where_woof/frontend/internal/handlers/scan.go

package handlers

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"

	"wherewoof/frontend/internal/db"
	"wherewoof/frontend/internal/sms"
)

const (
	alertWindow      = 10 * time.Minute
	alertMinDistance = 250.0 // metres
)

// ScanRequest is the JSON body posted by the geolocation script.
type ScanRequest struct {
	Lat *float64 `json:"lat"`
	Lng *float64 `json:"lng"`
}

// Scan records a scan (with optional location) and alerts the owner per the
// location-aware throttle rules: within the 10-minute window an alert is only
// re-sent when the new location is more than 250 m from the last alerted spot.
func (a *App) Scan(w http.ResponseWriter, r *http.Request) {
	tag, err := a.Queries.GetTagByCode(r.Context(), r.PathValue("tag_code"))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			http.Error(w, "tag not found", http.StatusNotFound)
			return
		}
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	var req ScanRequest
	_ = json.NewDecoder(r.Body).Decode(&req)
	hasLoc := req.Lat != nil && req.Lng != nil

	var lat, lng pgtype.Float8
	if hasLoc {
		lat = pgtype.Float8{Float64: *req.Lat, Valid: true}
		lng = pgtype.Float8{Float64: *req.Lng, Valid: true}
	}

	scan, err := a.Queries.InsertScan(r.Context(), db.InsertScanParams{
		TagID:          tag.ID,
		Lat:            lat,
		Lng:            lng,
		LocationShared: hasLoc,
	})
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	alertSent := a.shouldAlert(r.Context(), tag, scan, hasLoc, req.Lat, req.Lng)
	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})
		}
	}

	writeJSON(w, map[string]any{"ok": true, "alert_sent": alertSent})
}

// shouldAlert applies the throttle rules and sms_enabled flag.
func (a *App) shouldAlert(ctx context.Context, tag db.Tag, scan db.Scan, hasLoc bool, lat, lng *float64) bool {
	if !tag.SmsEnabled {
		return false
	}
	if !tag.Phone.Valid {
		return false
	}

	last, err := a.Queries.GetLastAlertByTag(ctx, tag.ID)
	if err != nil {
		return errors.Is(err, pgx.ErrNoRows) // no prior alert -> alert
	}

	// Within the window?
	if time.Since(last.ScannedAt.Time) < alertWindow {
		// Re-alert only if we have a location and it moved >250 m.
		if !hasLoc || !last.Lat.Valid || !last.Lng.Valid {
			return false
		}
		return sms.HaversineMeters(last.Lat.Float64, last.Lng.Float64, *lat, *lng) > alertMinDistance
	}
	return true
}

// alertOwner sends the SMS to the owner and reports success.
func (a *App) alertOwner(ctx context.Context, tag db.Tag, scan db.Scan, lat, lng *float64) bool {
	if a.Sender == nil {
		return false
	}
	msg := alertMessage(tag, scan.ScannedAt.Time, lat, lng)
	if err := a.Sender.Send(sms.NormalizeAU(tag.Phone.String), msg); err != nil {
		fmt.Println("alert sms failed:", err)
		return false
	}
	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 {
	itemType := "Item"
	if tag.ItemType.Valid {
		itemType = titleCase(tag.ItemType.String)
	}
	name := strings.TrimSpace(tag.Description.String)
	if len(name) > 30 {
		name = name[:30] + "…"
	}
	label := itemType
	if name != "" {
		label = itemType + ", " + name
	}

	msg := fmt.Sprintf("Where Woof: your %s was scanned at %s.", label, t.Local().Format("3:04 pm"))
	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."
	}
	msg += fmt.Sprintf(" See: https://where-woof.com/t/%s", tag.TagCode)
	return msg
}

// FinderContact stores a finder's number on the latest scan and alerts the owner.
func (a *App) FinderContact(w http.ResponseWriter, r *http.Request) {
	tag, err := a.Queries.GetTagByCode(r.Context(), r.PathValue("tag_code"))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			http.Error(w, "tag not found", http.StatusNotFound)
			return
		}
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	phone := sms.NormalizeAU(strings.TrimSpace(r.FormValue("phone")))
	if len(phone) < 8 || len(phone) > 15 {
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		fmt.Fprint(w, `<p class="mt-4 rounded border border-red-200 bg-red-50 px-4 py-2 text-sm text-red-700">Please enter a valid phone number.</p>`)
		return
	}

	latest, err := a.Queries.GetLatestScanByTag(r.Context(), tag.ID)
	if err != nil {
		if !errors.Is(err, pgx.ErrNoRows) {
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		// No scan yet: record one carrying the finder's number.
		_, err = a.Queries.InsertScan(r.Context(), db.InsertScanParams{
			TagID: tag.ID, ScannerPhone: pgtype.Text{String: phone, Valid: true},
		})
	} else {
		err = a.Queries.SetScanPhone(r.Context(), db.SetScanPhoneParams{ID: latest.ID, ScannerPhone: pgtype.Text{String: phone, Valid: true}})
	}
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	if tag.SmsEnabled && tag.Phone.Valid && a.Sender != nil {
		itemType := "item"
		if tag.ItemType.Valid {
			itemType = tag.ItemType.String
		}
		msg := fmt.Sprintf("Where Woof: a finder of your %s left their number: %s. See: https://where-woof.com/t/%s",
			itemType, phone, tag.TagCode)
		if err := a.Sender.Send(sms.NormalizeAU(tag.Phone.String), msg); err != nil {
			fmt.Println("contact sms failed:", err)
		}
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	fmt.Fprint(w, `<p class="mt-4 rounded border border-green-200 bg-green-50 px-4 py-2 text-sm text-green-800">Thanks! The owner has been notified with your number.</p>`)
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(v)
}