struct Train {
    let start: Int
    let path: Array<Domino>
    
    var final: Int {
        var s = start
        for t in path { s = t.numberOpposite(s) }
        return s
    }
    
    func print() {
        let hasVertical = path.filter { $0.isDouble }.count > 0
        var printedLines = Array<Array<Character>>(repeating: [], count: hasVertical ? 5 : 3)
        var start = self.start
        for t in path {
            
            var lines = t.tile(leading: start).split(separator: "\n").map { Array($0) }
            if hasVertical == true && t.isDouble == false {
                lines.insert(Array(repeating: " ", count: Domino.horizontalTileWidth), at: 0)
                lines.append(Array(repeating: " ", count: Domino.horizontalTileWidth))
            }
            
            start = t.numberOpposite(start)
            
            // append a space after this tile
            printedLines = printedLines.enumerated().map {
                $1 + lines[$0] + [" "]
            }
        }
        
        for l in printedLines { Swift.print(String(l)) }
    }
}