import { useGameStore } from '@/stores/gameStore'
import { useWorldStore } from '@/stores/worldStore'
import { usePlayerStore } from '@/stores/playerStore'
import { TICK_DURATION_MS, MAX_TICKS } from '@/engine/constants'

let lastTime = 0
let accumulatedTime = 0
let frameTime = 0
let tickTime = 0
let tickCount = 0
let frameCount = 0
let lastSecondTime = 0

/**
 * Main game loop that handles fixed timestep updates and rendering
 * @param timestamp Current timestamp from requestAnimationFrame
 */
function gameLoop(timestamp: number) {
  // Initialize time on first frame
  if (!lastTime) {
    lastTime = timestamp
  }

  // Calculate time differences
  const delta = timestamp - lastTime
  lastTime = timestamp
  accumulatedTime += delta

  // Update frame counter for FPS calculation
  frameCount++
  frameTime += delta

  // Process game ticks at fixed intervals
  while (accumulatedTime >= TICK_DURATION_MS) {
    // Update game state
    updateGame()
    
    // Update tick counter for TPS calculation
    tickCount++
    tickTime += TICK_DURATION_MS
    accumulatedTime -= TICK_DURATION_MS
  }

  // Calculate and update performance metrics
  updatePerformanceMetrics(timestamp)

  // Render the game
  renderGame()

  // Schedule next frame
  requestAnimationFrame(gameLoop)
}

/**
 * Update game state (fixed timestep)
 */
function updateGame() {
  const gameStore = useGameStore.getState()
  const worldStore = useWorldStore.getState()
  const playerStore = usePlayerStore.getState()

  // Skip updates if game is paused
  if (gameStore.paused) return

  // Update game tick counter
  gameStore.actions.incrementTick()

  // Update world time
  worldStore.actions.updateWorldTime()

  // Update player position and physics
  updatePlayerPhysics()

  // Update entities
  updateEntities()

  // Update scheduled block ticks
  updateScheduledTicks()

  // Update random block ticks
  updateRandomTicks()
}

/**
 * Update player physics and movement
 */
function updatePlayerPhysics() {
  const playerStore = usePlayerStore.getState()
  const player = playerStore.player

  if (!player) return

  // Apply gravity
  player.velocity[1] += -32 * (TICK_DURATION_MS / 1000)

  // Apply movement
  // This is a simplified version - actual implementation would handle input and collision detection
  player.position[0] += player.velocity[0] * (TICK_DURATION_MS / 1000)
  player.position[1] += player.velocity[1] * (TICK_DURATION_MS / 1000)
  player.position[2] += player.velocity[2] * (TICK_DURATION_MS / 1000)

  // Update player state
  playerStore.actions.updatePosition(player.position)
}

/**
 * Update all entities in the world
 */
function updateEntities() {
  // Implementation would iterate through all entities and update their state
  // including AI, physics, and animations
}

/**
 * Process scheduled block ticks
 */
function updateScheduledTicks() {
  // Implementation would handle scheduled block updates like redstone ticks
}

/**
 * Process random block ticks (like plant growth)
 */
function updateRandomTicks() {
  // Implementation would handle random block updates based on world's randomTickSpeed
}

/**
 * Render the game scene
 */
function renderGame() {
  // Implementation would handle rendering with Three.js
  // including camera updates, chunk rendering, and UI
}

/**
 * Update performance metrics (FPS, TPS)
 * @param timestamp Current timestamp
 */
function updatePerformanceMetrics(timestamp: number) {
  // Calculate FPS and TPS
  if (timestamp - lastSecondTime >= 1000) {
    const fps = frameCount / (frameTime / 1000)
    const tps = tickCount / (tickTime / 1000)
    
    useGameStore.getState().actions.updatePerformance({
      averageFPS: fps,
      averageTPS: tps,
    })
    
    // Update debug UI
    useUIStore.getState().actions.updateDebugInfo({
      fps: Math.round(fps),
      tps: Math.round(tps),
    })
    
    // Reset counters
    frameCount = 0
    frameTime = 0
    tickCount = 0
    tickTime = 0
    lastSecondTime = timestamp
  }
}

/**
 * Start the game loop
 */
export function startGameLoop() {
  requestAnimationFrame(gameLoop)
}