feat(markdown): render plebchan links as internal links, so the user doesn't have to leave the app

src/lib/utils/url-utils.ts

@@ -21,3 +21,120 @@ export const copyShareLinkToClipboard = async (subplebbitAddress: string, cid: s
   const shareLink = `https://pleb.bz/p/${subplebbitAddress}/c/${cid}?redirect=plebchan.app`;
   await copyToClipboard(shareLink);
 };
+
+const PLEBCHAN_HOSTNAMES = ['pleb.bz', 'plebchan.app', 'plebchan.eth.limo', 'plebchan.eth.link', 'plebchan.eth.sucks', 'plebchan.netlify.app'];
+
+// Check if a URL is a valid plebchan link that should be handled internally
+export const isPlebchanLink = (url: string): boolean => {
+  try {
+    const parsedUrl = new URL(url);
+    const hostname = parsedUrl.hostname.replace(/^www\./, '');
+
+    if (!PLEBCHAN_HOSTNAMES.includes(hostname)) {
+      return false;
+    }
+
+    // Check both pathname and hash for the route pattern
+    let routePath = parsedUrl.pathname;
+
+    // If there's a hash that starts with #/, use that as the route path
+    if (parsedUrl.hash && parsedUrl.hash.startsWith('#/')) {
+      routePath = parsedUrl.hash.substring(1); // Remove the # to get the path
+    }
+
+    // For pleb.bz, only support the exact sharelink format
+    if (hostname === 'pleb.bz') {
+      // Must match exactly: /p/{subplebbitAddress}/c/{cid}
+      // Allow redirect parameter since these are still valid internal links
+      return /^\/p\/[^/]+\/c\/[^/]+$/.test(routePath);
+    }
+
+    // For other plebchan hostnames, support:
+    // - /p/{subplebbitAddress}
+    // - /p/{subplebbitAddress}/c/{commentCid}
+    return /^\/p\/[^/]+(\/c\/[^/]+)?$/.test(routePath);
+  } catch {
+    return false;
+  }
+};
+
+// Transform a valid plebchan URL to an internal route
+export const transformPlebchanLinkToInternal = (url: string): string | null => {
+  if (!isPlebchanLink(url)) {
+    return null;
+  }
+
+  try {
+    const parsedUrl = new URL(url);
+
+    // Check if this is a hash-based route
+    if (parsedUrl.hash && parsedUrl.hash.startsWith('#/')) {
+      // Extract the route from the hash, preserving any query params within the hash
+      const hashPath = parsedUrl.hash.substring(1); // Remove the #
+      return hashPath;
+    }
+
+    // For regular pathname-based routes, remove redirect parameter from query string
+    const searchParams = new URLSearchParams(parsedUrl.search);
+    searchParams.delete('redirect'); // Remove redirect parameter for cleaner internal links
+
+    const cleanSearch = searchParams.toString();
+    const searchString = cleanSearch ? `?${cleanSearch}` : '';
+
+    return parsedUrl.pathname + searchString + parsedUrl.hash;
+  } catch {
+    return null;
+  }
+};
+
+// Check if a string is a valid IPNS public key (52 chars starting with 12D3KooW)
+const isValidIPNSKey = (str: string): boolean => {
+  return str.length === 52 && str.startsWith('12D3KooW');
+};
+
+// Check if a string is a valid domain (contains a dot)
+const isValidDomain = (str: string): boolean => {
+  return str.includes('.') && str.split('.').length >= 2 && str.split('.').every((part) => part.length > 0);
+};
+
+// Check if a plain text pattern is a valid plebchan subplebbit reference
+export const isValidSubplebbitPattern = (pattern: string): boolean => {
+  // Must start with "p/"
+  if (!pattern.startsWith('p/')) {
+    return false;
+  }
+
+  const pathPart = pattern.substring(2); // Remove "p/"
+
+  // Check if it's a post pattern: subplebbitAddress/c/cid
+  const postMatch = pathPart.match(/^([^/]+)\/c\/([^/]+)$/);
+  if (postMatch) {
+    const [, subplebbitAddress, cid] = postMatch;
+    // CID should be at least 10 characters (minimum reasonable CID length)
+    return (isValidDomain(subplebbitAddress) || isValidIPNSKey(subplebbitAddress)) && cid.length >= 10;
+  }
+
+  // Check if it's just a subplebbit pattern: subplebbitAddress
+  return isValidDomain(pathPart) || isValidIPNSKey(pathPart);
+};
+
+// Preprocess content to convert plain text plebchan patterns to markdown links
+export const preprocessPlebchanPatterns = (content: string): string => {
+  // Pattern to match "p/something" or "p/something/c/something"
+  // Negative lookbehind prevents matching patterns that are already part of URLs
+  const pattern = /(?<!https?:\/\/[^\s]*)\bp\/([a-zA-Z0-9\-.]+(?:\/c\/[a-zA-Z0-9]{10,100})?)[.,:;!?]*/g;
+
+  return content.replace(pattern, (match, capturedPath) => {
+    // Remove any trailing punctuation from the captured path
+    const cleanPath = capturedPath.replace(/[.,:;!?]+$/, '');
+    const fullPattern = `p/${cleanPath}`;
+
+    if (isValidSubplebbitPattern(fullPattern)) {
+      // Preserve trailing punctuation outside the link
+      const trailingPunctuation = match.slice(fullPattern.length);
+      return `[${fullPattern}](/${fullPattern})${trailingPunctuation}`;
+    }
+
+    return match;
+  });
+};