$fn = 64;

// --- PARAMETERS ---
num_slots = 3;               // Number of holding slots
wall_thickness = 4;          // Thickness of rigid dividers
relief_gap = 3;              // Gap behind the spring arm for flexing
spring_thickness = 2;        // Thickness of the flexible spring arm
grip_gap = 16;               // Resting width of the slot for pliers
depth = 30;                  // Depth of the holder
height = 30;                 // Height of the holder
back_thickness = 5;          // Thickness of the mounting backplate

// Calculated dimensions
slot_spacing = wall_thickness + relief_gap + spring_thickness + grip_gap;
total_width = num_slots * slot_spacing + wall_thickness;

// --- MODULES ---

// Generates the 2D profile of the flexible spring arm
module arm_profile() {
    r = spring_thickness / 2;
    
    // Control points for the spring arm curve
    p0 = [wall_thickness + relief_gap + r, -0.1];
    p1 = [wall_thickness + relief_gap + r, depth * 0.25];
    p2 = [wall_thickness + relief_gap + r + 4, depth * 0.65]; // Pinch point
    p3 = [wall_thickness + relief_gap + r + 1, depth * 0.9];  // Flared opening

    // Build continuous smooth arm using hulled circles
    hull() { translate(p0) circle(r); translate(p1) circle(r); }
    hull() { translate(p1) circle(r); translate(p2) circle(r); }
    hull() { translate(p2) circle(r); translate(p3) circle(r); }
}

// Generates the countersunk mounting hole
module mounting_hole() {
    translate([0, -back_thickness - 0.2, 0])
    rotate([-90, 0, 0]) {
        // Screw shaft clearance (M4 screw size)
        cylinder(d=4.5, h=back_thickness + 0.4);
        // Countersink for screw head
        translate([0, 0, back_thickness - 2])
            cylinder(d1=4.5, d2=8.5, h=2.5);
    }
}

// --- MAIN GEOMETRY ---

// Best printed on its bottom (Z=0 plane) for optimal spring layer strength
difference() {
    union() {
        // Backplate
        translate([0, -back_thickness, 0])
            cube([total_width, back_thickness, height]);

        // Rigid Dividers
        for (i = [0 : num_slots]) {
            translate([i * slot_spacing, -0.1, 0]) {
                // Main wall
                cube([wall_thickness, depth + 0.1 - wall_thickness/2, height]);
                // Rounded front edge
                translate([wall_thickness/2, depth + 0.1 - wall_thickness/2, 0])
                    cylinder(d=wall_thickness, h=height);
            }
        }

        // Spring Arms
        for (i = [0 : num_slots - 1]) {
            translate([i * slot_spacing, 0, 0])
                linear_extrude(height)
                arm_profile();
        }
    }

    // Mounting Holes (Placed in the center of the first and last slots)
    hole_offset = wall_thickness + relief_gap + spring_thickness + (grip_gap / 2);
    z_center = height / 2;

    // Hole 1 (First slot)
    translate([hole_offset, 0, z_center])
        mounting_hole();

    // Hole 2 (Last slot)
    translate([(num_slots - 1) * slot_spacing + hole_offset, 0, z_center])
        mounting_hole();
}