import path from "node:path";
import type {
  AttachmentAnalysisState,
  AttachmentKind,
  MessageAttachment,
} from "@/lib/boss-data";

const LARGE_ATTACHMENT_THRESHOLD_BYTES = 20 * 1024 * 1024;
const MAX_ATTACHMENT_TEXT_EXCERPT_CHARS = 12_000;

function extensionOf(fileName: string) {
  return path.extname(fileName).toLowerCase();
}

export function sanitizeFileName(fileName: string) {
  const normalized = path
    .basename(fileName || "attachment")
    .normalize("NFKC")
    .replace(/[\u0000-\u001f\u007f]/g, "")
    .replace(/[<>:"|?*]+/g, "-")
    .replace(/[\\/]+/g, "-")
    .replace(/\s+/g, " ")
    .trim()
    .replace(/^\.+/, "");
  return normalized || "attachment";
}

export function detectAttachmentKind(fileName: string, mimeType: string): AttachmentKind {
  const normalizedMime = (mimeType || "").toLowerCase();
  const ext = extensionOf(fileName);

  if (normalizedMime.startsWith("image/")) return "image";
  if (normalizedMime.startsWith("video/")) return "video";
  if (normalizedMime === "application/pdf" || ext === ".pdf") return "pdf";
  if (normalizedMime.startsWith("text/")) return "text";
  if (
    normalizedMime.includes("officedocument") ||
    normalizedMime.includes("msword") ||
    normalizedMime.includes("spreadsheet") ||
    normalizedMime.includes("presentation") ||
    [".doc", ".docx", ".xls", ".xlsx", ".ppt", ".pptx", ".odt", ".ods", ".odp"].includes(ext)
  ) {
    return "office";
  }
  if (
    [".txt", ".md", ".csv", ".log", ".json", ".yaml", ".yml", ".xml", ".html", ".htm"].includes(
      ext,
    )
  ) {
    return "text";
  }
  return "binary";
}

export function resolveAttachmentAnalysisState(
  kind: AttachmentKind,
  fileSizeBytes: number,
): AttachmentAnalysisState {
  if (fileSizeBytes > LARGE_ATTACHMENT_THRESHOLD_BYTES) {
    return "ready_manual";
  }
  if (kind === "image" || kind === "pdf" || kind === "text") {
    return "queued_auto";
  }
  return "ready_manual";
}

export function buildAttachmentDownloadHeaders(attachment: MessageAttachment) {
  const safeName = sanitizeFileName(attachment.fileName);
  const encodedName = encodeURIComponent(safeName);
  return {
    "Content-Type": attachment.mimeType || "application/octet-stream",
    "Content-Disposition": `inline; filename="${safeName}"; filename*=UTF-8''${encodedName}`,
    "Cache-Control": "private, no-store, max-age=0",
    "X-Content-Type-Options": "nosniff",
  };
}

export function canExtractAttachmentText(attachment: Pick<MessageAttachment, "attachmentKind" | "mimeType">) {
  return (
    attachment.attachmentKind === "text" ||
    (attachment.mimeType || "").toLowerCase().startsWith("text/")
  );
}

export function extractAttachmentTextExcerpt(buffer: Buffer | Uint8Array) {
  const normalized = Buffer.from(buffer)
    .toString("utf8")
    .replace(/\u0000/g, "")
    .trim();
  if (!normalized) {
    return "";
  }
  if (normalized.length <= MAX_ATTACHMENT_TEXT_EXCERPT_CHARS) {
    return normalized;
  }
  return `${normalized.slice(0, MAX_ATTACHMENT_TEXT_EXCERPT_CHARS)}\n...[已截断]`;
}