// PCIe Extension Riser Board Holder
// Configurable 3D printable holder with M3 mounting holes

// === Design Parameters ===
thickness = 3;           // Thickness of the holder (configurable)
hole_diameter = 2.8;     // M3 hole diameter (slightly smaller for 3D printing)
margin_x = 8;            // Margin on each side of the holes
margin_y = 6;            // Margin above and below the holes (currently unused)
holder_width = 6;       // Width of the rectangular plane

// === Hole Spacing Parameters ===
first_hole_spacing = 20.5;   // Distance from first to second hole
second_hole_spacing = 20.5;  // Distance from second to third hole
third_hole_spacing = 22;     // Distance from third to fourth hole

// === Technical Parameters ===
cylinder_overlap = 0.1;      // Small overlap to ensure clean boolean operations
cylinder_resolution = 32;    // Number of facets for cylinders (higher = smoother)
preview_cylinder_height = 2; // Height of preview cylinders
preview_cylinder_diameter = 3; // Diameter of preview cylinders

// === Main Function ===
module pcie_riser_holder(
    thickness = 3,
    hole_diameter = 2.8,
    margin_x = 8,
    holder_width = 12,
    first_spacing = 20.5,
    second_spacing = 20.5,
    third_spacing = 22,
    show_preview_holes = false
) {
    // Calculate hole positions
    hole_position_1 = 0;
    hole_position_2 = hole_position_1 + first_spacing;
    hole_position_3 = hole_position_2 + second_spacing;
    hole_position_4 = hole_position_3 + third_spacing;
    
    hole_positions = [
        hole_position_1,
        hole_position_2,
        hole_position_3,
        hole_position_4
    ];
    
    // Calculate total dimensions
    total_length = hole_position_4 + (margin_x * 2);
    total_width = holder_width;
    
    // Extension parameters for negative y direction
    extension_from_holes = 42; // 40mm extension in negative y direction from holes
    hole_y_position = total_width/2; // Current hole y position
    
    // New total width includes original width plus extension
    extended_total_width = total_width + extension_from_holes;
    
    // Main holder body
    difference() {
        // Create the main rectangular plane, translated to accommodate extension
        translate([0, -extension_from_holes, 0])
            cube([total_length, extended_total_width, thickness]);
        
        // Create M3 holes (position unchanged relative to original rectangle)
        for (i = [0 : len(hole_positions) - 1]) {
            translate([margin_x + hole_positions[i], hole_y_position, -cylinder_overlap])
                cylinder(
                    h = thickness + (cylinder_overlap * 2), 
                    d = hole_diameter, 
                    $fn = cylinder_resolution
                );
        }
    }
    
    // Optional preview holes for reference
    if (show_preview_holes) {
        for (i = [0 : len(hole_positions) - 1]) {
            translate([margin_x + hole_positions[i], hole_y_position, thickness])
                cylinder(
                    h = preview_cylinder_height, 
                    d = preview_cylinder_diameter, 
                    $fn = cylinder_resolution
                );
        }
    }
    
    // Display specifications
    echo("=== PCIe Riser Holder Specifications ===");
    echo(str("Total dimensions: ", total_length, "mm x ", extended_total_width, "mm x ", thickness, "mm"));
    echo(str("Extension: 40mm in negative y direction from holes"));
    echo(str("Hole spacing: ", first_spacing, "mm, ", second_spacing, "mm, ", third_spacing, "mm"));
    echo(str("Hole positions: ", hole_positions));
    echo(str("Hole diameter: ", hole_diameter, "mm (for M3 bolts)"));
    echo("=== End Specifications ===");
} 

// === Test the holder ===
// Default holder
pcie_riser_holder();