feat(routing): add hooks and utilities for directory-based board routing

src/hooks/use-resolved-subplebbit-address.ts

@@ -0,0 +1,48 @@
+import { useMemo } from 'react';
+import { useParams } from 'react-router-dom';
+import { useDefaultSubplebbits } from './use-default-subplebbits';
+import { getSubplebbitAddress, getBoardPath } from '../lib/utils/route-utils';
+
+/**
+ * Hook to resolve boardIdentifier from URL params to subplebbitAddress
+ * Handles both directory codes (e.g., "biz") and full addresses (e.g., "someboard.eth")
+ *
+ * Performance: Uses useMemo to avoid recalculating when params/defaultSubplebbits haven't changed.
+ * The defaultSubplebbits reference is stable (from cache) after initial load, so memoization works effectively.
+ */
+export const useResolvedSubplebbitAddress = (): string | undefined => {
+  const params = useParams();
+  const defaultSubplebbits = useDefaultSubplebbits();
+
+  // Try boardIdentifier first (new format), then subplebbitAddress (old format for backward compatibility)
+  const boardIdentifier = params.boardIdentifier || params.subplebbitAddress;
+
+  return useMemo(() => {
+    if (!boardIdentifier) {
+      return undefined;
+    }
+
+    // Resolve directory code to address if needed
+    // getSubplebbitAddress uses internal caching, so this is efficient
+    return getSubplebbitAddress(boardIdentifier, defaultSubplebbits);
+  }, [boardIdentifier, defaultSubplebbits]);
+};
+
+/**
+ * Hook to get the board path (directory code or address) for use in links
+ *
+ * Performance: Uses useMemo to avoid recalculating when subplebbitAddress/defaultSubplebbits haven't changed.
+ * The defaultSubplebbits reference is stable (from cache) after initial load, so memoization works effectively.
+ */
+export const useBoardPath = (subplebbitAddress: string | undefined): string | undefined => {
+  const defaultSubplebbits = useDefaultSubplebbits();
+
+  return useMemo(() => {
+    if (!subplebbitAddress) {
+      return undefined;
+    }
+
+    // getBoardPath uses internal caching, so this is efficient
+    return getBoardPath(subplebbitAddress, defaultSubplebbits);
+  }, [subplebbitAddress, defaultSubplebbits]);
+};

src/lib/utils/route-utils.ts

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+import { MultisubSubplebbit } from '../../hooks/use-default-subplebbits';
+
+/**
+ * Extract directory short code from title (e.g., "/biz/ - Business & Finance" -> "biz")
+ */
+export const extractDirectoryFromTitle = (title: string): string | null => {
+  const match = title.match(/^\/([^/]+)\//);
+  return match ? match[1] : null;
+};
+
+// Cache for maps to avoid recreating them on every call
+let cachedSubplebbits: MultisubSubplebbit[] | null = null;
+let cachedDirectoryToAddressMap: Map<string, string> | null = null;
+let cachedAddressToDirectoryMap: Map<string, string> | null = null;
+
+/**
+ * Create a map from directory codes to subplebbit addresses
+ * Uses caching to avoid recreating the map when subplebbits array hasn't changed
+ */
+export const getDirectoryToAddressMap = (subplebbits: MultisubSubplebbit[]): Map<string, string> => {
+  // Check if we can use cached map (same array reference)
+  if (cachedDirectoryToAddressMap && cachedSubplebbits === subplebbits) {
+    return cachedDirectoryToAddressMap;
+  }
+
+  const map = new Map<string, string>();
+  for (const subplebbit of subplebbits) {
+    if (subplebbit.title) {
+      const directory = extractDirectoryFromTitle(subplebbit.title);
+      if (directory && subplebbit.address) {
+        map.set(directory, subplebbit.address);
+      }
+    }
+  }
+
+  // Cache the map and array reference
+  cachedDirectoryToAddressMap = map;
+  cachedSubplebbits = subplebbits;
+  return map;
+};
+
+/**
+ * Create a map from subplebbit addresses to directory codes
+ * Uses caching to avoid recreating the map when subplebbits array hasn't changed
+ */
+export const getAddressToDirectoryMap = (subplebbits: MultisubSubplebbit[]): Map<string, string> => {
+  // Check if we can use cached map (same array reference)
+  if (cachedAddressToDirectoryMap && cachedSubplebbits === subplebbits) {
+    return cachedAddressToDirectoryMap;
+  }
+
+  const map = new Map<string, string>();
+  for (const subplebbit of subplebbits) {
+    if (subplebbit.title && subplebbit.address) {
+      const directory = extractDirectoryFromTitle(subplebbit.title);
+      if (directory) {
+        map.set(subplebbit.address, directory);
+      }
+    }
+  }
+
+  // Cache the map and array reference
+  cachedAddressToDirectoryMap = map;
+  cachedSubplebbits = subplebbits;
+  return map;
+};
+
+/**
+ * Convert subplebbit address to URL path (directory code if available, otherwise full address)
+ */
+export const getBoardPath = (subplebbitAddress: string, subplebbits: MultisubSubplebbit[]): string => {
+  const addressToDirectory = getAddressToDirectoryMap(subplebbits);
+  const directory = addressToDirectory.get(subplebbitAddress);
+  return directory || subplebbitAddress;
+};
+
+/**
+ * Convert URL path (directory code or address) to subplebbit address
+ */
+export const getSubplebbitAddress = (boardIdentifier: string, subplebbits: MultisubSubplebbit[]): string => {
+  const directoryToAddress = getDirectoryToAddressMap(subplebbits);
+
+  // Check if it's a directory code
+  const address = directoryToAddress.get(boardIdentifier);
+  if (address) {
+    return address;
+  }
+
+  // Otherwise, assume it's already an address
+  return boardIdentifier;
+};
+
+/**
+ * Check if an identifier is a directory short code
+ */
+export const isDirectoryBoard = (identifier: string, subplebbits: MultisubSubplebbit[]): boolean => {
+  const directoryToAddress = getDirectoryToAddressMap(subplebbits);
+  return directoryToAddress.has(identifier);
+};