refactor(server/api): resolveByID helper for parseUUID->fetch->404 (T4)

internal/api/resolve.go

@@ -0,0 +1,41 @@
+package api
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/apierror"
+)
+
+// resolveByID parses paramKey as a UUID, fetches the row via fetch, and
+// returns the row. On invalid UUID, returns BadRequest. On pgx.ErrNoRows,
+// returns NotFound with code "<notFoundCode>_not_found". On other fetch
+// errors, returns Internal (caller is responsible for logging if needed).
+//
+// Generic over T because dbq getters return concrete dbq row types.
+func resolveByID[T any](
+	r *http.Request,
+	paramKey string,
+	fetch func(context.Context, pgtype.UUID) (T, error),
+	notFoundCode string,
+) (T, *apierror.Error) {
+	var zero T
+	raw := chi.URLParam(r, paramKey)
+	id, ok := parseUUID(raw)
+	if !ok {
+		return zero, apierror.BadRequest("bad_request", "invalid "+paramKey+" id")
+	}
+	row, err := fetch(r.Context(), id)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return zero, apierror.NotFound(notFoundCode)
+		}
+		return zero, apierror.Internal(err)
+	}
+	return row, nil
+}