/*
  Double-sided magnetic board for TRIUMPH! (15 mm figures)

  All dimensions are millimetres. The default exposed playing area is
  960 x 640 mm: 24 x 16 standard 40 mm TRIUMPH! base widths.

  Construction represented here:
    - a 24 gauge cold-rolled carbon-steel core;
    - 30 mm wide wooden frames on both faces;
    - 30 mm total finished board depth, with the steel centred;
    - 10 mm square blind corner holes in the top frame only;
    - full-length short-end pieces, with long-edge pieces between them.

  The steel extends below the whole frame. This preserves a regulation-size
  exposed playing area and gives the blind holes a metal stop.
*/

// ---------- User parameters ----------

playing_length = 960;                  // long dimension of exposed gaming area
playing_width = 640;                   // short dimension of exposed gaming area
frame_width = 30;                      // wooden border width in plan
steel_thickness = 0.607;               // nominal 24 ga carbon steel (0.0239 in)
finished_depth = 60 + steel_thickness; // total board thickness, including steel

peg_hole_size = 10;  // square blind hole width
peg_hole_inset = 10; // from each outside edge to the hole edge

// "assembled", "exploded", "steel", "top_frame", "bottom_frame",
// "short_end_piece", or "long_edge_piece"
display = "assembled";
exploded_gap = 25;

// Rendering colors only
wood_color = [0.58, 0.34, 0.16];
steel_color = [0.50, 0.54, 0.58];

// ---------- Derived dimensions ----------

board_length = playing_length + 2 * frame_width;
board_width = playing_width + 2 * frame_width;
wood_face_depth = (finished_depth - steel_thickness) / 2;

steel_bottom = -steel_thickness / 2;
steel_top = steel_thickness / 2;
bottom_wood_bottom = -finished_depth / 2;
top_wood_bottom = steel_top;

epsilon = 0.02;

assert(playing_length > 0 && playing_width > 0,
       "The playing-area dimensions must be positive.");
assert(frame_width > 0 && finished_depth > steel_thickness,
       "The frame must be wider than zero and deeper than the steel.");
assert(peg_hole_size > 0 && 2 * peg_hole_inset + peg_hole_size <= frame_width,
       "Corner holes must fit completely inside the frame width.");

// ---------- Components ----------

module steel_core(z = steel_bottom) {
    color(steel_color)
        translate([0, 0, z])
            cube([board_length, board_width, steel_thickness]);
}

// Full-side pieces at the two short ends of the rectangular board.
module short_end_rails(height) {
    cube([frame_width, board_width, height]);
    translate([board_length - frame_width, 0, 0])
        cube([frame_width, board_width, height]);
}

// Long-edge pieces occupy the remaining distance between the end pieces.
module long_edge_rails(height) {
    translate([frame_width, 0, 0])
        cube([playing_length, frame_width, height]);
    translate([frame_width, board_width - frame_width, 0])
        cube([playing_length, frame_width, height]);
}

module wood_frame_blank(height) {
    union() {
        short_end_rails(height);
        long_edge_rails(height);
    }
}

module corner_holes(height) {
    hole_xy = [
        [peg_hole_inset, peg_hole_inset],
        [board_length - peg_hole_inset - peg_hole_size, peg_hole_inset],
        [peg_hole_inset, board_width - peg_hole_inset - peg_hole_size],
        [board_length - peg_hole_inset - peg_hole_size,
         board_width - peg_hole_inset - peg_hole_size]
    ];

    for (p = hole_xy)
        translate([p[0], p[1], -epsilon])
            cube([peg_hole_size, peg_hole_size, height + 2 * epsilon]);
}

module wood_frame(height, drilled = false) {
    color(wood_color)
        difference() {
            wood_frame_blank(height);
            if (drilled)
                corner_holes(height);
        }
}

module assembled_board(explode = 0) {
    // Sheet remains centred; the two frames move apart in exploded mode.
    steel_core();

    translate([0, 0, top_wood_bottom + explode])
        wood_frame(wood_face_depth, drilled = true);

    translate([0, 0, bottom_wood_bottom - explode])
        wood_frame(wood_face_depth, drilled = false);
}

// ---------- Display / export selector ----------

if (display == "assembled") {
    assembled_board();
} else if (display == "exploded") {
    assembled_board(exploded_gap);
} else if (display == "steel") {
    translate([0, 0, -steel_bottom]) steel_core();
} else if (display == "top_frame") {
    wood_frame(wood_face_depth, drilled = true);
} else if (display == "bottom_frame") {
    wood_frame(wood_face_depth, drilled = false);
} else if (display == "short_end_piece") {
    // One representative full-side rail, placed at the origin for export.
    color(wood_color) cube([frame_width, board_width, wood_face_depth]);
} else if (display == "long_edge_piece") {
    // One representative infill rail, placed at the origin for export.
    color(wood_color) cube([playing_length, frame_width, wood_face_depth]);
} else {
    assert(false, str("Unknown display mode: ", display));
}