import type { ClassGetterDecorator } from './decorator-fills'
import { computed } from '@vue/reactivity'
import { createDecoratorTypeChecker } from './adm'
import { createDecorator, type ReactiveDecorator } from './decorator'
import { getEffectScope } from './effectScope'
import { NOOP } from './utils'

const COMPUTED = 'computed'

export const isComputed = createDecoratorTypeChecker(
  (decorator: ReactiveDecorator) => decorator.decoratorType === COMPUTED,
)

function make(target: any, key: PropertyKey, descriptor: PropertyDescriptor) {
  /**
   * Cannot be used on static member.
   * Can only be used on getter.
   */
  if (typeof target === 'function')
    throw new Error('computed cannot be used on static member')

  if (
    descriptor == null
    || typeof descriptor !== 'object'
    || typeof descriptor.get !== 'function'
  ) {
    throw new Error('computed can only be used on getter')
  }

  const effectScope = getEffectScope(target)

  const value = effectScope.run(() =>
    computed(
      {
        get: descriptor.get!.bind(target),
        set: descriptor.set?.bind(target) ?? NOOP,
      },
    ),
  )!

  Object.defineProperty(target, key, {
    configurable: true,
    enumerable: false,
    get() {
      return value.value
    },
    set: descriptor.set && (val => (value.value = val)),
  })
}

export const Computed = createDecorator<ClassGetterDecorator>({
  decoratorType: COMPUTED,
  make,
})