// Dusk lantern: the prim named "shade" glows and casts light while the region's sun is down.
// Checks once a minute (cheap), and on touch tells you what it's doing. Tessel (Claude Opus 5.5), 2026-10-09.
// 2026-10-10: a few fireflies drift around it while it's lit (particles: drawn by viewers, no load on the region).

integer shade;              // link number of the shade
integer lit = -1;           // -1 unknown, 0 off, 1 on
float DUSK = 0.05;          // sun height (z of the unit sun vector) below which it lights
vector LIGHT_COLOR = <1.0, 0.78, 0.45>;

integer find_shade()
{
    integer n = llGetNumberOfPrims();
    integer i;
    for (i = 1; i <= n; ++i)
        if (llGetLinkName(i) == "shade") return i;
    return 0;
}

fireflies(integer on)
{
    if (!on) { llLinkParticleSystem(shade, []); return; }
    llLinkParticleSystem(shade, [
        PSYS_PART_FLAGS, PSYS_PART_EMISSIVE_MASK | PSYS_PART_INTERP_COLOR_MASK | PSYS_PART_BOUNCE_MASK,
        PSYS_SRC_PATTERN, PSYS_SRC_PATTERN_EXPLODE,
        PSYS_SRC_BURST_RADIUS, 1.6,
        PSYS_SRC_BURST_RATE, 0.5, PSYS_SRC_BURST_PART_COUNT, 1,
        PSYS_SRC_BURST_SPEED_MIN, 0.03, PSYS_SRC_BURST_SPEED_MAX, 0.15,
        PSYS_SRC_OMEGA, <0.0, 0.0, 0.3>,
        PSYS_SRC_ACCEL, <0.0, 0.0, 0.01>,
        PSYS_PART_MAX_AGE, 7.0,
        PSYS_PART_START_COLOR, <0.85, 1.0, 0.45>, PSYS_PART_END_COLOR, <0.6, 0.9, 0.3>,
        PSYS_PART_START_ALPHA, 0.9, PSYS_PART_END_ALPHA, 0.0,
        PSYS_PART_START_SCALE, <0.1, 0.1, 0.0>, PSYS_PART_END_SCALE, <0.08, 0.08, 0.0>,
        PSYS_PART_START_GLOW, 0.4, PSYS_PART_END_GLOW, 0.1
    ]);
}

set_lit(integer on)
{
    if (on == lit || !shade) return;
    lit = on;
    fireflies(on);
    if (on)
        llSetLinkPrimitiveParamsFast(shade, [PRIM_POINT_LIGHT, TRUE, LIGHT_COLOR, 0.9, 6.0, 0.6,
            PRIM_FULLBRIGHT, ALL_SIDES, TRUE, PRIM_GLOW, ALL_SIDES, 0.12]);
    else
        llSetLinkPrimitiveParamsFast(shade, [PRIM_POINT_LIGHT, FALSE, LIGHT_COLOR, 0.9, 6.0, 0.6,
            PRIM_FULLBRIGHT, ALL_SIDES, FALSE, PRIM_GLOW, ALL_SIDES, 0.0]);
}

check()
{
    vector sun = llGetSunDirection();
    set_lit(sun.z < DUSK);
}

default
{
    state_entry()
    {
        shade = find_shade();
        lit = -1;
        check();
        llSetTimerEvent(60.0);
    }
    on_rez(integer p) { llResetScript(); }
    changed(integer c) { if (c & CHANGED_LINK) llResetScript(); }
    timer() { check(); }
    touch_start(integer n)
    {
        string state_text = "resting; it's daytime here";
        if (lit) state_text = "lit; the sun is down";
        llRegionSayTo(llDetectedKey(0), 0, "The lantern is " + state_text + ". It lights itself at dusk.");
    }
}