sms-metering-location-link: per-tag SMS credits (allocated/used, admin top-up), short URLs + owner location page (map embed + finder details) — 13/13 scenarios

frontend/internal/handlers/scan.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math/rand"
 	"net"
 	"net/http"
 	"strings"
@@ -76,6 +77,10 @@ func (a *App) Scan(w http.ResponseWriter, r *http.Request) {
 	if alertSent {
 		if a.alertOwner(r.Context(), tag, scan, req.Lat, req.Lng) {
 			_ = a.Queries.SetScanAlertSent(r.Context(), db.SetScanAlertSentParams{ID: scan.ID, AlertSent: true})
+			// Metering: a successful alert consumes one credit on metered tags.
+			if tag.SmsAllocated > 0 {
+				_ = a.Queries.AddSmsUsed(r.Context(), tag.ID)
+			}
 		}
 	}
 
@@ -107,6 +112,11 @@ func (a *App) shouldAlert(ctx context.Context, tag db.Tag, scan db.Scan, hasLoc
 		}
 	}
 
+	// SMS metering: a positive allocation is required; exhausted credits block alerts.
+	if tag.SmsAllocated > 0 && tag.SmsUsed >= tag.SmsAllocated {
+		return false
+	}
+
 	// Per-tag daily cap.
 	if n, err := a.Queries.CountAlertsByTagSince(ctx, db.CountAlertsByTagSinceParams{
 		TagID:     tag.ID,
@@ -161,7 +171,15 @@ func (a *App) alertOwner(ctx context.Context, tag db.Tag, scan db.Scan, lat, lng
 	if a.Sender == nil {
 		return false
 	}
-	msg := alertMessage(tag, scan.ScannedAt.Time, lat, lng)
+	// When a location is present, mint a short link so the SMS stays short and
+	// the owner gets a map page instead of raw coordinates.
+	link := ""
+	if lat != nil && lng != nil {
+		if code, err := a.mintShortCode(ctx, scan.ID); err == nil {
+			link = "https://where-woof.com/s/" + code
+		}
+	}
+	msg := alertMessage(tag, scan.ScannedAt.Time, lat, lng, link)
 	if err := a.Sender.Send(sms.NormalizeAU(tag.Phone.String), msg); err != nil {
 		fmt.Println("alert sms failed:", err)
 		return false
@@ -169,8 +187,24 @@ func (a *App) alertOwner(ctx context.Context, tag db.Tag, scan db.Scan, lat, lng
 	return true
 }
 
-// alertMessage builds the owner alert: item type + name, time, maps link, tag link.
-func alertMessage(tag db.Tag, t time.Time, lat, lng *float64) string {
+// mintShortCode creates a short URL code for a scan (with retry on collision).
+func (a *App) mintShortCode(ctx context.Context, scanID int64) (string, error) {
+	const alphabet = "abcdefghijklmnopqrstuvwxyz23456789" // no 0/1/o/l
+	for i := 0; i < 3; i++ {
+		code := make([]byte, 6)
+		for j := range code {
+			code[j] = alphabet[rand.Intn(len(alphabet))]
+		}
+		c := string(code)
+		if _, err := a.Queries.InsertShortCode(ctx, db.InsertShortCodeParams{Code: c, ScanID: scanID}); err == nil {
+			return c, nil
+		}
+	}
+	return "", fmt.Errorf("short code collision")
+}
+
+// alertMessage builds the owner alert: item type + name, time, location link, tag link.
+func alertMessage(tag db.Tag, t time.Time, lat, lng *float64, link string) string {
 	itemType := "Item"
 	if tag.ItemType.Valid {
 		itemType = titleCase(tag.ItemType.String)
@@ -185,7 +219,9 @@ func alertMessage(tag db.Tag, t time.Time, lat, lng *float64) string {
 	}
 
 	msg := fmt.Sprintf("Where Woof: your %s was scanned at %s.", label, t.Local().Format("3:04 pm"))
-	if lat != nil && lng != nil {
+	if link != "" {
+		msg += " Location: " + link
+	} else if lat != nil && lng != nil {
 		msg += fmt.Sprintf(" Location: https://maps.google.com/?q=%.5f,%.5f", *lat, *lng)
 	} else {
 		msg += " The finder didn't share a location."
@@ -243,6 +279,10 @@ func (a *App) FinderContact(w http.ResponseWriter, r *http.Request) {
 	// Should we notify? Skip when the same phone was alerted within the window,
 	// or when this device (fingerprint) has already alerted in the last 24 h.
 	notify := tag.SmsEnabled && tag.Phone.Valid && a.Sender != nil
+	// Metering: metered tags must have credits remaining.
+	if notify && tag.SmsAllocated > 0 && tag.SmsUsed >= tag.SmsAllocated {
+		notify = false
+	}
 	if notify && fingerprint != "" {
 		if _, err := a.Queries.GetRecentScanByFingerprint(r.Context(), db.GetRecentScanByFingerprintParams{Fingerprint: pgtype.Text{String: fingerprint, Valid: true}, ID: latest.ID}); err == nil {
 			notify = false
@@ -267,6 +307,10 @@ func (a *App) FinderContact(w http.ResponseWriter, r *http.Request) {
 		} else {
 			// Mark alerted so dedup (same phone / same device) can see it.
 			_ = a.Queries.SetScanAlertSent(r.Context(), db.SetScanAlertSentParams{ID: latest.ID, AlertSent: true})
+			// Metering: successful contact SMS consumes a credit on metered tags.
+			if tag.SmsAllocated > 0 {
+				_ = a.Queries.AddSmsUsed(r.Context(), tag.ID)
+			}
 		}
 	}