doctorlectro/entity/player.go

package entity

import (
	"time"

	"github.com/hajimehoshi/ebiten/v2"

	"github.com/jakecoffman/cp"

	"code.rocketnine.space/tslocum/doctorlectro/world"

	"code.rocketnine.space/tslocum/doctorlectro/asset"

	"code.rocketnine.space/tslocum/doctorlectro/component"
	"code.rocketnine.space/tslocum/gohan"
)

const (
	playerVelocity        = 120.0
	playerGroundAccelTime = 0.1
	playerGroundAccel     = playerVelocity / playerGroundAccelTime
	playerAirAccelTime    = 0.5
	playerAirAccel        = playerVelocity / playerAirAccelTime
	fallVelocity          = 900.0
)

func NewPlayer() gohan.Entity {
	playerBody := world.Space.AddBody(cp.NewBody(1, cp.INFINITY))
	playerBody.SetPosition(cp.Vector{0, 0})
	playerBody.SetVelocityUpdateFunc(playerUpdateVelocity)

	playerShape := world.Space.AddShape(cp.NewCircle(playerBody, 7.5, cp.Vector{}))
	playerShape.SetElasticity(0)
	playerShape.SetFriction(0)

	world.PlayerBody = playerBody
	world.PlayerShape = playerShape

	player := gohan.NewEntity()

	player.AddComponent(&component.Position{
		Body: world.PlayerBody,
	})

	player.AddComponent(&component.Velocity{})

	player.AddComponent(&component.Sprite{
		Frames:    asset.PlayerIdleFrames,
		FrameTime: 150 * time.Millisecond,
		NumFrames: len(asset.PlayerIdleFrames),
		Layer:     world.LayerPlayer,
	})

	player.AddComponent(&component.Player{})

	world.PlayerIdleFrames = asset.PlayerIdleFrames
	world.PlayerWalkFrames = asset.PlayerWalkFrames

	return player
}

func playerUpdateVelocity(body *cp.Body, gravity cp.Vector, damping, dt float64) {
	var normal cp.Vector
	var grounded bool
	world.PlayerBody.EachArbiter(func(arb *cp.Arbiter) {
		normal = arb.Normal().Neg()
		if normal.X != 0 || normal.Y != 0 {
			grounded = true
		}
	})
	world.PlayerNormal = normal
	world.PlayerGrounded = grounded

	// Apply magnetization by overwriting gravity.
	// Case MagnetizeDown is not handled because gravity is already set to the normal vector.
	if world.MagnetActive {
		switch world.MagnetDirection {
		case world.MagnetizeDownLeft:
			gravity = cp.Vector{-world.Gravity / 4, world.Gravity / 4}
		case world.MagnetizeLeft:
			gravity = cp.Vector{-world.Gravity, 0}
		case world.MagnetizeUpLeft:
			gravity = cp.Vector{-world.Gravity / 4, -world.Gravity / 4}
		case world.MagnetizeUp:
			gravity = cp.Vector{0, -world.Gravity}
		case world.MagnetizeUpRight:
			gravity = cp.Vector{world.Gravity / 4, -world.Gravity / 4}
		case world.MagnetizeRight:
			gravity = cp.Vector{world.Gravity, 0}
		case world.MagnetizeDownRight:
			gravity = cp.Vector{world.Gravity / 4, world.Gravity / 4}
		}
	}
	body.UpdateVelocity(gravity, damping, dt)

	xDir := 0.0
	yDir := 0.0
	if ebiten.IsKeyPressed(ebiten.KeyW) && world.PlayerGrounded {
		yDir -= 1
		world.LastWalkDirU = true
	}
	if ebiten.IsKeyPressed(ebiten.KeyS) {
		yDir += 1
		world.LastWalkDirU = false
	}
	if ebiten.IsKeyPressed(ebiten.KeyA) {
		xDir -= 1
		world.LastWalkDirL = false
	}
	if ebiten.IsKeyPressed(ebiten.KeyD) {
		xDir += 1
		world.LastWalkDirL = true
	}

	targetVelocity := playerVelocity
	if world.Debug > 0 && ebiten.IsKeyPressed(ebiten.KeyShift) {
		targetVelocity *= 4
	}

	// Target velocities based on user input.
	targetVx := targetVelocity * xDir
	targetVy := targetVelocity * yDir
	if targetVx == 0 {
		targetVx = gravity.X
	}
	if targetVy == 0 {
		targetVy = gravity.Y
	}

	v := body.Velocity()
	vx, vy := cp.Clamp(v.X, -fallVelocity, fallVelocity), cp.Clamp(v.Y, -fallVelocity, fallVelocity)
	vx, vy = cp.LerpConst(vx, targetVx, playerAirAccel*dt), cp.LerpConst(vy, targetVy, playerAirAccel*dt)
	body.SetVelocity(vx, vy)
}