Validate max_retries on both target forms (closes #221)

internal/handlers/source_management.go

@@ -905,16 +905,7 @@ func (h *Handlers) loadTargetMap(
 
 // parsePage extracts a page number from the query string.
 func (h *Handlers) parsePage(r *http.Request) int {
-	page := 1
-
-	if p := r.URL.Query().Get("page"); p != "" {
-		v, err := strconv.Atoi(p)
-		if err == nil && v > 0 {
-			page = v
-		}
-	}
-
-	return page
+	return pageOrFirst(r.URL.Query().Get("page"))
 }
 
 // loadEventsWithDeliveries loads paginated events and their
@@ -1443,7 +1434,6 @@ func (h *Handlers) processTargetCreate(
 	// Referer headers and error trackers record.
 	name := r.PostFormValue("name")
 	targetType := database.TargetType(r.PostFormValue("type"))
-	maxRetriesStr := r.PostFormValue("max_retries")
 
 	if name == "" {
 		http.Error(
@@ -1469,7 +1459,14 @@ func (h *Handlers) processTargetCreate(
 		return
 	}
 
-	maxRetries := parseNonNegativeInt(maxRetriesStr)
+	// A new target has no stored retry count, so an absent field
+	// takes the fire-and-forget default. A field the operator filled
+	// in with something invalid is rejected rather than becoming
+	// that default.
+	maxRetries, ok := targetMaxRetries(w, r, 0)
+	if !ok {
+		return
+	}
 
 	target := &database.Target{
 		WebhookID:  webhook.ID,
@@ -1505,19 +1502,22 @@ func isValidTargetType(tt database.TargetType) bool {
 	}
 }
 
-// parseNonNegativeInt parses s as a non-negative integer,
-// returning 0 if s is empty or invalid.
-func parseNonNegativeInt(s string) int {
-	if s == "" {
-		return 0
+// pageOrFirst parses a paginated page number, answering 1 for
+// anything empty, unparseable or out of range.
+//
+// Falling back rather than rejecting is correct here and only here:
+// a page number is where to send the browser next, not configuration
+// the operator is storing, and the actions that submit one have
+// already completed by the time it is read — answering 400 would
+// report a failure that did not happen. Anything an operator SETS
+// must be validated instead; see parseMaxRetries.
+func pageOrFirst(s string) int {
+	v, err := strconv.Atoi(strings.TrimSpace(s))
+	if err != nil || v < 1 {
+		return 1
 	}
 
-	v, err := strconv.Atoi(s)
-	if err == nil && v >= 0 {
-		return v
-	}
-
-	return 0
+	return v
 }
 
 // targetFormInput carries the raw form values describing a target's