import md5 from 'md5'
import { forEach } from 'lodash'

export type AddChange = {
  type: 'add'
  key: string
  value: any
}

export type ModifyChange = {
  type: 'modify'
  key: string
  value: any
  oldValue: any
}

export type RemovedChange = {
  type: 'remove'
  key: string
  oldValue: any
}

export type Change = AddChange | ModifyChange | RemovedChange

export const computeHash = (value: any) => {
  if (value === null) {
    return 'null'
  }
  if (value === undefined) {
    return 'undefined'
  }
  let str = value

  try {
    if (typeof str === 'object') {
      str = JSON.stringify(value)
    } else {
      str = typeof value + '::' + value.toString()
    }
  } catch (error) {
    str = error.message + '::' + error.stack
  }

  return md5(str)
}

export const diffObjectShallow = (
  objectA: object,
  objectB: object,
  computeHashFn = computeHash,
) => {
  const changes: Change[] = []
  const docsMapACopy = { ...objectA }

  forEach(objectB, (valueB, key) => {
    const valueA = docsMapACopy[key]
    if (valueA) {
      delete docsMapACopy[key]
      const hashA = computeHashFn(valueA)
      const hashB = computeHashFn(valueB)
      if (hashA === hashB) {
        return
      }
      return changes.push({
        type: 'modify',
        key,
        oldValue: valueA,
        value: valueB,
      })
    }
    changes.push({
      type: 'add',
      key,
      value: valueB,
    })
  })

  forEach(docsMapACopy, (value, key) => {
    changes.push({
      type: 'remove',
      key,
      oldValue: value,
    })
  })

  return changes
}