package response

import (
	"fmt"
	"net/http"
)

// ErrorCode defines standardized error codes.
// Pattern follows Chatwoot's error response format in API controllers.
type ErrorCode string

const (
	// General errors
	ErrInternal      ErrorCode = "INTERNAL_ERROR"
	ErrNotFound      ErrorCode = "NOT_FOUND"
	ErrBadRequest    ErrorCode = "BAD_REQUEST"
	ErrUnauthorized  ErrorCode = "UNAUTHORIZED"
	ErrForbidden     ErrorCode = "FORBIDDEN"
	ErrConflict      ErrorCode = "CONFLICT"
	ErrValidation    ErrorCode = "VALIDATION_ERROR"
	ErrRateLimit     ErrorCode = "RATE_LIMITED"
	ErrServiceUnavail ErrorCode = "SERVICE_UNAVAILABLE"
	ErrPaymentRequired ErrorCode = "PAYMENT_REQUIRED"

	// Business-specific errors (ref: Chatwoot error patterns)
	ErrAccountNotFound  ErrorCode = "ACCOUNT_NOT_FOUND"
	ErrInboxNotFound    ErrorCode = "INBOX_NOT_FOUND"
	ErrChannelInvalid   ErrorCode = "CHANNEL_INVALID"
	ErrContactNotFound  ErrorCode = "CONTACT_NOT_FOUND"
	ErrConversationNotFound ErrorCode = "CONVERSATION_NOT_FOUND"
	ErrMessageNotFound  ErrorCode = "MESSAGE_NOT_FOUND"
	ErrUserNotFound     ErrorCode = "USER_NOT_FOUND"
	ErrDuplicateRecord  ErrorCode = "DUPLICATE_RECORD"
	ErrChannelNotEnabled ErrorCode = "CHANNEL_NOT_ENABLED"

	// Knowledge Base / Help Center errors (M4)
	ErrPortalNotFound       ErrorCode = "PORTAL_NOT_FOUND"
	ErrArticleNotFound      ErrorCode = "ARTICLE_NOT_FOUND"
	ErrCategoryNotFound     ErrorCode = "CATEGORY_NOT_FOUND"
	ErrFolderNotFound       ErrorCode = "FOLDER_NOT_FOUND"
	ErrPortalMemberNotFound ErrorCode = "PORTAL_MEMBER_NOT_FOUND"
	ErrKBFeatureNotEnabled  ErrorCode = "KB_FEATURE_NOT_ENABLED"
	ErrArticleSlugExists    ErrorCode = "ARTICLE_SLUG_EXISTS"
	ErrPortalSlugExists     ErrorCode = "PORTAL_SLUG_EXISTS"
)

// AppError is the unified application error type.
// All business errors should be wrapped as AppError for consistent API responses.
type AppError struct {
	Code    ErrorCode `json:"code"`
	Message string    `json:"message"`
	Detail  string    `json:"detail,omitempty"`
	Status  int       `json:"-"`
}

func (e *AppError) Error() string {
	if e.Detail != "" {
		return fmt.Sprintf("%s: %s (%s)", e.Code, e.Message, e.Detail)
	}
	return fmt.Sprintf("%s: %s", e.Code, e.Message)
}

// NewAppError creates a new AppError
func NewAppError(code ErrorCode, message string, status int) *AppError {
	return &AppError{
		Code:   code,
		Message: message,
		Status: status,
	}
}

// WithDetail adds detail to an AppError
func (e *AppError) WithDetail(detail string) *AppError {
	e.Detail = detail
	return e
}

// Convenience constructors for common error types
func ErrInternalError(msg string) *AppError {
	return NewAppError(ErrInternal, msg, http.StatusInternalServerError)
}

func ErrNotFoundError(resource string) *AppError {
	return NewAppError(ErrNotFound, fmt.Sprintf("%s not found", resource), http.StatusNotFound)
}

func ErrBadRequestError(msg string) *AppError {
	return NewAppError(ErrBadRequest, msg, http.StatusBadRequest)
}

func ErrUnauthorizedError(msg string) *AppError {
	return NewAppError(ErrUnauthorized, msg, http.StatusUnauthorized)
}

func ErrForbiddenError(msg string) *AppError {
	return NewAppError(ErrForbidden, msg, http.StatusForbidden)
}

func ErrValidationError(msg string) *AppError {
	return NewAppError(ErrValidation, msg, http.StatusBadRequest)
}

func ErrConflictError(msg string) *AppError {
	return NewAppError(ErrConflict, msg, http.StatusConflict)
}

func ErrRateLimitError(msg string) *AppError {
	return NewAppError(ErrRateLimit, msg, http.StatusTooManyRequests)
}

// HTTPStatus maps ErrorCode to HTTP status code
func ErrorToHTTPStatus(code ErrorCode) int {
	switch code {
	case ErrNotFound, ErrAccountNotFound, ErrInboxNotFound, ErrContactNotFound,
		ErrConversationNotFound, ErrMessageNotFound, ErrUserNotFound:
		return http.StatusNotFound
	case ErrBadRequest, ErrValidation:
		return http.StatusBadRequest
	case ErrUnauthorized:
		return http.StatusUnauthorized
	case ErrForbidden, ErrChannelNotEnabled:
		return http.StatusForbidden
	case ErrConflict, ErrDuplicateRecord, ErrChannelInvalid:
		return http.StatusConflict
	case ErrRateLimit:
		return http.StatusTooManyRequests
	case ErrServiceUnavail:
		return http.StatusServiceUnavailable
	default:
		return http.StatusInternalServerError
	}
}