/// title      : Basic Sleeved Rubber Bushing
// author     : Tim Farrell
// license    : MIT License
// revision   : 3
// tags       : Rubber
// file       : bushing.jscad

function getParameterDefinitions () {
  return [
    {name: 'overhang', type: 'float', initial: 7, min: 1, max: 40, step: 1, caption: 'Overhang'},
    {name: 'host_hole_diameter', type: 'float', initial: 13, min: 1, max: 40, step: 1, caption: 'Host hole diameter'},
    {name: 'host_hole_height', type: 'float', initial: 0.8, caption: 'Host hole height'},
    {name: 'bushing_height', type: 'float', initial: 4, min: 1, max: 40, step: 1, caption: 'Bushing height'},
    {name: 'bushing_diameter', type: 'float', initial: 10, min: 1, max: 40, step: 1, caption: 'Bushing diameter'},
    {name: 'taper', type: 'checkbox', checked: true, caption: 'Taper Edges?'},
    {name: 'knurling', type: 'checkbox', checked: false, caption: 'Add knurling?'}
  ];
}


function knurling(p) {
    const knurls = [];

    const bushing_radius = p.bushing_diameter / 2;
    const thread_radius = bushing_radius * 0.72
    const twist_angle = 45;
    const overlap = 2;
    const twist = twist_angle * p.bushing_height / thread_radius;
    const threads = 360 / twist_angle * overlap;
    const triangle = polygon([
        [thread_radius, thread_radius],
        [0, thread_radius],
        [0, 0],
        [thread_radius, 0]
    ]);

    for (let i=0; i < threads; ++i) {
        knurls.push(
            linear_extrude({height: p.bushing_height, twist, slices: 30}, triangle)
            .rotateZ(360 / threads * i)
            .translate([0, 0, -p.bushing_height/2])
        );
        knurls.push(
            linear_extrude({height: p.bushing_height, twist: -twist, slices: 30}, triangle)
            .rotateZ(360 / threads * i)
            .translate([0, 0, -p.bushing_height/2])
        );
    }
    return union(...knurls);
}

function donut(p) {
    const inner_radius = (p.bushing_height - p.host_hole_height) / 2;
    const outer_radius = p.overhang + p.host_hole_diameter/2 - inner_radius;
    const z_offset = p.bushing_height/2 - (p.bushing_height/2 - p.host_hole_height/2);
    return union(
        torus({ ri: inner_radius, ro: outer_radius }).translate([0, 0, z_offset]),
        torus({ ri: inner_radius, ro: outer_radius }).translate([0, 0, -z_offset])
    );
}

function bushing_main(p) {
    const outer_radius = p.overhang + p.host_hole_diameter/2;
    const main_cylinder = cylinder({
        r: outer_radius - (p.taper ? (p.bushing_height - p.host_hole_height) / 2 : 0),
        h: p.bushing_height,
        center: true
    });
    if (p.taper) {
        return union(
            main_cylinder,
            donut(p)
        );
    }
    return main_cylinder;
}

function host_hole(p) {
    const inner_radius = p.host_hole_diameter/2;
    const outer_radius = p.overhang + inner_radius;
    
    return difference(
        cylinder({r: outer_radius, h: p.host_hole_height, center: true}),
        cylinder({r: inner_radius, h: p.host_hole_height, center: true})
    );
}

function bushing_sleeve(p) {
    const sleeve = cylinder({r: p.bushing_diameter/2, h: p.bushing_height, center: true});
    if (p.knurling) {
        return union(sleeve, knurling(p));
    }
    return sleeve;
}

function main(p) {
    return difference(
        bushing_main(p),
        host_hole(p),
        bushing_sleeve(p)
    );
}