comparable-map.ts

comparable-map.ts

export interface ComparableMap<K = string, V = unknown> {
  keys: K[]
  get(key: K): V | undefined
  add(key: K, value: V): void
  remove(key: K): V | undefined
}

/**
 * We will use it where we can not use the default Map as the Map class do not allow custom compare function.
 *
 * @param equalityCheck Optional, a comparer to use
 */
export const getComparableMap = <K = string, V = unknown>(
  equalityCheck: (left: K, right: K) => boolean,
): ComparableMap<K, V> => {
  const keys: K[] = []

  const values: { [key: number]: V } = {}

  return {
    /**
     * Current set of keys.
     */
    keys,

    /**
     * Gets value for given key.
     *
     * @param key
     */
    get(key: K): V | undefined {
      const index = keys.findIndex(currentKey => equalityCheck(currentKey, key))

      if (index === -1) {
        return undefined
      }

      return values[index]
    },

    /**
     * Adds the given key and value.
     *
     * @param key
     * @param value
     */
    add(key: K, value: V) {
      const index = keys.findIndex(currentKey => equalityCheck(currentKey, key))

      if (index === -1) {
        keys.push(key)
        values[keys.length - 1] = value
      }
    },

    /**
     * Removes the given key and returns the value object if key was found.
     *
     * @param key
     */
    remove(key: K): V | undefined {
      const index = keys.findIndex(currentKey => equalityCheck(currentKey, key))

      if (index === -1) {
        return undefined
      }

      delete keys[index]

      const value = values[index]

      delete values[index]

      return value
    },
  }
}