// TODO: Enable exportDefaultFrom in Babel syntax
import React, { useReducer } from 'react'
import axios from 'axios'

import styles from './styles.module.css'
export const Input = require('./input.js').default
export const NumInput = require('./numInput.js').default
export const Button = require('./button.js').default

const errorReducer = (errors, action) => {
  switch (action.type) {
    case 'set_errors':
      const newErrors = {}
      for(const field of action.errors)
        newErrors[field.param] = field.msg
      return newErrors

    case 'clear_error':
      return {
        ...errors,
        [action.field]: undefined
      }

    default:
      return errors
  }
}

const formReducer = errorDispatch => (state, action)=>{
  let fields = {...state.fields}
  const prevField = state.fields[action.name]

  // If no value (onBlur), just mark touched and clear error
  if(action.value === undefined){
    errorDispatch({type: 'clear_error', field: action.name})

    return {
      fields: {
        ...fields,
        [action.name]: {
          ...prevField,
          touched: true,
          isValid: prevField.validate?prevField.validate(prevField.value, fields):true
        }
      }
    }
  }

  // Update currently changing field
  const updatedField = {
    ...prevField,
    value: action.value !== undefined ? action.value : prevField.value,
    isValid: prevField.validate?prevField.validate(action.value, fields):true
  }
  fields[action.name] = updatedField

  // Update other fields where the validate function takes whole state
  const fieldNames = Object.keys(fields)
  for(const name of fieldNames){
    if(name === action.name) continue

    const field = fields[name]

    if(field.validate && field.validate.length > 1)
      fields[name] = {
        ...field,
        isValid: field.validate(field.value, fields)
      }
  }

  return {fields}
}


export const FormController =  function FormController({children, className, url, method = 'POST', afterSubmit = ()=>null}){
  const initialState = {
    fields: {}
  }

  // Update initial state
  React.Children.forEach(children, child => {
    if(!child.props.name) return;

    initialState.fields[child.props.name] = {
      name: child.props.name,
      validate: child.props.validate,
      value: child.props.initialValue || "",
      isValid: child.props.validate
        ?(child.props.initialValue ? child.props.validate(child.props.initialValue): false)
        :true,
      touched: false
    }
  })

  // Create reducers
  const [errors, errorDispatch] = useReducer(errorReducer, {})
  const [state, dispatch] = useReducer(formReducer(errorDispatch), initialState)

  // Handle submitting form
  const handleSubmit = async (ev) => {
    if(ev) ev.preventDefault();

    const data = {}
    for(const name in state.fields){
      const field = state.fields[name]
      data[field.name] = field.value
    }

    if(url)
      try {
        const {data: response} = await axios({ method, url, data })
        return afterSubmit(response)
      } catch (err) {
        if(!err.response || err.response.status !== 422) throw err;

        return errorDispatch({
          type: 'set_errors',
          errors: err.response.data.errors
        })
      }

    afterSubmit(data)
  }

  // Map children
  const _children = React.Children.map(children, child => {
    if(child.type === Button && child.props.type.toLowerCase() === 'submit')
      return React.cloneElement(child, {
        // Allow enabled prop to disable, but not solely enable
        enabled: child.props.enabled !== false && !Object.values(state.fields).some(field=>!field.isValid),
        onClick: handleSubmit
      })

    const {name} = child.props;
    if(!name) return child;
    return React.cloneElement(child, {
      onChange: ev=>dispatch({name, value: ev.target.value}),
      onBlur: ev=>dispatch({name}),
      value: state.fields[name].value,
      isValid: state.fields[name].touched ? state.fields[name].isValid : true,
      error: errors ? errors[child.props.name] : undefined
    })
  })

  return (
    <form autoComplete="off" onSubmit={handleSubmit} className={styles.formContainer + (className?' ' + className:'')}>
      {_children}
    </form>
  )
}