$fn=64;

// --- Parameters ---
roll_dia = 36;           // Clearance diameter for standard poop bag roll
roll_height = 65;        // Clearance height for the roll
wall = 3;                // Wall thickness
slot_width = 5;          // Width of the dispensing slot
slot_height = 45;        // Height of the dispensing slot

// --- Derived Dimensions ---
outer_dia = roll_dia + wall * 2;
outer_height = roll_height + wall;

// --- Print Layout ---
// Main dispenser body
dispenser_body();

// Removable lid (placed side-by-side for printing)
translate([outer_dia + 15, 0, 0])
    lid();

// --- Modules ---
module dispenser_body() {
    difference() {
        union() {
            // Main cylindrical body
            cylinder(d=outer_dia, h=outer_height);
            // Wall mount backplate
            rounded_backplate();
        }
        
        // Inner cavity for the roll
        translate([0, 0, wall])
            cylinder(d=roll_dia, h=outer_height + 1);
            
        // Vertical dispensing slot
        translate([-slot_width/2, -outer_dia, wall + 10])
            cube([slot_width, outer_dia, slot_height]);
            
        // Easy-tear V-notch at the bottom of the slot
        // Catches the bag perforation for a clean tear
        translate([0, -outer_dia/2, wall + 10])
            rotate([90, 0, 0])
            linear_extrude(outer_dia, center=true)
            polygon([[-slot_width/2, 0.1], [slot_width/2, 0.1], [0, -8]]);
            
        // Mounting screw holes (Top and Bottom)
        // Positioned above and below the main cylinder for screwdriver access
        screw_hole(75);
        screw_hole(-15);
    }
}

module rounded_backplate() {
    // Backplate overlaps the cylinder slightly to ensure a manifold mesh
    translate([0, outer_dia/2 + 3.5, 0])
        rotate([90, 0, 0])
        linear_extrude(4) // 4mm thickness
        hull() {
            translate([-15, -20]) circle(d=10);
            translate([15, -20]) circle(d=10);
            translate([-15, 85]) circle(d=10);
            translate([15, 85]) circle(d=10);
        }
}

module screw_hole(z_pos) {
    // Countersunk screw hole cutouts (sized for standard #8 or 4mm screws)
    translate([0, outer_dia/2 + 5, z_pos])
        rotate([90, 0, 0]) {
            cylinder(d=4.5, h=10);                                 // Main screw shaft
            translate([0, 0, 5]) cylinder(d1=4.5, d2=8.5, h=2.01); // Countersink angle
            translate([0, 0, 7]) cylinder(d=8.5, h=10);            // Screw head clearance
        }
}

module lid() {
    // Simple drop-in lid to keep the roll contained
    difference() {
        union() {
            // Outer resting flange
            cylinder(d=outer_dia, h=wall);
            // Inner alignment plug (with 0.4mm clearance gap)
            translate([0, 0, wall])
                cylinder(d=roll_dia - 0.8, h=wall * 2);
        }
        // Center finger hole for easy removal
        translate([0, 0, -1])
            cylinder(d=16, h=wall * 4);
    }
}