// selection -> which handles the main map may show.
//
// Pure manifest filtering, deliberately free of any OpenLayers import so it can
// be unit-tested in node. `handle-layer.ts` is the OL adapter that renders the
// result.

import { isRoadKind, type EditHandle, type HandleManifest, type JunctionReserve } from './types';

/**
 * Road kinds only, and only for the selected road's segment.
 *
 * Junction kinds stay out even though the manifest carries them: reserve interiors
 * belong to JunctionTools, and the main map must not offer a second way to edit
 * them. Reserve-disabled road handles are *kept* rather than dropped, because the
 * user has to be able to see why that stretch refuses to move.
 *
 * Handle anchors carry a directional `roadId`, while `reserves` are keyed by
 * segment id, so callers pass a resolver instead of parsing ids apart.
 */
export function handlesForSegment(
  manifest: HandleManifest | null,
  segmentId: string | null,
  segmentOf: (roadId: string) => string | undefined,
): EditHandle[] {
  if (!manifest || !segmentId) return [];
  return manifest.handles.filter((handle) => {
    if (!isRoadKind(handle.kind)) return false;
    const roadId = 'roadId' in handle.anchor ? handle.anchor.roadId : undefined;
    return typeof roadId === 'string' && segmentOf(roadId) === segmentId;
  });
}

/** Reserves that apply to one segment, for the range window and the tooltip copy. */
export function reservesForSegment(manifest: HandleManifest | null, segmentId: string | null): JunctionReserve[] {
  if (!manifest || !segmentId) return [];
  return manifest.reserves.filter((reserve) => reserve.roadId === segmentId);
}

/** Why a handle refuses to move. Falls back to a generic reason so the UI never says nothing. */
export function disabledReasonOf(handle: EditHandle): string | undefined {
  if (handle.editable) return undefined;
  return handle.disabledReason || '该手柄位于路口保留区，请进入 JunctionTools 编辑。';
}