refactor(auto-thumbnail): [PKG-AUTO-THUMB-03] type internal extraction contracts

packages/artplayer-plugin-auto-thumbnail/src/extraction.ts

@@ -0,0 +1,67 @@
+import type { ExtractionConfig, ExtractionJob } from './types'
+import createFrameReader from './frames'
+import { sheetSize } from './options'
+import createVideo from './video'
+
+export default function extract(job: ExtractionJob, config: ExtractionConfig) {
+  const video = createVideo(job)
+  if (!job.active())
+    return
+  video.onerror = job.guard(() => {
+    throw video.error || new Error('Auto-thumbnail media failed to load')
+  })
+  video.onloadedmetadata = job.guard(() => {
+    video.onloadedmetadata = null
+    const duration = video.duration
+    const videoHeight = video.videoHeight
+    const videoWidth = video.videoWidth
+    const { height, canvasWidth, canvasHeight } = sheetSize(config, {
+      duration,
+      videoHeight,
+      videoWidth,
+    })
+    if (!job.active())
+      return
+    video.width = videoWidth
+    video.height = videoHeight
+    video.style.width = `${videoWidth}px`
+    video.style.height = `${videoHeight}px`
+    const canvas = document.createElement('canvas')
+    if (!job.active())
+      return
+    canvas.width = canvasWidth
+    canvas.height = canvasHeight
+    const ctx = canvas.getContext('2d')
+    if (!ctx)
+      throw new Error('Auto-thumbnail canvas context is unavailable')
+    if (!job.active())
+      return
+    const readFrame = createFrameReader(job, video)
+    let index = 0
+    const seek = job.guard(() => {
+      if (index >= config.number) {
+        job.dispose()
+        return
+      }
+      readFrame(duration * index / config.number, job.guard(() => {
+        ctx.drawImage(video, (index % 10) * config.width, Math.floor(index / 10) * height, config.width, height)
+        if (!job.active())
+          return
+        let delivered = false
+        canvas.toBlob(job.guard((blob) => {
+          if (delivered)
+            return
+          delivered = true
+          job.publish(blob, { height, column: 10, number: config.number, width: config.width, scale: config.scale })
+          if (job.active()) {
+            index += 1
+            seek()
+          }
+        }), 'image/jpeg')
+      }))
+    })
+    seek()
+  })
+  if (job.active())
+    video.src = config.url
+}