import JSZip from "jszip"

const imageExts = new Set([".jpg", ".jpeg", ".png", ".webp", ".gif", ".bmp"])

export async function loadPagesFromCbz(
  url: string,
  signal?: AbortSignal,
): Promise<{ pages: string[]; pageCount: number }> {
  const response = await fetch(url, { signal })
  if (!response.ok) throw new Error(`Failed to fetch CBZ: ${response.status}`)

  const blob = await response.blob()
  const zip = await JSZip.loadAsync(blob)

  const imageEntries = Object.entries(zip.files)
    .filter(([name, file]) => {
      const ext = name.toLowerCase().slice(name.lastIndexOf("."))
      return !file.dir && imageExts.has(ext)
    })
    .sort(([a], [b]) => {
      const numA = parseInt(a.match(/(\d+)/)?.[1] || "0", 10)
      const numB = parseInt(b.match(/(\d+)/)?.[1] || "0", 10)
      return numA - numB
    })

  const pageCount = imageEntries.length
  const pages: string[] = []

  for (const [, file] of imageEntries) {
    const blob = await file.async("blob")
    pages.push(URL.createObjectURL(blob))
  }

  return { pages, pageCount }
}

export function revokePageUrls(urls: string[]) {
  for (const url of urls) {
    URL.revokeObjectURL(url)
  }
}