// The Operator's Token — backlog E.F1.T1
// ◇ THE WINDOW — a fiction-layer physical artifact.
//
// 30 mm diameter disk, 3 mm thick.
//   front face — the 6-char Ledger batch code, raised 0.6 mm
//   back face  — a procedural symbol engraved 0.6 mm, derived
//                deterministically from the batch code (no two
//                batches carry the same mark)
//   rim        — a 1.2 mm circumferential groove holding a paper
//                insert strip (cut to 2.8 mm × ~92 mm)
//
// Render one batch:
//   openscad -o token-AAA-A1.stl -D 'batch="AAA-A1"' operators_token.scad
// Batch render for every ledger entry: tools/generate_token.py
//
// Print notes: front face up, 0.2 mm layers, no supports. The raised
// text survives at 0.4 mm nozzles; the back engraving prints face-down
// against the bed and comes out crisp on textured plates.

batch = "AAA-A1";

d         = 30;    // disk diameter, mm
th        = 3;     // disk thickness, mm
relief    = 0.6;   // raise / engrave depth, mm
groove_w  = 1.2;   // paper-insert groove width, mm
groove_dp = 1.2;   // groove depth into the rim, mm

$fn = 180;

// ── deterministic seed from the batch string ─────────────────────────
// Position-weighted character sum; stable across renders, distinct
// across batches. Drives every parameter of the back symbol.
function seed(s, i = 0, acc = 0) =
    i >= len(s) ? acc : seed(s, i + 1, acc + ord(s[i]) * (i * 31 + 7));

S = seed(batch);

// ── body with rim groove ─────────────────────────────────────────────
module body() {
    difference() {
        cylinder(d = d, h = th);
        // circumferential groove at mid-thickness for the paper strip
        translate([0, 0, th / 2])
            rotate_extrude()
                translate([d / 2 - groove_dp, -groove_w / 2])
                    square([groove_dp + 1, groove_w]);
    }
}

// ── front: raised batch code ─────────────────────────────────────────
module front_code() {
    translate([0, 0, th])
        linear_extrude(relief)
            text(batch, size = 5,
                 font = "Menlo:style=Bold",
                 spacing = 1.1,
                 halign = "center", valign = "center");
}

// ── back: the procedural symbol (engraved) ───────────────────────────
// Twelve radial ticks gated by the seed's low bits, an inner ring,
// and 2–5 outer arc segments from the seed's high bits. Engraved into
// the back face, so it reads correctly in relief and in rubbings.
module back_symbol_2d() {
    // radial ticks — bit i of S
    for (i = [0:11])
        if (floor(S / pow(2, i)) % 2 == 1)
            rotate(i * 30)
                translate([d * 0.20, -0.8])
                    square([d * 0.16, 1.6]);
    // inner ring
    difference() {
        circle(d = d * 0.24);
        circle(d = d * 0.24 - 2.4);
    }
    // outer arc segments — count and phase from the seed
    arcs  = 2 + S % 4;          // 2..5 segments
    phase = (S * 13) % 360;
    for (a = [0:arcs - 1])
        rotate(phase + a * (360 / arcs))
            arc_segment(r_in = d * 0.40, r_out = d * 0.40 + 1.4,
                        sweep = 360 / arcs * 0.55);
}

module arc_segment(r_in, r_out, sweep) {
    intersection() {
        difference() { circle(r = r_out); circle(r = r_in); }
        polygon([[0, 0],
                 [r_out * 2, 0],
                 [r_out * 2 * cos(sweep), r_out * 2 * sin(sweep)]]);
    }
}

module back_engraving() {
    translate([0, 0, -0.01])
        linear_extrude(relief + 0.01)
            back_symbol_2d();
}

// ── assembly ─────────────────────────────────────────────────────────
difference() {
    union() {
        body();
        front_code();
    }
    back_engraving();
}