// Negative sightings have the same ownership as visual reports: HQ may ingest
// this snapshot only after its physical source's uplink completes successfully.
class ERR_HQSearchReport
{
 string WatchSourceId;
 int WatchMessageId;
 int WatchRequestId;
 int SourceId;
 int MessageId;
 int BeliefId;
 int BeliefRevision;
 vector Position;
 float ObservedAt = -1;
 bool SweepCompleted;
 bool ContactFound;
}

class ERR_HQCoverageRules
{
 static bool PositionValid(vector position)
 {
  return ERR_HQPursuitRules.PositionValid(position)
   && Math.AbsFloat(position[0]) < 1000000 && Math.AbsFloat(position[2]) < 1000000;
 }
 static int Cell(float coordinate) { return Math.Floor(coordinate / 500); }
 // Bounded coordinates make this integer grid key collision-free, including
 // negative positions. No per-candidate string or collection allocation.
 static int Key(vector position)
 {
  return (Cell(position[0]) + 2000) * 4096 + Cell(position[2]) + 2000;
 }
 static bool Recent(float searchedAt, float now)
 {
  return ERR_HQPursuitRules.Finite(searchedAt) && ERR_HQPursuitRules.Finite(now)
   && searchedAt >= 0 && now >= searchedAt && now - searchedAt <= 900000;
 }
 static bool ValidReport(int sourceId, int messageId, int beliefId, int revision,
  bool completed, bool found, float observedAt, float now)
 {
  return sourceId > 0 && messageId > 0 && beliefId > 0 && revision > 0 && completed && !found
   && Recent(observedAt, now) && now - observedAt <= 120000;
 }
 static bool Point(int x, int z, vector center, float radius, out vector point)
 {
  point = Vector(x * 500 + 250, center[1], z * 500 + 250);
  if (vector.DistanceXZ(point, center) > radius)
  {
   // Small uncertainty circles need not include a grid center. Choose a point
   // in their intersecting cell; inset edges keep its key in the selected cell.
   point[0] = Math.Clamp(center[0], x * 500, x * 500 + 499.99);
   point[2] = Math.Clamp(center[2], z * 500, z * 500 + 499.99);
  }
  return PositionValid(point) && vector.DistanceXZ(point, center) <= radius;
 }
}

// A cell records a reported sweep visit, not proof that every building or hiding
// place in its 500m square was visible. New positive sightings invalidate that
// coarse exclusion; replay watermarks survive so old negatives cannot restore it.
class ERR_HQCoverage
{
 protected ref map<int, float> m_Cells = new map<int, float>();
 protected ref map<int, int> m_Messages = new map<int, int>();
 int Count() { return m_Cells.Count(); }
 void Forget(vector position)
 {
  if (ERR_HQCoverageRules.PositionValid(position)) m_Cells.Remove(ERR_HQCoverageRules.Key(position));
 }
 bool Recent(vector position, float now)
 {
  if (!ERR_HQCoverageRules.PositionValid(position)) return false;
  int key = ERR_HQCoverageRules.Key(position);
  return m_Cells.Contains(key) && ERR_HQCoverageRules.Recent(m_Cells.Get(key), now);
 }
 bool Ingest(ERR_HQSearchReport report, float now)
 {
  if (!report || !ERR_HQCoverageRules.PositionValid(report.Position)) return false;
  if (!ERR_HQCoverageRules.ValidReport(report.SourceId, report.MessageId, report.BeliefId,
   report.BeliefRevision, report.SweepCompleted, report.ContactFound, report.ObservedAt, now)) return false;
  if (m_Messages.Contains(report.SourceId) && report.MessageId <= m_Messages.Get(report.SourceId)) return false;
  // One uplink per source gives monotonic message order. Never evict replay
  // watermarks; the mission already caps its total physical formations at 128.
  if (!m_Messages.Contains(report.SourceId) && m_Messages.Count() >= 128) return false;
  m_Messages.Set(report.SourceId, report.MessageId);
  int key = ERR_HQCoverageRules.Key(report.Position);
  if (m_Cells.Contains(key) && m_Cells.Get(key) >= report.ObservedAt) return false;
  if (!m_Cells.Contains(key) && m_Cells.Count() >= 128)
  {
   int oldestKey;
   float oldest = 1e20;
   foreach (int known, float searched : m_Cells)
   {
    if (searched >= oldest) continue;
    oldest = searched;
    oldestKey = known;
   }
   if (oldest >= report.ObservedAt) return false;
   m_Cells.Remove(oldestKey);
  }
  // Store the observation time, not delivery time: radio delay never makes a
  // searched area newer than the physical sweep that justified it.
  m_Cells.Set(key, report.ObservedAt);
  return true;
 }
 protected bool Reserved(vector point, array<vector> reserved)
 {
  if (!reserved) return false;
  int key = ERR_HQCoverageRules.Key(point);
  foreach (vector position : reserved)
   if (ERR_HQCoverageRules.PositionValid(position) && ERR_HQCoverageRules.Key(position) == key) return true;
  return false;
 }
 bool Select(vector center, float radius, vector fromPosition, float now,
  out vector destination, array<vector> reserved = null)
 {
  destination = center;
  if (!ERR_HQCoverageRules.PositionValid(center) || !ERR_HQCoverageRules.PositionValid(fromPosition))
   return false;
  if (!ERR_HQPursuitRules.Finite(now) || now < 0 || !ERR_HQPursuitRules.Finite(radius)
   || radius < 0 || radius > 2000 || (reserved && reserved.Count() > 8)) return false;
  int lowX = ERR_HQCoverageRules.Cell(center[0] - radius);
  int highX = ERR_HQCoverageRules.Cell(center[0] + radius);
  int lowZ = ERR_HQCoverageRules.Cell(center[2] - radius);
  int highZ = ERR_HQCoverageRules.Cell(center[2] + radius);
  float best = 1e20;
  bool found;
  vector point;
  // Radius is bounded to 2 km: at most nine by nine candidate grid cells.
  for (int x = lowX; x <= highX; x++)
  {
   for (int z = lowZ; z <= highZ; z++)
   {
    if (!ERR_HQCoverageRules.Point(x, z, center, radius, point)) continue;
    if (Recent(point, now) || Reserved(point, reserved)) continue;
    float distance = vector.DistanceXZ(point, fromPosition);
    if (distance >= best) continue;
    best = distance;
    destination = point;
    found = true;
   }
  }
  return found;
 }
 void Clear() { m_Cells.Clear(); m_Messages.Clear(); }
}