yaak/src-web/lib/contentType.ts

import MimeType from "whatwg-mimetype";
import type { EditorProps } from "../components/core/Editor/Editor";

export function languageFromContentType(
  contentType: string | null,
  content: string | null = null,
): EditorProps["language"] {
  const justContentType = contentType?.split(";")[0] ?? contentType ?? "";
  if (justContentType.includes("json")) {
    return "json";
  }
  if (justContentType.includes("xml")) {
    return "xml";
  }
  if (justContentType.includes("html")) {
    const detected = languageFromContent(content);
    if (detected === "xml") {
      // If it's detected as XML, but is already HTML, don't change it
      return "html";
    }
    return detected;
  }
  if (justContentType.includes("javascript")) {
    // Sometimes `application/javascript` returns JSON, so try detecting that
    return languageFromContent(content, "javascript");
  }
  if (justContentType.includes("markdown")) {
    return "markdown";
  }

  return languageFromContent(content, "text");
}

export function languageFromContent(
  content: string | null,
  fallback?: EditorProps["language"],
): EditorProps["language"] {
  if (content == null) return "text";

  const firstBytes = content.slice(0, 20).trim();

  if (firstBytes.startsWith("{") || firstBytes.startsWith("[")) {
    return "json";
  }
  if (
    firstBytes.toLowerCase().startsWith("<!doctype") ||
    firstBytes.toLowerCase().startsWith("<html")
  ) {
    return "html";
  }
  if (firstBytes.startsWith("<")) {
    return "xml";
  }

  return fallback;
}

export function isJSON(content: string | null | undefined): boolean {
  if (typeof content !== "string") return false;

  try {
    JSON.parse(content);
    return true;
  } catch {
    return false;
  }
}

export function isProbablyTextContentType(contentType: string | null): boolean {
  if (contentType == null) return false;

  const mimeType = getMimeTypeFromContentType(contentType).essence;
  const normalized = mimeType.toLowerCase();

  // Check if it starts with "text/"
  if (normalized.startsWith("text/")) {
    return true;
  }

  // Common text mimetypes and suffixes
  return [
    "application/json",
    "application/xml",
    "application/javascript",
    "application/yaml",
    "+json",
    "+xml",
    "+yaml",
    "+text",
  ].some((textType) => normalized === textType || normalized.endsWith(textType));
}

export function getMimeTypeFromContentType(contentType: string): MimeType {
  try {
    return new MimeType(contentType);
  } catch {
    return new MimeType("text/plain");
  }
}