$fn = 64;

// --- PARAMETERS ---
rows = 2;
cols = 3;

cell_pitch = 40;          // Distance between cell centers
cell_height = 45;         // Total height of the tray
cell_bottom_inner = 25;   // Inner width of the cell at the bottom
wall_thickness = 1.2;     // Wall thickness

drain_hole_dia = 8;       // Diameter of bottom drainage holes
lip_width = 5;            // Width of the top rim
lip_height = 2;           // Height/thickness of the top rim

// --- DERIVED VARIABLES ---
cell_top_inner = cell_pitch - (wall_thickness * 2);
w_top_outer = cell_pitch + 0.1; // 0.1mm overlap to ensure manifold geometry
w_base_outer = cell_bottom_inner + (wall_thickness * 2);

// --- MODULES ---
module cell_outer() {
    hull() {
        translate([0, 0, 0]) 
            cube([w_base_outer, w_base_outer, 0.01], center=true);
        translate([0, 0, cell_height]) 
            cube([w_top_outer, w_top_outer, 0.01], center=true);
    }
}

module cell_inner() {
    hull() {
        translate([0, 0, wall_thickness]) 
            cube([cell_bottom_inner, cell_bottom_inner, 0.01], center=true);
        translate([0, 0, cell_height + 0.1]) 
            cube([cell_top_inner, cell_top_inner, 0.01], center=true);
    }
}

module seedling_tray() {
    difference() {
        // Main Body
        union() {
            // Outer cell bodies
            for(x = [0 : cols - 1]) {
                for(y = [0 : rows - 1]) {
                    translate([x * cell_pitch, y * cell_pitch, 0])
                        cell_outer();
                }
            }
            
            // Top Lip
            translate([
                ((cols - 1) * cell_pitch) / 2, 
                ((rows - 1) * cell_pitch) / 2, 
                cell_height - (lip_height / 2)
            ])
            cube([
                (cols * cell_pitch) + (lip_width * 2), 
                (rows * cell_pitch) + (lip_width * 2), 
                lip_height
            ], center=true);
        }

        // Cutouts
        for(x = [0 : cols - 1]) {
            for(y = [0 : rows - 1]) {
                translate([x * cell_pitch, y * cell_pitch, 0]) {
                    // Hollow out the cell
                    cell_inner();
                    
                    // Bottom drainage hole
                    translate([0, 0, -1])
                        cylinder(d=drain_hole_dia, h=wall_thickness + 2);
                }
            }
        }
    }
}

// --- RENDER ---
seedling_tray();