format.swift

    private func handleMessage(_ message: IRC.Message) {
        if let storage = chatTextView.textStorage,
            let render = format(message) {
            storage.append(render)
            //storage.insert(render, at: storage.length)
        }
        chatTextView.scrollToEndOfDocument(self)
    }

    private let chatFont = NSFont.systemFont(ofSize: 14)
    private let protocolFont = NSFont.systemFont(ofSize: 12)

    private func format(_ message: IRC.Message) -> NSAttributedString? {
        let p = NSMutableParagraphStyle()
        p.paragraphSpacing = 14.0

        switch message.command {
            case .NOTICE:
                let trailing = message.trailing.count > 0 ? String(message.trailing.dropFirst()) : ""
                let s = NSMutableAttributedString(string: "\(trailing)\r\n")
//                let r = NSMakeRange(0, s.length)
                let attributes: [NSAttributedString.Key: Any] = [
                    .font: protocolFont,
                    .foregroundColor: NSColor.systemRed,
                    .paragraphStyle: p
                ]
//                s.addAttribute(.font, value: protocolFont, range: r)
//                s.addAttribute(.foregroundColor, value: NSColor.systemRed, range: r)
                s.setAttributes(attributes, range: NSMakeRange(0, s.length))
                return s as NSAttributedString

            case .PRIVMSG:
                let user = NSMutableAttributedString(string: message.nick + ": ")
                user.addAttribute(.foregroundColor, value: NSColor.systemGreen, range: NSMakeRange(0, user.length))

                let channel = NSMutableAttributedString(string: (message.parameters.count > 0 ? message.parameters[0] : "-") + " ")
                channel.addAttribute(.foregroundColor, value: NSColor.systemBlue, range: NSMakeRange(0, channel.length))

                let text = NSMutableAttributedString()
                text.append(channel)
                //text.append(NSAttributedString(string:" "))
                text.append(user)
                //text.append(NSAttributedString(string:": "))
                text.append(NSAttributedString(string: (message.trailing.count > 0 ? String(message.trailing.dropFirst()) : "") + "\n"))
                text.addAttribute(.font, value: chatFont, range: NSMakeRange(0, text.length))

                return text as NSAttributedString

            default:
                let cmd = "\(message.command)".lowercased()
                let ps = message.parameters.joined(separator: ", ")
                let s = NSMutableAttributedString(string: "» \(cmd) \(ps) \(message.trailing)\r\n")
                let r = NSMakeRange(0, s.length)
                s.addAttribute(.font, value: protocolFont, range: r)
                s.addAttribute(.foregroundColor, value: NSColor.systemGray, range: r)
                return s as NSAttributedString
        }
        
    }