///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
list wasDualQuicksort(list a, list b) {
    if(llGetListLength(a) <= 1) return a+b;
 
    float pivot_a = llList2Float(a, 0);
    a = llDeleteSubList(a, 0, 0);
    vector pivot_b = llList2Vector(b, 0);
    b = llDeleteSubList(b, 0, 0);
 
    list less = [];
    list less_b = [];
    list more = [];
    list more_b = [];
 
    do {
        if(llList2Float(a, 0) > pivot_a) {
            less += llList2List(a, 0, 0);
            less_b += llList2List(b, 0, 0);
            jump continue;
        }
        more += llList2List(a, 0, 0);
        more_b += llList2List(b, 0, 0);
@continue;
        a = llDeleteSubList(a, 0, 0);
        b = llDeleteSubList(b, 0, 0);
    } while(llGetListLength(a));
    return wasDualQuicksort(less, less_b) + [ pivot_a ] + [ pivot_b ] + wasDualQuicksort(more, more_b);
}

///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2014 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
// determines whether the segment AB intersects the segment CD
integer wasSegmentIntersect(vector A, vector B, vector C, vector D) {
    vector s1 = <B.x - A.x, B.y - A.y, B.z - A.z>;
    vector s2 = <D.x - C.x, D.y - C.y, D.y - C.z>;
 
    float d = (s1.x * s2.y -s2.x * s1.y);
 
    if(d == 0) return FALSE;
 
    float s = (s1.x * (A.y - C.y) - s1.y * (A.x - C.x)) / d;
    float t = (s2.x * (A.y - C.y) - s2.y * (A.x - C.x)) / d;
 
    // intersection at <A.x + (t * s1.x), A.y + (t * s1.y), A.z + (t * s1.z)>;
    return (integer)(s >= 0 && s <= 1 && t >= 0 && t <= 1 && 
            A.z + t*(B.z - A.z) == C.z + s*(D.z - C.z));
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
//    www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html    //
///////////////////////////////////////////////////////////////////////////
integer wasPointInPolygon(vector p, list polygon) {
    integer inside = FALSE;
    integer i = 0;
    integer nvert = llGetListLength(polygon);
    integer j = nvert-1;
    do {
        vector pi = llList2Vector(polygon, i);
        vector pj = llList2Vector(polygon, j);
        if ((pi.y > p.y) != (pj.y > p.y))
            if(p.x < (pj.x - pi.x) * (p.y - pi.y) / (pj.y - pi.y) + pi.x)
                inside = !inside;
        j = i++;
    } while(i<nvert);
    return inside;
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
//    www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html    //
///////////////////////////////////////////////////////////////////////////
list wasPointToPolygon(list polygon, vector point) {
    integer i = llGetListLength(polygon)-1;
    list l = [];
    do {
        l = llListInsertList(l, (list)llVecDist(point, llList2Vector(polygon, i)), 0);
    } while(--i>-1);
    l = wasDualQuicksort(l, polygon);
    return [llList2Float(l, 0), llList2Vector(l, 1)];
 
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
//    www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html    //
///////////////////////////////////////////////////////////////////////////
vector wasPolygonCentroid(list polygon, vector start, float tollerance, integer power) {
    // calculate the distance to the point farthest away from the start.
    list wpf = wasPointToPolygon(polygon, start);
    float dist = llList2Float(wpf, 0);
    vector next = llList2Vector(wpf, 1);
 
    // now calculate the next jump point
    next = start + ((dist/power)/dist) * (next-start);
 
    // if it falls withing the tollerance range, return it;
    if(llVecMag(start-next) < tollerance) return next;
    return wasPolygonCentroid(polygon, next, tollerance, power*power);
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2011 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
vector wasCirclePoint(float radius) {
    float x = llPow(-1, 1 + (integer) llFrand(2)) * llFrand(radius*2);
    float y = llPow(-1, 1 + (integer) llFrand(2)) * llFrand(radius*2);
    if(llPow(x,2) + llPow(y,2) <= llPow(radius,2))
        return <x, y, 0>;
    return wasCirclePoint(radius);
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2011 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
vector wasPolygonPoint(list polygon) {
    vector c = wasPolygonCentroid(polygon, llList2Vector(polygon, 0), 0.05, 2);
    float r = llList2Float(wasPointToPolygon(polygon, c), 0);
    vector d;
    do {
        d = c + wasCirclePoint(r);
    } while(wasPointInPolygon(d, polygon) == FALSE);
    return d;
}

///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2015 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
// determines whether the path between the current positon m and the 
// computed next position d will intersect any two sides of the polygon
vector wasPolygonPath(vector m, list polygon) {
    integer c = llGetListLength(polygon) - 1;
    vector d = wasPolygonPoint(polygon);
    integer i = 0;
    do {
        vector s = llList2Vector(polygon, c);
        vector p = llList2Vector(polygon, c-1);
        // project in plane
        if(wasSegmentIntersect(
            <m.x, m.y, 0>, 
            <d.x, d.y, 0>, 
            <s.x, s.y, 0>, 
            <p.x, p.y, 0>))
            ++i;
    } while(--c > 0);
    if(i > 1) return wasPolygonPath(m, polygon);
    return d;
}
 
integer _targetID = 0;
moveTo(vector position) {
    llTargetRemove(_targetID);
    _targetID = llTarget(position, .1);
    llLookAt(position, .6, .6);
    llMoveToTarget(position, 1);    
}

///////////////////////////////////////////////////////////////////////////
// these points represent the coordinates of the points that define the  //
// contour (permimeter) of the polgyon                                   //
///////////////////////////////////////////////////////////////////////////
list polygonPoints = [
    <163.349121, 171.559189, 3400.894287>,
    <165.56424, 170.422821, 3400.894287>,
    <164.364594, 169.194382, 3400.894287>,
    <165.171875, 167.453903, 3400.894287>,
    <162.345123, 167.61731, 3400.894287> 
];
 
default
{
    state_entry() {
        llVolumeDetect(TRUE);
        // first move to any point within the polygon
        moveTo(wasPolygonPoint(polygonPoints));
    }
    at_target(integer tnum, vector targetpos, vector ourpos) {
        if(tnum != _targetID) return;
        // now perform additional ray-cast
        moveTo(wasPolygonPath(llGetPos(), polygonPoints));
    }
}