export class HashTable {
  private readonly _table: any[];
  private _size: number;

  constructor() {
    this._table = new Array(257);
    this._size = 0;
  }

  _hash(key: string) {
    let hash = 0;
    for (let i = 0; i < key.length; i++) {
      hash += key.charCodeAt(i);
    }
    return hash % this._table.length;
  }

  add(key: string, value) {
    const index = this._hash(key);

    // Initialize bucket as array if it doesn't exist
    if (!this._table[index]) {
      this._table[index] = [];
    }

    // Check if key already exists in the bucket
    const bucket = this._table[index];
    for (let i = 0; i < bucket.length; i++) {
      if (bucket[i][0] === key) {
        // Key exists, update value
        bucket[i][1] = value;
        return;
      }
    }

    // Key doesn't exist, add new entry
    bucket.push([key, value]);
    this._size++;
  }

  get(key: string) {
    const index = this._hash(key);
    const bucket = this._table[index];

    if (!bucket) {
      return null;
    }

    // Search through the bucket for the matching key
    for (let i = 0; i < bucket.length; i++) {
      if (bucket[i][0] === key) {
        return bucket[i][1];
      }
    }

    return null;
  }

  set(key: string, value) {
    const index = this._hash(key);

    // Initialize bucket as array if it doesn't exist
    if (!this._table[index]) {
      this._table[index] = [];
    }

    const bucket = this._table[index];

    // Search for existing key
    for (let i = 0; i < bucket.length; i++) {
      if (bucket[i][0] === key) {
        // Key exists, update value
        bucket[i][1] = value;
        return;
      }
    }

    // Key doesn't exist, add new entry
    bucket.push([key, value]);
    this._size++;
  }

  exists(key) {
    const index = this._hash(key);
    const bucket = this._table[index];

    if (!bucket) {
      return false;
    }

    // Search through the bucket for the matching key
    for (let i = 0; i < bucket.length; i++) {
      if (bucket[i][0] === key) {
        return true;
      }
    }

    return false;
  }

  remove(key: string) {
    const index = this._hash(key);
    const bucket = this._table[index];

    if (!bucket) {
      return;
    }

    // Search for the key and remove it
    for (let i = 0; i < bucket.length; i++) {
      if (bucket[i][0] === key) {
        bucket.splice(i, 1);
        this._size--;

        // Clean up empty bucket
        if (bucket.length === 0) {
          this._table[index] = undefined;
        }
        return;
      }
    }
  }

  list() {
    const result: any[] = [];
    for (let i = 0; i < this._table.length; i++) {
      const bucket = this._table[i];
      if (bucket) {
        for (let j = 0; j < bucket.length; j++) {
          result.push({
            key: bucket[j][0],
            value: bucket[j][1],
          });
        }
      }
    }
    return result;
  }

  count() {
    return this._size;
  }
}