import { forget } from '@xylabs/forget'
import type { Log } from '@xylabs/log'
import { useUserEvents } from '@xylabs/react-pixel'
import { getLocalStorageObject, setLocalStorageObject } from '@xylabs/react-shared'
import type { ReactElement } from 'react'
import type React from 'react'

import type { ExperimentProps } from './Experiment.tsx'
import type { ExperimentsProps } from './ExperimentsProps.ts'
import type { ExperimentsData, OutcomesData } from './models/index.ts'
import { ExperimentsLocalStorageKey, OutcomesLocalStorageKey } from './models/index.ts'

const defaultLocalStorageKey = 'testData'

let experimentsTestData: { [index: string]: string } = {}
let outcomes: OutcomesData = {} // prevent multi-outcome

const saveOutcomes = () => {
  setLocalStorageObject(OutcomesLocalStorageKey, outcomes)
}

const saveExperimentsTestData = (key: string) => {
  const mergeData = (data: { [index: string]: string }, log?: Log): string => {
    const dataArray: string[] = []
    for (const key in data) {
      dataArray.push(`${key}-${data[key]}`)
    }
    log?.info('MergeData', dataArray.join('|'))
    return dataArray.join('|')
  }
  localStorage.setItem(key, mergeData(experimentsTestData))
}

const loadOutcomes = () => {
  outcomes = getLocalStorageObject(OutcomesLocalStorageKey)
}
const loadExperimentsTestData = (key: string) => {
  experimentsTestData
    = localStorage
      .getItem(key)
      ?.split('|')
      // eslint-disable-next-line unicorn/no-array-reduce
      .reduce(
        (acc, current) => {
          const data = current.split('-')
          acc[data[0]] = data[1]
          return acc
        },
        {} as { [index: string]: string },
      ) ?? {}
}

const missingKeyError = new Error('Experiment Elements must have Keys')

const makeChildrenArray = (children: ReactElement<ExperimentProps>[] | ReactElement<ExperimentProps>) => {
  return Array.isArray(children) ? (children as ReactElement<ExperimentProps>[]) : ([children] as ReactElement<ExperimentProps>[])
}

const buildLocalStorageKey = (localStorageProp: boolean | string) => {
  return (
    localStorageProp === true
      ? defaultLocalStorageKey
      : typeof localStorageProp === 'string'
        ? localStorageProp ?? defaultLocalStorageKey
        : ''
  )
}

const calcTotalWeight = (childList: ReactElement<ExperimentProps>[]) => {
  let totalWeight = 0
  for (const child of childList) {
    totalWeight += child.props.weight
  }
  return totalWeight
}

const saveExperimentDebugRanges = (name: string, totalWeight: number, childList: ReactElement<ExperimentProps>[]) => {
  const experiments = getLocalStorageObject<ExperimentsData>(ExperimentsLocalStorageKey) || {}
  experiments[name] = {
    totalWeight,
    variants: childList.map(child => ({
      name: child.key?.toString(),
      weight: child.props.weight,
    })),
  }
  setLocalStorageObject(ExperimentsLocalStorageKey, experiments)
}

const Experiments: React.FC<ExperimentsProps> = (props) => {
  const {
    name, children, localStorageProp = true,
  } = props
  const userEvents = useUserEvents()
  const localStorageKey = buildLocalStorageKey(localStorageProp)
  const childList = makeChildrenArray(children)
  const totalWeight = calcTotalWeight(childList)

  loadOutcomes()
  loadExperimentsTestData(localStorageKey)
  saveExperimentDebugRanges(name, totalWeight, childList)

  const firstTime = outcomes[name] === undefined
  let targetWeight = outcomes[name] ?? Math.random() * totalWeight
  outcomes[name] = targetWeight
  saveOutcomes()

  for (const child of childList) {
    targetWeight -= child.props.weight
    if (targetWeight > 0) continue
    if (!child.key) {
      throw missingKeyError
    }
    experimentsTestData[name] = child.key?.toString()
    if (firstTime) {
      if (localStorageProp !== false) {
        saveExperimentsTestData(localStorageKey)
      }
      if (userEvents) {
        forget(userEvents.testStarted({ name, variation: child.key }))
      }
    }

    return child
  }
  throw new Error('Experiment Choice Failed')
}

export { Experiments }