$fn=64;

// --- Parameters ---
bridge_length = 160;       // Total length of the bridge
bridge_width = 50;         // Total width of the bridge
total_height = 60;         // Total height from base to top of parapet

arch_span = 100;           // Width of the arch opening
arch_height = 35;          // Height of the arch opening

channel_width = 30;        // Width of the cable tray channel
channel_depth = 15;        // Depth of the cable tray channel

stone_groove_depth = 1;    // Depth of the decorative stone lines
stone_groove_width = 1.5;  // Width of the decorative stone lines
block_height = 15;         // Height of each stone block row
block_width = 25;          // Width of each stone block

module stone_bridge_cable_tray() {
    difference() {
        // Main Solid Block
        translate([-bridge_length/2, -bridge_width/2, 0])
            cube([bridge_length, bridge_width, total_height]);

        // 1. Central Arch Cutout
        translate([0, -bridge_width/2 - 1, 0]) {
            // Elliptical arch
            scale([arch_span/2, 1, arch_height])
                rotate([-90, 0, 0])
                cylinder(r=1, h=bridge_width + 2);

            // Clear out the area below the arch center to the floor
            translate([-arch_span/2, 0, -arch_height])
                cube([arch_span, bridge_width + 2, arch_height]);
        }

        // 2. Top Cable Channel Cutout
        translate([-bridge_length/2 - 1, -channel_width/2, total_height - channel_depth])
            cube([bridge_length + 2, channel_width, channel_depth + 1]);

        // 3. Decorative Stone Block Pattern
        // Horizontal grooves
        for(z = [block_height : block_height : total_height - 1]) {
            // Front face
            translate([-bridge_length/2 - 1, -bridge_width/2 - 0.1, z])
                cube([bridge_length + 2, stone_groove_depth + 0.1, stone_groove_width]);
            // Back face
            translate([-bridge_length/2 - 1, bridge_width/2 - stone_groove_depth, z])
                cube([bridge_length + 2, stone_groove_depth + 0.1, stone_groove_width]);
        }

        // Vertical staggered grooves (Brick bond pattern)
        for(z_step = [0 : block_height : total_height - 1]) {
            // Offset every other row
            offset = ((z_step / block_height) % 2 == 0) ? 0 : (block_width / 2);

            for(x = [-bridge_length/2 + offset : block_width : bridge_length/2]) {
                // Front face vertical cuts
                translate([x, -bridge_width/2 - 0.1, z_step])
                    cube([stone_groove_width, stone_groove_depth + 0.1, block_height + stone_groove_width]);
                // Back face vertical cuts
                translate([x, bridge_width/2 - stone_groove_depth, z_step])
                    cube([stone_groove_width, stone_groove_depth + 0.1, block_height + stone_groove_width]);
            }
        }
    }
}

// Render the model
stone_bridge_cable_tray();