package theme

import "image"
import "image/color"
import "golang.org/x/image/font"
import "git.tebibyte.media/sashakoshka/tomo/artist"
import "git.tebibyte.media/sashakoshka/tomo/canvas"

// IconSize is a type representing valid icon sizes.
type IconSize int

const (
	IconSizeSmall IconSize = 16
	IconSizeLarge IconSize = 48
)

// Pattern lists a number of cannonical pattern types, each with its own ID.
// This allows custom elements to follow themes, even those that do not
// explicitly support them.
type Pattern int; const (
	// PatternBackground is the window background of the theme. It appears
	// in things like containers and behind text.
	PatternBackground Pattern = iota

	// PatternDead is a pattern that is displayed on a "dead area" where no
	// controls exist, but there still must be some indication of visual
	// structure (such as in the corner between two scroll bars).
	PatternDead

	// PatternRaised is a generic raised pattern.
	PatternRaised

	// PatternSunken is a generic sunken pattern.
	PatternSunken

	// PatternPinboard is similar to PatternSunken, but it is textured.
	PatternPinboard

	// PatternButton is a button pattern.
	PatternButton

	// PatternInput is a pattern for input fields, editable text areas, etc.
	PatternInput

	// PatternGutter is a track for things to slide on.
	PatternGutter

	// PatternHandle is a handle that slides along a gutter.
	PatternHandle

	// PatternLine is an engraved line that separates things.
	PatternLine
)

type Color int; const (
	// ColorAccent is the accent color of the theme.
	ColorAccent Color = iota

	// ColorForeground is the text/icon color of the theme.
	ColorForeground
)

// Hints specifies rendering hints for a particular pattern. Elements can take
// these into account in order to gain extra performance.
type Hints struct {
	// StaticInset defines an inset rectangular area in the middle of the
	// pattern that does not change between PatternStates. If the inset is
	// zero on all sides, this hint does not apply.
	StaticInset artist.Inset

	// Uniform specifies a singular color for the entire pattern. If the
	// alpha channel is zero, this hint does not apply.
	Uniform color.RGBA
}

// Theme represents a visual style configuration,
type Theme interface {
	// FontFace returns the proper font for a given style, size, and case.
	FontFace (FontStyle, FontSize, Case) font.Face

	// Icon returns an appropriate icon given an icon name, size, and case.
	Icon (string, IconSize, Case) canvas.Image

	// Pattern returns an appropriate pattern given a pattern name, case,
	// and state.
	Pattern (Pattern, State, Case) artist.Pattern

	// Color returns an appropriate pattern given a color name, case, and
	// state.
	Color (Color, State, Case) color.RGBA

	// Padding returns how much space should be between the bounds of a
	// pattern whatever an element draws inside of it.
	Padding (Pattern, Case) artist.Inset

	// Margin returns the left/right (x) and top/bottom (y) margins that
	// should be put between any self-contained objects drawn within this
	// pattern (if applicable).
	Margin (Pattern, Case) image.Point

	// Sink returns a vector that should be added to an element's inner
	// content when it is pressed down (if applicable) to simulate a 3D
	// sinking effect.
	Sink (Pattern, Case) image.Point

	// Hints returns rendering optimization hints for a particular pattern.
	// These are optional, but following them may result in improved
	// performance.
	Hints (Pattern, Case) Hints
}