go/webutil/formscanner.go

package webutil

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

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

type FormScanner struct {
	form url.Values
	err  error
}

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
	}

	setError := func(name string, err error) {
		s.err = fmt.Errorf("Error in field %s: %w", name, err)
	}

	switch v := val.(type) {
	case *bool:
		*v = s.form.Has(name)
	case *string:
		*v = s.form.Get(name)
	case *int:
		if i, err := strconv.ParseInt(s.form.Get(name), 10, 64); err != nil {
			setError(name, err)
		} else {
			*v = int(i)
		}
	case *int8:
		if i, err := strconv.ParseInt(s.form.Get(name), 10, 8); err != nil {
			setError(name, err)
		} else {
			*v = int8(i)
		}
	case *int16:
		if i, err := strconv.ParseInt(s.form.Get(name), 10, 16); err != nil {
			setError(name, err)
		} else {
			*v = int16(i)
		}
	case *int32:
		if i, err := strconv.ParseInt(s.form.Get(name), 10, 32); err != nil {
			setError(name, err)
		} else {
			*v = int32(i)
		}
	case *int64:
		if i, err := strconv.ParseInt(s.form.Get(name), 10, 64); err != nil {
			setError(name, err)
		} else {
			*v = int64(i)
		}
	case *uint:
		if i, err := strconv.ParseUint(s.form.Get(name), 10, 64); err != nil {
			setError(name, err)
		} else {
			*v = uint(i)
		}
	case *uint8:
		if i, err := strconv.ParseUint(s.form.Get(name), 10, 8); err != nil {
			setError(name, err)
		} else {
			*v = uint8(i)
		}
	case *uint16:
		if i, err := strconv.ParseUint(s.form.Get(name), 10, 16); err != nil {
			setError(name, err)
		} else {
			*v = uint16(i)
		}
	case *uint32:
		if i, err := strconv.ParseUint(s.form.Get(name), 10, 32); err != nil {
			setError(name, err)
		} else {
			*v = uint32(i)
		}
	case *uint64:
		if i, err := strconv.ParseUint(s.form.Get(name), 10, 64); err != nil {
			setError(name, err)
		} else {
			*v = uint64(i)
		}
	case *float32:
		if f, err := strconv.ParseFloat(s.form.Get(name), 32); err != nil {
			setError(name, err)
		} else {
			*v = float32(f)
		}
	case *float64:
		if f, err := strconv.ParseFloat(s.form.Get(name), 64); err != nil {
			setError(name, err)
		} else {
			*v = float64(f)
		}
	default:
		setError(name, ErrUnsupportedType)
	}

	return s
}

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