using System;
using System.Collections.Generic;
using System.IO;


namespace util
{
	internal class ConfigEntry
	{
		public string value;
		public ISet<string> list;
		public ConfigEntry(string v)
		{
			this.value = v;
		}
	}

	public static class Config
	{
		private static Dictionary<String,Dictionary<string,ConfigEntry>> Data;
		private static bool ready = false;
		private static string file_name;

		// return values for Load
		public const int LOAD_OK = 0;
		public const int LOAD_NO_INPUT_FILE = 1;
		public static int Load (String FileName)
		{
			Config.file_name = FileName;
			Data = new Dictionary<string, Dictionary<string,ConfigEntry>>();

			if (!System.IO.File.Exists (FileName)) {
				ready = true;
				return LOAD_NO_INPUT_FILE;
			}

			using (StreamReader File = new StreamReader (FileName)) {
				String Line;
				string section = null;
				string key = "no_key";
				Dictionary<string,ConfigEntry> SectionDic = null;
				bool listProcessing = false;
				while (File.Peek() != -1) {
					Line = File.ReadLine ();
					if (listProcessing) {
						if (Line == "LIST")
							listProcessing = false;
						else
							SectionDic [key].list.Add (Line);
					} else if (Line.Length == 0 || Line.Substring (0, 1) == "#") {
						; // this is a comment line
					} else if (Line.Substring (0, 1) == "[") {
						// new section
						if (section != null) {
							// append old section
							Data [section] = SectionDic;
						}
						// start new section
						section = Line.Substring (1, Line.IndexOf (']') - 1);
						SectionDic = new Dictionary<string, ConfigEntry> ();
					} else {
						key = Line.Substring (0, Line.IndexOf (':'));
						String Value = Line.Substring (Line.IndexOf (':') + 1);
						var ce = new ConfigEntry (Value);
						if (Value == "LIST") {
							listProcessing = true;
							ce.list = new SortedSet<string> ();
						}
						SectionDic [key] = ce;
					}
				}
				if (listProcessing)
					throw new ApplicationException ("Configuration list has no end");
				if (SectionDic != null) Data [section] = SectionDic;
			}
			ready = true;
			return LOAD_OK;
		}
		/*
		public static Config GetInstance()
		{
			if (Config.Instance == null) Config.Instance = new Config ();
			return Config.Instance;
		}*/
		public static String GetConfig(string section, string key){
			Check ();
			if (Data.ContainsKey(section)){
				if (Data[section].ContainsKey(key)) return Data [section][key].value;
			}
			return null;
		}
		public static ISet<string> GetList(string section, string key){
			Check ();
			if (!Data.ContainsKey (section))
				return null;
			if (!Data [section].ContainsKey (key))
				return null;
			if (Data [section] [key].value != "LIST")
				throw new ApplicationException ("Required List-Config is not a list");
			return Data [section] [key].list;
		}
		public static ISet<string> RequireList(string section, string key){
			ISet<string> result = GetList (section, key);
			if (result == null)
				throw new ApplicationException ("Config missing:"+ section+ key);
			return result;
		}
		public static String RequireConfig(string section, string key){
			string value = GetConfig (section, key);
			if (value == null)
				throw new ApplicationException ("No Config Entry for " + section + "/"+key);
			return value;
		}
		public static void Set(string section, string key, string value){
			Check ();
			if (! Data.ContainsKey (section)) {
				Data [section] = new Dictionary<string, ConfigEntry> ();
			}
			Data [section] [key] = new ConfigEntry(value);
		}
		public static void Set(string section, string key, ISet<string> value){
			Set (section, key, "LIST");
			Data [section] [key].list = value;
		}
		public static void Write(){
			Check ();
			StreamWriter File = new StreamWriter (Config.file_name, false);
			foreach (var section in Data) {
				File.WriteLine ();
				File.WriteLine ("[" + section.Key + "]");
				foreach (var elem in section.Value) {
					File.WriteLine (elem.Key + ":" + elem.Value.value);
					if (elem.Value.value == "LIST") {
						foreach (string list_ele in elem.Value.list) {
							File.WriteLine (list_ele);
						}
						File.WriteLine ("LIST");
					}
				}
			}
			File.Close();
		}
		public static void Remove(string section)
		{
			Check ();
			Data.Remove (section);
		}
		private static void Check()
		{
			if (!ready)
				throw new ApplicationException ("Configuration data not loaded");
		}
	}
}