package main

import (
	"fmt"
	"errors"
)

func main(){
	arrayExample := []interface{}{1, []interface{}{2, 3}, []interface{}{[]interface{}{4}}, []interface{}{5, []interface{}{6}}}
	result, _ := flattenArray(arrayExample)

	fmt.Println("Input array");
	fmt.Println(arrayExample);

	fmt.Println("Result array");
	fmt.Println(result);

}

func flattenArray(array []interface{}) (flattened []int , err error){
	currentFlattened := []int{}
	return flattenArrayRecursive(array, currentFlattened)
}

func flattenArrayRecursive(array interface{}, currentFlattened []int) (flattened []int , err error){
	switch copy := array.(type) {
	case int :
			currentFlattened = append(currentFlattened, copy)

	case []int :
			currentFlattened = append(currentFlattened, copy...)
	case []interface{}:
		for index := range copy {
			currentFlattened, err = flattenArrayRecursive(copy[index], currentFlattened)
			if err != nil {
				return nil, err
			}
		}
	default:
		return nil, errors.New("Unable to flatten array")
	}
	return currentFlattened, nil
}