SukkaSurge/Build/lib/trie.ts

/**
 * Suffix Trie based on Mnemonist Trie
 */

// import { Trie } from 'mnemonist';

export const SENTINEL = Symbol('SENTINEL');
const PARENT = Symbol('Parent Node');

type TrieNode = {
  [SENTINEL]: boolean,
  [PARENT]: TrieNode | null,
  [Bun.inspect.custom]: () => string
} & Map<string, TrieNode>;

const deepTrieNodeToJSON = (node: TrieNode) => {
  const obj: Record<string, any> = {};
  if (node[SENTINEL]) {
    obj['[start]'] = node[SENTINEL];
  }
  node.forEach((value, key) => {
    obj[key] = deepTrieNodeToJSON(value);
  });
  return obj;
};

function trieNodeInspectCustom(this: TrieNode) {
  return JSON.stringify(deepTrieNodeToJSON(this), null, 2);
}

const createNode = (parent: TrieNode | null = null): TrieNode => {
  const node = new Map<string, TrieNode>() as TrieNode;
  node[SENTINEL] = false;
  node[PARENT] = parent;
  node[Bun.inspect.custom] = trieNodeInspectCustom;
  return node;
};

const hostnameToTokens = (hostname: string): string[] => {
  let buf = '';
  const tokens: string[] = [];
  for (let i = 0, l = hostname.length; i < l; i++) {
    const c = hostname[i];
    if (c === '.') {
      if (buf) {
        tokens.push(buf, /* . */ c);
        buf = '';
      } else {
        tokens.push(/* . */ c);
      }
    } else {
      buf += c;
    }
  }
  if (buf) {
    tokens.push(buf);
  }
  return tokens;
};

export const createTrie = (from?: string[] | Set<string> | null, hostnameMode = false, smolTree = false) => {
  let size = 0;
  const root: TrieNode = createNode();

  const isHostnameMode = (_token: string | string[]): _token is string[] => hostnameMode;

  const suffixToTokens = hostnameMode
    ? hostnameToTokens
    : (suffix: string) => suffix;

  /**
   * Method used to add the given prefix to the trie.
   */
  const add = (suffix: string): void => {
    let node: TrieNode = root;
    let token: string;

    const tokens = suffixToTokens(suffix);

    for (let i = tokens.length - 1; i >= 0; i--) {
      token = tokens[i];

      if (node.has(token)) {
        node = node.get(token)!;

        // During the adding of `[start]blog.skk.moe` and find out that there is a `[start].skk.moe` in the trie
        // Dedupe the covered subdomain by skipping
        if (smolTree && (node.get('.')?.[SENTINEL])) {
          return;
        }
      } else {
        const newNode = createNode(node);
        node.set(token, newNode);
        node = newNode;
      }
    }

    // If we are in smolTree mode, we need to do something at the end of the loop
    if (smolTree) {
      if (tokens[0] === '.') {
        // Trying to add `[start].sub.example.com` where there is already a `[start]blog.sub.example.com` in the trie

        const parent = node[PARENT]!;

        // Make sure parent `[start]sub.example.com` (without dot) is removed (SETINEL to false)
        parent[SENTINEL] = false;

        // Removing the rest of the parent's child nodes by disconnecting the old one and creating a new node
        const newNode = createNode(node);
        // The SENTINEL of this newNode will be set to true at the end of the function, so we don't need to set it here

        parent.set('.', newNode);

        // Now the real leaf-est node is the new node, change the pointer to it
        node = newNode;
      }

      if (node.get('.')?.[SENTINEL] === true) {
        // Trying to add `example.com` when there is already a `.example.com` in the trie
        // No need to increment size and set SENTINEL to true (skip this "new" item)
        return;
      }
    }

    // Do we need to increase size?
    if (!node[SENTINEL]) {
      size++;
    }
    node[SENTINEL] = true;
  };

  /**
   * @param {string} $suffix
   */
  const contains = (suffix: string): boolean => {
    let node: TrieNode | undefined = root;
    let token: string;

    const tokens = suffixToTokens(suffix);

    for (let i = tokens.length - 1; i >= 0; i--) {
      token = tokens[i];

      node = node.get(token);
      if (!node) return false;
    }

    return true;
  };

  /**
   * Method used to retrieve every item in the trie with the given prefix.
   */
  const find = (inputSuffix: string, /** @default true */ includeEqualWithSuffix = true): string[] => {
    if (smolTree) {
      throw new Error('A Trie with smolTree enabled cannot perform find!');
    }

    let node: TrieNode | undefined = root;
    let token: string;

    const inputTokens = suffixToTokens(inputSuffix);

    for (let i = inputTokens.length - 1; i >= 0; i--) {
      token = inputTokens[i];

      if (hostnameMode && token === '') {
        break;
      }

      node = node.get(token);
      if (!node) return [];
    }

    const matches: Array<string | string[]> = [];

    // Performing DFS from prefix
    const nodeStack: TrieNode[] = [node];
    const suffixStack: Array<string | string[]> = [inputTokens];

    do {
      const suffix: string | string[] = suffixStack.pop()!;
      node = nodeStack.pop()!;

      if (node[SENTINEL]) {
        if (includeEqualWithSuffix) {
          matches.push(suffix);
        } else if (isHostnameMode(suffix)) {
          if (suffix.some((t, i) => t !== inputTokens[i])) {
            matches.push(suffix);
          }
        } else if (suffix !== inputTokens) {
          matches.push(suffix);
        }
      }

      node.forEach((childNode, k) => {
        nodeStack.push(childNode);

        if (isHostnameMode(suffix)) {
          suffixStack.push([k, ...suffix]);
        } else {
          suffixStack.push(k + suffix);
        }
      });
    } while (nodeStack.length);

    return hostnameMode ? matches.map((m) => (m as string[]).join('')) : matches as string[];
  };

  /**
   * Works like trie.find, but instead of returning the matches as an array, it removes them from the given set in-place.
   */
  const substractSetInPlaceFromFound = (inputSuffix: string, set: Set<string>) => {
    if (smolTree) {
      throw new Error('A Trie with smolTree enabled cannot perform substractSetInPlaceFromFound!');
    }

    let node: TrieNode | undefined = root;
    let token: string;

    const inputTokens = suffixToTokens(inputSuffix);

    // Find the leaf-est node, and early return if not any
    for (let i = inputTokens.length - 1; i >= 0; i--) {
      token = inputTokens[i];

      node = node.get(token);
      if (!node) return;
    }

    // Performing DFS from prefix
    const nodeStack: TrieNode[] = [node];
    const suffixStack: Array<string | string[]> = [inputTokens];

    do {
      const suffix = suffixStack.pop()!;
      node = nodeStack.pop()!;

      if (node[SENTINEL]) {
        // found match, delete it from set
        if (isHostnameMode(suffix)) {
          set.delete(suffix.join(''));
        } else if (suffix !== inputTokens) {
          set.delete(suffix);
        }
      }

      node.forEach((childNode, k) => {
        nodeStack.push(childNode);
        if (isHostnameMode(suffix)) {
          const stack = [k, ...suffix];
          suffixStack.push(stack);
        } else {
          suffixStack.push(k + suffix);
        }
      });
    } while (nodeStack.length);
  };

  /**
   * Method used to delete a prefix from the trie.
   */
  const remove = (suffix: string): boolean => {
    let node: TrieNode | undefined = root;
    let toPrune: TrieNode | null = null;
    let tokenToPrune: string | null = null;
    let parent: TrieNode = node;
    let token: string;

    const suffixTokens = suffixToTokens(suffix);

    for (let i = suffixTokens.length - 1; i >= 0; i--) {
      token = suffixTokens[i];

      parent = node;
      node = node.get(token);

      if (!node) return false;

      // Keeping track of a potential branch to prune

      // Even if the node size is 1, but the single child is ".", we should retain the branch
      // Since the "." could be special if it is the leaf-est node
      const onlyChild = node.size < 2 && (!hostnameMode || !node.has('.'));

      if (toPrune != null) { // the top-est branch that could potentially being pruned
        if (!onlyChild) {
          // The branch has moew than single child, retain the branch.
          // And we need to abort prune the parent, so we set it to null
          toPrune = null;
          tokenToPrune = null;
        }
      } else if (onlyChild) {
        // There is only one token child, or no child at all, we can prune it safely
        // It is now the top-est branch that could potentially being pruned
        toPrune = parent;
        tokenToPrune = token;
      }
    }

    if (!node[SENTINEL]) return false;

    size--;

    if (tokenToPrune && toPrune) {
      toPrune.delete(tokenToPrune);
    } else {
      node[SENTINEL] = false;
    }

    return true;
  };

  /**
 * Method used to assert whether the given prefix exists in the Trie.
 */
  const has = (suffix: string): boolean => {
    let node: TrieNode = root;

    const tokens = suffixToTokens(suffix);

    for (let i = tokens.length - 1; i >= 0; i--) {
      const token = tokens[i];

      if (!node.has(token)) {
        return false;
      }

      node = node.get(token)!;
    }

    return node[SENTINEL];
  };

  const dump = () => {
    const nodeStack: TrieNode[] = [];
    const suffixStack: Array<string | string[]> = [];

    nodeStack.push(root);
    // Resolving initial string (begin the start of the stack)
    suffixStack.push(hostnameMode ? [] : '');

    const results: string[] = [];

    let node: TrieNode;

    do {
      node = nodeStack.pop()!;
      const suffix = suffixStack.pop()!;

      node.forEach((childNode, k) => {
        // Pushing the child node to the stack for next iteration of DFS
        nodeStack.push(childNode);

        suffixStack.push(isHostnameMode(suffix) ? [k, ...suffix] : k + suffix);
      });

      // If the node is a sentinel, we push the suffix to the results
      if (node[SENTINEL]) {
        results.push(isHostnameMode(suffix) ? suffix.join('') : suffix);
      }
    } while (nodeStack.length);

    return results;
  };

  const whitelist = (suffix: string) => {
    if (!hostnameMode && !smolTree) {
      throw new Error('whitelist method is only available in hostname mode or smolTree mode.');
    }

    let node: TrieNode | undefined = root;

    let toPrune: TrieNode | null = null;
    let tokenToPrune: string | null = null;
    let parent: TrieNode = node;

    const tokens = suffixToTokens(suffix);
    let token: string;

    for (let i = tokens.length - 1; i >= 0; i--) {
      token = tokens[i];

      parent = node;
      node = node.get(token);

      if (!node) return;

      // Keeping track of a potential branch to prune

      // Even if the node size is 1, but the single child is ".", we should retain the branch
      // Since the "." could be special if it is the leaf-est node
      const onlyChild = node.size < 2 && !node.has('.');
      // const onlyChild = node.size < 2 && (!hostnameMode || !node.has('.'));

      if (toPrune !== null) { // the top-est branch that could potentially being pruned
        if (!onlyChild) {
          // The branch has moew than single child, retain the branch.
          // And we need to abort prune the parent, so we set it to null
          toPrune = null;
          tokenToPrune = null;
        }
      } else if (onlyChild) {
        // There is only one token child, or no child at all, we can prune it safely
        // It is now the top-est branch that could potentially being pruned
        toPrune = parent;
        tokenToPrune = token;
      }
    }

    // Trying to whitelist `[start].sub.example.com` where there is already a `[start]blog.sub.example.com` in the trie
    if (tokens[0] === '.') {
      // If there is a `[start]sub.example.com` here, remove it
      parent[SENTINEL] = false;
      // Removing all the child nodes by disconnecting "."
      parent.delete('.');
    }

    // Trying to whitelist `example.com` when there is already a `.example.com` in the trie
    const dotNode = node.get('.');
    if (dotNode?.[SENTINEL] === true) {
      dotNode[SENTINEL] = false;
    }

    // if (!node[SENTINEL]) return;

    if (tokenToPrune && toPrune) {
      toPrune.delete(tokenToPrune);
    } else {
      node[SENTINEL] = false;
    }
  };

  if (Array.isArray(from)) {
    for (let i = 0, l = from.length; i < l; i++) {
      add(from[i]);
    }
  } else if (from) {
    from.forEach(add);
  }

  return {
    add,
    contains,
    find,
    substractSetInPlaceFromFound,
    remove,
    delete: remove,
    has,
    dump,
    get size() {
      if (smolTree) {
        throw new Error('A Trie with smolTree enabled cannot have correct size!');
      }
      return size;
    },
    get root() {
      return root;
    },
    whitelist,

    [Bun.inspect.custom]: (depth: number) => JSON.stringify(deepTrieNodeToJSON(root), null, 2).split('\n').map((line) => ' '.repeat(depth) + line).join('\n'),

    hostnameMode,
    smolTree
  };
};

export type Trie = ReturnType<typeof createTrie>;

export default createTrie;