invader.go

package main

import (
	"github.com/faiface/pixel"
	"github.com/faiface/pixel/pixelgl"
)

/*
Invader represents a single alien invader
*/
type Invader struct {
	assetManager *AssetManager
	window       *pixelgl.Window
	sprite       *pixel.Sprite
	color        int
	pos          pixel.Vec
	width        float64
	height       float64
	leftEdge     float64
	rightEdge    float64
	dead         bool
}

/*
NewInvader makes a new invader struct. It is initialized with one of
three colors: blue(1), green(2), or red(3).
*/
func NewInvader(window *pixelgl.Window, color int, assetManager *AssetManager) (*Invader, error) {
	var sprite *pixel.Sprite

	switch color {
	case 1:
		sprite = assetManager.GetBlueInvaderSprite()

	case 2:
		sprite = assetManager.GetGreenInvaderSprite()

	default:
		sprite = assetManager.GetRedInvaderSprite()
	}

	result := &Invader{
		assetManager: assetManager,
		window:       window,
		sprite:       sprite,
		color:        color,
		pos:          pixel.V(0, 0),
		width:        sprite.Frame().W(),
		height:       sprite.Frame().H(),
		dead:         false,

		leftEdge:  sprite.Frame().W() / 2,
		rightEdge: window.Bounds().W() - (sprite.Frame().W() / 2),
	}

	return result, nil
}

/*
Draw renders this invader onto the window
*/
func (invader *Invader) Draw() {
	if !invader.dead {
		invader.sprite.Draw(invader.assetManager.Batch, pixel.IM.Moved(invader.pos))
		// invader.sprite.Draw(invader.window, pixel.IM.Moved(invader.pos))
	}
}

/*
GetRect returns a bounding rectangle for this invader
*/
func (invader *Invader) GetRect() pixel.Rect {
	return pixel.R(invader.pos.X, invader.pos.Y, invader.pos.X+invader.width, invader.pos.Y+invader.height)
}

/*
IsAlive returns true if the invader isn't dead
*/
func (invader *Invader) IsAlive() bool {
	return !invader.dead
}

/*
IsLeftEdge returns true if the invader is on the left edge of the window
*/
func (invader *Invader) IsLeftEdge() bool {
	return invader.pos.X <= invader.leftEdge
}

/*
IsRightEdge returns true if the invader is on the right edge of the window
*/
func (invader *Invader) IsRightEdge() bool {
	return invader.pos.X >= invader.rightEdge
}

/*
Move advances the invader to the left or right. Direction
is either 1 for right, or -1 for left.
*/
func (invader *Invader) Move(direction float64, dt float64) {
	move := 140.0 * direction
	x := invader.pos.X + (move * dt)
	invader.pos.X = pixel.Clamp(x, invader.leftEdge, invader.rightEdge)
}

/*
PushDown moves the invader down a row
*/
func (invader *Invader) PushDown() {
	invader.pos.Y -= invader.height
}

/*
Resurrect brings this invader back to life
*/
func (invader *Invader) Resurrect() {
	invader.dead = false
}

/*
SetPosition sets the invader's vector
*/
func (invader *Invader) SetPosition(pos pixel.Vec) {
	invader.pos = pos
}