package main

import (
	"fmt"
	"log"
	"strings"

	"github.com/twharmon/govalid"
)

type Post struct {
	// ID has no constraints
	ID int

	// Title is required, must be at least 3 characters long, cannot be
	// more than 20 characters long, and must match ^[a-zA-Z ]+$
	Title string `govalid:"req|min:3|max:20|regex:^[a-zA-Z ]+$"`

	// Body is not required, cannot be more than 10000 charachers,
	// and must be "fun" (a custom rule defined below).
	Body string `govalid:"max:10000|fun"`

	// Category is not required, but if not zero value ("") it must be
	// either "announcement" or "bookreview".
	Category string `govalid:"in:announcement,bookreview"`
}

var v = govalid.New()

func main() {
	// Add Custom validation to the struct `Post`
	v.AddCustom(Post{}, func(val interface{}) string {
		post := val.(*Post)
		if post.Category != "" && !strings.Contains(post.Body, post.Category) {
			return fmt.Sprintf("Body must contain %s", post.Category)
		}
		return ""
	})
	
	// Add custom string "fun" that can be used on any string field
	// in any struct.
	v.AddCustomStringRule("fun", func(field string, value string) string {
		if float64(strings.Count(value, "!")) / float64(utf8.RuneCountInString(value)) > 0.001 {
			return ""
		}
		return fmt.Sprintf("%s must contain more exclamation marks", field)
	})

	p := Post{
		ID:       5,
		Title:    "Hi",
		Body:     "Hello world!",
		Category: "announcement",
	}

	vio, err := v.Violations(&p)
	if err != nil {
		log.Fatalln(err)
	}

	fmt.Println(vio)
}