Show figures of the routing table on the home page (closes #154)

The home page gets cards for the newest and oldest kept route, the newest
and oldest updated AS, the AS with the most prefixes, the ASes with a
single prefix and fifteen well-known networks. Two more cards count the
bogon announcements and the prefixes with several origin ASes. They link
to the new pages /bogons and /multiple-origins, which list up to 1,000
entries each.

The new package internal/bogon tells reserved prefixes and AS numbers,
from the IANA special-purpose and address space registries. Table.Overview
walks the table and lets the read lock go every 10,000 prefixes. The
server works the cards out once a minute and serves that copy. A new index
on asns(last_seen) finds the newest and oldest updated AS.

Model: opus-5-5

internal/database/database.go

@@ -972,6 +972,34 @@ func (d *Database) GetAS(ctx context.Context, asn int) (*ASN, bool, error) {
 	return &asnInfo, true, nil
 }
 
+// The queries of GetLastSeenASes. The index on last_seen answers each without
+// reading the whole table.
+const (
+	newestLastSeenASQuery = `
+	SELECT asn, handle, description, first_seen, last_seen
+	FROM asns ORDER BY last_seen DESC LIMIT 1`
+	oldestLastSeenASQuery = `
+	SELECT asn, handle, description, first_seen, last_seen
+	FROM asns ORDER BY last_seen ASC LIMIT 1`
+)
+
+// GetLastSeenASes returns two ASes of the asns table, with their handles,
+// descriptions and seen times: the one last seen most recently, and the one
+// last seen longest ago. Both are nil when the table holds no AS.
+func (d *Database) GetLastSeenASes(ctx context.Context) (*ASN, *ASN, error) {
+	newest, found, err := d.readOneAS(ctx, newestLastSeenASQuery)
+	if err != nil || !found {
+		return nil, nil, err
+	}
+
+	oldest, _, err := d.readOneAS(ctx, oldestLastSeenASQuery)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return newest, oldest, nil
+}
+
 // asWHOISQuery reads the handle, description and WHOIS details of one AS, and
 // when the WHOIS details were fetched.
 const asWHOISQuery = `
@@ -1379,6 +1407,29 @@ func (d *Database) Ping(ctx context.Context) error {
 	return nil
 }
 
+// readOneAS returns the AS that query reads, and whether it read one.
+func (d *Database) readOneAS(ctx context.Context, query string) (*ASN, bool, error) {
+	var (
+		asnInfo             ASN
+		handle, description sql.NullString
+	)
+
+	err := d.db.QueryRowContext(ctx, query).Scan(&asnInfo.ASN, &handle,
+		&description, &asnInfo.FirstSeen, &asnInfo.LastSeen)
+	if errors.Is(err, sql.ErrNoRows) {
+		return nil, false, nil
+	}
+
+	if err != nil {
+		return nil, false, fmt.Errorf("failed to query AS by last seen: %w", err)
+	}
+
+	asnInfo.Handle = handle.String
+	asnInfo.Description = description.String
+
+	return &asnInfo, true, nil
+}
+
 // truncateWAL runs the TRUNCATE checkpoint of Checkpoint on a WAL file of
 // walBytes, with the writing connection's busy timeout lowered to
 // truncateBusyTimeoutMs for it, and logs how long it took. The caller holds the

internal/database/database_internal_test.go

@@ -1003,6 +1003,62 @@ func TestGetASReadsTheRecordOrTheBuiltInList(t *testing.T) {
 	}
 }
 
+// TestGetLastSeenASes stores three ASes, each last seen at another time, and
+// expects the one last seen most recently and the one last seen longest ago.
+// An empty asns table gives neither.
+func TestGetLastSeenASes(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	newest, oldest, err := db.GetLastSeenASes(t.Context())
+	if err != nil || newest != nil || oldest != nil {
+		t.Fatalf("GetLastSeenASes() on an empty table = %+v, %+v, %v; want "+
+			"neither", newest, oldest, err)
+	}
+
+	const (
+		newestASN = 13335
+		middleASN = 15169
+		oldestASN = 3
+	)
+
+	start := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	err = db.GetOrCreateASNBatch(map[int]SeenTimes{
+		middleASN: {First: start, Last: start.Add(time.Hour)},
+		newestASN: {First: start, Last: start.Add(2 * time.Hour)},
+		oldestASN: {First: start, Last: start.Add(time.Minute)},
+	})
+	if err != nil {
+		t.Fatalf("GetOrCreateASNBatch: %v", err)
+	}
+
+	newest, oldest, err = db.GetLastSeenASes(t.Context())
+	if err != nil {
+		t.Fatalf("GetLastSeenASes: %v", err)
+	}
+
+	listed, _ := asinfo.Get(newestASN)
+
+	if newest == nil || newest.ASN != newestASN ||
+		!newest.LastSeen.Equal(start.Add(2*time.Hour)) ||
+		newest.Description != listed.Description {
+		t.Errorf("newest = %+v, want AS%d (%s) last seen %v", newest, newestASN,
+			listed.Description, start.Add(2*time.Hour))
+	}
+
+	if oldest == nil || oldest.ASN != oldestASN ||
+		!oldest.LastSeen.Equal(start.Add(time.Minute)) {
+		t.Errorf("oldest = %+v, want AS%d last seen %v", oldest, oldestASN,
+			start.Add(time.Minute))
+	}
+}
+
 // TestGetASWHOISReadsTheStoredDetails stores an AS with WHOIS details and asks
 // GetASWHOIS for it and for an AS the asns table does not hold. The first gets
 // its stored handle, description and details, and the time they were fetched.

internal/database/interface.go

@@ -62,6 +62,7 @@ type Store interface {
 
 	// AS and prefix detail operations
 	GetAS(ctx context.Context, asn int) (*ASN, bool, error)
+	GetLastSeenASes(ctx context.Context) (*ASN, *ASN, error)
 	GetASWHOIS(ctx context.Context, asn int) (*ASN, error)
 	GetPrefixFirstSeen(ctx context.Context, prefix netip.Prefix) (time.Time, error)
 	GetASPeers(asn int) ([]ASPeer, error)

internal/database/schema.sql

@@ -83,6 +83,9 @@ CREATE INDEX IF NOT EXISTS idx_peerings_lookup ON peerings(as_a, as_b);
 -- Indexes for asns table
 CREATE INDEX IF NOT EXISTS idx_asns_asn ON asns(asn);
 CREATE INDEX IF NOT EXISTS idx_asns_whois_updated_at ON asns(whois_updated_at);
+-- Finds the AS last seen most recently and the one last seen longest ago, for
+-- the home page.
+CREATE INDEX IF NOT EXISTS idx_asns_last_seen ON asns(last_seen);
 
 -- Indexes for bgp_peers table
 CREATE INDEX IF NOT EXISTS idx_bgp_peers_asn ON bgp_peers(peer_asn);