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
  {
    /// 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	OUTDATED,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
      };

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

    private MDatabaseTag tag;
    private MDatabaseLoader loader;
    private object extra_info;

    private bool system_database;
    private DirectoryInfo dir;
    private FileInfo file;
    private FileInfo validater;
    private int major_version, minor_version, release_number;
    private MDBType type;
    private MDBStatus status;
    private MSymbol format;
    private MSymbol schema;
    private DateTime mtime;
    private DateTime ltime;
    private MPlist props;

    public static string ApplicationDirectory;

    public MDatabase (MDatabaseTag tag, MDatabaseLoader loader,
		      object extra_info)
    {
      this.tag = tag;
      this.loader = loader;
      this.extra_info = extra_info;
    }

    public MDatabase (MDatabaseTag tag, string filename)
    {
      this.tag = tag;
      this.loader = load;
    }

    public MDatabaseTag Tag { get { return tag; } }

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

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

    public object Load ()
    {
      return loader (tag, extra_info);
    }

    private object load (MDatabaseTag tag, object extra_info)
    {
      ltime = DateTime.Now;
      return null;
    }

  }

}