Add server-side web usage metrics with !petestats command

Track per-page/per-channel view counts and a privacy-preserving daily
unique-visitor estimate (salted IP+UA hash, salt rotated daily and never
persisted). No third-party analytics, no JS beacon. Surfaced via the
admin-gated !petestats Matrix command (named to avoid an existing !stats
bot in the rooms).

internal/storage/db.go

@@ -116,6 +116,11 @@ func RunMaintenance() {
 	exec("prune old reactions",
 		`DELETE FROM reactions WHERE reacted_at < ?`, storyCutoff)
 
+	// Daily unique tokens are only useful for the recent window; their salts are
+	// long gone. page_views is kept forever (tiny aggregate, all-time totals).
+	exec("prune old daily_visitors",
+		`DELETE FROM daily_visitors WHERE day < ?`, unixDay()-30)
+
 	exec("wal checkpoint", "PRAGMA wal_checkpoint(TRUNCATE)")
 	exec("optimize", "PRAGMA optimize")
 }

internal/storage/metrics.go

@@ -0,0 +1,114 @@
+package storage
+
+import (
+	"log/slog"
+	"sort"
+)
+
+const secondsPerDay = 86400
+
+// unixDay returns the current UTC day number (floor(unix / 86400)).
+func unixDay() int64 { return nowUnix() / secondsPerDay }
+
+// RecordPageView increments the all-time and per-day view counter for a coarse
+// path label ("home", a channel slug, …). Fire-and-forget: a failure here must
+// never affect serving a page, so errors are logged and swallowed.
+func RecordPageView(path string) {
+	exec("record page view",
+		`INSERT INTO page_views (path, day, views) VALUES (?, ?, 1)
+		 ON CONFLICT(path, day) DO UPDATE SET views = views + 1`,
+		path, unixDay())
+}
+
+// RecordVisitor records a (already-hashed, salted) visitor token for today's
+// unique estimate. Duplicate tokens within the same day are ignored.
+func RecordVisitor(token string) {
+	exec("record visitor",
+		`INSERT OR IGNORE INTO daily_visitors (day, visitor) VALUES (?, ?)`,
+		unixDay(), token)
+}
+
+// PathStat is one row of the per-page usage breakdown.
+type PathStat struct {
+	Path  string
+	Total int // all-time views
+	Today int // views since the start of the current UTC day
+}
+
+// DayStat is one day's unique-visitor estimate.
+type DayStat struct {
+	Day     int64 // unix day number
+	Uniques int
+}
+
+// MetricsSummary is the aggregate usage readout surfaced by !petestats.
+type MetricsSummary struct {
+	Pages        []PathStat // per-path, busiest first
+	TotalViews   int        // all-time, all paths
+	ViewsToday   int        // all paths, current UTC day
+	UniquesToday int        // distinct visitor tokens, current UTC day
+	Last7Days    []DayStat  // daily uniques, oldest → newest (note: salt rotates
+	// daily, so these CANNOT be summed into a cross-day unique count)
+}
+
+// GetMetricsSummary assembles the usage readout. Best-effort: any sub-query
+// failure leaves that field at its zero value rather than failing the whole
+// command.
+func GetMetricsSummary() MetricsSummary {
+	today := unixDay()
+	var m MetricsSummary
+
+	rows, err := Get().Query(
+		`SELECT path,
+		        SUM(views)                                    AS total,
+		        COALESCE(SUM(CASE WHEN day = ? THEN views END), 0) AS today
+		 FROM page_views
+		 GROUP BY path`, today)
+	if err != nil {
+		slog.Error("metrics: page_views query failed", "err", err)
+	} else {
+		defer rows.Close()
+		for rows.Next() {
+			var p PathStat
+			if err := rows.Scan(&p.Path, &p.Total, &p.Today); err != nil {
+				slog.Error("metrics: scan page stat failed", "err", err)
+				continue
+			}
+			m.Pages = append(m.Pages, p)
+			m.TotalViews += p.Total
+			m.ViewsToday += p.Today
+		}
+	}
+	sort.Slice(m.Pages, func(i, j int) bool {
+		if m.Pages[i].Total != m.Pages[j].Total {
+			return m.Pages[i].Total > m.Pages[j].Total
+		}
+		return m.Pages[i].Path < m.Pages[j].Path
+	})
+
+	if err := Get().QueryRow(
+		`SELECT COUNT(*) FROM daily_visitors WHERE day = ?`, today,
+	).Scan(&m.UniquesToday); err != nil {
+		slog.Error("metrics: uniques-today query failed", "err", err)
+	}
+
+	since := today - 6 // inclusive 7-day window
+	vrows, err := Get().Query(
+		`SELECT day, COUNT(*) FROM daily_visitors
+		 WHERE day >= ? GROUP BY day ORDER BY day`, since)
+	if err != nil {
+		slog.Error("metrics: 7-day uniques query failed", "err", err)
+	} else {
+		defer vrows.Close()
+		for vrows.Next() {
+			var d DayStat
+			if err := vrows.Scan(&d.Day, &d.Uniques); err != nil {
+				slog.Error("metrics: scan day stat failed", "err", err)
+				continue
+			}
+			m.Last7Days = append(m.Last7Days, d)
+		}
+	}
+
+	return m
+}

internal/storage/metrics_test.go

@@ -0,0 +1,42 @@
+package storage
+
+import "testing"
+
+func TestMetrics_ViewsAndUniques(t *testing.T) {
+	setupTestDB(t)
+
+	// Three views on home, two on gaming.
+	RecordPageView("home")
+	RecordPageView("home")
+	RecordPageView("home")
+	RecordPageView("gaming")
+	RecordPageView("gaming")
+
+	// Two distinct visitors today; the repeat token must not double-count.
+	RecordVisitor("tok-a")
+	RecordVisitor("tok-a")
+	RecordVisitor("tok-b")
+
+	m := GetMetricsSummary()
+
+	if m.TotalViews != 5 {
+		t.Errorf("TotalViews = %d, want 5", m.TotalViews)
+	}
+	if m.ViewsToday != 5 {
+		t.Errorf("ViewsToday = %d, want 5", m.ViewsToday)
+	}
+	if m.UniquesToday != 2 {
+		t.Errorf("UniquesToday = %d, want 2 (deduped)", m.UniquesToday)
+	}
+	if len(m.Pages) == 0 || m.Pages[0].Path != "home" || m.Pages[0].Total != 3 {
+		t.Errorf("Pages[0] = %+v, want home with 3 views first", m.Pages)
+	}
+}
+
+func TestMetrics_EmptyIsZero(t *testing.T) {
+	setupTestDB(t)
+	m := GetMetricsSummary()
+	if m.TotalViews != 0 || m.ViewsToday != 0 || m.UniquesToday != 0 || len(m.Pages) != 0 {
+		t.Errorf("expected zero-value summary, got %+v", m)
+	}
+}

internal/storage/schema.go

@@ -53,6 +53,26 @@ CREATE TABLE IF NOT EXISTS user_preferences (
     updated_at INTEGER NOT NULL
 );
 
+-- Aggregate web usage. page_views holds running view counts keyed by a coarse
+-- path label ("home", channel slug, …) and the UTC day, so we can report both
+-- all-time totals and per-day breakdowns without storing any per-request rows.
+CREATE TABLE IF NOT EXISTS page_views (
+    path  TEXT NOT NULL,
+    day   INTEGER NOT NULL,           -- unix day (floor(unix / 86400)), UTC
+    views INTEGER NOT NULL DEFAULT 0,
+    PRIMARY KEY (path, day)
+);
+
+-- Privacy-preserving daily unique estimate. visitor is a salted hash of
+-- IP+User-Agent; the salt rotates every UTC day and is never persisted, so the
+-- hashes are irreversible and cannot be linked across days. We keep only enough
+-- to dedup within a single day, then prune.
+CREATE TABLE IF NOT EXISTS daily_visitors (
+    day     INTEGER NOT NULL,
+    visitor TEXT NOT NULL,
+    PRIMARY KEY (day, visitor)
+);
+
 CREATE UNIQUE INDEX IF NOT EXISTS idx_post_log_guid_channel ON post_log(guid, channel);
 CREATE INDEX IF NOT EXISTS idx_post_log_event_id ON post_log(event_id);
 CREATE INDEX IF NOT EXISTS idx_post_log_channel_posted ON post_log(channel, posted_at);
@@ -65,6 +85,8 @@ CREATE UNIQUE INDEX IF NOT EXISTS idx_stories_url_canonical ON stories(url_canon
 CREATE UNIQUE INDEX IF NOT EXISTS idx_stories_source_headline_norm ON stories(source, headline_norm) WHERE headline_norm IS NOT NULL AND headline_norm <> '';
 CREATE INDEX IF NOT EXISTS idx_reactions_post_guid ON reactions(post_guid);
 CREATE UNIQUE INDEX IF NOT EXISTS idx_reactions_event_id ON reactions(event_id);
+CREATE INDEX IF NOT EXISTS idx_page_views_day ON page_views(day);
+CREATE INDEX IF NOT EXISTS idx_daily_visitors_day ON daily_visitors(day);
 `
 
 const ftsSchema = `

internal/web/handlers.go

@@ -123,6 +123,7 @@ func (s *Server) base(r *http.Request) pageData {
 }
 
 func (s *Server) handleIndex(w http.ResponseWriter, r *http.Request) {
+	s.track(r, "home")
 	const (
 		justPostedLimit = 6
 		latestLimit     = 16
@@ -177,6 +178,7 @@ func (s *Server) handleIndex(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Server) handleChannel(w http.ResponseWriter, r *http.Request, ch Channel) {
+	s.track(r, ch.Slug)
 	page := 1
 	if p := r.URL.Query().Get("page"); p != "" {
 		if n, err := strconv.Atoi(p); err == nil && n > 0 {

internal/web/metrics.go

@@ -0,0 +1,93 @@
+package web
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"log/slog"
+	"net"
+	"net/http"
+	"strings"
+	"time"
+
+	"pete/internal/storage"
+)
+
+// track records one page view plus a privacy-preserving unique-visitor token
+// for the given coarse label ("home", a channel slug, …). It is deliberately
+// cheap and best-effort: the visitor token is derived synchronously (so it sees
+// the live request) but the DB writes are fired in the background so page
+// rendering never waits on them.
+func (s *Server) track(r *http.Request, label string) {
+	token := s.visitorToken(r)
+	go func() {
+		storage.RecordPageView(label)
+		if token != "" {
+			storage.RecordVisitor(token)
+		}
+	}()
+}
+
+// visitorToken returns an irreversible per-day token for the requester: a
+// SHA-256 of (daily salt || client IP || User-Agent), truncated. Because the
+// salt rotates each UTC day and is never stored, tokens cannot be reversed back
+// to an IP or linked across days. Returns "" if no client IP can be determined.
+func (s *Server) visitorToken(r *http.Request) string {
+	ip := clientIP(r)
+	if ip == "" {
+		return ""
+	}
+	salt := s.dailySalt()
+	h := sha256.New()
+	h.Write(salt[:])
+	h.Write([]byte(ip))
+	h.Write([]byte{0})
+	h.Write([]byte(r.UserAgent()))
+	return hex.EncodeToString(h.Sum(nil)[:16])
+}
+
+// dailySalt returns the current day's salt, generating a fresh random one
+// whenever the UTC day rolls over. The previous salt is discarded, which is
+// what makes cross-day correlation impossible.
+func (s *Server) dailySalt() [16]byte {
+	day := time.Now().UTC().Unix() / 86400
+	s.metricsMu.Lock()
+	defer s.metricsMu.Unlock()
+	if day != s.saltDay || isZero(s.salt) {
+		if _, err := rand.Read(s.salt[:]); err != nil {
+			// crypto/rand should never fail; if it does, fall back to a
+			// day-derived constant so we still dedup within the day.
+			slog.Error("web: salt generation failed; using weak fallback", "err", err)
+			for i := range s.salt {
+				s.salt[i] = byte(day >> (uint(i%8) * 8))
+			}
+		}
+		s.saltDay = day
+	}
+	return s.salt
+}
+
+func isZero(b [16]byte) bool {
+	for _, x := range b {
+		if x != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+// clientIP extracts the requester's IP, honoring the leftmost X-Forwarded-For
+// entry when present (Pete runs behind a reverse proxy) and otherwise falling
+// back to RemoteAddr. Only used to derive a one-way hash, never stored.
+func clientIP(r *http.Request) string {
+	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
+		if first := strings.TrimSpace(strings.Split(xff, ",")[0]); first != "" {
+			return first
+		}
+	}
+	host, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		return r.RemoteAddr
+	}
+	return host
+}

internal/web/server.go

@@ -9,6 +9,7 @@ import (
 	"io/fs"
 	"log/slog"
 	"net/http"
+	"sync"
 	"time"
 
 	"pete/internal/config"
@@ -56,6 +57,12 @@ type Server struct {
 	srv     *http.Server
 	tpls    map[string]*template.Template // keyed by page name (e.g. "index", "channel")
 	auth    *Authenticator                // nil when sign-in is disabled or unavailable
+
+	// Daily-rotated salt for the privacy-preserving unique-visitor estimate.
+	// Guarded by metricsMu; never persisted (see metrics.go).
+	metricsMu sync.Mutex
+	saltDay   int64
+	salt      [16]byte
 }
 
 // New builds the server. Templates are parsed once at startup. Each page