package validation

import (
	"fmt"
	"slices"
	"strings"
	"unicode"
)

type StringField struct {
	Field
	Value string
}

func newStringField(key string, g Getter) *StringField {
	return &StringField{
		Value: g.Get(key),
		Field: newField(key, g),
	}
}

// Required enforces a non empty string
func (s *StringField) Required() *StringField {
	if s.Value == "" {
		s.getter.AddCheck(newFailedCheck(
			"Field not provided",
			fmt.Sprintf("%s is required", s.Key),
		))
	}
	return s
}

// Optional will skip all validations if value is empty
func (s *StringField) Optional() *StringField {
	if s.Value == "" {
		s.optional = true
	}
	return s
}

// MaxLength enforces a maximum string length
func (s *StringField) MaxLength(length int) *StringField {
	if len(s.Value) > length && !s.optional {
		s.getter.AddCheck(newFailedCheck(
			"Input too long",
			fmt.Sprintf("%s is too long, max %v chars", s.Key, length),
		))
	}
	return s
}

// MinLength enforces a minimum string length
func (s *StringField) MinLength(length int) *StringField {
	if len(s.Value) < length && !s.optional {
		s.getter.AddCheck(newFailedCheck(
			"Input too short",
			fmt.Sprintf("%s is too short, min %v chars", s.Key, length),
		))
	}
	return s
}

// AlphaNumeric enforces the string contains only letters and numbers
func (s *StringField) AlphaNumeric() *StringField {
	if s.optional {
		return s
	}
	for _, r := range s.Value {
		if !unicode.IsLetter(r) && !unicode.IsDigit(r) {
			s.getter.AddCheck(newFailedCheck(
				"Invalid characters",
				fmt.Sprintf("%s must contain only letters and numbers.", s.Key),
			))
			return s
		}
	}
	return s
}

func (s *StringField) AllowedValues(allowed []string) *StringField {
	if !slices.Contains(allowed, s.Value) && !s.optional {
		s.getter.AddCheck(newFailedCheck(
			"Value not allowed",
			fmt.Sprintf("%s must be one of: %s", s.Key, strings.Join(allowed, ",")),
		))
	}
	return s
}

// ToUpper transforms the string to uppercase
func (s *StringField) ToUpper() *StringField {
	s.Value = strings.ToUpper(s.Value)
	return s
}

// ToLower transforms the string to lowercase
func (s *StringField) ToLower() *StringField {
	s.Value = strings.ToLower(s.Value)
	return s
}

// TrimSpace removes leading and trailing whitespace
func (s *StringField) TrimSpace() *StringField {
	s.Value = strings.TrimSpace(s.Value)
	return s
}

// Replace replaces all occurances of the given substring
func (s *StringField) Replace(old, new string) *StringField {
	s.Value = strings.ReplaceAll(s.Value, old, new)
	return s
}