## Enemy tracker — deterministic radar lock + dead reckoning for PPO_Bot.
## No bot API imports; takes plain floats.

import std/math

type
  EnemyState* = object
    x*, y*: float64
    direction*: float64
    speed*: float64
    energy*: float64
    ticksSinceLastScan*: int
    hasFired*: bool
    lastFirePower*: float64

  EnemyTracker* = object
    current*: EnemyState
    history*: array[5, tuple[x, y, direction, speed: float64]]  # sliding window
    historyCount*: int   # valid entries 0-5
    prevEnergy*: float64
    hasContact*: bool

proc initEnemyTracker*(): EnemyTracker = discard

proc update*(tracker: var EnemyTracker;
             scanX, scanY, scanDir, scanSpeed, scanEnergy: float64) =
  ## Call on ScannedBotEvent. Detects enemy fire from energy delta.

  # Shift history window
  if tracker.historyCount > 0:
    for i in countdown(min(tracker.historyCount, 4), 1):
      tracker.history[i] = tracker.history[i - 1]
  tracker.history[0] = (tracker.current.x, tracker.current.y,
                         tracker.current.direction, tracker.current.speed)
  if tracker.historyCount < 5:
    inc tracker.historyCount

  # Detect firing: energy drop in [0.1, 3.0] means enemy fired
  let delta = tracker.prevEnergy - scanEnergy
  if tracker.hasContact and delta >= 0.1 and delta <= 3.0:
    tracker.current.hasFired = true
    tracker.current.lastFirePower = delta
  else:
    tracker.current.hasFired = false

  tracker.prevEnergy = scanEnergy
  tracker.current.x = scanX
  tracker.current.y = scanY
  tracker.current.direction = scanDir
  tracker.current.speed = scanSpeed
  tracker.current.energy = scanEnergy
  tracker.current.ticksSinceLastScan = 0
  tracker.hasContact = true

proc deadReckon*(tracker: var EnemyTracker) =
  ## Call on missed ticks. Predict position from last known velocity.
  if not tracker.hasContact:
    return
  let rad = tracker.current.direction * PI / 180.0
  tracker.current.x += tracker.current.speed * sin(rad)
  tracker.current.y += tracker.current.speed * cos(rad)
  inc tracker.current.ticksSinceLastScan

proc normalizeRelative(angle: float64): float64 {.inline.} =
  result = angle mod 360.0
  if result >= 180.0: result -= 360.0
  elif result < -180.0: result += 360.0

proc getRadarTurnRate*(tracker: var EnemyTracker;
                       botX, botY, botDirection, radarDirection: float64): float64 =
  ## Returns radar turn rate (degrees/tick, positive = right).
  ## Before contact: full 45° sweep.
  ## After contact: lock with overshoot; widen if stale.
  if not tracker.hasContact:
    return 45.0

  if tracker.current.ticksSinceLastScan >= 8:
    # Lost lock — widen sweep
    return 45.0

  # Bearing from radar to enemy.
  # Tank Royale radar directions use standard math convention (0=east, CCW+).
  # arctan2(dy, dx) gives the standard math angle matching radarDirection units.
  let dx = tracker.current.x - botX
  let dy = tracker.current.y - botY
  let absoluteDir = (180.0 * arctan2(dy, dx) / PI + 360.0) mod 360.0
  var radarTurn = normalizeRelative(absoluteDir - radarDirection)

  # Width Lock: overshoot proportional to arctan(36 / distance)
  let distance = sqrt(dx * dx + dy * dy)
  let extraTurn = min(arctan(36.0 / distance) * 180.0 / PI, 45.0)
  if radarTurn < 0.0: radarTurn -= extraTurn
  else:               radarTurn += extraTurn
  result = radarTurn.clamp(-45.0, 45.0)