Function diff

packages/effect/src/internal/differ/hashMapPatch.ts:117–149

(
  options: {
    readonly oldValue: HashMap.HashMap<Key, Value>
    readonly newValue: HashMap.HashMap<Key, Value>
    readonly differ: Differ.Differ<Value, Patch>
  }
)

/** @internal */
export const diff = <Key, Value, Patch>(
  options: {
    readonly oldValue: HashMap.HashMap<Key, Value>
    readonly newValue: HashMap.HashMap<Key, Value>
    readonly differ: Differ.Differ<Value, Patch>
  }
): Differ.Differ.HashMap.Patch<Key, Value, Patch> => {
  const [removed, patch] = HashMap.reduce(
    [options.oldValue, empty<Key, Value, Patch>()] as const,
    ([map, patch], newValue: Value, key: Key) => {
      const option = HashMap.get(key)(map)
      switch (option._tag) {
        case "Some": {
          const valuePatch = options.differ.diff(option.value, newValue)
          if (Equal.equals(valuePatch, options.differ.empty)) {
            return [HashMap.remove(key)(map), patch] as const
          }
          return [
            HashMap.remove(key)(map),
            combine<Key, Value, Patch>(makeUpdate(key, valuePatch))(patch)
          ] as const
        }
        case "None": {
          return [map, combine<Key, Value, Patch>(makeAdd(key, newValue))(patch)] as const
        }
      }
    }
  )(options.newValue)
  return HashMap.reduce(
    patch,
    (patch, _, key: Key) => combine<Key, Value, Patch>(makeRemove(key))(patch)
  )(removed)
}

/** @internal */
export const combine = Dual.dual<