package validator

import (
	"fmt"
	"net/mail"
	"strings"
	"unicode/utf8"
)

// Errors collects validation errors for a request.
type Errors struct {
	Fields map[string]string `json:"fields"`
}

// New creates a new Errors instance.
func New() *Errors {
	return &Errors{Fields: make(map[string]string)}
}

// Add records a validation error for a field.
func (e *Errors) Add(field, message string) {
	e.Fields[field] = message
}

// Valid returns true if there are no validation errors.
func (e *Errors) Valid() bool {
	return len(e.Fields) == 0
}

// Error implements the error interface.
func (e *Errors) Error() string {
	parts := make([]string, 0, len(e.Fields))
	for field, msg := range e.Fields {
		parts = append(parts, fmt.Sprintf("%s: %s", field, msg))
	}
	return strings.Join(parts, "; ")
}

// --- Common validators ---

// Required checks that a string is not empty.
func Required(v *Errors, field, value string) {
	if strings.TrimSpace(value) == "" {
		v.Add(field, "is required")
	}
}

// MaxLength checks that a string doesn't exceed a maximum length.
func MaxLength(v *Errors, field, value string, max int) {
	if utf8.RuneCountInString(value) > max {
		v.Add(field, fmt.Sprintf("must be at most %d characters", max))
	}
}

// MinLength checks that a string meets a minimum length.
func MinLength(v *Errors, field, value string, min int) {
	if utf8.RuneCountInString(value) < min {
		v.Add(field, fmt.Sprintf("must be at least %d characters", min))
	}
}

// Email checks that a string is a valid email address.
func Email(v *Errors, field, value string) {
	if _, err := mail.ParseAddress(value); err != nil {
		v.Add(field, "must be a valid email address")
	}
}

// In checks that a string is one of the allowed values.
func In(v *Errors, field, value string, allowed ...string) {
	for _, a := range allowed {
		if value == a {
			return
		}
	}
	v.Add(field, fmt.Sprintf("must be one of: %s", strings.Join(allowed, ", ")))
}