package main

import (
	"encoding/json"
	"fmt"
	"math/rand"

	"github.com/creasty/defaults"
)

type Gender string

type Sample struct {
	Name    string `default:"John Smith" default_alt:"Jane Doe"`
	Age     int    `default:"27" default_alt:"28"`
	Gender  Gender `default:"m" default_alt:"f"`
	Working bool   `default:"true"`

	SliceInt    []int    `default:"[1, 2, 3]" default_alt:"[4, 5, 6]"`
	SlicePtr    []*int   `default:"[1, 2, 3]" default_alt:"[4, 5, 6]"`
	SliceString []string `default:"[\"a\", \"b\"]" default_alt:"[\"c\", \"d\"]"`

	MapNull            map[string]int          `default:"{}"` // Using default_alt would leave as a nil map
	Map                map[string]int          `default:"{\"key1\": 123}" default_alt:"{\"key1\": 456}"`
	MapOfStruct        map[string]OtherStruct  `default:"{\"Key2\": {\"Foo\":123}}" default_alt:"{\"Key2\": {\"Foo\":456}}"`
	MapOfPtrStruct     map[string]*OtherStruct `default:"{\"Key3\": {\"Foo\":123}}" default_alt:"{\"Key3\": {\"Foo\":456}}"`
	MapOfStructWithTag map[string]OtherStruct  `default:"{\"Key4\": {\"Foo\":123}}" default_alt:"{\"Key4\": {\"Foo\":456}}"`

	Struct    OtherStruct  `default:"{\"Foo\": 123}" default:"{\"Foo\": 456}"`
	StructPtr *OtherStruct `default:"{\"Foo\": 123}" default:"{\"Foo\": 456}"`

	NoTag    OtherStruct // Recurses into a nested struct by default
	NoOption OtherStruct `default:"-"` // no option
}

type OtherStruct struct {
	Hello  string `default:"world" default_alt:"person"` // Tags in a nested struct also work
	Foo    int    `default:"-"`
	Random int    `default:"-"`
}

// SetDefaults implements defaults.Setter interface
func (s *OtherStruct) SetDefaults() {
	if defaults.CanUpdate(s.Random) { // Check if it's a zero value (recommended)
		s.Random = rand.Int() // Set a dynamic value
	}
}

func main() {
	obj := &Sample{}
	if err := defaults.Set(obj); err != nil {
		panic(err)
	}

	out, err := json.MarshalIndent(obj, "", "	")
	if err != nil {
		panic(err)
	}
	fmt.Println(string(out))

	// Output:
	/*
		{
			"Name": "John Smith",
			"Age": 27,
			"Gender": "m",
			"Working": true,
			"SliceInt": [
				1,
				2,
				3
			],
			"SlicePtr": [
				1,
				2,
				3
			],
			"SliceString": [
				"a",
				"b"
			],
			"MapNull": {},
			"Map": {
				"key1": 123
			},
			"MapOfStruct": {
				"Key2": {
					"Hello": "world",
					"Foo": 123,
					"Random": 7924310560672650386
				}
			},
			"MapOfPtrStruct": {
				"Key3": {
					"Hello": "world",
					"Foo": 123,
					"Random": 5864827752208870454
				}
			},
			"MapOfStructWithTag": {
				"Key4": {
					"Hello": "world",
					"Foo": 123,
					"Random": 9020930397672710767
				}
			},
			"Struct": {
				"Hello": "world",
				"Foo": 123,
				"Random": 2100809313953071154
			},
			"StructPtr": {
				"Hello": "world",
				"Foo": 123,
				"Random": 4589638854976076769
			},
			"NoTag": {
				"Hello": "world",
				"Foo": 0,
				"Random": 93481895446446669
			},
			"NoOption": {
				"Hello": "",
				"Foo": 0,
				"Random": 0
			}
		}
	*/

	// Or with a specific tag name:
	otherObj := &Sample{}
	if err = defaults.SetWithTag(otherObj, "default_alt"); err != nil {
		panic(err)
	}

	out, err = json.MarshalIndent(otherObj, "", "	")
	if err != nil {
		panic(err)
	}
	fmt.Println(string(out))

	// Output:
	/*
		{
			"Name": "Jane Doe",
			"Age": 28,
			"Gender": "f",
			"Working": false,
			"SliceInt": [
				4,
				5,
				6
			],
			"SlicePtr": [
				4,
				5,
				6
			],
			"SliceString": [
				"c",
				"d"
			],
			"MapNull": null,
			"Map": {
				"key1": 456
			},
			"MapOfStruct": {
				"Key2": {
					"Hello": "person",
					"Foo": 456,
					"Random": 3527321973631593020
				}
			},
			"MapOfPtrStruct": {
				"Key3": {
					"Hello": "person",
					"Foo": 456,
					"Random": 6391170103701304261
				}
			},
			"MapOfStructWithTag": {
				"Key4": {
					"Hello": "person",
					"Foo": 456,
					"Random": 5779747168002044569
				}
			},
			"Struct": {
				"Hello": "person",
				"Foo": 0,
				"Random": 4391597250420769051
			},
			"StructPtr": null,
			"NoTag": {
				"Hello": "person",
				"Foo": 0,
				"Random": 5000048969203402981
			},
			"NoOption": {
				"Hello": "person",
				"Foo": 0,
				"Random": 4800395242796521920
			}
		}
	*/
}