refactored for maintainability

internal/handlers/isunique.go

@@ -0,0 +1,49 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+
+	"git.haelnorr.com/h/golib/hws"
+	"git.haelnorr.com/h/oslstats/internal/db"
+	"git.haelnorr.com/h/oslstats/internal/validation"
+	"github.com/pkg/errors"
+	"github.com/uptrace/bun"
+)
+
+// IsUnique creates a handler that checks field uniqueness
+// Returns 200 OK if unique, 409 Conflict if not unique
+func IsUnique(
+	s *hws.Server,
+	conn *bun.DB,
+	model any,
+	field string,
+) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		getter, err := validation.ParseForm(r)
+		if err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		value := getter.String(field).TrimSpace().Required().Value
+		if !getter.Validate() {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		unique := false
+		if ok := db.WithNotifyTx(s, w, r, conn, func(ctx context.Context, tx bun.Tx) (bool, error) {
+			unique, err = db.IsUnique(ctx, tx, model, field, value)
+			if err != nil {
+				return false, errors.Wrap(err, "db.IsUnique")
+			}
+			return true, nil
+		}); !ok {
+			return
+		}
+		if unique {
+			w.WriteHeader(http.StatusOK)
+		} else {
+			w.WriteHeader(http.StatusConflict)
+		}
+	})
+}