package screens

import (
	"fmt"
	"image/color"
	"time"

	"github.com/hajimehoshi/ebiten/v2"

	"github.com/atridad/BigFeelings/internal/hero"
	"github.com/atridad/BigFeelings/internal/save"
	"github.com/atridad/BigFeelings/internal/status"
	"github.com/atridad/BigFeelings/internal/ui/hud"
)

var (
	backgroundColor = color.NRGBA{R: 0, G: 0, B: 0, A: 255}
)

// Hero settings.
const (
	heroStartX       = 960 / 2 // ScreenWidth / 2
	heroStartY       = 540 / 2 // ScreenHeight / 2
	heroRadius       = 28.0
	heroSpeed        = 180.0
	heroMaxStamina   = 100.0
	heroStaminaDrain = 50.0
	heroStaminaRegen = 30.0
)

var (
	heroColor = color.NRGBA{R: 210, G: 220, B: 255, A: 255}
)

// HUD settings.
const (
	hudX = 960 - 220 // ScreenWidth - 220
	hudY = 20
)

// HUD colors.
var (
	staminaNormalColor = color.NRGBA{R: 0, G: 255, B: 180, A: 255}
	staminaLowColor    = color.NRGBA{R: 255, G: 60, B: 60, A: 255}
	fpsGoodColor       = color.NRGBA{R: 120, G: 255, B: 120, A: 255}
	fpsWarnColor       = color.NRGBA{R: 255, G: 210, B: 100, A: 255}
	fpsPoorColor       = color.NRGBA{R: 255, G: 120, B: 120, A: 255}
)

const (
	staminaLowThreshold = 0.2
	fpsWarnThreshold    = 0.85
	fpsPoorThreshold    = 0.6
	fpsSampleWindow     = time.Second
	targetTPS           = 60
)

// Player input for the gameplay screen.
type GameplayInput struct {
	Left   bool
	Right  bool
	Up     bool
	Down   bool
	Sprint bool
}

// Manages the main gameplay state including the hero, HUD, and game world.
// This is where the actual game logic and rendering happens during active play.
type GameplayScreen struct {
	hero           *hero.Hero
	hud            hud.Overlay
	bounds         hero.Bounds
	lastTick       time.Time
	gameStartTime  time.Time
	totalPlayTime  time.Duration
	fpsEnabled     *bool
	fpsFrames      int
	fpsAccumulator time.Duration
	fpsValue       float64
}

// Creates a new gameplay screen instance.
func NewGameplayScreen(screenWidth, screenHeight int, fpsEnabled *bool) *GameplayScreen {
	return &GameplayScreen{
		hero: hero.New(hero.Config{
			StartX:       heroStartX,
			StartY:       heroStartY,
			Radius:       heroRadius,
			Speed:        heroSpeed,
			Color:        heroColor,
			MaxStamina:   heroMaxStamina,
			StaminaDrain: heroStaminaDrain,
			StaminaRegen: heroStaminaRegen,
		}),
		hud: hud.Overlay{
			X:     hudX,
			Y:     hudY,
			Color: color.White,
		},
		bounds: hero.Bounds{
			Width:  float64(screenWidth),
			Height: float64(screenHeight),
		},
		lastTick:      time.Now(),
		gameStartTime: time.Now(),
		fpsEnabled:    fpsEnabled,
	}
}

// Processes gameplay logic with the given input and delta time.
func (g *GameplayScreen) Update(input GameplayInput, delta time.Duration) {
	dt := delta.Seconds()

	g.hero.Update(hero.Input{
		Left:   input.Left,
		Right:  input.Right,
		Up:     input.Up,
		Down:   input.Down,
		Sprint: input.Sprint,
	}, dt, g.bounds)

	// Track total play time
	g.totalPlayTime += delta

	g.trackFPS(delta)
}

// Calculates the current FPS if FPS monitoring is enabled.
func (g *GameplayScreen) trackFPS(delta time.Duration) {
	if g.fpsEnabled == nil || !*g.fpsEnabled {
		return
	}

	g.fpsAccumulator += delta
	g.fpsFrames++

	if g.fpsAccumulator >= fpsSampleWindow {
		g.fpsValue = float64(g.fpsFrames) / g.fpsAccumulator.Seconds()
		g.fpsAccumulator = 0
		g.fpsFrames = 0
	}
}

// Renders the gameplay screen.
func (g *GameplayScreen) Draw(screen *ebiten.Image) {
	screen.Fill(backgroundColor)
	g.hero.Draw(screen)

	staminaColor := staminaNormalColor
	if g.hero.Stamina < g.hero.MaxStamina*staminaLowThreshold {
		staminaColor = staminaLowColor
	}

	staminaMeter := status.Meter{
		Label: "Stamina",
		Base:  g.hero.MaxStamina,
		Level: g.hero.Stamina,
		Color: staminaColor,
	}

	meters := []status.Meter{staminaMeter}

	if g.fpsEnabled != nil && *g.fpsEnabled {
		// Color based on target FPS (60).
		ratio := g.fpsValue / float64(targetTPS)
		fpsColor := fpsGoodColor
		switch {
		case ratio < fpsPoorThreshold:
			fpsColor = fpsPoorColor
		case ratio < fpsWarnThreshold:
			fpsColor = fpsWarnColor
		}

		fpsMeter := status.Meter{
			Label: fmt.Sprintf("Framerate: %3.0f FPS", g.fpsValue),
			Base:  -1, // Negative base means text-only display.
			Level: 0,
			Color: fpsColor,
		}
		meters = append(meters, fpsMeter)
	}

	g.hud.Draw(screen, meters)
}

// Resets the gameplay screen to its initial state.
func (g *GameplayScreen) Reset() {
	g.hero = hero.New(hero.Config{
		StartX:       heroStartX,
		StartY:       heroStartY,
		Radius:       heroRadius,
		Speed:        heroSpeed,
		Color:        heroColor,
		MaxStamina:   heroMaxStamina,
		StaminaDrain: heroStaminaDrain,
		StaminaRegen: heroStaminaRegen,
	})
	g.lastTick = time.Now()
	g.gameStartTime = time.Now()
	g.totalPlayTime = 0
	g.fpsFrames = 0
	g.fpsAccumulator = 0
	g.fpsValue = 0
}

// SaveState converts the current gameplay state to a saveable format.
func (g *GameplayScreen) SaveState() *save.GameState {
	return &save.GameState{
		HeroX:       g.hero.X,
		HeroY:       g.hero.Y,
		HeroStamina: g.hero.Stamina,
		PlayTimeMS:  g.totalPlayTime.Milliseconds(),
	}
}

// LoadState restores gameplay state from saved data.
func (g *GameplayScreen) LoadState(state *save.GameState) {
	g.hero = hero.New(hero.Config{
		StartX:       state.HeroX,
		StartY:       state.HeroY,
		Radius:       heroRadius,
		Speed:        heroSpeed,
		Color:        heroColor,
		MaxStamina:   heroMaxStamina,
		StaminaDrain: heroStaminaDrain,
		StaminaRegen: heroStaminaRegen,
	})
	g.hero.Stamina = state.HeroStamina
	g.totalPlayTime = time.Duration(state.PlayTimeMS) * time.Millisecond
	g.lastTick = time.Now()
	g.gameStartTime = time.Now()
	g.fpsFrames = 0
	g.fpsAccumulator = 0
	g.fpsValue = 0
}