using System;
using System.Collections.Generic;
using System.IO;
using M17N;
using M17N.Core;

namespace M17N.Core
{
  public delegate object MDatabaseLoader (MDatabaseTag tag,
					  object extra_info);

  public struct MDatabaseTag
  {
    public MSymbol Tag0, Tag1, Tag2, Tag3;

    public MDatabaseTag (MSymbol tag0)
      {
	Tag0 = tag0; Tag1 = Tag2 = Tag3 = MSymbol.nil;
      }

    public MDatabaseTag (MSymbol tag0, MSymbol tag1)
      {
	Tag0 = tag0; Tag1 = tag1; Tag2 = Tag3 = MSymbol.nil;
      }

    public MDatabaseTag (MSymbol tag0, MSymbol tag1, MSymbol tag2)
      {
	Tag0 = tag0; Tag1 = tag1; Tag2 = tag2; Tag3 = MSymbol.nil;
      }

    public MDatabaseTag (MSymbol tag0, MSymbol tag1,
			 MSymbol tag2, MSymbol tag3)
      {
	Tag0 = tag0; Tag1 = tag1; Tag2 = tag2; Tag3 = tag3;
      }
  }

  public class MDatabase
  {
    private class MDatabaseDir
    {
      public string Dirname;
      public DirectoryInfo Info;
      public DateTime LastScanned;

      public MDatabaseDir (string dirname)
      {
	Dirname = dirname;
	try {
	  Info = new DirectoryInfo (dirname);
	} finally {
	  Info = null;
	}
      }

      public bool StatusChanged {
	get {
	  bool exists = Directory.Exists (Dirname);

	  if (Info != null)
	    {
	      if (! exists)
		{
		  Info = null;
		  return true;
		}
	      Info.Refresh ();
	      return (LastScanned < Info.LastWriteTime);
	    }
	  else
	    {
	      if (exists)
		{
		  Info = new DirectoryInfo (Dirname);
		  return true;
		}
	      return false;
	    }
	}
      }

      public void UpdateStatus ()
      {
	LastScanned = DateTime.Now;
      }
    }

    private class MDatabaseDefinition
    {
      private static readonly MSymbol Mversion;
      public MDatabaseTag Tag;
      public string Description;
      public MText Filename;
      public bool IsWildcard;
      public MSymbol Format;
      public MSymbol Schema;
      public MText SchemaFile;
      public MPlist props;
      public bool Supported;

      static MDatabaseDefinition ()
      {
	Mversion = new MSymbol ("version");
      }

      public MDatabaseDefinition (MPlist plist)
      {
	MSymbol[] tags = new MSymbol[4];
	int i;

	for (i = 0; plist.IsSymbol; i++, plist = plist.Next)
	  tags[i] = plist.Symbol;
	while (i < 4)
	  tags[i++] = MSymbol.nil;
	Tag = new MDatabaseTag (tags[0], tags[1], tags[2], tags[3]);
	if (plist.IsMText)
	  {
	    Filename = plist.Text;
	    plist = plist.Next;
	  }
	else if (plist.IsPlist)
	  {
	    MPlist p = plist.Plist;

	    if (p.IsMText)
	      Filename = plist.Text;
	    p = p.Next;
	    if (! p.IsEmpty)
	      {
		if (p.IsSymbol)
		  Format = p.Symbol;
		p = p.Next;
		if (! p.IsEmpty)
		  {
		    if (p.IsSymbol)
		      Schema = p.Symbol;
		    p = p.Next;
		    if (p.IsMText)
		      SchemaFile = p.Text;
		  }		    
	      }
	    plist = plist.Next;
	  }
	Supported = true;
	props = new MPlist ();
	foreach (MPlist pl in plist)
	  {
	    if (pl.IsPlist)
	      {
		MPlist p = pl.Plist;
	      
		if (p.IsSymbol && p.Symbol == Mversion
		    && ! check_version (p.Next))
		  Supported = false;
		props.Put (pl);
	      }
	  }
      }

      private bool check_version (MPlist plist)
      {
	string[] str;
	int major, minor, release;

	if (! plist.IsMText)
	  return false;
	str = plist.Text.ToString ().Split ('.');
	if (str.Length != 3)
	  return false;
	try { major = int.Parse (str[0]); } catch { return false; }
	try { minor = int.Parse (str[1]); } catch { return false; }
	try { release = int.Parse (str[2]); } catch { return false; }
	return (M17N.MajorVersion > major
		|| (M17N.MajorVersion == major
		    && (M17N.MinorVersion > minor
			|| (M17N.MinorVersion == minor
			    && M17N.ReleaseNumber >= release))));
      }
    }

    private static MDatabaseDir[] DBDirs = new MDatabaseDir[3];

    private const string SystemDirectory = "/usr/share/m17n";

    private static Dictionary<MDatabaseTag, MDatabase> DBDict
      = new Dictionary<MDatabaseTag, MDatabase> ();

    /// Type of database
    private enum MDBType
      {
	/// The database was defined automatically (from mdb.dir
	/// file(s)) with no wildcard tag.
	AUTO,
	/// The database was defined automatically (from mdb.dir
	/// file(s)) with a wildcard tag to define multiple databases
	/// of the same kind.
	AUTO_WILDCARD,
	/// The database was defined explicitely (by MDatabaseDefine).
	EXPLICIT
      };

    /// Status of database
    private enum MDBStatus
      {
	// The database file is currently disabled.  It means that the
	// database file is not readable or the database is deleted by
	// the modification of "mdb.dir".
	DISABLED,
	// The database file has not yet been loaded, or was modified
	// after the previous loading.
	OUTDATED,
	// The database file has not been modified after the previous
	// loading.
	UPDATED,
	// The database file is updated but the validation was failed.
	// If this is for a database directory, the directory is
	// readable but "mdb.dir" doesn't exist in it.
	INVALID
      };

    public readonly MDatabaseTag Tag;
    private MDatabaseLoader Loader;
    private object ExtraInfo;

    private bool IsSystemDatabase;
    private DirectoryInfo Dir;
    private MText Filename;
    private FileInfo FileInfo;
    private FileInfo Validater;
    private int MajorVersion, MinorVersion, ReleaseNumber;
    private MDBType DBType;
    private MDBStatus DBStatus;
    private MSymbol Format;
    private MSymbol Schema;
    private DateTime Mtime;
    private DateTime Ltime;
    private MPlist Props;

    public static string ApplicationDirectory;

    private MDatabase (MDatabaseTag tag, MDatabaseLoader loader,
		      object extra_info)
    {
      Tag = tag;
      Loader = loader;
      ExtraInfo = extra_info;
    }

    private MDatabase (MDatabaseTag tag, string filename)
    {
      Tag = tag;
      Filename = new MText (filename);
    }

    public static MDatabase Define (MDatabaseTag tag, MDatabaseLoader loader,
				    object extra_info)
    {
      MDatabase db = MDatabase.Find (tag);

      if (db != null)
	{
	  db.Loader = loader;
	  db.ExtraInfo = extra_info;
	  return db;
	}
      return new MDatabase (tag, loader, extra_info);
    }

    public static  MDatabase Define (MDatabaseTag tag, string filename)
    {
      MDatabase db = MDatabase.Find (tag);

      if (db != null)
	{
	  db.Loader = null;
	  db.Filename = new MText (filename);
	  return db;
	}
      return new MDatabase (tag, filename);
    }

    static MDatabase ()
    {
      string share_dir = (Environment.GetFolderPath
			  (Environment.SpecialFolder.CommonApplicationData));
      string usr_dir = (Environment.GetFolderPath
			(Environment.SpecialFolder.ApplicationData));

      try {
	DBDirs[0] = new MDatabaseDir (Path.Combine (usr_dir, ".m17n.d"));
      } catch (ArgumentException) {
	DBDirs[0] = new MDatabaseDir (Path.Combine (usr_dir, "_m17n.d"));
      }
      DBDirs[1] = null;
      DBDirs[2] = new MDatabaseDir (Path.Combine (share_dir, "m17n"));
    }

    internal static void Update ()
    {

    }


    public static MDatabase Find (MDatabaseTag tag)
    {
      MDatabase db;

      return (DBDict.TryGetValue (tag, out db) ? db : null);
    }

    public object Load ()
    {
      return (Loader != null ? Loader (Tag, ExtraInfo)
	      : load (MSymbol.nil, MSymbol.nil));
    }

    public object Load (MSymbol key, MSymbol stop)
    {
      if (Loader != null)
	return null;
      return load (key, stop);
    }

    private object load (MSymbol key, MSymbol stop)
    {
      Ltime = DateTime.Now;

      

      return null;
    }

  }

}