import TurndownService from "turndown";
import { gfm } from "turndown-plugin-gfm";
// Create a singleton TurndownService instance configured for Teams HTML
const turndownService = new TurndownService({
headingStyle: "atx",
hr: "---",
bulletListMarker: "-",
codeBlockStyle: "fenced",
emDelimiter: "*",
strongDelimiter: "**",
});
// Enable GitHub Flavored Markdown (tables, strikethrough, task lists)
turndownService.use(gfm);
// Custom rule: Teams @mentions — <at id="N">Name</at> → @Name
turndownService.addRule("teamsMention", {
filter: (node: HTMLElement) => node.nodeName === "AT",
replacement: (content: string) => `@${content}`,
});
// Custom rule: Teams attachments — <attachment id="N"></attachment> → remove
turndownService.addRule("teamsAttachment", {
filter: (node: HTMLElement) => node.nodeName === "ATTACHMENT",
replacement: () => "",
});
// Custom rule: Teams system events — <systemEventMessage/> → remove
turndownService.addRule("teamsSystemEvent", {
filter: (node: HTMLElement) =>
node.nodeName === "SYSTEMEVENTMESSAGE" ||
(node.textContent || "").trim() === "systemEventMessage/",
replacement: () => "",
});
/**
* Converts Teams HTML content to clean Markdown.
* Handles Teams-specific elements like @mentions, attachments, and system events.
*
* @param html - Raw HTML content from Microsoft Graph API
* @returns Clean Markdown string
*/
export function htmlToMarkdown(html: string): string {
// Handle empty/null content
if (!html || html.trim() === "") {
return "";
}
return turndownService.turndown(html).trim();
}
/**
* Formats message content based on the requested format.
*
* @param content - Raw message content from Graph API (HTML)
* @param format - "markdown" to convert HTML to Markdown, "raw" to return as-is
* @returns Formatted content string, or the original value if null/undefined
*/
export function formatMessageContent(
content: string | null | undefined,
format: "raw" | "markdown"
): string | null | undefined {
if (content == null) {
return content;
}
if (format === "raw") {
return content;
}
return htmlToMarkdown(content);
}
