LilGuy/internal/hero/hero.go

package hero

import (
	"image/color"
	"math"

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

// Default values and gameplay constants.

const (
	// Default values if not specified in config
	defaultRadius       = 24.0
	defaultSpeed        = 180.0
	defaultMaxStamina   = 100.0
	defaultStaminaDrain = 50.0 // Per second when sprinting
	defaultStaminaRegen = 30.0 // Per second when not sprinting

	// Sprint mechanics
	sprintSpeedMultiplier   = 2.0
	sprintRecoveryThreshold = 0.2 // 20% stamina needed to sprint again

	// Animation
	normalAnimSpeed = 0.15 // Seconds per frame when walking
	sprintAnimSpeed = 0.08 // Seconds per frame when sprinting

	// Visual state thresholds
	exhaustedThreshold = 0.2 // Show exhausted state below 20% stamina
)

type Input struct {
	Left   bool
	Right  bool
	Up     bool
	Down   bool
	Sprint bool
}

type Bounds struct {
	Width  float64
	Height float64
}

type VisualState int

const (
	StateIdle VisualState = iota
	StateSprinting
	StateExhausted
)

type Direction int

const (
	DirDown Direction = iota
	DirUp
	DirLeft
	DirRight
)

type Hero struct {
	// Position and size
	X      float64
	Y      float64
	Radius float64

	// Movement
	Speed float64

	// Appearance
	Color color.NRGBA

	// Stamina system
	Stamina      float64
	MaxStamina   float64
	StaminaDrain float64
	StaminaRegen float64

	// Internal state
	canSprint     bool
	wasSprintHeld bool
	isSprinting   bool
	direction     Direction
	animFrame     int
	animTimer     float64
}

type Config struct {
	StartX       float64
	StartY       float64
	Radius       float64
	Speed        float64
	Color        color.NRGBA
	MaxStamina   float64
	StaminaDrain float64
	StaminaRegen float64
}

func New(cfg Config) *Hero {
	if cfg.Radius <= 0 {
		cfg.Radius = defaultRadius
	}
	if cfg.Speed <= 0 {
		cfg.Speed = defaultSpeed
	}
	if cfg.Color.A == 0 {
		cfg.Color = color.NRGBA{R: 210, G: 220, B: 255, A: 255}
	}
	if cfg.MaxStamina <= 0 {
		cfg.MaxStamina = defaultMaxStamina
	}
	if cfg.StaminaDrain <= 0 {
		cfg.StaminaDrain = defaultStaminaDrain
	}
	if cfg.StaminaRegen <= 0 {
		cfg.StaminaRegen = defaultStaminaRegen
	}

	return &Hero{
		X:             cfg.StartX,
		Y:             cfg.StartY,
		Radius:        cfg.Radius,
		Speed:         cfg.Speed,
		Color:         cfg.Color,
		Stamina:       cfg.MaxStamina,
		MaxStamina:    cfg.MaxStamina,
		StaminaDrain:  cfg.StaminaDrain,
		StaminaRegen:  cfg.StaminaRegen,
		canSprint:     true,
		wasSprintHeld: false,
		direction:     DirDown,
		animFrame:     0,
		animTimer:     0,
	}
}

func (h *Hero) Update(input Input, dt float64, bounds Bounds) {
	h.updateMovement(input, dt, bounds)
	h.updateStamina(input, dt)
	h.updateAnimation(input, dt)
}

func (h *Hero) updateMovement(input Input, dt float64, bounds Bounds) {
	dx, dy := 0.0, 0.0

	if input.Left {
		dx -= 1
		h.direction = DirLeft
	}
	if input.Right {
		dx += 1
		h.direction = DirRight
	}
	if input.Up {
		dy -= 1
		h.direction = DirUp
	}
	if input.Down {
		dy += 1
		h.direction = DirDown
	}

	isMoving := dx != 0 || dy != 0

	if isMoving {
		length := math.Hypot(dx, dy)
		dx /= length
		dy /= length
	}

	speed := h.Speed
	h.isSprinting = input.Sprint && h.canSprint && h.Stamina > 0 && isMoving
	if h.isSprinting {
		speed *= sprintSpeedMultiplier
	}

	h.X += dx * speed * dt
	h.Y += dy * speed * dt

	maxX := math.Max(h.Radius, bounds.Width-h.Radius)
	maxY := math.Max(h.Radius, bounds.Height-h.Radius)

	h.X = clamp(h.X, h.Radius, maxX)
	h.Y = clamp(h.Y, h.Radius, maxY)
}

func (h *Hero) updateStamina(input Input, dt float64) {
	if !input.Sprint {
		h.wasSprintHeld = false
		if h.Stamina >= h.MaxStamina*sprintRecoveryThreshold {
			h.canSprint = true
		}
	}

	if h.isSprinting {
		h.wasSprintHeld = true
		h.Stamina -= h.StaminaDrain * dt
		if h.Stamina <= 0 {
			h.Stamina = 0
			h.canSprint = false
		}
	} else {
		h.Stamina += h.StaminaRegen * dt
		if h.Stamina > h.MaxStamina {
			h.Stamina = h.MaxStamina
		}
	}
}

func (h *Hero) updateAnimation(input Input, dt float64) {
	isMoving := input.Left || input.Right || input.Up || input.Down

	if isMoving {
		animSpeed := normalAnimSpeed
		if h.isSprinting {
			animSpeed = sprintAnimSpeed
		}
		h.animTimer += dt
		if h.animTimer >= animSpeed {
			h.animTimer = 0
			h.animFrame = 1 - h.animFrame
		}
	} else {
		h.animFrame = 0
		h.animTimer = 0
	}
}

func (h *Hero) getVisualState() VisualState {
	if h.Stamina < h.MaxStamina*exhaustedThreshold {
		return StateExhausted
	}

	if h.isSprinting {
		return StateSprinting
	}

	return StateIdle
}

func (h *Hero) Draw(screen *ebiten.Image) {
	sprite := h.getCurrentSprite()

	if sprite != nil {
		op := &ebiten.DrawImageOptions{}
		bounds := sprite.Bounds()
		w, height := float64(bounds.Dx()), float64(bounds.Dy())
		op.GeoM.Translate(-w/2, -height/2)
		op.GeoM.Translate(h.X, h.Y)

		state := h.getVisualState()
		switch state {
		case StateExhausted:
			op.ColorScale.ScaleWithColor(color.RGBA{R: 255, G: 100, B: 100, A: 255})
		case StateSprinting:
			// No color change
		case StateIdle:
			// No color change
		}

		screen.DrawImage(sprite, op)
	}
}

func (h *Hero) getCurrentSprite() *ebiten.Image {
	var sprite *ebiten.Image

	switch h.direction {
	case DirUp:
		if h.animFrame == 0 {
			sprite = spriteBack1
		} else {
			sprite = spriteBack2
		}
	case DirDown:
		if h.animFrame == 0 {
			sprite = spriteFront1
		} else {
			sprite = spriteFront2
		}
	case DirLeft:
		if h.animFrame == 0 {
			sprite = spriteLeft1
		} else {
			sprite = spriteLeft2
		}
	case DirRight:
		if h.animFrame == 0 {
			sprite = spriteRight1
		} else {
			sprite = spriteRight2
		}
	}

	return sprite
}

func clamp(value, min, max float64) float64 {
	if value < min {
		return min
	}
	if value > max {
		return max
	}
	return value
}