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

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

export const FormController =  function FormController({errors, errorDispatch, children, onSubmit}){
  const initialState = {
    fields: {}
  }

  const reducer = (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}
  }

  // 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: false,
      touched: false
    }
  })

  // Create reducer
  const [state, dispatch] = useReducer(reducer, initialState)

  const submitForm = ev=>{
    if(ev) ev.preventDefault();

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

    onSubmit(fields)
  }

  const _children = React.Children.map(children, child => {
    if(child.type === Button && child.props.type.toLowerCase() === 'submit')
      return React.cloneElement(child, {
        enabled: !Object.values(state.fields).some(field=>!field.isValid),
        onClick: submitForm
      })
      
    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 onSubmit={onSubmit} className={styles.formContainer}>
      {_children}
    </form>
  )
}