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//
// G4Navigator
//
// Class description:
//
// A class for use by the tracking management, able to obtain/calculate
// dynamic tracking time information such as the distance to the next volume,
// or to find the physical volume containing a given point in the world
// reference system. The navigator maintains a transformation history and
// other information to optimise the tracking time performance.

// - Created.                                  Paul Kent,     Jul 95/96
// - Made Navigator Abstract                   G. Cosmo,      Nov  2003
// - Added check mode                          G. Cosmo,      Mar  2004
// - Zero step protections                     J.A. / G.C.,   Nov  2004
// --------------------------------------------------------------------
#ifndef G4NAVIGATOR_HH
#define G4NAVIGATOR_HH 1

#include "geomdefs.hh"

#include "G4ThreeVector.hh"
#include "G4AffineTransform.hh"
#include "G4RotationMatrix.hh"

#include "G4LogicalVolume.hh"             // Used in inline methods
#include "G4TouchableHandle.hh"           //    "         "

#include "G4NavigationHistory.hh"
#include "G4NormalNavigation.hh"
#include "G4VoxelNavigation.hh"
#include "G4ParameterisedNavigation.hh"
#include "G4ReplicaNavigation.hh"
#include "G4RegularNavigation.hh"
#include "G4VExternalNavigation.hh"

#include <iostream>

class G4VPhysicalVolume;
class G4SafetyCalculator;

class G4Navigator
{
  public:

    friend std::ostream& operator << (std::ostream &os, const G4Navigator &n);

    G4Navigator();
      // Constructor - initialisers and setup.

    G4Navigator(const G4Navigator&) = delete;
    G4Navigator& operator=(const G4Navigator&) = delete;
      // Copy constructor & assignment operator not allowed.

    virtual ~G4Navigator();
      // Destructor. No actions.

    virtual G4double ComputeStep(const G4ThreeVector& pGlobalPoint,
                                 const G4ThreeVector& pDirection,
                                 const G4double pCurrentProposedStepLength,
                                       G4double& pNewSafety);
      // Calculate the distance to the next boundary intersected
      // along the specified NORMALISED vector direction and
      // from the specified point in the global coordinate
      // system. LocateGlobalPointAndSetup or LocateGlobalPointWithinVolume 
      // must have been called with the same global point prior to this call.
      // The isotropic distance to the nearest boundary is also
      // calculated (usually an underestimate). The current
      // proposed Step length is used to avoid intersection
      // calculations: if it can be determined that the nearest
      // boundary is >pCurrentProposedStepLength away, kInfinity
      // is returned together with the computed isotropic safety
      // distance. Geometry must be closed.

    G4double CheckNextStep(const G4ThreeVector& pGlobalPoint,
                           const G4ThreeVector& pDirection,
                           const G4double pCurrentProposedStepLength,
                                 G4double& pNewSafety); 
      // Same as above, but do not disturb the state of the Navigator.

    virtual
    G4VPhysicalVolume* ResetHierarchyAndLocate(const G4ThreeVector& point,
                                               const G4ThreeVector& direction,
                                               const G4TouchableHistory& h);

      // Resets the geometrical hierarchy and search for the volumes deepest
      // in the hierarchy containing the point in the global coordinate space.
      // The direction is used to check if a volume is entered.
      // The search begin is the geometrical hierarchy at the location of the
      // last located point, or the endpoint of the previous Step if
      // SetGeometricallyLimitedStep() has been called immediately before.
      // 
      // Important Note: In order to call this the geometry MUST be closed.

    virtual
    G4VPhysicalVolume* LocateGlobalPointAndSetup(const G4ThreeVector& point,
                                       const G4ThreeVector* direction = nullptr,
                                       const G4bool pRelativeSearch = true,
                                       const G4bool ignoreDirection = true);
      // Search the geometrical hierarchy for the volumes deepest in hierarchy
      // containing the point in the global coordinate space. Two main cases
      // are:
      //  i) If pRelativeSearch=false it makes use of no previous/state
      //     information. Returns the physical volume containing the point, 
      //     with all previous mothers correctly set up.
      // ii) If pRelativeSearch is set to true, the search begin is the
      //     geometrical hierarchy at the location of the last located point,
      //     or the endpoint of previous Step if SetGeometricallyLimitedStep()
      //     has been called immediately before.
      // The direction is used (to check if a volume is entered) if either
      //   - the argument ignoreDirection is false, or
      //   - the Navigator has determined that it is on an edge shared by two
      //     or more volumes.  (This is state information.)
      // 
      // Important Note: In order to call this the geometry MUST be closed.

    virtual
    void LocateGlobalPointWithinVolume(const G4ThreeVector& position);
      // Notify the Navigator that a track has moved to the new Global point
      // 'position', that is known to be within the current safety.
      // No check is performed to ensure that it is within  the volume. 
      // This method can be called instead of LocateGlobalPointAndSetup ONLY if
      // the caller is certain that the new global point (position) is inside
      // the same volume as the previous position.
      // Usually this can be guaranteed only if the point is within safety.

    inline void LocateGlobalPointAndUpdateTouchableHandle(
                  const G4ThreeVector&       position,
                  const G4ThreeVector&       direction,
                        G4TouchableHandle&   oldTouchableToUpdate,
                  const G4bool               RelativeSearch = true);
      // First, search the geometrical hierarchy like the above method
      // LocateGlobalPointAndSetup(). Then use the volume found and its
      // navigation history to update the touchable.

    inline void LocateGlobalPointAndUpdateTouchable(
                  const G4ThreeVector&       position,
                  const G4ThreeVector&       direction,
                        G4VTouchable*        touchableToUpdate,
                  const G4bool               RelativeSearch = true);
      // First, search the geometrical hierarchy like the above method
      // LocateGlobalPointAndSetup(). Then use the volume found and its
      // navigation history to update the touchable.

    inline void LocateGlobalPointAndUpdateTouchable(
                  const G4ThreeVector&       position,
                        G4VTouchable*        touchableToUpdate,
                  const G4bool               RelativeSearch = true);
      // Same as the method above but missing direction.

    inline void SetGeometricallyLimitedStep();
      // Inform the navigator that the previous Step calculated
      // by the geometry was taken in its entirety.

    virtual G4double ComputeSafety(const G4ThreeVector& globalpoint,
                                   const G4double pProposedMaxLength = DBL_MAX,
                                   const G4bool keepState = true);
      // Calculate the isotropic distance to the nearest boundary from the
      // specified point in the global coordinate system. 
      // The globalpoint utilised must be within the current volume.
      // The value returned is usually an underestimate.  
      // The proposed maximum length is used to avoid volume safety
      // calculations.  The geometry must be closed.
      // To ensure minimum side effects from the call, keepState must be true.

    inline G4VPhysicalVolume* GetWorldVolume() const;
      // Return the current  world (`topmost') volume.

    inline void SetWorldVolume(G4VPhysicalVolume* pWorld);
      // Set the world (`topmost') volume. This must be positioned at
      // origin (0,0,0) and unrotated.

    inline G4TouchableHistory* CreateTouchableHistory() const;
    inline G4TouchableHistory* CreateTouchableHistory(const G4NavigationHistory*) const;
      // `Touchable' creation methods: caller has deletion responsibility.

    virtual G4TouchableHandle CreateTouchableHistoryHandle() const;
      // Returns a reference counted handle to a touchable history.

    virtual G4ThreeVector GetLocalExitNormal(G4bool* valid);
    virtual G4ThreeVector GetLocalExitNormalAndCheck(const G4ThreeVector& point,
                                                           G4bool* valid);
    virtual G4ThreeVector GetGlobalExitNormal(const G4ThreeVector& point,
                                                    G4bool* valid);
      // Return Exit Surface Normal and validity too.
      // Can only be called if the Navigator's last Step has crossed a
      // volume geometrical boundary.
      // It returns the Normal to the surface pointing out of the volume that
      // was left behind and/or into the volume that was entered.
      // Convention:
      //   The *local* normal is in the coordinate system of the *final* volume.
      // Restriction:
      //   Normals are not available for replica volumes (returns valid= false)
      // These methods takes full care about how to calculate this normal,
      // but if the surfaces are not convex it will return valid=false.

    inline G4int GetVerboseLevel() const;
    inline void  SetVerboseLevel(G4int level);
      // Get/Set Verbose(ness) level.
      // [if level>0 && G4VERBOSE, printout can occur]

    inline G4bool IsActive() const;
      // Verify if the navigator is active.
    inline void  Activate(G4bool flag);
      // Activate/inactivate the navigator.

    inline G4bool EnteredDaughterVolume() const;
      // The purpose of this function is to inform the caller if the track is
      // entering a daughter volume while exiting from the current volume.
      // This method returns 
      // - True only in case 1) above, that is when the Step has caused
      //   the track to arrive at a boundary of a daughter.
      // - False in cases 2), 3) and 4), i.e. in all other cases.
      // This function is not guaranteed to work if SetGeometricallyLimitedStep()
      // was not called when it should have been called.
    inline G4bool ExitedMotherVolume() const;
      // Verify if the step has exited the mother volume.

    inline void CheckMode(G4bool mode);
      // Run navigation in "check-mode", therefore using additional
      // verifications and more strict correctness conditions.
      // Is effective only with G4VERBOSE set.
    inline G4bool IsCheckModeActive() const;
    inline void SetPushVerbosity(G4bool mode);
      // Set/unset verbosity for pushed tracks (default is true).

    void PrintState() const;
      // Print the internal state of the Navigator (for debugging).
      // The level of detail is according to the verbosity.

    inline const G4AffineTransform& GetGlobalToLocalTransform() const;
    inline const G4AffineTransform  GetLocalToGlobalTransform() const;
      // Obtain the transformations Global/Local (and inverse).
      // Clients of these methods must copy the data if they need to keep it.

    G4AffineTransform GetMotherToDaughterTransform(G4VPhysicalVolume* dVolume, 
                                                   G4int dReplicaNo,
                                                   EVolume dVolumeType );
      // Obtain mother to daughter transformation.

    inline void ResetStackAndState();
      // Reset stack and minimum or navigator state machine necessary for reset
      // as needed by LocalGlobalPointAndSetup.
      // Does not perform clears, resizes, or reset fLastLocatedPointLocal.

    inline G4int SeverityOfZeroStepping( G4int* noZeroSteps ) const; 
      // Report on severity of error and number of zero steps,
      // in case Navigator is stuck and is returning zero steps.
      // Values: 1 (small problem),  5 (correcting), 
      //         9 (ready to abandon), 10 (abandoned)

    inline G4ThreeVector GetCurrentLocalCoordinate() const;
      // Return the local coordinate of the point in the reference system
      // of its containing volume that was found by LocalGlobalPointAndSetup.
      // The local coordinate of the last located track.

    inline G4ThreeVector NetTranslation() const;
    inline G4RotationMatrix NetRotation() const;
      // Compute+return the local->global translation/rotation of current volume.

    inline void EnableBestSafety( G4bool value = false );
      // Enable best-possible evaluation of isotropic safety.

    inline G4VExternalNavigation* GetExternalNavigation() const;
    void SetExternalNavigation(G4VExternalNavigation* externalNav);
      // Accessor & modifier for custom external navigation.
   
    inline G4VoxelNavigation& GetVoxelNavigator();
    void SetVoxelNavigation(G4VoxelNavigation* voxelNav);
      // Alternative navigator for voxel volumes.

    inline G4Navigator* Clone() const;
      // Cloning feature for use in MT applications to clone
      // navigator, including external sub-navigator.
      // Client has responsibility for ownership of returned allocated pointer.

    inline G4ThreeVector GetLastStepEndPoint() const { return fStepEndPoint;}
      // Get endpoint of last step.

    void InformLastStep(G4double lastStep,
                        G4bool entersDaughtVol,
                        G4bool exitsMotherVol );
      // Derived navigators which rely on LocateGlobalPointAndSetup() need to
      // inform size of step, to maintain logic about arriving on boundary
      // for challenging cases.
      // Required in order to cope with multiple trials at boundaries
      // => Locate with use direction rather than simple, fast logic.

  protected:

    void SetSavedState();
      // ( fValidExitNormal, fExitNormal, fExiting, fEntering,
      //   fBlockedPhysicalVolume, fBlockedReplicaNo, fLastStepWasZero);
      // Extended to include:
      // ( fLastLocatedPointLocal, fLocatedOutsideWorld;
      //   fEnteredDaughter, fExitedMother
      //   fPreviousSftOrigin, sPreviousSafety)  Safety Sphere.

    void RestoreSavedState();
      // Copy aspects of the state, to enable a non-state changing
      // call to ComputeStep().
  
    virtual void ResetState();
      // Utility method to reset the navigator state machine.

    inline G4ThreeVector ComputeLocalPoint(const G4ThreeVector& rGlobPoint) const;
      // Return position vector in local coordinate system, given a position
      // vector in world coordinate system.

    inline G4ThreeVector ComputeLocalAxis(const G4ThreeVector& pVec) const;
      // Return the local direction of the specified vector in the reference
      // system of the volume that was found by LocalGlobalPointAndSetup.
      // The Local Coordinates of point in world coordinate system.

    inline EVolume VolumeType(const G4VPhysicalVolume *pVol) const;
      // Characterise `type' of volume - normal/replicated/parameterised.

    inline EVolume CharacteriseDaughters(const G4LogicalVolume *pLog) const;
      // Characterise daughter of logical volume.

    inline G4int GetDaughtersRegularStructureId(const G4LogicalVolume *pLv) const;
      // Get regular structure ID of first daughter.

    virtual void SetupHierarchy();
      // Renavigate & reset hierarchy described by current history:
      // o Reset volumes and recompute transforms and/or solids of
      // replicated/parameterised volumes.

    G4bool CheckOverlapsIterative(G4VPhysicalVolume* vol);
      // Utility method to trigger overlaps check on a volume with reported
      // overlaps ordered by relevance. Used in ComputeStep() when loopings
      // with zero step are detected.

  private:

    void ComputeStepLog(const G4ThreeVector& pGlobalpoint,
                              G4double moveLenSq) const;
      // Log and checks for steps larger than the tolerance.

  protected:

    G4double kCarTolerance, fMinStep, fSqTol;
      // Cached tolerances.

    //
    // BEGIN State information
    //

    G4NavigationHistory fHistory;
      // Transformation and history of the current path
      // through the geometrical hierarchy.

    G4ThreeVector fStepEndPoint;
      // Endpoint of last ComputeStep 
      // can be used for optimisation (e.g. when computing safety).
    G4ThreeVector fLastStepEndPointLocal; 
      // Position of the end-point of the last call to ComputeStep 
      // in last Local coordinates.

    G4int fVerbose = 0;
      // Verbose(ness) level  [if > 0, printout can occur].
   
    G4bool fEnteredDaughter;
      // A memory of whether in this Step a daughter volume is entered 
      // (set in Compute & Locate).
      // After Compute: it expects to enter a daughter
      // After Locate:  it has entered a daughter.

    G4bool fExitedMother;
      // A similar memory whether the Step exited current "mother" volume
      // completely, not entering daughter.

    G4bool fWasLimitedByGeometry = false;
      // Set true if last Step was limited by geometry.

  private:

    G4ThreeVector fLastLocatedPointLocal;
      // Position of the last located point relative to its containing volume.
      //  This is coupled with the bool member fLocatedOutsideWorld;

    G4ThreeVector fExitNormal;
      // Leaving volume normal, in the volume containing the exited
      // volume's coordinate system.
      // This is closely coupled with fValidExitNormal, which signals whether
      // we have a (valid) normal for volume we're leaving.
   
    G4ThreeVector fGrandMotherExitNormal;
      // Leaving volume normal, in its own coordinate system.
    G4ThreeVector fExitNormalGlobalFrame;
      // Leaving volume normal, in the global coordinate system.

    G4ThreeVector fPreviousSftOrigin;
    G4double fPreviousSafety; 
      // Memory of last safety origin & value. Used in ComputeStep() to ensure
      // that origin of current Step is in the same volume as the point of the
      // last relocation.

    G4VPhysicalVolume* fLastMotherPhys = nullptr;
      // Memory of the mother volume during previous step.
      // Intended use: inform user in case of stuck track.
   
    G4VPhysicalVolume* fBlockedPhysicalVolume;
    G4int fBlockedReplicaNo;
      // Identifies the volume and copy / replica number that is blocked
      // (after exiting -- because the exit direction is along the exit normal)
      // or a candidate for entry (after compute step).
   
    G4int fNumberZeroSteps;
      // Count zero steps, as one or two can occur due to changing momentum at
      // a boundary or at an edge common between volumes; several zero steps
      // are likely a problem in the geometry description or in the navigation.
      // Number of preceding moves that were Zero. Reset to 0 after finite step.
    G4int fActionThreshold_NoZeroSteps = 10;  
      // After this many failed/zero steps, act (push etc).
    G4int fAbandonThreshold_NoZeroSteps = 25; 
      // After this many failed/zero steps, abandon track.

    G4bool fActive = false;
      // States if the navigator is activated or not.

    G4bool fLastTriedStepComputation = false; 
      // Whether ComputeStep() was called since the last call to a Locate().
      // Uses: distinguish parts of state which differ before/after calls
      // to ComputeStep() or one of the Locate() methods; avoid two consecutive
      // calls to compute-step (illegal).

    G4bool fEntering, fExiting;
      // Entering/Exiting volumes blocking/setup.
      // o If exiting, volume ptr & replica number (set & used by Locate..())
      //   used for blocking on redescent of geometry;
      // o If entering, volume ptr & replica number (set by ComputeStep(),
      //   used by Locate..()) of volume for 'automatic' entry.
   
    G4bool fValidExitNormal;
      // Set true if have leaving volume normal.
    G4bool fLastStepWasZero;
      // Whether the last ComputeStep moved Zero. Used to check for edges.
    G4bool fLocatedOnEdge;       
      // Whether the Navigator has detected an edge.
    G4bool fLocatedOutsideWorld;
      // Whether the last call to Locate methods left the world.
   
    G4bool  fChangedGrandMotherRefFrame;
      // Whether frame is changed.
    G4bool  fCalculatedExitNormal;
      // Has it been computed since the last call to ComputeStep().
      // Covers both Global and GrandMother.

    // END State information
    //

    // Optional State information (created/used as needed)
    // 
   
    // Save key state information (NOT the navigation history stack)
    //
    struct G4SaveNavigatorState
    { 
       G4ThreeVector sExitNormal;  
       G4bool sValidExitNormal;    
       G4bool sEntering, sExiting;
       G4VPhysicalVolume* spBlockedPhysicalVolume;
       G4int sBlockedReplicaNo;  
       G4int sLastStepWasZero; 
       G4bool sWasLimitedByGeometry;

       //  Potentially relevant
       //
       G4bool sLocatedOutsideWorld;
       G4ThreeVector sLastLocatedPointLocal; 
       G4bool sEnteredDaughter, sExitedMother;
       G4ThreeVector sPreviousSftOrigin;
       G4double sPreviousSafety; 
    } fSaveState; 

    // BEGIN -- Tracking Invariants
    // ===========================================

    G4VPhysicalVolume* fTopPhysical = nullptr;
      // A link to the topmost physical volume in the detector.
      // Must be positioned at the origin and unrotated.

    // Helpers/Utility classes
    //
    G4NormalNavigation fnormalNav;
    G4VoxelNavigation* fpvoxelNav;
    G4ParameterisedNavigation fparamNav;
    G4ReplicaNavigation freplicaNav;
    G4RegularNavigation fregularNav;
    G4VExternalNavigation* fpExternalNav = nullptr;
    G4VoxelSafety* fpVoxelSafety;
    G4SafetyCalculator* fpSafetyCalculator = nullptr;

    // Utility information
    //
    G4bool fCheck = false;
      // Check-mode flag  [if true, more strict checks are performed].
    G4bool fPushed = false, fWarnPush = true;
      // Push flags  [if true, means a stuck particle has been pushed].

    // End -- Tracking Invariants
};

#include "G4Navigator.icc"

#endif


// NOTES:
//
// The following methods provide detailed information when a Step has
// arrived at a geometrical boundary.  They distinguish between the different
// causes that can result in the track leaving its current volume.
//
// Four cases are possible:
//
// 1) The particle has reached a boundary of a daughter of the current volume:
//     (this could cause the relocation to enter the daughter itself
//     or a potential granddaughter or further descendant)
//     
// 2) The particle has reached a boundary of the current
//     volume, exiting into a mother (regardless the level
//     at which it is located in the tree):
//
// 3) The particle has reached a boundary of the current
//     volume, exiting into a volume which is not in its
//     parental hierarchy:
//
// 4) The particle is not on a boundary between volumes:
//     the function returns an exception, and the caller is
//     reccomended to compare the G4touchables associated
//     to the preStepPoint and postStepPoint to handle this case.
//
//   G4bool        EnteredDaughterVolume()
//   G4bool        IsExitNormalValid()
//   G4ThreeVector GetLocalExitNormal()
//
// The expected usefulness of these methods is to allow the caller to
// determine how to compute the surface normal at the volume boundary. The two
// possibilities are to obtain the normal from:
//
//   i) the solid associated with the volume of the initial point of the Step.
//      This is valid for cases 2 and 3.  
//      (Note that the initial point is generally the PreStepPoint of a Step).
//   or
// 
//  ii) the solid of the final point, ie of the volume after the relocation.
//      This is valid for case 1.
//      (Note that the final point is generally the PreStepPoint of a Step).
//
// This way the caller can always get a valid normal, pointing outside
// the solid for which it is computed, that can be used at his own
// discretion.
