// ----------------------------------------------------------------------------
//
//
// OpenSteer -- Steering Behaviors for Autonomous Characters
//
// Copyright (c) 2002-2003, Sony Computer Entertainment America
// Original author: Craig Reynolds <craig_reynolds@playstation.sony.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
//
// ----------------------------------------------------------------------------
//
//
// SteerLibraryMixin
//
// This mixin (class with templated superclass) adds the "steering library"
// functionality to a given base class.  SteerLibraryMixin assumes its base
// class supports the Ship interface.
//
// 10-04-04 bk:  put everything into the OpenSteer namespace
// 02-06-03 cwr: create mixin (from "SteerMass")
// 06-03-02 cwr: removed TS dependencies
// 11-21-01 cwr: created
//
//
// ----------------------------------------------------------------------------
module openmelee.steer;

    class Steer
    {
        // Constructor: initializes state
        this ()
        {
            // set inital state
            reset ();
        }

        // reset state
        void reset (void)
        {
            // initial state of wander behavior
            wanderSide = 0;
            wanderUp = 0;

            // default to non-gaudyPursuitAnnotation
            gaudyPursuitAnnotation = false;
        }

        // -------------------------------------------------- steering behaviors

        // Wander behavior
        float wanderSide;
        float wanderUp;

        bzVec2 steerForWander (float dt) {
            // random walk wanderSide and wanderUp between -1 and +1
            float speed = 12 * dt; // maybe this (12) should be an argument?
            wanderSide = scalarRandomWalk (wanderSide, speed, -1, +1);
            wanderUp   = scalarRandomWalk (wanderUp,   speed, -1, +1);

            // return a pure lateral steering vector: (+/-Side) + (+/-Up)
            return (side() * wanderSide) + (up() * wanderUp);
        }

        // Seek behavior
        bzVec2 steerForSeek (bzVec2 target) {
            bzVec2 desiredVelocity = target - position;
            return desiredVelocity - velocity;
        }

        // Flee behavior
        bzVec2 steerForFlee (bzVec2 target) {
            bzVec2 desiredVelocity = position - target;
            return desiredVelocity - velocity();
        }

        // xxx proposed, experimental new seek/flee [cwr 9-16-02]
        bzVec2 xxxsteerForFlee (bzVec2 target) {
            bzVec2 offset = position - target;
            bzVec2 desiredVelocity = offset.truncateLength (maxSpeed ());
            return desiredVelocity - velocity();
        }

        bzVec2 xxxsteerForSeek (bzVec2 target) {
            //  bzVec2 offset = target - position;
            bzVec2 offset = target - position;
            bzVec2 desiredVelocity = offset.truncateLength (maxSpeed ()); //xxxnew
            return desiredVelocity - velocity();
        }

        // ------------------------------------------------------------------------
        // Obstacle Avoidance behavior
        //
        // Returns a steering force to avoid a given obstacle.  The purely
        // lateral steering force will turn our vehicle towards a silhouette edge
        // of the obstacle.  Avoidance is required when (1) the obstacle
        // intersects the vehicle's current path, (2) it is in front of the
        // vehicle, and (3) is within minTimeToCollision seconds of travel at the
        // vehicle's current velocity.  Returns a zero vector value (bzVec2::zero)
        // when no avoidance is required.
        bzVec2 steerToAvoidObstacle (float minTimeToCollision, Obstacle obstacle) {

            bzVec2 avoidance = obstacle.steerToAvoid (this, minTimeToCollision);
            // XXX more annotation modularity problems (assumes spherical obstacle)
            if (avoidance != bzVec2::zero)
                annotateAvoidObstacle (minTimeToCollision * speed());

            return avoidance;
        }

        // avoids all obstacles in an ObstacleGroup

        bzVec2 steerToAvoidObstacles (float minTimeToCollision, 
                                      ObstacleGroup obstacles) {

            bzVec2 avoidance;
            PathIntersection nearest, next;
            float minDistanceToCollision = minTimeToCollision * speed();

            next.intersect = false;
            nearest.intersect = false;

            // test all obstacles for intersection with my forward axis,
            // select the one whose point of intersection is nearest
            for (ObstacleIterator o = obstacles.begin(); o != obstacles.end(); o++)
            {
                // xxx this should be a generic call on Obstacle, rather than
                // xxx this code which presumes the obstacle is spherical
                findNextIntersectionWithSphere ((SphericalObstacle)**o, next);

                if ((nearest.intersect == false) ||
                    ((next.intersect != false)
                     (next.distance < nearest.distance)))
                    nearest = next;
            }

            // when a nearest intersection was found
            if ((nearest.intersect != false)
                (nearest.distance < minDistanceToCollision))
            {
                // show the corridor that was checked for collisions
                annotateAvoidObstacle (minDistanceToCollision);

                // compute avoidance steering force: take offset from obstacle to me,
                // take the component of that which is lateral (perpendicular to my
                // forward direction), set length to maxForce, add a bit of forward
                // component (in capture the flag, we never want to slow down)
                bzVec2 offset = position - nearest.obstacle.center;
                avoidance = offset.perpendicularComponent (forward());
                avoidance = avoidance.normalize ();
                avoidance *= maxForce ();
                avoidance += forward() * maxForce () * 0.75;
            }

            return avoidance;
        }

        // ------------------------------------------------------------------------
        // Unaligned collision avoidance behavior: avoid colliding with other
        // nearby vehicles moving in unconstrained directions.  Determine which
        // (if any) other other vehicle we would collide with first, then steers
        // to avoid the site of that potential collision.  Returns a steering
        // force vector, which is zero length if there is no impending collision.

        bzVec2 steerToAvoidNeighbors (float minTimeToCollision, AVGroup others) {

            // first priority is to prevent immediate interpenetration
            bzVec2 separation = steerToAvoidCloseNeighbors (0, others);
            if (separation != bzVec2::zero) return separation;

            // otherwise, go on to consider potential future collisions
            float steer = 0;
            Ship* threat = NULL;

            // Time (in seconds) until the most immediate collision threat found
            // so far.  Initial value is a threshold: don't look more than this
            // many frames into the future.
            float minTime = minTimeToCollision;

            // xxx solely for annotation
            bzVec2 xxxThreatPositionAtNearestApproach;
            bzVec2 xxxOurPositionAtNearestApproach;

            // for each of the other vehicles, determine which (if any)
            // pose the most immediate threat of collision.
            for (AVIterator i = others.begin(); i != others.end(); i++)
            {
                Ship other = **i;
                if (other != this)
                {
                    // avoid when future positions are this close (or less)
                    float collisionDangerThreshold = radius() * 2;

                    // predicted time until nearest approach of "this" and "other"
                    float time = predictNearestApproachTime (other);

                    // If the time is in the future, sooner than any other
                    // threatened collision...
                    if ((time >= 0)  (time < minTime))
                    {
                        // if the two will be close enough to collide,
                        // make a note of it
                        if (computeNearestApproachPositions (other, time)
                            < collisionDangerThreshold)
                        {
                            minTime = time;
                            threat = other;
                            xxxThreatPositionAtNearestApproach
                                = hisPositionAtNearestApproach;
                            xxxOurPositionAtNearestApproach
                                = ourPositionAtNearestApproach;
                        }
                    }
                }
            }

            // if a potential collision was found, compute steering to avoid
            if (threat)
            {
                // parallel: +1, perpendicular: 0, anti-parallel: -1
                float parallelness = forward.dot(threat.forward);
                float angle = 0.707f;

                if (parallelness < -angle)
                {
                    // anti-parallel "head on" paths:
                    // steer away from future threat position
                    bzVec2 offset = xxxThreatPositionAtNearestApproach - position;
                    float sideDot = offset.dot(side());
                    steer = (sideDot > 0) ? -1.0f : 1.0f;
                }
                else
                {
                    if (parallelness > angle)
                    {
                        // parallel paths: steer away from threat
                        bzVec2 offset = threat.position - position;
                        float sideDot = offset.dot(side());
                        steer = (sideDot > 0) ? -1.0f : 1.0f;
                    }
                    else
                    {
                        // perpendicular paths: steer behind threat
                        // (only the slower of the two does this)
                        if (threat.speed() <= speed())
                        {
                            float sideDot = side().dot(threat.velocity);
                            steer = (sideDot > 0) ? -1.0f : 1.0f;
                        }
                    }
                }
            }

            return side() * steer;
        }

        // Given two vehicles, based on their current positions and velocities,
        // determine the time until nearest approach
        float predictNearestApproachTime (Ship other) {

            // imagine we are at the origin with no velocity,
            // compute the relative velocity of the other vehicle
            bzVec2 myVelocity = velocity;
            bzVec2 otherVelocity = other.velocity;
            bzVec2 relVelocity = otherVelocity - myVelocity;
            float relSpeed = relVelocity.length;

            // for parallel paths, the vehicles will always be at the same distance,
            // so return 0 (aka "now") since "there is no time like the present"
            if (relSpeed == 0) return 0;

            // Now consider the path of the other vehicle in this relative
            // space, a line defined by the relative position and velocity.
            // The distance from the origin (our vehicle) to that line is
            // the nearest approach.

            // Take the unit tangent along the other vehicle's path
            bzVec2 relTangent = relVelocity / relSpeed;

            // find distance from its path to origin (compute offset from
            // other to us, find length of projection onto path)
            bzVec2 relPosition = position - other.position;
            float projection = relTangent.dot(relPosition);

            return projection / relSpeed;
        }

        // Given the time until nearest approach (predictNearestApproachTime)
        // determine position of each vehicle at that time, and the distance
        // between them
        float computeNearestApproachPositions (Ship other, float time) {

            bzVec2 myTravel =  forward *  speed * time;
            bzVec2 otherTravel = other.forward * other.speed * time;

            bzVec2 myFinal =  position + myTravel;
            bzVec2 otherFinal = other.position + otherTravel;

            // xxx for annotation
            ourPositionAtNearestApproach = myFinal;
            hisPositionAtNearestApproach = otherFinal;

            return bzVec2::distance (myFinal, otherFinal);
        }

            // otherwise return zero
            return bzVec2::zero;
        }

        // ------------------------------------------------------------------------
        // pursuit of another vehicle ( version with ceiling on prediction time)

        bzVec2 steerForPursuit (Ship quarry) {
            return steerForPursuit (quarry, FLT_MAX);
        }

        bzVec2 steerForPursuit (Ship quarry, float maxPredictionTime) {

            // offset from this to quarry, that distance, unit vector toward quarry
            bzVec2 offset = quarry.position - position;
            float distance = offset.length ();
            bzVec2 unitOffset = offset / distance;

            // how parallel are the paths of "this" and the quarry
            // (1 means parallel, 0 is pependicular, -1 is anti-parallel)
            float parallelness = forward.dot(quarry.forward());

            // how "forward" is the direction to the quarry
            // (1 means dead ahead, 0 is directly to the side, -1 is straight back)
            float forwardness = forward.dot(unitOffset);

            float directTravelTime = distance / speed;
            int f = intervalComparison (forwardness,  -0.707f, 0.707f);
            int p = intervalComparison (parallelness, -0.707f, 0.707f);

            float timeFactor = 0; // to be filled in below
            bzVec2 color;           // to be filled in below (xxx just for debugging)

            // Break the pursuit into nine cases, the cross product of the
            // quarry being [ahead, aside, or behind] us and heading
            // [parallel, perpendicular, or anti-parallel] to us.
            switch (f)
            {
            case +1:
                switch (p)
                {
                case +1:          // ahead, parallel
                    timeFactor = 4;
                    color = gBlack;
                    break;
                case 0:           // ahead, perpendicular
                    timeFactor = 1.8f;
                    color = gGray50;
                    break;
                case -1:          // ahead, anti-parallel
                    timeFactor = 0.85f;
                    color = gWhite;
                    break;
                }
                break;
            case 0:
                switch (p)
                {
                case +1:          // aside, parallel
                    timeFactor = 1;
                    color = gRed;
                    break;
                case 0:           // aside, perpendicular
                    timeFactor = 0.8f;
                    color = gYellow;
                    break;
                case -1:          // aside, anti-parallel
                    timeFactor = 4;
                    color = gGreen;
                    break;
                }
                break;
            case -1:
                switch (p)
                {
                case +1:          // behind, parallel
                    timeFactor = 0.5f;
                    color= gCyan;
                    break;
                case 0:           // behind, perpendicular
                    timeFactor = 2;
                    color= gBlue;
                    break;
                case -1:          // behind, anti-parallel
                    timeFactor = 2;
                    color = gMagenta;
                    break;
                }
                break;
            }

            // estimated time until intercept of quarry
            float et = directTravelTime * timeFactor;

            // xxx experiment, if kept, this limit should be an argument
            float etl = (et > maxPredictionTime) ? maxPredictionTime : et;

            // estimated position of quarry at intercept
            bzVec2 target = quarry.predictFuturePosition (etl);

            // annotation
            annotationLine (position,
                            target,
                            gaudyPursuitAnnotation ? color : gGray40);

            return steerForSeek (target);
        }

        // ------------------------------------------------------------------------
        // evasion of another vehicle
        bzVec2 steerForEvasion (Ship menace,  float maxPredictionTime)  {

            // offset from this to menace, that distance, unit vector toward menace
            bzVec2 offset = menace.position - position;
            float distance = offset.length;

            float roughTime = distance / menace.speed;
            float predictionTime = ((roughTime > maxPredictionTime) ? maxPredictionTime : roughTime);
            bzVec2 target = menace.predictFuturePosition (predictionTime);

            return steerForFlee (target);
        }


        // ------------------------------------------------------------------------
        // tries to maintain a given speed, returns a maxForce-clipped steering
        // force along the forward/backward axis
        bzVec2 steerForTargetSpeed (float targetSpeed) {
            float mf = maxForce();
            float speedError = targetSpeed - speed ();
            return forward () * clip (speedError, -mf, +mf);
        }


        // ----------------------------------------------------------- utilities
        bool isAhead (bzVec2 target) {return isAhead (target, 0.707f);};
        bool isAside (bzVec2 target) {return isAside (target, 0.707f);};
        bool isBehind (bzVec2 target) {return isBehind (target, -0.707f);};

        bool isAhead (bzVec2 target, float cosThreshold)
        {
            bzVec2 targetDirection = (target - position ()).normalize ();
            return forward().dot(targetDirection) > cosThreshold;
        }

        bool isAside (bzVec2 target, float cosThreshold)
        {
            bzVec2 targetDirection = (target - position ()).normalize ();
            float dp = forward().dot(targetDirection);
            return (dp < cosThreshold)  (dp > -cosThreshold);
        }

        bool isBehind (bzVec2 target, float cosThreshold)
        {
            bzVec2 targetDirection = (target - position).normalize ();
            return forward().dot(targetDirection) < cosThreshold;
        }
    }