package theme

import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/data"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/canvas"

// Role describes the role of an object.
type Role struct {
	// Package is an optional namespace field. If specified, it should be
	// the package name or module name the object is from.
	Package string

	// Object specifies what type of object it is. For example:
	//   - TextInput
	//   - Table
	//   - Label
	//   - Dial
	// This should correspond directly to the type name of the object.
	Object string

	// Variant is an optional field to be used when an object has one or
	// more soft variants under one type. For example, an object "Slider"
	// may have variations "horizontal" and "vertical".
	Variant string
}

// R is shorthand for creating a Role structure.
func R (pack, object, variant string) Role {
	return Role { Package: pack, Object: object, Variant: variant }
}

// Color represents a color ID.
type Color int; const (
	ColorBackground Color = iota
	ColorForeground
	ColorRaised
	ColorSunken
	ColorAccent
)

// RGBA satisfies the color.Color interface.
func (id Color) RGBA () (r, g, b, a uint32) {
	if current == nil { return }
	return current.RGBA(id)
}

// Theme is an object that can apply a visual style to different objects.
type Theme interface {
	// Apply applies the theme to the given object, according to the given
	// role. This may register event listeners with the given object;
	// closing the returned cookie will remove them.
	Apply (tomo.Object, Role) event.Cookie

	// RGBA returns the RGBA values of the corresponding color ID.
	RGBA (Color) (r, g, b, a uint32)

	// Icon returns a texture of the corresponding icon ID. This texture
	// should be protected, unless a new copy of it is returned with each
	// subsequent call.
	Icon (Icon, IconSize) canvas.Texture

	// MimeIcon returns an icon corresponding to a MIME type. This texture
	// should be protected, unless a new copy of it is returned with each
	// subsequent call.
	MimeIcon (data.Mime, IconSize) canvas.Texture

	// ApplicationIcon returns an icon corresponding to an application. This
	// texture should be protected, unless a new copy of it is returned with
	// each subsequent call.
	ApplicationIcon (ApplicationIcon, IconSize) canvas.Texture
}

var current Theme

// SetTheme sets the theme.
func SetTheme (theme Theme) {
	current = theme
}

// Apply applies the current theme to the given object, according to the given
// role. This may register event listeners with the given object; closing the
// returned cookie will remove them.
func Apply (object tomo.Object, role Role) event.Cookie {
	if current == nil { return event.NoCookie { } }
	return current.Apply(object, role)
}