Add check for first control point

packages/common/src/controlPoints/ControlPointInfo.ts

@@ -231,7 +231,11 @@ export class ControlPointInfo extends AbstractCrdt<ControlPointMutation> {
     return this.controlPointLists.flatMap(list => list.filter(it => almostEquals(it.time, time, 1)));
   }
 
-  override get childObjects(): AbstractCrdt[] {
+  override get childObjects(): AbstractCrdt<any>[] {
+    return this.allControlPoints;
+  }
+
+  get allControlPoints(): ControlPoint[] {
     return this.controlPointLists.flatMap(it => it.items);
   }
 }

packages/common/src/verifier/checks/timing/CheckFirstLine.ts

@@ -0,0 +1,39 @@
+import type { CheckMetadata } from '../../BeatmapCheck';
+import type { Issue } from '../../Issue';
+import type { VerifierBeatmap } from '../../VerifierBeatmap';
+import { TimingPoint } from '../../../controlPoints/TimingPoint';
+import { minBy } from '../../../utils/arrayUtils';
+import { BeatmapCheck } from '../../BeatmapCheck';
+import { IssueTemplate } from '../../template/IssueTemplate';
+
+export class CheckFirstLine extends BeatmapCheck<any> {
+  override get metadata(): CheckMetadata {
+    return {
+      category: 'Timing',
+      message: 'First line toggles kiai or is inherited.',
+      author: 'Naxess',
+    };
+  }
+
+  override templates = {
+    inherited: new IssueTemplate('problem', '{0:timestamp} First timing line is inherited.', 'timestamp - ').withCause('The first timing line of a beatmap is inherited.'),
+    togglesKiai: new IssueTemplate('problem', '{0:timestamp} First timing line toggles kiai.', 'timestamp - ').withCause('The first timing line of a beatmap has kiai enabled.'),
+    noLines: new IssueTemplate('problem', 'There are no timing lines.').withCause('A beatmap has no timing lines.'),
+  };
+
+  override async * getIssues(beatmap: VerifierBeatmap<any>): AsyncGenerator<Issue, void, undefined> {
+    const firstTimingPoint = beatmap.controlPoints.timingPoints.first;
+    if (!firstTimingPoint) {
+      yield this.createIssue(this.templates.noLines, beatmap);
+      return;
+    }
+
+    const firstControlPoint = minBy(beatmap.controlPoints.allControlPoints, it => it.time);
+
+    if (!(firstControlPoint instanceof TimingPoint) && firstControlPoint.time < firstTimingPoint.time)
+      yield this.createIssue(this.templates.inherited, beatmap, firstControlPoint.time);
+
+    if (beatmap.controlPoints.effectPointAt(firstTimingPoint.time).kiaiMode)
+      yield this.createIssue(this.templates.togglesKiai, beatmap, firstControlPoint.time);
+  }
+}