const UnknownPrefix = "UnknownTag_"

var (
	// ErrStopWalking is a sentinel error to signal that the walk should stop.
	ErrStopWalking = fmt.Errorf("stop walking")
)

type HandleTagFunc func(info TagInfo) error

type ImageFormat int

const (
	// ImageFormatAuto signals that the image format should be detected automatically (not implemented yet).
	ImageFormatAuto ImageFormat = iota
	// JPEG is the JPEG image format.
	JPEG
	// TIFF is the TIFF image format.
	TIFF
	// PNG is the PNG image format.
	PNG
	// WebP is the WebP image format.
	WebP
)

type InvalidFormatError struct {
	Err error
}

type Options struct {
	// The Reader (typically a *os.File) to read image metadata from.
	R io.ReadSeeker

	// The image format in R.
	ImageFormat ImageFormat

	// If set, the decoder skip tags in which this function returns false.
	// If not set, a default function is used that skips all EXIF tags except those in IFD0.
	ShouldHandleTag func(tag TagInfo) bool

	// The function to call for each tag.
	HandleTag HandleTagFunc

	// The default XMP handler is currently very simple:
	// It decodes the RDF.Description.Attrs using Go's xml package and passes each tag to HandleTag.
	// If HandleXMP is set, the decoder will call this function for each XMP packet instead.
	// Note that r must be read completely.
	HandleXMP func(r io.Reader) error

	// If set, the decoder will only read the given tag sources.
	// Note that this is a bitmask and you may send multiple sources at once.
	Sources Source

	// Warnf will be called for each warning.
	Warnf func(string, ...any)

	// Timeout is the maximum time the decoder will spend on reading metadata.
	// Mostly useful for testing.
	// If set to 0, the decoder will not time out.
	Timeout time.Duration
}

type Rat[T int32 | uint32] interface {
	Num() T
	Den() T
	Float64() float64

	// String returns the string representation of the rational number.
	// If the denominator is 1, the string will be the numerator only.
	String() string
}

type Source uint32

const (
	// EXIF is the EXIF tag source.
	EXIF Source = 1 << iota
	// IPTC is the IPTC tag source.
	IPTC
	// XMP is the XMP tag source.
	XMP
)

type TagInfo struct {
	// The tag source.
	Source Source
	// The tag name.
	Tag string
	// The tag namespace.
	// For EXIF, this is the path to the IFD, e.g. "IFD0/GPSInfoIFD"
	// For XMP, this is the namespace, e.g. "http://ns.adobe.com/camera-raw-settings/1.0/"
	// For IPTC, this is the record tag name as defined https://exiftool.org/TagNames/IPTC.html
	Namespace string
	// The tag value.
	Value any
}

type Tags struct {
	// contains filtered or unexported fields
}