package fieldgroups

import (
	"fmt"

	"pdf-wizard/internal/models"
)

// GroupHandler defines the interface for a field group type.
type GroupHandler interface {
	// Type returns the group type name (e.g., "multiline", "single_select").
	Type() string

	// Validate checks that the submitted values for this group are valid.
	// fieldValues maps field_id -> submitted value.
	// Returns an error if validation fails.
	Validate(fields []models.FormField, fieldValues map[int]string) error

	// ConvertToFillValues converts the submitted values back to individual
	// field values suitable for filling the PDF. For groups like "multiline",
	// this splits a single textarea value across multiple text fields.
	// fieldValues maps field_id -> submitted value.
	ConvertToFillValues(fields []models.FormField, fieldValues map[int]string) map[int]string
}

var registry = make(map[string]GroupHandler)

// Register adds a handler to the global registry.
func Register(h GroupHandler) {
	registry[h.Type()] = h
}

// Get returns the handler for the given group type.
func Get(groupType string) (GroupHandler, error) {
	h, ok := registry[groupType]
	if !ok {
		return nil, fmt.Errorf("unknown group type: %s", groupType)
	}
	return h, nil
}

// GetFillValuesForGroup gets the fill-ready values for a group's fields.
func GetFillValuesForGroup(group models.FieldGroup, fields []models.FormField, fieldValues map[int]string) (map[int]string, error) {
	handler, err := Get(group.GroupType)
	if err != nil {
		return nil, err
	}
	return handler.ConvertToFillValues(fields, fieldValues), nil
}

// ValidateGroup validates the submitted values for a group.
func ValidateGroup(group models.FieldGroup, fields []models.FormField, fieldValues map[int]string) error {
	handler, err := Get(group.GroupType)
	if err != nil {
		return err
	}
	return handler.Validate(fields, fieldValues)
}

// AllTypes returns all registered group type names.
func AllTypes() []string {
	types := make([]string, 0, len(registry))
	for t := range registry {
		types = append(types, t)
	}
	return types
}