import type { TipTapJSON } from "@/lib/drive/richtext-import"
import type { DocPageHeaderFooter, DocPageSetup } from "@/lib/drive/doc-page-setup"

type DocxArchive = Record<string, Uint8Array>

function decodeXml(bytes: Uint8Array | undefined): string {
  if (!bytes) return ""
  return new TextDecoder().decode(bytes)
}

function xmlTextToParagraphs(xml: string): TipTapJSON[] {
  const paragraphs: TipTapJSON[] = []
  const pBlocks = [...xml.matchAll(/<w:p\b[^>]*>[\s\S]*?<\/w:p>/gi)]

  if (pBlocks.length === 0) {
    const text = xml.replace(/<[^>]+>/g, " ").replace(/\s+/g, " ").trim()
    if (text) {
      paragraphs.push({ type: "paragraph", content: [{ type: "text", text }] })
    }
    return paragraphs
  }

  for (const pMatch of pBlocks) {
    const pXml = pMatch[0]
    const runs = [...pXml.matchAll(/<w:t\b[^>]*>([^<]*)<\/w:t>/gi)]
    const text = runs.map((r) => r[1] ?? "").join("")
    const content: TipTapJSON[] = []

    if (text) {
      const marks: TipTapJSON[] = []
      if (/<w:b\b[^>]*\/>|<w:b\b[^>]*>/.test(pXml)) marks.push({ type: "bold" })
      if (/<w:i\b[^>]*\/>|<w:i\b[^>]*>/.test(pXml)) marks.push({ type: "italic" })
      if (/<w:u\b[^>]*\/>|<w:u\b[^>]*>/.test(pXml)) marks.push({ type: "underline" })
      content.push({ type: "text", text, ...(marks.length ? { marks } : {}) })
    }

    paragraphs.push({ type: "paragraph", content })
  }

  return paragraphs
}

function parseHeaderFooterPart(
  archive: DocxArchive,
  partName: string
): DocPageHeaderFooter | null {
  const xml = decodeXml(archive[`word/${partName}.xml`])
  if (!xml) return null

  const contentBlocks = xmlTextToParagraphs(xml)
  if (contentBlocks.length === 0) return null

  return {
    content: { type: "doc", content: contentBlocks },
    heightMm: 15,
  }
}

export type DocxHeaderFooterResult = Pick<
  DocPageSetup,
  "header" | "footer" | "headerFooterDifferentFirstPage"
>

/** Extract header/footer body content from DOCX archive. */
export async function extractDocxHeaderFooter(
  buffer: ArrayBuffer
): Promise<DocxHeaderFooterResult> {
  try {
    const { unzipSync } = await import("fflate")
    const archive = unzipSync(new Uint8Array(buffer)) as DocxArchive

    const header =
      parseHeaderFooterPart(archive, "header1") ??
      parseHeaderFooterPart(archive, "header2")
    const footer =
      parseHeaderFooterPart(archive, "footer1") ??
      parseHeaderFooterPart(archive, "footer2")

    const documentXml = decodeXml(archive["word/document.xml"])
    const differentFirst =
      documentXml != null &&
      /<w:titlePg\b/i.test(documentXml)

    return {
      header: header ?? null,
      footer: footer ?? null,
      headerFooterDifferentFirstPage: differentFirst,
    }
  } catch {
    return {
      header: null,
      footer: null,
      headerFooterDifferentFirstPage: false,
    }
  }
}