// Tidewater greeter: a 3-prim arm on a post that turns toward whoever arrives and waves for a few seconds,
// then lowers. Link 1 = post (root), links named "upper" and "fore" are the arm segments; their positions and
// rotations are solved each tick from the shoulder (top of the post), so it's a tiny two-bone rig.
// Idea and tips from a builder friend, 2026-10-11. Claude Opus 5.5 (Tessel).
float L1 = 0.5;          // upper arm
float L2 = 0.45;         // forearm
vector SHOULDER;         // local, top of the post
integer UPPER; integer FORE;
key greeted;             // last person waved at
float until;             // llGetTime() when the wave ends
vector aim = <1, 0, 0>;  // horizontal local direction toward the visitor

integer link_named(string n)
{
    integer i = llGetNumberOfPrims();
    for (; i > 1; --i) if (llGetLinkName(i) == n) return i;
    return 0;
}

pose(vector u, vector f)
{
    u = llVecNorm(u); f = llVecNorm(f);
    vector elbow = SHOULDER + u * L1;
    llSetLinkPrimitiveParamsFast(UPPER, [PRIM_POS_LOCAL, SHOULDER + u * (L1 / 2), PRIM_ROT_LOCAL, llRotBetween(<0, 0, 1>, u),
        PRIM_LINK_TARGET, FORE, PRIM_POS_LOCAL, elbow + f * (L2 / 2), PRIM_ROT_LOCAL, llRotBetween(<0, 0, 1>, f)]);
}

rest() { pose(<0.15, 0, -1>, <0.35, 0, -1>); llSetTimerEvent(0.0); }

default
{
    state_entry()
    {
        UPPER = link_named("upper"); FORE = link_named("fore");
        vector s = llGetScale();
        SHOULDER = <0, 0, s.z / 2>;
        rest();
        llSensorRepeat("", NULL_KEY, AGENT, 12.0, PI, 2.0);
    }
    on_rez(integer p) { llResetScript(); }
    changed(integer c) { if (c & CHANGED_LINK) llResetScript(); }

    sensor(integer n)
    {
        key who = llDetectedKey(0);
        if (who == greeted) return;
        greeted = who;
        vector d = (llDetectedPos(0) - llGetPos()) / llGetRot();
        d.z = 0;
        if (llVecMag(d) > 0.01) aim = llVecNorm(d);
        until = llGetTime() + 6.0;
        llSetTimerEvent(0.2);
    }
    no_sensor() { greeted = NULL_KEY; }

    touch_start(integer n)                                          // touch it and it waves at you
    {
        vector d = (llDetectedPos(0) - llGetPos()) / llGetRot();
        d.z = 0;
        if (llVecMag(d) > 0.01) aim = llVecNorm(d);
        until = llGetTime() + 6.0;
        llSetTimerEvent(0.2);
    }

    timer()
    {
        if (llGetTime() > until) { rest(); return; }
        vector side = llVecNorm(aim % <0, 0, 1>);
        vector u = aim * 0.45 + <0, 0, 0.9>;                       // raised, reaching toward them
        float th = 0.35 + 0.45 * llSin(llGetTime() * 7.0);          // the wave, side to side at the elbow
        vector f = <0, 0, 1> * llCos(th) + side * llSin(th) + aim * 0.2;
        pose(u, f);
    }
}