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

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

@@ -0,0 +1,24 @@
+import type { ExtractionConfig, ThumbnailOptions } from './types'
+
+export function readOptions(option: ThumbnailOptions, getFallbackUrl: () => string): ExtractionConfig {
+  const config = {
+    url: option.url || getFallbackUrl(),
+    width: option.width || 160,
+    number: option.number || 100,
+    scale: option.scale || 1,
+  }
+  if (!Number.isFinite(Number(config.width)) || config.width <= 0 || !Number.isFinite(Number(config.number)) || config.number <= 0)
+    throw new TypeError('Auto-thumbnail width and number must be finite positive numbers')
+  return config
+}
+
+export function sheetSize(config: ExtractionConfig, video: Pick<HTMLVideoElement, 'duration' | 'videoWidth' | 'videoHeight'>) {
+  if (!Number.isFinite(video.duration) || video.duration <= 0 || !Number.isFinite(video.videoWidth) || video.videoWidth <= 0 || !Number.isFinite(video.videoHeight) || video.videoHeight <= 0)
+    throw new TypeError('Auto-thumbnail requires finite media duration and dimensions')
+  const height = Math.floor(config.width * video.videoHeight / video.videoWidth)
+  const canvasWidth = Math.trunc(config.width * 10)
+  const canvasHeight = Math.trunc(height * Math.ceil(config.number / 10))
+  if (![height, canvasWidth, canvasHeight].every(value => Number.isSafeInteger(value) && value > 0 && value <= 0xFFFFFFFF))
+    throw new RangeError('Auto-thumbnail canvas dimensions are invalid')
+  return { height, canvasWidth, canvasHeight }
+}