package server

import (
	"context"
	"net/netip"
	"strconv"
	"strings"
	"testing"
	"time"

	"git.eeqj.de/sneak/routewatch/internal/database"
	"git.eeqj.de/sneak/routewatch/internal/routetable"
)

// The ASes of the routing table that newCardsTable fills. Each card test
// finds one of them on its card.
const (
	twoPrefixASN   = 13335 // originates two prefixes, the most
	newestRouteASN = 15169 // the newest route
	oldestRouteASN = 3     // the oldest route
	secondOrigin   = 16509 // a second origin AS of twoPrefixASN's prefix
	privateUseASN  = 64512 // reserved, so its route is a bogon announcement
)

// Paths of the pages that list what two of the home page's cards count.
const (
	bogonsPath          = "/bogons"
	multipleOriginsPath = "/multiple-origins"
)

// cardsNotReadyText is what the pages say before the cards are first worked
// out.
const cardsNotReadyText = "being worked out"

// newCardsTable returns a routing table in which:
//   - twoPrefixASN originates 1.0.0.0/24 and 1.0.4.0/22;
//   - secondOrigin originates 1.0.0.0/24 too, which so has two origin ASes;
//   - newestRouteASN's 8.8.8.0/24 has the newest route;
//   - oldestRouteASN's 18.0.0.0/8 has the oldest;
//   - privateUseASN originates 10.0.0.0/8, carried by two peers: a bogon
//     announcement for both its prefix and its AS.
//
// The last four ASes originate one prefix each.
func newCardsTable() *routetable.Table {
	table := emptyTable()
	announce(table, "1.0.0.0/24", twoPrefixASN, testPeer(1), testRouteTime(10))
	announce(table, "1.0.4.0/22", twoPrefixASN, testPeer(1), testRouteTime(5))
	announce(table, "1.0.0.0/24", secondOrigin, testPeer(3), testRouteTime(12))
	announce(table, "8.8.8.0/24", newestRouteASN, testPeer(2), testRouteTime(20))
	announce(table, "18.0.0.0/8", oldestRouteASN, testPeer(2), testRouteTime(1))
	announce(table, "10.0.0.0/8", privateUseASN, testPeer(1), testRouteTime(15))
	announce(table, "10.0.0.0/8", privateUseASN, testPeer(2), testRouteTime(15))

	return table
}

// homeCard returns the HTML of the home page's card with heading, up to the
// end of the card.
func homeCard(t *testing.T, page, heading string) string {
	t.Helper()

	_, card, found := strings.Cut(page, "<h2>"+heading+"</h2>")
	if !found {
		t.Fatalf("the home page has no card %q", heading)
	}

	card, _, _ = strings.Cut(card, "</div>")

	return card
}

// asLink returns the HTML attribute of a link to the AS page of asn.
func asLink(asn int) string {
	return `href="/as/` + strconv.Itoa(asn) + `"`
}

// TestHomePageCardsShowTheTableFigures fills a routing table and the asns
// table, works out the cards, and checks that each card shows its figure.
func TestHomePageCardsShowTheTableFigures(t *testing.T) {
	t.Parallel()

	const (
		newestSeenASN = 6939
		oldestSeenASN = 174
	)

	s := newServerWithTable(t, newCardsTable())

	err := s.db.GetOrCreateASNBatch(map[int]database.SeenTimes{
		newestSeenASN: {First: testRouteTime(0), Last: testRouteTime(30)},
		oldestSeenASN: {First: testRouteTime(-30), Last: testRouteTime(-30)},
	})
	if err != nil {
		t.Fatalf("GetOrCreateASNBatch: %v", err)
	}

	s.refreshHomeCards(t.Context())

	page := get(t, s, "/").Body.String()

	tests := []struct {
		heading string
		want    []string
	}{
		{"Newest Updated Route", []string{
			"8.8.8.0/24", asLink(newestRouteASN),
			testRouteTime(20).Format(routeTimeFormat),
		}},
		{"Oldest Updated Route", []string{
			"18.0.0.0/8", asLink(oldestRouteASN),
			testRouteTime(1).Format(routeTimeFormat),
		}},
		{"Newest Updated AS", []string{
			asLink(newestSeenASN), testRouteTime(30).Format(routeTimeFormat),
		}},
		{"Oldest Updated AS", []string{
			asLink(oldestSeenASN), testRouteTime(-30).Format(routeTimeFormat),
		}},
		{"AS with the Most Prefixes", []string{
			asLink(twoPrefixASN), "Prefixes it originates: 2",
		}},
		{"ASes with the Fewest Prefixes", []string{
			"ASes that originate a single prefix: 4", asLink(newestRouteASN),
			"8.8.8.0/24",
		}},
		{"Bogon Announcements", []string{`href="/bogons">1<`}},
		{"Prefixes with Several Origins", []string{`href="/multiple-origins">1<`}},
	}

	for _, tc := range tests {
		card := homeCard(t, page, tc.heading)
		for _, want := range tc.want {
			if !strings.Contains(card, want) {
				t.Errorf("card %q does not hold %s: %s", tc.heading, want, card)
			}
		}
	}

	// The well-known networks come newest update first, and those without
	// a route after them.
	networks := homeCard(t, page, "Well-Known Networks")
	order := []int{newestRouteASN, secondOrigin, twoPrefixASN, oldestRouteASN, 714}
	last := -1

	for _, asn := range order {
		i := strings.Index(networks, asLink(asn))
		if i <= last {
			t.Fatalf("well-known networks: AS%d is not after the ASes before "+
				"it in %v: %s", asn, order, networks)
		}

		last = i
	}

	if !strings.Contains(networks, "<td>2</td>") {
		t.Errorf("well-known networks: no network with 2 prefixes: %s", networks)
	}
}

// TestListPagesListTheirEntries checks the rows of the bogon and multiple-origin
// pages for the table of newCardsTable.
func TestListPagesListTheirEntries(t *testing.T) {
	t.Parallel()

	s := newServerWithTable(t, newCardsTable())
	s.refreshHomeCards(t.Context())

	pages := map[string][]string{
		bogonsPath: {
			"Bogon announcements: 1.", "10.0.0.0/8", asLink(privateUseASN),
			"<td>2</td>",
			"Private-Use (10.0.0.0/8); Private-Use (AS64512-AS65534)",
		},
		multipleOriginsPath: {
			"Prefixes announced by more than one origin AS: 1.", "1.0.0.0/24",
			asLink(twoPrefixASN), asLink(secondOrigin), ">1 peer<",
		},
	}

	for path, wants := range pages {
		page := get(t, s, path).Body.String()
		for _, want := range wants {
			if !strings.Contains(page, want) {
				t.Errorf("%s does not hold %s", path, want)
			}
		}
	}
}

// TestListPagesListAtMostMaxListedEntries fills a table with more prefixes than
// the list pages list, each announced by two origin ASes in reserved address
// space. Each page lists maxListedEntries of them and gives how many there are
// in all.
func TestListPagesListAtMostMaxListedEntries(t *testing.T) {
	t.Parallel()

	const prefixCount = maxListedEntries + 1

	table := emptyTable()
	addr := netip.MustParseAddr("10.0.0.0")

	for range prefixCount {
		prefix := netip.PrefixFrom(addr, addr.BitLen()).String()
		announce(table, prefix, twoPrefixASN, testPeer(1), testRouteTime(0))
		announce(table, prefix, secondOrigin, testPeer(2), testRouteTime(0))

		addr = addr.Next()
	}

	s := newServerWithTable(t, table)
	s.refreshHomeCards(t.Context())

	listed := "The first " + strconv.Itoa(maxListedEntries) + " are listed"
	tests := []struct {
		path  string
		total string
	}{
		{bogonsPath, "Bogon announcements: " + strconv.Itoa(2*prefixCount) + "."},
		{multipleOriginsPath, "Prefixes announced by more than one origin AS: " +
			strconv.Itoa(prefixCount) + "."},
	}

	for _, tc := range tests {
		page := get(t, s, tc.path).Body.String()

		rows := strings.Count(page, `class="prefix-link"`)
		if rows != maxListedEntries {
			t.Errorf("%s lists %d entries, want %d", tc.path, rows,
				maxListedEntries)
		}

		if !strings.Contains(page, tc.total) || !strings.Contains(page, listed) {
			t.Errorf("%s does not say %q and %q", tc.path, tc.total, listed)
		}
	}
}

// TestPagesServeTheCopyOfTheCards checks that the pages show the cards as they
// were last worked out, not as the routing table is now, and that they say so
// before the cards are first worked out.
func TestPagesServeTheCopyOfTheCards(t *testing.T) {
	t.Parallel()

	table := emptyTable()
	announce(table, "1.0.0.0/24", twoPrefixASN, testPeer(1), testRouteTime(0))

	s := newServerWithTable(t, table)

	for _, path := range []string{"/", bogonsPath, multipleOriginsPath} {
		if !strings.Contains(get(t, s, path).Body.String(), cardsNotReadyText) {
			t.Errorf("%s does not say the cards are %s", path, cardsNotReadyText)
		}
	}

	s.refreshHomeCards(t.Context())
	announce(table, "8.8.8.0/24", newestRouteASN, testPeer(2), testRouteTime(1))

	card := homeCard(t, get(t, s, "/").Body.String(), "Newest Updated Route")
	if !strings.Contains(card, "1.0.0.0/24") {
		t.Errorf("before the cards are worked out again, the newest route "+
			"is not the one they were worked out with: %s", card)
	}

	s.refreshHomeCards(t.Context())

	card = homeCard(t, get(t, s, "/").Body.String(), "Newest Updated Route")
	if !strings.Contains(card, "8.8.8.0/24") {
		t.Errorf("after the cards are worked out again, the newest route is "+
			"not the table's: %s", card)
	}
}

// TestKeepHomeCardsFreshWorksThemOutEveryInterval runs keepHomeCardsFresh with
// a short interval. It works the cards out at once, again after the table
// changes, and stops when its context ends.
func TestKeepHomeCardsFreshWorksThemOutEveryInterval(t *testing.T) {
	t.Parallel()

	const (
		interval = 10 * time.Millisecond
		maxWait  = 5 * time.Second
	)

	table := emptyTable()
	announce(table, "1.0.0.0/24", twoPrefixASN, testPeer(1), testRouteTime(0))

	s := newServerWithTable(t, table)

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

	go func() {
		s.keepHomeCardsFresh(ctx, interval)
		close(stopped)
	}()

	newestRouteASNIs := func(asn int) bool {
		cards := s.cards.Load()

		return cards != nil && cards.NewestRoute != nil &&
			cards.NewestRoute.OriginASN == asn
	}

	waitUntil(t, maxWait, func() bool { return newestRouteASNIs(twoPrefixASN) })

	announce(table, "8.8.8.0/24", newestRouteASN, testPeer(2), testRouteTime(1))
	waitUntil(t, maxWait, func() bool { return newestRouteASNIs(newestRouteASN) })

	cancel()

	select {
	case <-stopped:
	case <-time.After(maxWait):
		t.Fatal("keepHomeCardsFresh did not stop when its context ended")
	}
}

// TestStartedServerWorksOutTheCards starts a server and waits until its home
// page shows the cards.
func TestStartedServerWorksOutTheCards(t *testing.T) {
	t.Parallel()

	const maxWait = 5 * time.Second

	s := newServerWithTable(t, newCardsTable())

	err := s.Start(t.Context())
	if err != nil {
		t.Fatalf("Start: %v", err)
	}

	defer func() { _ = s.Stop(context.Background()) }()

	waitUntil(t, maxWait, func() bool {
		return !strings.Contains(get(t, s, "/").Body.String(), cardsNotReadyText)
	})

	card := homeCard(t, get(t, s, "/").Body.String(), "Newest Updated Route")
	if !strings.Contains(card, "8.8.8.0/24") {
		t.Errorf("the newest route is not the table's: %s", card)
	}
}

// waitUntil fails the test unless done reports true within maxWait.
func waitUntil(t *testing.T, maxWait time.Duration, done func() bool) {
	t.Helper()

	const pollInterval = 5 * time.Millisecond

	deadline := time.Now().Add(maxWait)
	for !done() {
		if time.Now().After(deadline) {
			t.Fatalf("the cards did not change within %s", maxWait)
		}

		time.Sleep(pollInterval)
	}
}