## phantom_meteor.nim — PhantomMeteor gravity engine as a MovementModule.
## Wraps gravity.nim (GravityEngine) to satisfy the MovementModule concept.
## Fire detection, phantom bullets, waves, and danger histogram are all internal.
## All angles in radians internally; interface outputs degrees for bot API.

import std/math
import gun_harness/gun_interface
import movement_harness/movement_interface

# Inline the gravity engine types and logic here to keep the module self-contained.
# We re-export nothing from gravity.nim — it's not on the common_libs path.
# ponytail: copy instead of import; if gravity.nim moves to common_libs, collapse.

# ── Vec2 (local, unexported) ──────────────────────────────────────────────────

type
  Vec2 = object
    x, y: float64

proc vec2(x, y: float64): Vec2 {.inline.} = Vec2(x: x, y: y)
proc `+`(a, b: Vec2): Vec2 {.inline.} = vec2(a.x+b.x, a.y+b.y)
proc `-`(a, b: Vec2): Vec2 {.inline.} = vec2(a.x-b.x, a.y-b.y)
proc `*`(a: Vec2, s: float64): Vec2 {.inline.} = vec2(a.x*s, a.y*s)
proc magnitude(v: Vec2): float64 {.inline.} = sqrt(v.x*v.x + v.y*v.y)
proc normalize(v: Vec2): Vec2 =
  let m = v.magnitude
  if m < 1e-9: vec2(0.0, 0.0) else: vec2(v.x/m, v.y/m)
proc dist(a, b: Vec2): float64 {.inline.} = (a-b).magnitude

# ── Gravity engine types ──────────────────────────────────────────────────────

const NumBins = 41

type
  DangerHistogram = object
    bins: array[NumBins, float64]

  PhantomBullet = object
    pos, vel: Vec2
    weight:   float64
    alive:    bool
    ticks:    int

  Wave = object
    origin:    Vec2
    heading:   float64
    speed:     float64
    radius:    float64
    startDist: float64

  GravityEngine = object
    histogram:       DangerHistogram
    phantoms:        seq[PhantomBullet]
    waves:           seq[Wave]
    prevEnemyEnergy: float64

# ── Gravity engine internals ──────────────────────────────────────────────────

const
  KBullet       = 1500.0
  KWall         = 4000.0
  KEnemy        = 300.0
  PreferredDist = 400.0
  NumPhantoms   = 25
  MinDist       = 20.0
  WallMinDist   = 40.0
  VeryClose     = 40.0

proc initEngine(): GravityEngine =
  var h: DangerHistogram
  for i in 0..<NumBins: h.bins[i] = 1.0
  GravityEngine(histogram: h, phantoms: @[], waves: @[], prevEnemyEnergy: 100.0)

proc gfToBin(gf: float64): int =
  int(((gf.clamp(-1.0,1.0) + 1.0) / 2.0 * float64(NumBins-1)).round).clamp(0, NumBins-1)

proc mea(speed: float64): float64 = arcsin(min(8.0/speed, 1.0))

proc detectFire(eng: var GravityEngine, energy: float64): tuple[fired: bool; power: float64] =
  let drop = eng.prevEnemyEnergy - energy
  eng.prevEnemyEnergy = energy
  if drop >= 0.1 and drop <= 3.0: (true, drop) else: (false, 0.0)

proc spawnPhantoms(eng: var GravityEngine, enemyPos, botPos: Vec2, bspeed: float64) =
  let base = arctan2(botPos.y - enemyPos.y, botPos.x - enemyPos.x)
  let maxA = mea(bspeed)
  for i in 0..<NumPhantoms:
    let gf     = if NumPhantoms == 1: 0.0 else: -1.0 + float64(i)/float64(NumPhantoms-1)*2.0
    let angle  = base + gf * maxA
    let weight = eng.histogram.bins[gfToBin(gf)]
    eng.phantoms.add PhantomBullet(
      pos: enemyPos, vel: vec2(bspeed*cos(angle), bspeed*sin(angle)),
      weight: weight, alive: true, ticks: 0)

proc tickPhantoms(eng: var GravityEngine) =
  for i in 0..<eng.phantoms.len:
    if not eng.phantoms[i].alive: continue
    eng.phantoms[i].pos = eng.phantoms[i].pos + eng.phantoms[i].vel
    inc eng.phantoms[i].ticks
    if eng.phantoms[i].ticks >= 50: eng.phantoms[i].alive = false
  if eng.phantoms.len > 200:
    var live: seq[PhantomBullet]
    for p in eng.phantoms:
      if p.alive: live.add p
    eng.phantoms = live

proc spawnWave(eng: var GravityEngine, enemyPos, botPos: Vec2, bspeed: float64) =
  eng.waves.add Wave(
    origin: enemyPos,
    heading: arctan2(botPos.y - enemyPos.y, botPos.x - enemyPos.x),
    speed: bspeed, radius: 0.0, startDist: dist(enemyPos, botPos))

proc tickWaves(eng: var GravityEngine, botPos: Vec2) =
  var i = 0
  while i < eng.waves.len:
    eng.waves[i].radius += eng.waves[i].speed
    if eng.waves[i].radius >= eng.waves[i].startDist:
      let toBot = arctan2(botPos.y - eng.waves[i].origin.y,
                          botPos.x - eng.waves[i].origin.x)
      var off = toBot - eng.waves[i].heading
      while off >  PI: off -= 2.0*PI
      while off < -PI: off += 2.0*PI
      let maxA = mea(eng.waves[i].speed)
      if maxA >= 1e-9:
        let gf = (off / maxA).clamp(-1.0, 1.0)
        eng.histogram.bins[gfToBin(gf)] += 1.0
      eng.waves.del(i)
    else:
      inc i

proc computeForces(eng: GravityEngine, botPos, enemyPos: Vec2, arenaW, arenaH: float64): Vec2 =
  var total = vec2(0.0, 0.0)

  # Priority 1: nearby phantoms
  var hasClose = false
  for ph in eng.phantoms:
    if ph.alive:
      let d = dist(ph.pos, botPos)
      if d < 150.0:
        hasClose = true
        total = total + normalize(botPos - ph.pos) * (KBullet * (1.0 - d/150.0))

  # Priority 2: wall escape (hard override)
  let minW = min(min(botPos.x, arenaW-botPos.x), min(botPos.y, arenaH-botPos.y))
  if minW < VeryClose:
    var ex = 0.0; var ey = 0.0
    if botPos.x         < VeryClose: ex =  1.0
    if arenaW - botPos.x < VeryClose: ex = -1.0
    if botPos.y         < VeryClose: ey =  1.0
    if arenaH - botPos.y < VeryClose: ey = -1.0
    let m = sqrt(ex*ex + ey*ey)
    if m > 0.1: return normalize(vec2(ex,ey)) * 500.0

  # Priority 3: distance to enemy
  let de = dist(enemyPos, botPos)
  if not hasClose and de > 100.0:
    if de < PreferredDist:
      total = total + normalize(botPos - enemyPos) * KEnemy
    elif de > PreferredDist + 100.0:
      total = total + normalize(enemyPos - botPos) * (KEnemy * 0.3)

  # Priority 4: weak wall repulsion
  let dL = max(botPos.x,         WallMinDist)
  let dR = max(arenaW - botPos.x, WallMinDist)
  let dB = max(botPos.y,         WallMinDist)
  let dT = max(arenaH - botPos.y, WallMinDist)
  total = total + vec2(KWall*0.5/(dL*dL) - KWall*0.5/(dR*dR),
                       KWall*0.5/(dB*dB) - KWall*0.5/(dT*dT))
  total

# ── MovementModule wrapper ────────────────────────────────────────────────────

type PhantomMeteorModule* = object
  engine: GravityEngine

proc initPhantomMeteor*(): PhantomMeteorModule =
  PhantomMeteorModule(engine: initEngine())

proc resetRound*(m: var PhantomMeteorModule) =
  ## Clear per-round transients (phantoms, waves, energy baseline), keep histogram.
  m.engine.phantoms        = @[]
  m.engine.waves           = @[]
  m.engine.prevEnemyEnergy = 100.0

proc computeMove*(m: var PhantomMeteorModule, ws: WorldState): MoveCommand =
  let botPos   = vec2(ws.selfX, ws.selfY)
  let enemyPos = vec2(ws.enemyX, ws.enemyY)

  # Advance simulation
  m.engine.tickPhantoms()
  m.engine.tickWaves(botPos)

  # Fire detection → spawn phantoms + wave
  let (fired, power) = m.engine.detectFire(ws.enemyEnergy)
  if fired:
    let bspeed = 20.0 - 3.0 * power
    m.engine.spawnPhantoms(enemyPos, botPos, bspeed)
    m.engine.spawnWave(enemyPos, botPos, bspeed)

  # Compute force vector
  let force = m.engine.computeForces(botPos, enemyPos, ws.arenaWidth, ws.arenaHeight)

  if force.magnitude < 1e-9:
    return (speed: 0.0, turnRate: 0.0)

  # Enemy bearing (radians, math convention: 0=East, CCW+)
  let enemyBearingRad = arctan2(enemyPos.y - botPos.y, enemyPos.x - botPos.x)

  # Two perpendicular directions to enemy bearing (±90°)
  let perpCCW = vec2(-sin(enemyBearingRad),  cos(enemyBearingRad))  # +90°
  let perpCW  = vec2( sin(enemyBearingRad), -cos(enemyBearingRad))  # -90°

  # Pick perpendicular direction that aligns with force vector
  let fn = force.normalize
  let desiredDeg =
    if fn.x * perpCCW.x + fn.y * perpCCW.y >= fn.x * perpCW.x + fn.y * perpCW.y:
      radToDeg(arctan2(perpCCW.y, perpCCW.x))
    else:
      radToDeg(arctan2(perpCW.y, perpCW.x))

  # Delta from current heading
  var delta = desiredDeg - ws.selfHeading
  while delta >  180.0: delta -= 360.0
  while delta < -180.0: delta += 360.0

  # Dot-product trick: if |delta| > 90 → reverse, less turning
  let goForward = abs(delta) <= 90.0
  if not goForward:
    delta = if delta >= 0.0: delta - 180.0 else: delta + 180.0

  (speed: if goForward: 8.0 else: -8.0,
   turnRate: delta.clamp(-10.0, 10.0))