$fn = 64;

// Parametric Dimensions (in mm)
length = 160;
width = 100;
height = 80;
wall_thickness = 3;      // 3mm walls for 2kg load capacity
corner_radius = 8;       // Outer corner rounding
rim_width = 4;           // Reinforcement lip width
rim_height = 6;          // Reinforcement lip height

// Calculated Inner Dimensions
inner_length = length - (wall_thickness * 2);
inner_width = width - (wall_thickness * 2);
inner_radius = max(0.1, corner_radius - wall_thickness);

// Helper module for rounded rectangular prisms
module rounded_box(l, w, h, r) {
    hull() {
        for (x = [-1, 1]) {
            for (y = [-1, 1]) {
                translate([x * (l/2 - r), y * (w/2 - r), 0])
                    cylinder(r=r, h=h);
            }
        }
    }
}

union() {
    // Main bin body
    difference() {
        // Outer shell
        rounded_box(length, width, height, corner_radius);
        
        // Inner cavity (height + 1 prevents Z-fighting at the top)
        translate([0, 0, wall_thickness])
            rounded_box(inner_length, inner_width, height + 1, inner_radius);
    }
    
    // Structural top rim for rigidity
    difference() {
        // Outer rim volume
        translate([0, 0, height - rim_height])
            rounded_box(
                length + (rim_width * 2), 
                width + (rim_width * 2), 
                rim_height, 
                corner_radius + rim_width
            );
            
        // Inner rim cutout (extended to prevent Z-fighting)
        translate([0, 0, height - rim_height - 1])
            rounded_box(
                inner_length, 
                inner_width, 
                rim_height + 2, 
                inner_radius
            );
    }
}