// Cutout geometry for accessories that mount to the IKEA Skadis pegboard
// via the printable T-Clip system from
// https://www.printables.com/model/256896-skadis-t-clip-system
//
// Provides:
//   skadis_t_clip_cutout(plate_thickness, slot_w, slot_h,
//                        recess_d, recess_depth, recess_fillet_r)
//     Negative geometry for one mount: pill-shaped through-slot plus a
//     cylindrical recess on the front face whose two outer joints (the
//     rim where the front face meets the wall, and the inner edge where
//     the wall meets the recess floor) are filleted by recess_fillet_r.
//     Place at the desired (x, z) of the slot center and subtract from
//     the back plate.
//
// Coordinate system at the cutout's origin:
//   X = horizontal (slot's short axis)
//   Y = pegboard outward; back face at Y=0, front face at Y=plate_thickness
//   Z = vertical (slot's long axis)

// Standard Skadis grid pitch (mm) — for callers that stack multiple mounts
SKADIS_PITCH = 40;

module skadis_t_clip_cutout(
    plate_thickness,
    slot_w          = 5.0,
    slot_h          = 15.0,
    recess_d        = 22.2,
    recess_depth    = 2.9,
    recess_fillet_r = 0.8
) {
    // Pill-shaped through-slot: hull of two cylinders aligned with Y.
    slot_pad = 1;
    e = (slot_h - slot_w) / 2;
    hull()
        for (zc = [-e, e])
            translate([0, -slot_pad, zc])
                rotate([-90, 0, 0])
                    cylinder(h = plate_thickness + 2 * slot_pad, d = slot_w);

    // Cylindrical recess of diameter recess_d with proper fillets at
    // both joints. The wall-to-floor joint (interior, concave from
    // inside the recess) tightens the floor by recess_fillet_r; the
    // wall-to-front-face joint (exterior, rounded plate corner) opens
    // the rim by recess_fillet_r so it joins the front face smoothly.
    recess_pad = 0.5;
    translate([0, plate_thickness - recess_depth, 0])
        rotate([-90, 0, 0])
            rotate_extrude($fn = 96)
                polygon(_skadis_recess_profile(
                    r     = recess_d / 2,
                    depth = recess_depth,
                    f     = recess_fillet_r,
                    pad   = recess_pad));
}

// Radial-axial 2D profile of the filleted-recess negative. X is the
// radial direction, Y is the axial direction (Y=0 at the recess floor,
// Y=depth at the front face, with a pad above for clean Boolean cuts).
//
// Two proper fillets, each bulging toward the corner being rounded:
//   - bottom fillet: rounds the negative's convex floor-to-wall joint
//     (arc center at (r-f, f), inside the negative)
//   - top fillet: rounds the plate's convex wall-to-front-face joint
//     (arc center at (r+f, depth-f), inside the plate material)
// The bottom narrows the floor by f; the top opens the rim wider by f.
function _skadis_recess_profile(r, depth, f, pad, n_arc = 16) =
    let (
        bottom_arc = [
            for (i = [0 : n_arc])
                let (a = 270 + 90 * i / n_arc)
                    [(r - f) + f * cos(a), f + f * sin(a)]
        ],
        top_arc = [
            for (i = [0 : n_arc])
                let (a = 180 - 90 * i / n_arc)
                    [(r + f) + f * cos(a), (depth - f) + f * sin(a)]
        ]
    )
    concat(
        [[0, 0]],
        bottom_arc,
        top_arc,
        [[r + f, depth + pad]],
        [[0, depth + pad]]
    );