refactor(danmuku): [PKG-DANMUKU-06] migrate runtime and preserve public types

packages/artplayer-plugin-danmuku/src/heatmap-sampling.ts

@@ -0,0 +1,35 @@
+import type { DanmuItem, HeatmapPoint } from './types'
+
+export const MAX_HEATMAP_POINTS = 0xFFFFFFFF
+
+function upperBound(values: readonly number[], value: number): number {
+  let start = 0
+  let end = values.length
+  while (start < end) {
+    const middle = Math.floor((start + end) / 2)
+    // The binary-search interval guarantees middle is an existing index.
+    if (values[middle]! <= value)
+      start = middle + 1
+    else end = middle
+  }
+  return start
+}
+
+export function sampleHeatmap(queue: readonly Pick<DanmuItem, 'time'>[], width: number, duration: number, sampling: number): HeatmapPoint[] {
+  if (!Number.isFinite(width) || width <= 0 || !Number.isFinite(duration) || duration <= 0
+    || !Number.isFinite(sampling) || sampling <= 0 || Math.floor(width / sampling) + 1 > MAX_HEATMAP_POINTS) { return [] }
+  const times = queue.map(item => item.time).filter(time => typeof time === 'number' && !Number.isNaN(time)).sort((a, b) => a - b)
+  const points: HeatmapPoint[] = []
+  const gap = duration / width
+  if (!Number.isFinite(gap))
+    return []
+  // Keep the old floating-point x progression and strict-left/inclusive-right bins.
+  for (let x = 0; x <= width; x += sampling) {
+    if (points.length >= MAX_HEATMAP_POINTS || x + sampling === x)
+      return []
+    const left = x * gap
+    const right = (x + sampling) * gap
+    points.push([x, upperBound(times, right) - upperBound(times, left)])
+  }
+  return points
+}