import MarkdownIt from "markdown-it";

export type WidgetMessageAssetPayload = {
  assetId: string;
  filename?: string;
  fileSize?: number;
  mimeType?: string;
  url?: string;
};

const messageMarkdown = new MarkdownIt({
  html: false,
  linkify: true,
  breaks: true,
});

export function parseMessageAssetPayload(
  payload?: string,
): WidgetMessageAssetPayload | null {
  if (!payload?.trim()) {
    return null;
  }
  try {
    const parsed = JSON.parse(payload) as WidgetMessageAssetPayload;
    if (!parsed?.assetId?.trim()) {
      return null;
    }
    return parsed;
  } catch {
    return null;
  }
}

export function renderMessageHTML(message: {
  messageType: string;
  content: string;
  payload?: string;
}) {
  if (message.messageType === "html") {
    return message.content;
  }

  const asset = parseMessageAssetPayload(message.payload);
  if (message.messageType === "image") {
    if (asset?.url) {
      return `<p><img src="${escapeHTMLAttr(asset.url)}" alt="${escapeHTMLAttr(
        asset.filename || "image",
      )}"></p>`;
    }
    return "<p>[图片]</p>";
  }

  if (message.messageType === "attachment") {
    if (asset?.url) {
      const title = escapeHTML(asset.filename || message.content || "附件");
      const meta = formatFileSize(asset.fileSize ?? 0);
      const metaHTML = meta
        ? `<div class="im-attachment-meta">${escapeHTML(meta)}</div>`
        : "";
      return `<div class="im-attachment"><a href="${escapeHTMLAttr(
        asset.url,
      )}" target="_blank" rel="noreferrer" download="${escapeHTMLAttr(
        asset.filename || "",
      )}" class="im-attachment-link"><span class="im-attachment-icon" aria-hidden="true">${getAttachmentIconSVG()}</span><span class="im-attachment-content"><span class="im-attachment-title">${title}</span>${metaHTML}</span></a></div>`;
    }
    return `<p>${escapeHTML(message.content || "[附件]")}</p>`;
  }

  return renderTextMessageHTML(message.content || "");
}

export function summarizeMessage(message: {
  messageType: string;
  content: string;
  payload?: string;
}) {
  if (message.messageType === "image") {
    return "[图片]";
  }
  if (message.messageType === "attachment") {
    const asset = parseMessageAssetPayload(message.payload);
    return asset?.filename?.trim() ? `[附件] ${asset.filename.trim()}` : "[附件]";
  }
  if (message.messageType === "html") {
    const text = extractTextFromHTML(message.content);
    if (text.trim()) {
      return text.substring(0, 100);
    }
    if (message.content.includes("<img")) {
      return "[图片]";
    }
    return "[消息]";
  }
  return message.content?.substring(0, 100) || "[消息]";
}

function formatFileSize(size: number) {
  if (!Number.isFinite(size) || size <= 0) {
    return "";
  }
  const units = ["B", "KB", "MB", "GB"];
  let value = size;
  let index = 0;
  while (value >= 1024 && index < units.length - 1) {
    value /= 1024;
    index += 1;
  }
  const digits = value >= 10 || index === 0 ? 0 : 1;
  return `${value.toFixed(digits)} ${units[index]}`;
}

function extractTextFromHTML(html: string): string {
  if (typeof document === "undefined") {
    return "";
  }
  const div = document.createElement("div");
  div.innerHTML = html;
  return div.textContent || div.innerText || "";
}

function renderTextMessageHTML(content: string) {
  const value = content.trim();
  if (!value) {
    return "<p></p>";
  }
  return messageMarkdown.render(value);
}

function escapeHTML(value: string) {
  return value
    .replaceAll("&", "&amp;")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
    .replaceAll('"', "&quot;")
    .replaceAll("'", "&#39;")
    .replaceAll("\n", "<br>");
}

function escapeHTMLAttr(value: string) {
  return value
    .replaceAll("&", "&amp;")
    .replaceAll('"', "&quot;")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;");
}

function getAttachmentIconSVG() {
  return `<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round"><path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"></path><path d="M14 2v6h6"></path><path d="M9 15h6"></path><path d="M9 11h2"></path></svg>`;
}