package validators

import (
	"fmt"
	"strings"

	"github.com/go-playground/validator/v10"
	"veza-backend-api/internal/dto"
)

// Validator est un wrapper autour de go-playground/validator
// GO-013: Validation input centralisée avec go-validator
type Validator struct {
	validate *validator.Validate
}

// NewValidator crée une nouvelle instance de Validator
func NewValidator() *Validator {
	v := validator.New()

	// Enregistrer des validations personnalisées
	registerCustomValidations(v)

	return &Validator{
		validate: v,
	}
}

// Validate valide une structure et retourne des erreurs formatées
func (v *Validator) Validate(s interface{}) []dto.ValidationError {
	var validationErrors []dto.ValidationError

	err := v.validate.Struct(s)
	if err != nil {
		if validationErrs, ok := err.(validator.ValidationErrors); ok {
			for _, fieldErr := range validationErrs {
				validationErrors = append(validationErrors, dto.ValidationError{
					Field:   getFieldName(fieldErr),
					Message: getErrorMessage(fieldErr),
					Value:   fmt.Sprintf("%v", fieldErr.Value()),
				})
			}
		}
	}

	return validationErrors
}

// ValidateVar valide une variable unique
func (v *Validator) ValidateVar(field interface{}, tag string) error {
	return v.validate.Var(field, tag)
}

// getFieldName extrait le nom du champ depuis l'erreur de validation
// GO-013: Extrait le tag JSON si disponible via StructNamespace, sinon convertit en camelCase
func getFieldName(fieldErr validator.FieldError) string {
	// Utiliser StructNamespace qui donne le chemin complet (ex: "TestStruct.Name")
	// et extraire le dernier segment
	structNamespace := fieldErr.StructNamespace()
	if structNamespace != "" {
		parts := strings.Split(structNamespace, ".")
		if len(parts) > 0 {
			fieldName := parts[len(parts)-1]
			// Convertir en camelCase pour JSON (première lettre en minuscule)
			if len(fieldName) > 0 {
				return strings.ToLower(fieldName[:1]) + fieldName[1:]
			}
			return fieldName
		}
	}

	// Fallback: utiliser Field() et convertir en camelCase
	fieldName := fieldErr.Field()
	if len(fieldName) > 0 {
		return strings.ToLower(fieldName[:1]) + fieldName[1:]
	}

	return fieldName
}

// getErrorMessage génère un message d'erreur lisible depuis l'erreur de validation
// BE-SVC-020: Messages d'erreur améliorés et plus descriptifs
func getErrorMessage(fieldErr validator.FieldError) string {
	fieldName := getFieldName(fieldErr)
	param := fieldErr.Param()

	switch fieldErr.Tag() {
	case "required":
		return fmt.Sprintf("The field '%s' is required and cannot be empty", fieldName)
	case "email":
		return fmt.Sprintf("The field '%s' must be a valid email address (e.g., user@example.com)", fieldName)
	case "min":
		if fieldErr.Type().Kind().String() == "string" {
			return fmt.Sprintf("The field '%s' must be at least %s characters long", fieldName, param)
		}
		return fmt.Sprintf("The field '%s' must be at least %s", fieldName, param)
	case "max":
		if fieldErr.Type().Kind().String() == "string" {
			return fmt.Sprintf("The field '%s' must be at most %s characters long", fieldName, param)
		}
		return fmt.Sprintf("The field '%s' must be at most %s", fieldName, param)
	case "len":
		return fmt.Sprintf("The field '%s' must be exactly %s characters long", fieldName, param)
	case "oneof":
		return fmt.Sprintf("The field '%s' must be one of the following values: %s", fieldName, param)
	case "eqfield":
		return fmt.Sprintf("The field '%s' must equal the value of '%s'", fieldName, param)
	case "nefield":
		return fmt.Sprintf("The field '%s' must not equal the value of '%s'", fieldName, param)
	case "uuid":
		return fmt.Sprintf("The field '%s' must be a valid UUID format (e.g., 550e8400-e29b-41d4-a716-446655440000)", fieldName)
	case "url":
		return fmt.Sprintf("The field '%s' must be a valid URL (e.g., https://example.com)", fieldName)
	case "uri":
		return fmt.Sprintf("The field '%s' must be a valid URI", fieldName)
	case "numeric":
		return fmt.Sprintf("The field '%s' must be a numeric value", fieldName)
	case "alpha":
		return fmt.Sprintf("The field '%s' must contain only letters (a-z, A-Z)", fieldName)
	case "alphanum":
		return fmt.Sprintf("The field '%s' must contain only letters and numbers", fieldName)
	case "alphaunicode":
		return fmt.Sprintf("The field '%s' must contain only unicode letters", fieldName)
	case "alphanumunicode":
		return fmt.Sprintf("The field '%s' must contain only unicode letters and numbers", fieldName)
	case "number":
		return fmt.Sprintf("The field '%s' must be a valid number", fieldName)
	case "gte":
		return fmt.Sprintf("The field '%s' must be greater than or equal to %s", fieldName, param)
	case "lte":
		return fmt.Sprintf("The field '%s' must be less than or equal to %s", fieldName, param)
	case "gt":
		return fmt.Sprintf("The field '%s' must be greater than %s", fieldName, param)
	case "lt":
		return fmt.Sprintf("The field '%s' must be less than %s", fieldName, param)
	case "eq":
		return fmt.Sprintf("The field '%s' must equal %s", fieldName, param)
	case "ne":
		return fmt.Sprintf("The field '%s' must not equal %s", fieldName, param)
	case "contains":
		return fmt.Sprintf("The field '%s' must contain the substring '%s'", fieldName, param)
	case "excludes":
		return fmt.Sprintf("The field '%s' must not contain the substring '%s'", fieldName, param)
	case "startswith":
		return fmt.Sprintf("The field '%s' must start with '%s'", fieldName, param)
	case "endswith":
		return fmt.Sprintf("The field '%s' must end with '%s'", fieldName, param)
	case "ip":
		return fmt.Sprintf("The field '%s' must be a valid IP address", fieldName)
	case "ipv4":
		return fmt.Sprintf("The field '%s' must be a valid IPv4 address", fieldName)
	case "ipv6":
		return fmt.Sprintf("The field '%s' must be a valid IPv6 address", fieldName)
	case "datetime":
		return fmt.Sprintf("The field '%s' must be a valid datetime in format '%s'", fieldName, param)
	case "date":
		return fmt.Sprintf("The field '%s' must be a valid date", fieldName)
	case "timezone":
		return fmt.Sprintf("The field '%s' must be a valid timezone", fieldName)
	case "base64":
		return fmt.Sprintf("The field '%s' must be a valid base64 encoded string", fieldName)
	case "json":
		return fmt.Sprintf("The field '%s' must be a valid JSON string", fieldName)
	case "username":
		return fmt.Sprintf("The field '%s' must be a valid username (3-30 characters, alphanumeric and underscore only)", fieldName)
	case "uuid_string":
		return fmt.Sprintf("The field '%s' must be a valid UUID string", fieldName)
	default:
		// Pour les tags personnalisés ou inconnus, fournir un message générique mais informatif
		return fmt.Sprintf("The field '%s' failed validation for tag '%s'", fieldName, fieldErr.Tag())
	}
}

// registerCustomValidations enregistre des validations personnalisées
// BE-SVC-020: Ajout de validations personnalisées supplémentaires
func registerCustomValidations(v *validator.Validate) {
	// Validation pour username (alphanumeric + underscore, 3-30 chars)
	v.RegisterValidation("username", func(fl validator.FieldLevel) bool {
		username := fl.Field().String()
		if len(username) < 3 || len(username) > 30 {
			return false
		}
		for _, char := range username {
			if !((char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') ||
				(char >= '0' && char <= '9') || char == '_') {
				return false
			}
		}
		return true
	})

	// Validation pour UUID string
	v.RegisterValidation("uuid_string", func(fl validator.FieldLevel) bool {
		uuidStr := fl.Field().String()
		if uuidStr == "" {
			return true // Optionnel
		}
		// Utiliser le même validator pour éviter la récursion
		uuidValidator := validator.New()
		err := uuidValidator.Var(uuidStr, "uuid")
		return err == nil
	})

	// Validation pour slug (alphanumeric + dash/underscore, utilisé dans les URLs)
	v.RegisterValidation("slug", func(fl validator.FieldLevel) bool {
		slug := fl.Field().String()
		if len(slug) < 1 || len(slug) > 100 {
			return false
		}
		for _, char := range slug {
			if !((char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') ||
				(char >= '0' && char <= '9') || char == '-' || char == '_') {
				return false
			}
		}
		return true
	})

	// Validation pour phone (format basique international)
	v.RegisterValidation("phone", func(fl validator.FieldLevel) bool {
		phone := fl.Field().String()
		if phone == "" {
			return true // Optionnel
		}
		// Format basique: + suivi de 7-15 chiffres, ou 10-15 chiffres sans +
		// Enlever les espaces, tirets, parenthèses pour la validation
		cleaned := strings.ReplaceAll(phone, " ", "")
		cleaned = strings.ReplaceAll(cleaned, "-", "")
		cleaned = strings.ReplaceAll(cleaned, "(", "")
		cleaned = strings.ReplaceAll(cleaned, ")", "")

		if len(cleaned) < 7 || len(cleaned) > 16 {
			return false
		}

		// Doit commencer par + ou être uniquement des chiffres
		if cleaned[0] == '+' {
			cleaned = cleaned[1:]
		}

		// Vérifier que ce sont tous des chiffres
		for _, char := range cleaned {
			if char < '0' || char > '9' {
				return false
			}
		}
		return true
	})

	// Validation pour date ISO 8601 (YYYY-MM-DD)
	v.RegisterValidation("date_iso", func(fl validator.FieldLevel) bool {
		dateStr := fl.Field().String()
		if dateStr == "" {
			return true // Optionnel
		}
		// Format YYYY-MM-DD
		if len(dateStr) != 10 {
			return false
		}
		if dateStr[4] != '-' || dateStr[7] != '-' {
			return false
		}
		// Vérifier que les parties sont numériques
		for i, char := range dateStr {
			if i == 4 || i == 7 {
				continue
			}
			if char < '0' || char > '9' {
				return false
			}
		}
		return true
	})

	// Validation pour non-empty string (après trim)
	v.RegisterValidation("not_empty", func(fl validator.FieldLevel) bool {
		if fl.Field().Kind().String() != "string" {
			return false
		}
		str := strings.TrimSpace(fl.Field().String())
		return len(str) > 0
	})
}