// ============================================
// Filament Spool Cover
// ============================================
// A circular dust cover that clips onto the outer rim
// of a filament spool. Snap-fit clips around the
// perimeter grip the spool edge to hold the cover
// in place.
//
// Coordinate system:
//   Origin (0,0,0) = center of the cover disc, bottom face
//   X/Y = radial plane of the disc
//   Z = upward (skirt and clips extend in +Z)

// ============================================
// CUSTOMIZABLE PARAMETERS
// ============================================

/* [Spool] */

// Outer diameter of the filament spool
spool_outer_diameter = 200; // [150:1:220]

// Thickness of the spool rim (the edge clips grab)
spool_rim_thickness = 1; // [1:0.5:5]

/* [Cover] */

// Thickness of the cover disc
cover_thickness = 1.5; // [1:0.5:3]

// Height of the skirt that wraps around the spool rim
skirt_height = 5; // [3:0.5:10]

// Thickness of the skirt wall
skirt_wall = 1.2; // [0.8:0.1:2.0]

/* [Clips] */

// Number of clips around the perimeter
clip_count = 3; // [3:1:12]

// Angular width of each clip in degrees
clip_arc = 15; // [5:1:30]

// Depth of the clip lip that hooks under the rim
clip_lip_depth = 1.5; // [0.5:0.1:3]

// Clearance gap for snap fit
clip_clearance = 0.3; // [0.1:0.05:0.6]

/* [Quality] */

// Rendering resolution
resolution = 120; // [60:10:200]

// ============================================
// PARAMETER VALIDATION
// ============================================

assert(spool_outer_diameter > 0, "Spool outer diameter must be positive");
assert(spool_rim_thickness > 0, "Spool rim thickness must be positive");
assert(cover_thickness >= 1, "Cover thickness should be at least 1mm");
assert(skirt_height > spool_rim_thickness, "Skirt must be taller than rim thickness to clip");
assert(clip_count >= 3, "Need at least 3 clips for a secure hold");
assert(clip_lip_depth > 0, "Clip lip depth must be positive");

// ============================================
// DERIVED DIMENSIONS
// ============================================

spool_radius = spool_outer_diameter / 2;
// Inner radius of the skirt sits just outside the spool rim
skirt_inner_radius = spool_radius + clip_clearance;
skirt_outer_radius = skirt_inner_radius + skirt_wall;

// ============================================
// MAIN ASSEMBLY
// ============================================

cover();

// ============================================
// COMPONENT MODULES
// ============================================

// Full cover assembly: disc + skirt + clips
module cover() {
    union() {
        cover_disc();
        skirt();
        clips();
    }
}

// Flat circular disc that covers the spool face (sits on the build plate)
module cover_disc() {
    cylinder(h=cover_thickness, r=skirt_outer_radius, $fn=resolution);
}

// Continuous ring around the edge that extends upward from the disc
module skirt() {
    translate([0, 0, cover_thickness])
        difference() {
            cylinder(h=skirt_height, r=skirt_outer_radius, $fn=resolution);
            translate([0, 0, -0.01])
                cylinder(h=skirt_height + 0.02, r=skirt_inner_radius, $fn=resolution);
        }
}

// Evenly spaced snap clips at the top of the skirt
module clips() {
    for (i = [0 : clip_count - 1]) {
        rotate([0, 0, i * (360 / clip_count)])
            clip();
    }
}

// Single snap clip: lip at top grabs the rim, diagonal ramp below for supportless printing
// Cross-section profile (radial view, outer left, inner right):
//
//   |_____|   <- skirt top: lip extends inward to grab rim
//   |   / |
//   |  /  |
//   | /   |
//   |/    |
//   |     |   <- skirt base
//
// The diagonal ramp prints without supports.
module clip() {
    eps = 0.01;
    base_z = cover_thickness;
    ramp_height = skirt_height - spool_rim_thickness;

    // Full clip profile as a single polygon, extruded as an arc
    // Coordinates in (r, z) space, relative to (0, base_z)
    translate([0, 0, base_z])
        rotate_extrude(angle=clip_arc, $fn=resolution)
            translate([skirt_inner_radius - clip_lip_depth, 0, 0])
                polygon([
                    // Bottom-right: flush with skirt inner wall at base
                    [clip_lip_depth, 0],
                    // Bottom-right: outer edge (into skirt wall)
                    [clip_lip_depth + skirt_wall + eps, 0],
                    // Top-right: outer edge at skirt top
                    [clip_lip_depth + skirt_wall + eps, skirt_height],
                    // Top-left: inner edge of lip at skirt top
                    [0, skirt_height],
                    // Ramp starts: flush with skirt inner wall
                    [clip_lip_depth, skirt_height - spool_rim_thickness]
                ]);
}