$fn = 64;

// --- Parameters ---
rail_length = 800;
rail_height = 40;
rail_depth = 15;

// Dovetail dimensions
dovetail_front_width = 15;
dovetail_back_width = 25;
dovetail_depth = 8;

// Mounting hole dimensions
num_holes = 5;
hole_margin = 50;
screw_dia = 5;
head_dia = 10;

module dovetail_rail() {
    difference() {
        // Main rail body with dovetail profile
        rotate([0, 90, 0])
        linear_extrude(height = rail_length)
        polygon(points=[
            [0, 0],
            [0, rail_height],
            [-rail_depth, rail_height],
            [-rail_depth, (rail_height + dovetail_front_width)/2],
            [-(rail_depth - dovetail_depth), (rail_height + dovetail_back_width)/2],
            [-(rail_depth - dovetail_depth), (rail_height - dovetail_back_width)/2],
            [-rail_depth, (rail_height - dovetail_front_width)/2],
            [-rail_depth, 0]
        ]);

        // Countersunk mounting holes
        hole_interval = (num_holes > 1) ? (rail_length - 2 * hole_margin) / (num_holes - 1) : 0;
        
        for(i = [0 : num_holes - 1]) {
            x_pos = hole_margin + i * hole_interval;
            y_pos = rail_height / 2;
            z_dovetail_bottom = rail_depth - dovetail_depth;
            cs_height = (head_dia - screw_dia) / 2;
            
            translate([x_pos, y_pos, 0]) {
                // Screw shaft
                translate([0, 0, -1])
                    cylinder(d=screw_dia, h=rail_depth + 2);
                
                // Countersink
                translate([0, 0, z_dovetail_bottom - cs_height])
                    cylinder(d1=screw_dia, d2=head_dia, h=cs_height + 0.01);
                    
                // Clearance for screw head above countersink
                translate([0, 0, z_dovetail_bottom])
                    cylinder(d=head_dia, h=rail_depth);
            }
        }
    }
}

// Render the model
dovetail_rail();