package main

import "strings"

// Define a new errors type, which we will use to hold the validation errors for
// a form. The name of the form field will be used as the key.
type errors map[string]string

// Implement an Add() method to add error messages for a given field to the map.
func (e errors) Add(field, message string) {
    e[field] = message
}

// Implement a Get() method to retrieve the first error message for a given
// field from the map.
func (e errors) Get(field string) string {
    return e[field]
}

// Define a new validator type which contains a map of validation errors for our
// form fields.
type validator struct {
    Errors errors
}

// Create a new validator instance with an empty errors map.
func newValidator() *validator {
    return &validator{Errors: make(errors)}
}

// Valid() returns true if the errors map doesn't contain any entries.
func (v *validator) Valid() bool {
    return len(v.Errors) == 0
}

// NotBlank() returns true if a value is not an empty string.
func (v *validator) NotBlank(value string) bool {
    return strings.TrimSpace(value) != ""
}

// MaxChars() returns true if a value contains no more than n characters.
func (v *validator) MaxChars(value string, n int) bool {
    return len(value) <= n
}

// PermittedInt() returns true if a value is in a list of permitted integers.
func (v *validator) PermittedInt(value int, permittedValues ...int) bool {
    for i := range permittedValues {
        if value == i {
            return true
        }
    }
    return false
}