package main

import (
	"encoding/json"
	"log"
	"strconv"
)

func main() {
	//unmarshalIdealData()
	// unmarshalRealWorldData()
	// unmarshalBoth()
}

// In an ideal world all data is consistent. idealData is an example of some
// json (it represents an event)
var idealData = []byte(`
{
    "name": "event name",
    "id":   1
}
`)

// IdealEvent is a struct that we can use to unmarshal the data into for using
// in bookie
type IdealEvent struct {
	Name string `json:"name"`
	ID   int    `json:"id"`
}

// unmarshalIdealData  unmarshals some data in an ideal world
func unmarshalIdealData() {
	var event IdealEvent
	err := json.Unmarshal(idealData, &event)
	log.Println(err)
	log.Println(event)
}

// In the real world, this aren't always quite so simple. Sometimes things come
// in an incorrect format
var realWorldData = []byte(`
{
    "name": "event name",
    "id":   "1"
}
`)

// unmarshalRealWorldData unmarshals some incorrectly formatted data.
func unmarshalRealWorldData() {
	var event IdealEvent
	err := json.Unmarshal(realWorldData, &event)
	log.Println(err)
	log.Println(event)
}

// in golang you can define a new type to handle this
type intSometimesString int

// RealWorldEvent represents an event that we often see delivered from a feed
// where the id is often delivered as an int or a string, for example:
type RealWorldEvent struct {
	Name string             `json:"name"`
	ID   intSometimesString `json:"id"`
}

// UnmarshalJSON is a custom unmarshaller for the intSometimesString type
func (ri *intSometimesString) UnmarshalJSON(buf []byte) (err error) {
	var i int
	var s string

	// Check to see if string - if it is, unmarshal and convert to an integer
	if buf[0] == '"' {
		if err = json.Unmarshal(buf, &s); err != nil {
			return err
		}
		if s == "" {
			s = "0"
		}
		if i, err = strconv.Atoi(s); err != nil {
			return err
		}
	} else {
		// otherwise we expect it is an integer
		if err = json.Unmarshal(buf, &i); err != nil {
			return err
		}
	}

	*ri = intSometimesString(i)
	return nil
}

func unmarshalBoth() {
	var event RealWorldEvent
	err := json.Unmarshal(realWorldData, &event)
	log.Println(err)
	log.Println(event)
	err = json.Unmarshal(idealData, &event)
	log.Println(err)
	log.Println(event)
}