package server

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"slices"
	"strconv"
	"strings"
	"testing"
	"time"

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

// The origin ASes in the routing table that newTwoOriginTable fills.
const (
	mostPeersASN  = 64500
	fewerPeersASN = 64501
	v6OriginASN   = 64502
)

// noKeptRoutePrefix is the prefix of newTwoOriginTable whose origin keeps no
// route.
const noKeptRoutePrefix = "198.51.100.0/24"

// routeTimeFormat is how the pages write a route's time.
const routeTimeFormat = "2006-01-02 15:04:05"

// newTwoOriginTable returns a routing table that holds:
//   - testPrefixV4 with two origin ASes. Peers 1, 2 and 3 carry it with
//     mostPeersASN, which keeps the routes of peers 3 and 2. Peer 4 carries
//     it with fewerPeersASN, in the prefix's newest route.
//   - noKeptRoutePrefix with mostPeersASN. Only peer 7 carries it, and its
//     route is not kept: peers 5 and 6, whose routes were, withdrew it.
//   - testPrefixV6 with v6OriginASN.
func newTwoOriginTable() *routetable.Table {
	table := emptyTable()

	for n := 1; n <= 3; n++ {
		announce(table, testPrefixV4, mostPeersASN, testPeer(n), testRouteTime(n))
	}

	announce(table, testPrefixV4, fewerPeersASN, testPeer(4), testRouteTime(5))

	announce(table, noKeptRoutePrefix, mostPeersASN, testPeer(5), testRouteTime(4))
	announce(table, noKeptRoutePrefix, mostPeersASN, testPeer(6), testRouteTime(6))
	announce(table, noKeptRoutePrefix, mostPeersASN, testPeer(7), testRouteTime(0))
	withdraw(table, noKeptRoutePrefix, testPeer(5))
	withdraw(table, noKeptRoutePrefix, testPeer(6))

	announce(table, testPrefixV6, v6OriginASN, testPeerV6, testRouteTime(0))

	return table
}

// get sends a GET for path through s's router and fails the test unless it
// answers 200.
func get(t *testing.T, s *Server, path string) *httptest.ResponseRecorder {
	t.Helper()

	rec := httptest.NewRecorder()
	s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, path, nil))

	if rec.Code != http.StatusOK {
		t.Fatalf("%s: status %d, want %d; body %s",
			path, rec.Code, http.StatusOK, rec.Body)
	}

	return rec
}

// TestIPLookupGivesTheOriginMostPeersCarry looks up an address in a prefix
// with two origin ASes, through each IP lookup route. The answer names the
// origin AS that more peers carry, counts every peer, and gives the time of
// the prefix's newest kept route. The prefix's first-seen time and the AS's
// WHOIS details come from the database.
func TestIPLookupGivesTheOriginMostPeersCarry(t *testing.T) {
	t.Parallel()

	s := newServerWithTable(t, newTwoOriginTable())
	s.resolver = &fakeResolver{}

	firstSeen := testRouteTime(-1)

	err := s.db.UpdatePrefixesBatch(map[string]time.Time{testPrefixV4: firstSeen})
	if err != nil {
		t.Fatalf("UpdatePrefixesBatch: %v", err)
	}

	_, err = s.db.GetOrCreateASN(mostPeersASN, firstSeen)
	if err != nil {
		t.Fatalf("GetOrCreateASN: %v", err)
	}

	whois := &database.ASNWHOISUpdate{
		ASN: mostPeersASN, ASName: "TEST-AS", CountryCode: "DE",
	}

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

	// ownAddressPath looks up the request's own address, which httptest
	// gives as addrInTestPrefixV4.
	for _, path := range []string{
		"/api/v1/ip/" + addrInTestPrefixV4, "/ip/" + addrInTestPrefixV4,
		ownAddressPath,
	} {
		var body struct {
			Data IPLookupResponse `json:"data"`
		}

		err := json.Unmarshal(get(t, s, path).Body.Bytes(), &body)
		if err != nil || len(body.Data.Results) != 1 ||
			body.Data.Results[0].IPInfo == nil {
			t.Fatalf("%s: answer %+v (%v), want one result with a route",
				path, body.Data, err)
		}

		got := body.Data.Results[0].IPInfo
		if got.Netblock != testPrefixV4 || got.ASN != mostPeersASN ||
			got.NumPeers != 4 || !got.LastSeen.Equal(testRouteTime(5)) ||
			!got.FirstSeen.Equal(firstSeen) || got.ASName != whois.ASName ||
			got.CountryCode != whois.CountryCode {
			t.Errorf("%s: route %+v, want %s from AS%d, 4 peers, last seen %v, "+
				"first seen %v, %s in %s", path, *got, testPrefixV4,
				mostPeersASN, testRouteTime(5), firstSeen, whois.ASName,
				whois.CountryCode)
		}
	}
}

// TestIPLookupAsksForNoWHOISLookupOfOriginZero checks that the IP lookup asks
// for no WHOIS lookup of AS 0, which means no known origin. It asks for one of
// an AS whose WHOIS details were never fetched or are stale, and not of one
// whose details are fresh.
func TestIPLookupAsksForNoWHOISLookupOfOriginZero(t *testing.T) {
	t.Parallel()

	fresh := time.Now().Add(-time.Hour)
	stale := time.Now().Add(-2 * whoisStaleThreshold)

	tests := []struct {
		name   string
		asInfo database.ASN
		want   bool
	}{
		{"no known origin", database.ASN{ASN: ristypes.NoOrigin}, false},
		{"details never fetched", database.ASN{ASN: mostPeersASN}, true},
		{"stale details", database.ASN{ASN: mostPeersASN, WHOISUpdatedAt: &stale}, true},
		{"fresh details", database.ASN{ASN: mostPeersASN, WHOISUpdatedAt: &fresh}, false},
	}

	for _, tt := range tests {
		if got := needsWHOISRefresh(&tt.asInfo); got != tt.want {
			t.Errorf("%s: needsWHOISRefresh = %t, want %t", tt.name, got, tt.want)
		}
	}
}

// prefixRoute is one route of the prefix API's answer. A field the answer
// leaves out stays nil.
//
//nolint:tagliatelle // field names are the existing JSON API
type prefixRoute struct {
	OriginASN   int        `json:"origin_asn"`
	PeerIP      string     `json:"peer_ip"`
	ASPath      []int      `json:"as_path"`
	NextHop     *string    `json:"next_hop"`
	LastUpdated *time.Time `json:"last_updated"`
}

// TestPrefixAnswersListEveryPeer asks the prefix API and page for a prefix
// with two origin ASes, and for one whose origin keeps no route. Each answer
// lists every peer that carries the prefix, by origin AS. Only the kept routes
// have an AS path, a next hop and a time, newest first. The other peers follow
// without them.
func TestPrefixAnswersListEveryPeer(t *testing.T) {
	t.Parallel()

	s := newServerWithTable(t, newTwoOriginTable())

	// keptAt[peer] is the time of the peer's kept route; a peer not in it is
	// listed without a route.
	keptAt := map[string]time.Time{
		testPeer(3): testRouteTime(3),
		testPeer(2): testRouteTime(2),
		testPeer(4): testRouteTime(5),
	}

	tests := []struct {
		prefix      string
		wantPeers   []string
		wantOrigins []int
	}{
		{
			testPrefixV4,
			[]string{testPeer(3), testPeer(2), testPeer(1), testPeer(4)},
			[]int{mostPeersASN, mostPeersASN, mostPeersASN, fewerPeersASN},
		},
		{noKeptRoutePrefix, []string{testPeer(7)}, []int{mostPeersASN}},
	}

	for _, tt := range tests {
		//nolint:tagliatelle // field names are the existing JSON API
		var body struct {
			Data struct {
				Routes      []prefixRoute `json:"routes"`
				PeerCount   int           `json:"peer_count"`
				OriginCount int           `json:"origin_count"`
			} `json:"data"`
		}

		path := "/api/v1/prefix/" + tt.prefix

		err := json.Unmarshal(get(t, s, path).Body.Bytes(), &body)
		if err != nil {
			t.Fatalf("%s: decoding the answer: %v", path, err)
		}

		wantOriginCount := len(slices.Compact(slices.Clone(tt.wantOrigins)))
		if body.Data.PeerCount != len(tt.wantPeers) ||
			body.Data.OriginCount != wantOriginCount {
			t.Errorf("%s: %d peers and %d origins, want %d and %d", path,
				body.Data.PeerCount, body.Data.OriginCount, len(tt.wantPeers),
				wantOriginCount)
		}

		checkPrefixRoutes(t, path, body.Data.Routes, tt.wantPeers, tt.wantOrigins,
			keptAt)
		checkPrefixPage(t, s, tt.prefix, tt.wantPeers, keptAt)
	}
}

// checkPrefixRoutes checks that routes come from wantPeers, in that order,
// with wantOrigins as their origin ASes. The route of a peer in keptAt must
// have an AS path, the peer as next hop, and the time keptAt gives. Any other
// route must have none of the three.
func checkPrefixRoutes(
	t *testing.T, path string, routes []prefixRoute, wantPeers []string,
	wantOrigins []int, keptAt map[string]time.Time,
) {
	t.Helper()

	if len(routes) != len(wantPeers) {
		t.Fatalf("%s: routes %+v, want one each from %v", path, routes, wantPeers)
	}

	for i, route := range routes {
		if route.PeerIP != wantPeers[i] || route.OriginASN != wantOrigins[i] {
			t.Errorf("%s: route %d from %s with AS%d, want from %s with AS%d",
				path, i, route.PeerIP, route.OriginASN, wantPeers[i], wantOrigins[i])
		}

		at, kept := keptAt[route.PeerIP]
		if !kept {
			if route.ASPath != nil || route.NextHop != nil || route.LastUpdated != nil {
				t.Errorf("%s: route from %s is not kept but has %+v",
					path, route.PeerIP, route)
			}

			continue
		}

		if route.ASPath == nil || route.NextHop == nil ||
			*route.NextHop != route.PeerIP || route.LastUpdated == nil ||
			!route.LastUpdated.Equal(at) {
			t.Errorf("%s: kept route from %s is %+v, want its AS path, the peer "+
				"as next hop and the time %v", path, route.PeerIP, route, at)
		}
	}
}

// checkPrefixPage checks that the page of prefix shows each of wantPeers, the
// time of each kept route among them, and no time that was never set.
func checkPrefixPage(
	t *testing.T, s *Server, prefix string, wantPeers []string,
	keptAt map[string]time.Time,
) {
	t.Helper()

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

	for _, peer := range wantPeers {
		want := `<td class="peer-ip">` + peer + `</td>`
		if !strings.Contains(page, want) {
			t.Errorf("%s does not list the peer %s", path, peer)
		}

		at, kept := keptAt[peer]
		if kept && !strings.Contains(page, at.Format(routeTimeFormat)) {
			t.Errorf("%s does not show the time %v of the route from %s",
				path, at, peer)
		}
	}

	if strings.Contains(page, zeroDate) {
		t.Errorf("%s shows the date %s", path, zeroDate)
	}
}

// TestASAnswersGiveEachPrefixItsNewestKeptRoute asks the AS API and page for
// mostPeersASN. Its prefixes are testPrefixV4, whose newest kept route with
// that origin AS is peer 3's, and noKeptRoutePrefix, which keeps no route. The
// first has that route's time. The second is listed without a time.
func TestASAnswersGiveEachPrefixItsNewestKeptRoute(t *testing.T) {
	t.Parallel()

	s := newServerWithTable(t, newTwoOriginTable())
	path := "/api/v1/as/" + strconv.Itoa(mostPeersASN)

	//nolint:tagliatelle // field names are the existing JSON API
	var body struct {
		Data struct {
			IPv4Prefixes []struct {
				Prefix      string     `json:"prefix"`
				LastUpdated *time.Time `json:"last_updated"`
			} `json:"ipv4_prefixes"`
		} `json:"data"`
	}

	err := json.Unmarshal(get(t, s, path).Body.Bytes(), &body)
	if err != nil {
		t.Fatalf("%s: decoding the answer: %v", path, err)
	}

	prefixes := body.Data.IPv4Prefixes
	if len(prefixes) != 2 || prefixes[0].Prefix != testPrefixV4 ||
		prefixes[0].LastUpdated == nil ||
		!prefixes[0].LastUpdated.Equal(testRouteTime(3)) ||
		prefixes[1].Prefix != noKeptRoutePrefix || prefixes[1].LastUpdated != nil {
		t.Errorf("%s: prefixes %+v, want %s updated %v and %s without a time",
			path, prefixes, testPrefixV4, testRouteTime(3), noKeptRoutePrefix)
	}

	path = "/as/" + strconv.Itoa(mostPeersASN)
	page := get(t, s, path).Body.String()

	for _, want := range []string{
		testPrefixV4, noKeptRoutePrefix, testRouteTime(3).Format(routeTimeFormat),
	} {
		if !strings.Contains(page, want) {
			t.Errorf("%s does not show %s", path, want)
		}
	}

	if strings.Contains(page, zeroDate) {
		t.Errorf("%s shows the date %s", path, zeroDate)
	}
}

// TestPrefixLengthPagesShowTheOriginMostPeersCarry asks for the IPv4 /24
// page and the IPv6 /32 page. The first lists both /24 prefixes with
// mostPeersASN, the origin AS more peers carry testPrefixV4 with, and gives
// noKeptRoutePrefix no age. The second lists testPrefixV6.
func TestPrefixLengthPagesShowTheOriginMostPeersCarry(t *testing.T) {
	t.Parallel()

	s := newServerWithTable(t, newTwoOriginTable())

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

	for _, want := range []string{
		">" + testPrefixV4 + "<", ">" + noKeptRoutePrefix + "<",
		`href="/as/` + strconv.Itoa(mostPeersASN) + `"`,
	} {
		if !strings.Contains(page, want) {
			t.Errorf("%s does not show %s", prefixLengthPagePath, want)
		}
	}

	if strings.Contains(page, `href="/as/`+strconv.Itoa(fewerPeersASN)+`"`) {
		t.Errorf("%s links to AS%d, which fewer peers carry",
			prefixLengthPagePath, fewerPeersASN)
	}

	const noAge = `<td class="age"></td>`
	if strings.Count(page, noAge) != 1 {
		t.Errorf("%s gives %d prefixes no age, want 1 (%s)",
			prefixLengthPagePath, strings.Count(page, noAge), noKeptRoutePrefix)
	}

	const v6PagePath = "/prefixlength6/32"

	page = get(t, s, v6PagePath).Body.String()
	if !strings.Contains(page, ">"+testPrefixV6+"<") ||
		!strings.Contains(page, `href="/as/`+strconv.Itoa(v6OriginASN)+`"`) {
		t.Errorf("%s does not show %s with AS%d", v6PagePath, testPrefixV6,
			v6OriginASN)
	}
}