package webutil

import (
	"errors"
	"fmt"
	"net/url"
)

var ErrUnsupportedType = errors.New("unsupported type")

// FormScanFunc is a custom form scanner that can be used to scan custom
// types using the form scanner.
//
// It returns true if it recognizes the type of val, and an error if scanning
// fails.
type FormScanFunc func(form url.Values, name string, val any) (bool, error)

type FormScanner struct {
	form     url.Values
	err      error
	ScanFunc FormScanFunc
}

func NewFormScanner(form url.Values) *FormScanner {
	return &FormScanner{form: form}
}

func (s *FormScanner) Scan(name string, val any) *FormScanner {
	if s.err != nil {
		return s
	}

	if s.ScanFunc != nil {
		if ok, err := s.ScanFunc(s.form, name, val); ok {
			s.err = err
			return s
		}
	}

	switch v := val.(type) {
	case *bool:
		*v = s.form.Has(name)
	default:
		if err := scan(s.form.Get(name), v); err != nil {
			s.err = fmt.Errorf("Error in field %s: %w", name, err)
		}
	}

	return s
}

func (s *FormScanner) Error() error {
	return s.err
}