@nyteshade/lattice-legacy/es6/decorators/Memoize.js

OO Underpinnings for ease of GraphQL Implementation

// @flow

const cache = new Map()

function isValidKey(): boolean {
  return false
}

export function Memoize(
  target: mixed,
  prop: string,
  descriptor: Object
): ?Object {
  // This won't make sense if we are a class prop; if so, bug out
  if (typeof descriptor.initializer) return descriptor

  // If we have only a setter, we can skip out
  if (descriptor.set && !descriptor.get && !descriptor.value) return descriptor

  // If we do not have a get function and value is not a function, jet
  if (
    typeof descriptor.value !== 'function'
    && !descriptor.get
  ) {
    return descriptor
  }

  // Our passed arguments and function make our key
  const key = {
    target,
    prop,
    descriptor,

    func: descriptor.get || descriptor.value,
    args: [],
    validate: isValidKey
  }

  // In order to determine if we have a match on key we must allow execution
  // of a wrapper function that does so
  const wrapper = (...args) => {
    key.args = args;

    // TODO check for cache hit by comparing objects
    // return the cache if a hit or run the function and store otherwise
    if (key.validate()) {
      return cache.get(key)
    }
    else {
      let results

      try {
        let results = key.func.apply(target, key.args)
        cache.set(key, results)
      }
      catch (error) {
        results = error;
      }
    }
  }

  if (descriptor.get) {
    descriptor.get = wrapper
  }
  else {
    descriptor.value = wrapper
  }

  return descriptor
}