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

packages/artplayer-plugin-danmuku/src/worker.ts

@@ -0,0 +1,154 @@
+import type { PlacementMessage, PlacementReply, PlacementRequest, PlacementRow, VisibleDanmu } from './worker-types'
+
+function getDanmuTop({ target, visibles, clientWidth, clientHeight, marginBottom, marginTop, antiOverlap }: PlacementRequest): number | undefined {
+  // 弹幕最大高度
+  const maxTop = clientHeight - marginBottom
+
+  // 过滤同模式的弹幕，即每种模式各不影响
+  const danmus: PlacementRow[] = visibles
+    .filter(item => item.mode === target.mode && item.top <= maxTop)
+    .sort((prev, next) => prev.top - next.top)
+
+  // 如果没有同模式的弹幕，直接返回
+  if (danmus.length === 0) {
+    if (target.mode === 2) {
+      return maxTop - target.height
+    }
+    else {
+      return marginTop
+    }
+  }
+
+  // 上下各加一个虚拟弹幕，方便计算
+  danmus.unshift({
+    type: 'top',
+    top: 0,
+    left: 0,
+    right: 0,
+    height: marginTop,
+    width: clientWidth,
+    speed: 0,
+    distance: clientWidth,
+  })
+
+  danmus.push({
+    type: 'bottom',
+    top: maxTop,
+    left: 0,
+    right: 0,
+    height: marginBottom,
+    width: clientWidth,
+    speed: 0,
+    distance: clientWidth,
+  })
+
+  // 查找是否有多余的缝隙足以容纳当前弹幕
+  if (target.mode === 2) {
+    // 倒序查找
+    for (let index = danmus.length - 2; index >= 0; index -= 1) {
+      const item = danmus[index]!
+      const prev = danmus[index + 1]!
+      const itemBottom = item.top + item.height
+      const diff = prev.top - itemBottom
+      if (diff >= target.height) {
+        return prev.top - target.height
+      }
+    }
+  }
+  else {
+    // 顺序查找
+    for (let index = 1; index < danmus.length; index += 1) {
+      const item = danmus[index]!
+      const prev = danmus[index - 1]!
+      const prevBottom = prev.top + prev.height
+      const diff = item.top - prevBottom
+      if (diff >= target.height) {
+        return prevBottom
+      }
+    }
+  }
+
+  const topMap: VisibleDanmu[][] = []
+  for (let index = 1; index < danmus.length - 1; index += 1) {
+    // The loop excludes the two virtual boundary rows inserted above.
+    const item = danmus[index] as VisibleDanmu
+    if (topMap.length) {
+      const last = topMap[topMap.length - 1]!
+      if (last[0]!.top === item.top) {
+        last.push(item)
+      }
+      else {
+        topMap.push([item])
+      }
+    }
+    else {
+      topMap.push([item])
+    }
+  }
+
+  if (antiOverlap) {
+    switch (target.mode) {
+      case 0: {
+        const result = topMap.find((list) => {
+          return list.every((danmu) => {
+            if (clientWidth < danmu.distance)
+              return false
+            if (target.speed < danmu.speed)
+              return true
+            const overlapTime = danmu.right / (target.speed - danmu.speed)
+            if (overlapTime > danmu.time)
+              return true
+            return false
+          })
+        })
+
+        return result && result[0] ? result[0].top : undefined
+      }
+
+      // 静止弹幕没有重叠问题
+      case 1:
+      case 2:
+        return undefined
+      default:
+        break
+    }
+  }
+  else {
+    switch (target.mode) {
+      case 0:
+        topMap.sort((prev, next) => {
+          const nextMinRight = Math.min(...next.map(item => item.right))
+          const prevMinRight = Math.min(...prev.map(item => item.right))
+          return nextMinRight * next.length - prevMinRight * prev.length
+        })
+        break
+      case 1:
+      case 2:
+        topMap.sort((prev, next) => {
+          const nextMaxWidth = Math.max(...next.map(item => item.width))
+          const prevMaxWidth = Math.max(...prev.map(item => item.width))
+          return prevMaxWidth * prev.length - nextMaxWidth * next.length
+        })
+        break
+      default:
+        break
+    }
+
+    return topMap[0]![0]!.top
+  }
+}
+
+onmessage = (event: MessageEvent<PlacementMessage>) => {
+  const { data } = event
+  if (!data.id || !data.type)
+    return
+
+  const fns = { getDanmuTop }
+  const fn = fns[data.type]
+  const result = fn(data)
+
+  globalThis.postMessage({
+    result,
+    id: data.id,
+  } satisfies PlacementReply)
+}