file.groovy

import groovy.json.JsonSlurper 
import groovy.json.JsonOutput 


def formatJson(json) {
    def obj = new JsonSlurper().parseText(json) 
    def map = [:]

    if(obj instanceof Map) {
        obj.each { 
            def tmp = [:]
            def tmpKey = "$it.key"
            if(tmpKey.contains(".")) {
                def parent_key = tmpKey.substring(0, tmpKey.indexOf("."))
                def sub_key = tmpKey.substring(tmpKey.indexOf(".") + 1)
                // if(!map.containsKey(parent_key)) {
                tmp = formatJson(JsonOutput.toJson(["$sub_key" : it.value]))
                if(!map.containsKey(parent_key))
                    map.put(parent_key, tmp)
                else {
                    prev_val = map.get(parent_key)
                    tmp.each {                       
                        if(prev_val.containsKey(it.key)) {
                            sub_map = prev_val.get(it.key)
                            another_map = tmp.get(it.key)
                            sub_map = process_nested(another_map, sub_map)
                            prev_val.put(it.key, sub_map)
                        }
                        else
                        prev_val.put(it.key, it.value)
                    }
                    map.put(parent_key, prev_val)
                }
                
            } else {
                map.put(it.key, it.value)
            }
            
        }
        
       return map;
    }
    
}

def process_nested(another_map, sub_map){
    another_map.each {
        if(it.value instanceof Map ){
            sub_map.put(it.key,process_nested(it.value, sub_map.get(it.key)))
        }else{
            sub_map.put(it.key, it.value)
        }
    }
    return sub_map
}

def screwy = "{\"flip.flop.grab.hello.abc\": \"this\", \"tick.tock\": \"that\", \"flip.switch\" : \"swatch\", \"flip.flop.grab.hello.pick\": \"another\"}"
println JsonOutput.toJson(formatJson(screwy))