began.Add(refresh)) {
			t.Errorf("the copy in use was fetched at %s, want %s", fetched,
				began.Add(refresh))
		}
	})
}

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

	for _, tc := range []struct {
		name string
		// fail has the stand-in answer the fetches after the first so that
		// they fail with error.
		fail  func(servers *standIn)
		error string
	}{
		{
			"an answer other than 200",
			func(servers *standIn) { servers.set(dropURL, "") },
			"the server answered 503 Service Unavailable",
		},
		{
			"a line that does not read",
			func(servers *standIn) { servers.set(dropURL, "203.0.113.10\n<html>\n") },
			"line 2 is not an address or a netblock, such as 192.0.2.0/24",
		},
		{
			"a list longer than 16 MiB",
			func(servers *standIn) {
				servers.set(dropURL, strings.Repeat("#\n", 8<<20+1))
			},
			"the list is longer than 16 MiB",
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			synctest.Test(t, func(t *testing.T) {
				var log bytes.Buffer

				servers := &standIn{lists: map[string]string{dropURL: drop}}
				queue := newQueue()
				p := params(dropURL)
				p.ProcessLog = slog.New(slog.NewJSONHandler(&log, nil))
				p.Alerts = queue
				lists := start(t, servers, p)
				kept := lists.Snapshot()

				tc.fail(servers)

				// Each failure is tried again once refresh has passed since it.
				for range 2 {
					time.Sleep(refresh)
					synctest.Wait()
				}

				wantFetches(t, servers, 3)
				wantListedBy(t, lists, "203.0.113.9", dropURL)

				want := kept[0]
				want.Tried = time.Now()

				if got := lists.Snapshot(); !reflect.DeepEqual(got, []reputation.List{want}) {
					t.Errorf("lists %+v, want the first copy, last tried now, %+v", got, want)
				}

				if lists.Failures(dropURL) != 2 {
					t.Errorf("%d failures, want 2", lists.Failures(dropURL))
				}

				// One alert for the first failure; the cooldown holds back the
				// second.
				wantAlert(t, queue, fetchFailure(time.Now().Add(-refresh), dropURL, tc.error))

				if !strings.Contains(log.String(), `"msg":"fetching a list failed",`+
					`"url":"`+dropURL+`","error":"`+tc.error) {
					t.Errorf("logged\n%s\nwant the failures", log.String())
				}
			})
		})
	}
}

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{}, hanging: true}
		lists := start(t, servers, params(dropURL))

		time.Sleep(time.Minute - time.Nanosecond)
		synctest.Wait()

		if lists.Failures(dropURL) != 0 {
			t.Errorf("%d failures before a minute, want none", lists.Failures(dropURL))
		}

		time.Sleep(time.Nanosecond)
		synctest.Wait()

		if lists.Failures(dropURL) != 1 {
			t.Errorf("%d failures after a minute, want 1", lists.Failures(dropURL))
		}
	})
}

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{
			dropURL: "203.0.113.10\n", torURL: "198.51.100.10\n",
		}}
		lists := reputation.New(params(dropURL, torURL))
		lists.SetTransport(servers)

		// drop.txt was fetched an hour ago, and tor.txt a refresh ago, as
		// reputation.json says at start.
		err := lists.Load([]reputation.List{
			{URL: dropURL, Fetched: time.Now().Add(-time.Hour), Lines: []string{"203.0.113.9"}},
			{URL: torURL, Fetched: time.Now().Add(-refresh), Lines: []string{"198.51.100.9"}},
		})
		if err != nil {
			t.Fatalf("load: %v", err)
		}

		run(t, lists)

		wantFetches(t, servers, 1)
		wantListedBy(t, lists, "203.0.113.9", dropURL)
		wantListedBy(t, lists, "198.51.100.10", torURL)

		time.Sleep(refresh - time.Hour - time.Nanosecond)
		wantFetches(t, servers, 1)

		time.Sleep(time.Nanosecond)
		wantFetches(t, servers, 2)
		wantListedBy(t, lists, "203.0.113.10", dropURL)
	})
}

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

	synctest.Test(t, func(t *testing.T) {
		// drop.txt is fetched, and a refresh later the fetch downloads it
		// whole but fails on a line that does not read.
		servers := &standIn{lists: map[string]string{dropURL: "198.51.100.1\n"}}
		lists := start(t, servers, params(dropURL))

		servers.set(dropURL, "198.51.100.2\n<html>\n")
		time.Sleep(refresh)
		wantFetches(t, servers, 2)

		// Restarted with what reputation.json keeps, it waits a refresh
		// after the failed try, as it does while it runs.
		restarted := &standIn{lists: map[string]string{dropURL: "198.51.100.2\n"}}
		again := reputation.New(params(dropURL))
		again.SetTransport(restarted)

		err := again.Load(lists.Snapshot())
		if err != nil {
			t.Fatalf("load: %v", err)
		}

		run(t, again)
		wantFetches(t, restarted, 0)
		wantListedBy(t, again, "198.51.100.1", dropURL)

		time.Sleep(refresh - time.Nanosecond)
		wantFetches(t, restarted, 0)

		time.Sleep(time.Nanosecond)
		wantFetches(t, restarted, 1)
		wantListedBy(t, again, "198.51.100.2", dropURL)
	})
}

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

	synctest.Test(t, func(t *testing.T) {
		// Stopped 30 seconds into the fetch of drop.txt, before tor.txt's.
		servers := &standIn{lists: map[string]string{}, hanging: true}
		queue := newQueue()
		p := params(dropURL, torURL)
		p.Alerts = queue

		lists := reputation.New(p)
		lists.SetTransport(servers)

		ctx, stop := context.WithCancel(t.Context())
		stopped := make(chan struct{})

		go func() {
			lists.Run(ctx)
			close(stopped)
		}()

		time.Sleep(30 * time.Second)
		stop()
		<-stopped

		wantFetches(t, servers, 1)

		if lists.Failures(dropURL) != 0 || len(waiting(queue)) != 0 {
			t.Errorf("%d failures and alerts %+v, want none", lists.Failures(dropURL),
				waiting(queue))
		}

		// Restarted an hour later with what reputation.json keeps, it fetches
		// tor.txt, never tried, at once, and drop.txt a refresh after its
		// cut-off try.
		time.Sleep(time.Hour)

		restarted := &standIn{lists: map[string]string{
			dropURL: "203.0.113.7\n", torURL: "198.51.100.7\n",
		}}
		again := reputation.New(params(dropURL, torURL))
		again.SetTransport(restarted)

		err := again.Load(lists.Snapshot())
		if err != nil {
			t.Fatalf("load: %v", err)
		}

		run(t, again)
		wantFetches(t, restarted, 1)
		wantListedBy(t, again, "198.51.100.7", torURL)

		time.Sleep(refresh - time.Hour - time.Nanosecond)
		wantFetches(t, restarted, 1)

		time.Sleep(time.Nanosecond)
		wantFetches(t, restarted, 2)
		wantListedBy(t, again, "203.0.113.7", dropURL)
	})
}

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

	synctest.Test(t, func(t *testing.T) {
		servers := &standIn{lists: map[string]string{
			asnURL: "# hosting networks\nAS14061:50 ; DigitalOcean\nas16276:25\n\n" +
				"AS14061:10\nAS14061:30\n",
		}}
		p := params()
		p.ASNLimitPercentURL = asnURL
		lists := start(t, servers, p)

		for asn, want := range map[string]int64{"AS14061": 10, "AS16276": 25} {
			percent, listed := lists.ASNLimitPercent(asn)
			if !listed || percent != want {
				t.Errorf("%s has %d (listed %t), want %d", asn, percent, listed, want)
			}
		}

		if _, listed := lists.ASNLimitPercent("AS64496"); listed {
			t.Error("AS64496 is listed")
		}

		// A line that does not read fails the fetch.
		servers.set(asnURL, "AS14061:50\nAS16276\n")
		time.Sleep(refresh)
		synctest.Wait()

		if lists.Failures(asnURL) != 1 {
			t.Errorf("%d failures, want 1", lists.Failures(asnURL))
		}
	})
}

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

	fetched := time.Date(2026, 10, 6, 0, 0, 0, 0, time.UTC)
	kept := reputation.List{
		URL: dropURL, Tried: fetched, Fetched: fetched, Lines: []string{"203.0.113.9"},
	}
	lists := reputation.New(params(dropURL))

	err := lists.Load([]reputation.List{kept, {
		URL: torURL, Tried: fetched, Fetched: fetched, Lines: []string{"198.51.100.9"},
	}})
	if err != nil {
		t.Fatalf("load: %v", err)
	}

	if got := lists.Snapshot(); !reflect.DeepEqual(got, []reputation.List{kept}) {
		t.Errorf("copies %+v, want only %+v", got, kept)
	}

	err = lists.Load([]reputation.List{{URL: dropURL, Fetched: fetched, Lines: []string{
		"; DROP", "203.0.113.300",
	}}})

	const want = "the copy of " + dropURL +
		": line 2 is not an address or a netblock, such as 192.0.2.0/24"
	if err == nil || err.Error() != want {
		t.Errorf("error %v, want %s", err, want)
	}

	if got := lists.Snapshot(); !reflect.DeepEqual(got, []reputation.List{kept}) {
		t.Errorf("copies %+v after the error, want %+v still", got, kept)
	}
}

// standIn is a stand-in for the servers the lists are fetched from. It
// notes the URL of each fetch.
type standIn struct {
	mu sync.Mutex
	// lists are what it answers with, by URL; it answers a URL it has no
	// list for with 503, and none at all while hanging.
	lists   map[string]string
	hanging bool
	fetches []string
}

// RoundTrip has the stand-in answer req, in place of the network. A fetch
// abandoned before the stand-in answers fails, as over the network.
func (s *standIn) RoundTrip(req *http.Request) (*http.Response, error) {
	s.mu.Lock()
	s.fetches = append(s.fetches, req.URL.String())
	list, found := s.lists[req.URL.String()]
	hanging := s.hanging
	s.mu.Unlock()

	if hanging {
		<-req.Context().Done()

		return nil, req.Context().Err()
	}

	status := http.StatusOK
	if !found {
		status = http.StatusServiceUnavailable
	}

	return &http.Response{
		StatusCode: status,
		Status:     fmt.Sprintf("%d %s", status, http.StatusText(status)),
		Header:     http.Header{},
		Body:       io.NopCloser(strings.NewReader(list)),
		Request:    req,
	}, nil
}

// set has the stand-in answer listURL with list, or with 503 for "".
func (s *standIn) set(listURL, list string) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if list == "" {
		delete(s.lists, listURL)

		return
	}

	s.lists[listURL] = list
}

// params returns the Params of the blocklists at urls, refreshed every
// refresh, by the bubble's clock, with alerts to a queue that sends none.
func params(urls ...string) reputation.Params {
	return reputation.Params{
		BlocklistURLs: urls,
		Refresh:       refresh,
		Now:           time.Now,
		ProcessLog:    slog.New(slog.DiscardHandler),
		Alerts:        newQueue(),
	}
}

// newQueue returns a queue of alerts to a webhook that is never sent
// them, with a cooldown of cooldown.
func newQueue() *alerts.Queue {
	return alerts.New(alerts.Params{
		WebhookURL: &url.URL{Scheme: "https", Host: "alerts.example"},
		Events:     alerts.Events(),
		Cooldown:   cooldown,
		Now:        time.Now,
	})
}

// start returns the lists of p, fetched through servers by Run, which runs
// until the test ends, once Run has fetched those due at start.
func start(
	t *testing.T, servers http.RoundTripper, p reputation.Params,
) *reputation.Lists {
	t.Helper()

	lists := reputation.New(p)
	lists.SetTransport(servers)
	run(t, lists)

	return lists
}

// run runs lists' Run until the test ends, and waits until it has fetched
// the lists due.
func run(t *testing.T, lists *reputation.Lists) {
	t.Helper()

	ctx, stop := context.WithCancel(t.Context())
	stopped := make(chan struct{})

	go func() {
		lists.Run(ctx)
		close(stopped)
	}()

	t.Cleanup(func() {
		stop()
		<-stopped
	})

	synctest.Wait()
}

// wantFetches waits until Run has made the fetches due, and checks how
// many the servers have had.
func wantFetches(t *testing.T, servers *standIn, want int) {
	t.Helper()

	synctest.Wait()

	servers.mu.Lock()
	got := len(servers.fetches)
	servers.mu.Unlock()

	if got != want {
		t.Errorf("%d fetches, want %d", got, want)
	}
}

// wantListedBy checks the URLs of the blocklists lists says list addr.
func wantListedBy(t *testing.T, lists *reputation.Lists, addr string, want ...string) {
	t.Helper()

	got := lists.ListedBy(netip.MustParseAddr(addr))
	if !slices.Equal(got, want) {
		t.Errorf("%s is listed by %v, want %v", addr, got, want)
	}
}

// waiting returns the alerts waiting in queue.
func waiting(queue *alerts.Queue) []alerts.Alert {
	return queue.Snapshot().Waiting[alerts.DestinationWebhook]
}

// fetchFailure is the source_failure alert raised at the time raised for
// a fetch of the list at listURL that failed with err.
func fetchFailure(raised time.Time, listURL, err string) alerts.Alert {
	return alerts.Alert{
		Time:   raised,
		Event:  alerts.EventSourceFailure,
		Reason: "fetching a list failed",
		Detail: map[string]any{"source": listURL, "error": err},
	}
}

// wantAlert checks that want is the one alert waiting in queue, and that
// the cooldown has held back one repeat of it.
func wantAlert(t *testing.T, queue *alerts.Queue, want alerts.Alert) {
	t.Helper()

	got := waiting(queue)
	if len(got) != 1 || !reflect.DeepEqual(got[0], want) || queue.Suppressed() != 1 {
		t.Errorf("alerts waiting %+v, %d held back, want only %+v and 1", got,
			queue.Suppressed(), want)
	}
}