using System;
using System.Runtime.InteropServices;

namespace BusinessERP.Helpers
{
    public class Syslog
    {
        [Flags]
        private enum Option
        {
            Pid = 0x01,
            Console = 0x02,
            Delay = 0x04,
            NoDelay = 0x08,
            NoWait = 0x10,
            PrintError = 0x20
        }

        [Flags]
        private enum Facility
        {
            User = 1 << 3, //removed other unused enum values for brevity
        }

        [Flags]
        public enum Level
        {
            Emerg = 0,
            Alert = 1,
            Crit = 2,
            Err = 3,
            Warning = 4,
            Notice = 5,
            Info = 6,
            Debug = 7
        }

        [DllImport("libc")]
        private static extern void openlog(IntPtr ident, Option option, Facility facility);

        [DllImport("libc")]
        private static extern void syslog(int priority, string message);

        [DllImport("libc")]
        private static extern void closelog();

        public static void Write(Syslog.Level level, string identity, string message)
        {
            //are we on linux?
            if (!OperatingSystem.IsLinux()) return;

            //validate input
            if (string.IsNullOrWhiteSpace(message) && string.IsNullOrWhiteSpace(identity)) return;

            IntPtr ident = Marshal.StringToHGlobalAnsi(identity);
            openlog(ident, Option.Console | Option.Pid | Option.PrintError, Facility.User);

            //split multiline messages, otherwise we end up with "line1 #012 line2 #012 line3" etc
            foreach (var line in message.Split('\n', StringSplitOptions.RemoveEmptyEntries))
            {
                syslog((int)Facility.User | (int)level, line.Trim());
            }

            closelog();
            Marshal.FreeHGlobal(ident);
        }
    }
}