$fn = $preview ? 18 : 360;

include <BOSL/constants.scad>
use <BOSL/threading.scad>

// dimensions of the esp
esp_w = 23;
esp_d = 19+4;
lid_h = 0.75
;
// horizontal spacing between the case and the esp
esp_s = 3;
// wall thickness of the case
wall_t = 2;
// screw alignment wall thickness 
screw_wall_t = 2;
inner_screw_t = 5;
//make sure that this is thicker then the diameter of a wall edge
//assert(screw_wall_t > sqrt(2*pow(wall_t,2)), "screw wall too thin, screw may intersect with the interiour of the case");

module case() {
    module esp_space(offset) {
        cube([
            esp_w + esp_s + offset*2,
            esp_d + esp_s + offset*2,
            lid_h + offset + 0.001
        ]);
    }
    esp_space(wall_t);
}

a = (sqrt(2)*(screw_wall_t*2 + inner_screw_t)*0.25)-wall_t;
module screw_cylinder(d, h_diff, offset_x, offset_y) {
    translate([offset_x,offset_y,-h_diff/2])
        cylinder(
            lid_h + wall_t+h_diff,
            d = d
        );
}

difference() {
    union() {
        case();
        screw_cylinder(screw_wall_t*2 + inner_screw_t, 0, -a, -a);
        //screw_cylinder(screw_wall_t*2 + inner_screw_t, 0, a+esp_w+esp_s+wall_t*2, -a);
        //screw_cylinder(screw_wall_t*2 + inner_screw_t, 0, -a, a+esp_d+esp_s+wall_t*2);
        screw_cylinder(screw_wall_t*2 + inner_screw_t, 0, a+esp_w+esp_s+wall_t*2, a+esp_d+esp_s+wall_t*2);
    }
    screw_cylinder(inner_screw_t, 0.01, -a, -a);
    //screw_cylinder(inner_screw_t, 0.01, a+esp_w+esp_s+wall_t*2, -a);
    //screw_cylinder(inner_screw_t, 0.01, -a, a+esp_d+esp_s+wall_t*2);
    screw_cylinder(inner_screw_t, 0.01, a+esp_w+esp_s+wall_t*2, a+esp_d+esp_s+wall_t*2);
}