package world

import (
	"image"
	"image/color"
)

// BackgroundTileMode defines how the background image is tiled.
type BackgroundTileMode uint8

const (
	BackgroundTileNone BackgroundTileMode = iota
	BackgroundTileRepeat
)

// BackgroundAnchorMode defines whether the background image scrolls with the world or stays fixed to viewport.
type BackgroundAnchorMode uint8

const (
	BackgroundAnchorWorld BackgroundAnchorMode = iota
	BackgroundAnchorViewport
)

// BackgroundScaleMode defines how the background image is scaled.
// (Step 1: defined for API completeness; used later when rendering background image.)
type BackgroundScaleMode uint8

const (
	BackgroundScaleNone BackgroundScaleMode = iota
	BackgroundScaleFit
	BackgroundScaleFill
)

// StyleTheme describes a cohesive style set (theme) for rendering.
// Step 1: we store it in World and use it for background and default base styles.
// Step 2+: theme-relative overrides and background image drawing.
type StyleTheme interface {
	ID() string
	Name() string

	BackgroundColor() color.Color
	BackgroundImage() image.Image

	BackgroundTileMode() BackgroundTileMode
	BackgroundScaleMode() BackgroundScaleMode
	BackgroundAnchorMode() BackgroundAnchorMode

	PointStyle() Style
	LineStyle() Style
	CircleStyle() Style

	// Class overrides (relative to base kind style).
	// Return (override, true) when class is supported; (zero, false) means "no override".
	PointClassOverride(class PointClassID) (StyleOverride, bool)
	LineClassOverride(class LineClassID) (StyleOverride, bool)
	CircleClassOverride(class CircleClassID) (StyleOverride, bool)
}

// DefaultTheme is a conservative theme matching built-in default styles.
type DefaultTheme struct{}

func (DefaultTheme) ID() string   { return "default" }
func (DefaultTheme) Name() string { return "Default" }

func (DefaultTheme) BackgroundColor() color.Color { return color.RGBA{A: 255} }
func (DefaultTheme) BackgroundImage() image.Image { return nil }

func (DefaultTheme) BackgroundTileMode() BackgroundTileMode     { return BackgroundTileNone }
func (DefaultTheme) BackgroundScaleMode() BackgroundScaleMode   { return BackgroundScaleNone }
func (DefaultTheme) BackgroundAnchorMode() BackgroundAnchorMode { return BackgroundAnchorWorld }

func (DefaultTheme) PointStyle() Style {
	s, _ := NewStyleTable().Get(StyleIDDefaultPoint)
	return s
}
func (DefaultTheme) LineStyle() Style {
	s, _ := NewStyleTable().Get(StyleIDDefaultLine)
	return s
}
func (DefaultTheme) CircleStyle() Style {
	s, _ := NewStyleTable().Get(StyleIDDefaultCircle)
	return s
}

func (DefaultTheme) PointClassOverride(PointClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (DefaultTheme) LineClassOverride(LineClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (DefaultTheme) CircleClassOverride(CircleClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}