package hero

import (
	"image/color"

	"github.com/hajimehoshi/ebiten/v2"

	"github.com/atridad/LilGuy/internal/config"
	"github.com/atridad/LilGuy/internal/projectile"
	"github.com/atridad/LilGuy/internal/world"
)

const (
	defaultRadius       = 24.0
	defaultSpeed        = 200.0
	defaultMaxStamina   = 100.0
	defaultStaminaDrain = 50.0
	defaultStaminaRegen = 30.0

	heroSpriteScale = 0.175
)

// Input and bounds

type Input struct {
	Left   bool
	Right  bool
	Jump   bool
	Sprint bool
}

type Bounds struct {
	Width  float64
	Height float64
	Ground float64
}

type VisualState int

const (
	StateIdle VisualState = iota
	StateSprinting
	StateExhausted
)

type Direction int

const (
	DirLeft Direction = iota
	DirRight
)

// Tags

type Tag int

const (
	TagGravity Tag = iota
)

// Hero state

type Hero struct {
	X      float64
	Y      float64
	Radius float64

	VelocityX float64
	VelocityY float64

	Speed float64

	Color color.NRGBA

	Tags map[Tag]bool

	Stamina      float64
	MaxStamina   float64
	StaminaDrain float64
	StaminaRegen float64

	canSprint     bool
	wasSprintHeld bool
	isSprinting   bool
	isMoving      bool
	isGrounded    bool
	direction     Direction
	animFrame     int
	animTimer     float64
	lastAnimKey   animationKey

	ProjectileConfig projectile.ProjectileConfig
}

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,
		Tags:          map[Tag]bool{TagGravity: true},
		Stamina:       cfg.MaxStamina,
		MaxStamina:    cfg.MaxStamina,
		StaminaDrain:  cfg.StaminaDrain,
		StaminaRegen:  cfg.StaminaRegen,
		canSprint:     true,
		wasSprintHeld: false,
		direction:     DirRight,
		animFrame:     0,
		animTimer:     0,
		lastAnimKey:   animationKey{direction: DirRight, state: animIdle},
		ProjectileConfig: projectile.ProjectileConfig{
			Speed:  500.0,
			Radius: 4.0,
			Color:  color.NRGBA{R: 255, G: 0, B: 0, A: 255},
		},
	}
}

func (h *Hero) Update(input Input, dt float64, bounds Bounds, w *world.World) {
	if dt > 0.1 {
		dt = 0.1
	}
	h.updateMovement(input, dt, bounds, w)
	h.updateStamina(input, dt)
	h.updateAnimation(dt)
}

// Movement and physics

func (h *Hero) updateMovement(input Input, dt float64, bounds Bounds, w *world.World) {
	if h.HasTag(TagGravity) {
		h.VelocityY += config.Gravity * dt
	}
	if h.VelocityY > config.MaxFallSpeed {
		h.VelocityY = config.MaxFallSpeed
	}

	newY := h.Y + h.VelocityY*dt

	h.isGrounded = false

	if w != nil && h.VelocityY >= 0 {
		feetX := h.X
		var landedSurface *world.Surface

		for _, s := range w.Surfaces {
			if !s.IsWalkable() {
				continue
			}

			if feetX >= s.X && feetX <= s.X+s.Width {
				if h.Y <= s.Y && newY >= s.Y {
					if landedSurface == nil || s.Y < landedSurface.Y {
						landedSurface = s
					}
				}
			}
		}

		if landedSurface != nil {
			newY = landedSurface.Y
			h.VelocityY = 0
			h.isGrounded = true
		}
	}

	if !h.isGrounded {
		if newY >= bounds.Ground {
			newY = bounds.Ground
			h.VelocityY = 0
			h.isGrounded = true
		}
	}

	h.Y = newY

	if input.Jump && h.isGrounded {
		h.VelocityY = config.JumpStrength
		h.isGrounded = false
	}

	targetVelocityX := 0.0
	if input.Left {
		targetVelocityX -= h.Speed
		h.direction = DirLeft
	}
	if input.Right {
		targetVelocityX += h.Speed
		h.direction = DirRight
	}

	h.isMoving = targetVelocityX != 0

	h.isSprinting = input.Sprint && h.canSprint && h.Stamina > 0 && h.isMoving
	if h.isSprinting {
		targetVelocityX *= config.SprintSpeedMultiplier
	}

	friction := config.GroundFriction
	if !h.isGrounded {
		friction = config.AirFriction
	}

	frictionFactor := 1.0 - (1.0-friction)*dt*60.0
	if frictionFactor < 0 {
		frictionFactor = 0
	}
	h.VelocityX = h.VelocityX*frictionFactor + targetVelocityX*(1.0-frictionFactor)

	newX := h.X + h.VelocityX*dt

	if newX < h.Radius {
		h.X = h.Radius
		h.VelocityX = 0
	} else if newX > bounds.Width-h.Radius {
		h.X = bounds.Width - h.Radius
		h.VelocityX = 0
	} else {
		h.X = newX
	}
}

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

// Animation

func (h *Hero) updateAnimation(dt float64) {
	isMoving := h.isMoving
	key := animationKey{direction: h.direction, state: animIdle}
	if isMoving {
		key.state = animMove
	}

	// reset animation on state change
	if key != h.lastAnimKey {
		h.animFrame = 0
		h.animTimer = 0
		h.lastAnimKey = key
	}

	// advance animation only when moving
	if isMoving {
		animSpeed := config.NormalAnimSpeed * 0.5
		if h.isSprinting {
			animSpeed = config.SprintAnimSpeed * 0.5
		}
		if !h.isGrounded {
			animSpeed = config.JumpingAnimSpeed * 0.5
		}

		h.animTimer += dt

		// precise frame advancement
		if h.animTimer >= animSpeed {
			frameAdvance := int(h.animTimer / animSpeed)
			h.animTimer -= animSpeed * float64(frameAdvance)
			h.animFrame = (h.animFrame + frameAdvance) % config.AnimFrameWrap
		}
	} else {
		h.animTimer = 0
	}
}

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

	if h.isSprinting {
		return StateSprinting
	}

	return StateIdle
}

// Rendering

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

	if sprite != nil {
		bounds := sprite.Bounds()
		actualHeight := float64(bounds.Dy())
		actualWidth := float64(bounds.Dx())

		op := &ebiten.DrawImageOptions{}

		// center sprite horizontally, align bottom to feet
		op.GeoM.Translate(-actualWidth/2, -actualHeight)
		op.GeoM.Scale(config.HeroSpriteScale, config.HeroSpriteScale)

		// round position to nearest pixel for crisp rendering
		drawX := float64(int(h.X + 0.5))
		drawY := float64(int(h.Y + 0.5))
		op.GeoM.Translate(drawX, drawY)

		// apply visual state coloring
		state := h.getVisualState()
		switch state {
		case StateExhausted:
			op.ColorScale.ScaleWithColor(color.RGBA{R: 255, G: 100, B: 100, A: 255})
		case StateSprinting:
			// no color modification for sprinting
		case StateIdle:
			// no color modification for idle
		}

		op.Filter = ebiten.FilterNearest
		screen.DrawImage(sprite, op)
	}
}

func (h *Hero) getCurrentSprite() *ebiten.Image {
	return getKnightSprite(h.direction, h.isMoving, h.animFrame)
}

func (h *Hero) AddTag(tag Tag) {
	if h.Tags == nil {
		h.Tags = make(map[Tag]bool)
	}
	h.Tags[tag] = true
}

func (h *Hero) RemoveTag(tag Tag) {
	if h.Tags == nil {
		return
	}
	delete(h.Tags, tag)
}

func (h *Hero) HasTag(tag Tag) bool {
	if h.Tags == nil {
		return false
	}
	return h.Tags[tag]
}

func (h *Hero) GetDirection() Direction {
	return h.direction
}