package groovy

import (
	"os"

	"github.com/hajimehoshi/ebiten/v2"
)

const (
	defaultWidth  = 1024
	defaultHeight = 768
)

type Area struct {
	Width  int
	Height int
}

type GameInfo struct {
	Name      string
	Version   string
	Dimension Area
}

type Manager struct {
	Info           GameInfo
	currentScene   Scene
	currentSceneId int
	scenes         []Scene
}

// can be used to create default manager instance
func NewManager() Manager {
	return Manager{
		Info: GameInfo{
			Name:    "groovy",
			Version: "1.0",
			Dimension: Area{
				Width:  defaultWidth,
				Height: defaultHeight},
		},
		currentSceneId: 0,
	}
}

// ebitengine update proxy
// manages scene transition and exists, then calls scene's update method
func (m *Manager) Update() error {
	if m.currentScene == nil {
		return nil
	}

	m.CheckTransitions()
	m.CheckExit()

	//call the current scene's update method
	return m.currentScene.Update()

}

// check for exit condition
func (m *Manager) CheckExit() {
	if m.currentSceneId >= len(m.scenes) {
		os.Exit(0)
	}
}

// check for scene completion and if reached, set up next scene (if available)
func (m *Manager) CheckTransitions() {
	if m.currentScene.Completed() {
		m.currentSceneId++
		if m.currentSceneId < len(m.scenes) {
			m.currentScene = m.scenes[m.currentSceneId]
		}
	}
}

// calls current scene's draw method if the currentscene is valid
func (m *Manager) Draw(screen *ebiten.Image) {
	if m.currentScene != nil {
		m.currentScene.Draw(screen)
	}
}

// ebitengine proxy for layout
func (m *Manager) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int) {
	return m.Info.Dimension.Width, m.Info.Dimension.Height
}

// appends scene to the managed scenes
func (m *Manager) AddScene(s Scene) {
	m.scenes = append(m.scenes, s)
}

// sets the current scene, based on sceneindex
func (m *Manager) SetCurrentScene(sceneId int) {
	if sceneId >= 0 && sceneId < len(m.scenes) {
		m.currentSceneId = sceneId
		m.currentScene = m.scenes[m.currentSceneId]
	}
}

// check for exit condition
func (m *Manager) SetDimensions(a Area) {
	m.Info.Dimension = a
}