YesPlayMusic/packages/web/states/scrollPositions.ts

class ScrollPositions {
  private _nestedPaths: string[] = ['/artist', '/album', '/playlist', '/search']
  private _positions: Record<string, { path: string; top: number }[]> = {}
  private _generalPositions: Record<string, number> = {}

  constructor() {
    this._nestedPaths.forEach(path => (this._positions[path] = []))
  }

  get(pathname: string) {
    const nestedPath = `/${pathname.split('/')[1]}`
    const restPath = pathname.split('/').slice(2).join('/')
    if (this._nestedPaths.includes(nestedPath)) {
      return this._positions?.[nestedPath]?.find(
        ({ path }) => path === restPath
      )?.top
    } else {
      return this._generalPositions?.[pathname]
    }
  }

  set(pathname: string, top: number) {
    const nestedPath = `/${pathname.split('/')[1]}`
    const restPath = pathname.split('/').slice(2).join('/')

    // set general position
    if (!this._nestedPaths.includes(nestedPath)) {
      this._generalPositions[pathname] = top
      return
    }

    // set nested position
    const existsPath = this._positions[nestedPath].find(
      p => p.path === restPath
    )
    if (existsPath) {
      existsPath.top = top
      this._positions[nestedPath] = this._positions[nestedPath].filter(
        p => p.path !== restPath
      )
      this._positions[nestedPath].push(existsPath)
    } else {
      this._positions[nestedPath].push({ path: restPath, top })
    }

    // delete oldest position when there are more than 10
    if (this._positions[nestedPath].length > 10) {
      this._positions[nestedPath].shift()
    }
  }
}

const scrollPositions = new ScrollPositions()

if (import.meta.env.DEV) {
  // eslint-disable-next-line @typescript-eslint/no-extra-semi
  ;(window as any).scrollPositions = scrollPositions
}

export default scrollPositions