/*
Copyright (c) 2008  Franklin Schmidt <fschmidt@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

package fschmidt.db.cache;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Map;
import java.util.HashMap;
import java.util.Set;
import java.util.HashSet;
import java.util.Collections;
import java.util.Collection;
import java.util.NoSuchElementException;
import fschmidt.db.util.Unique;
import fschmidt.db.util.WeakCacheMap;
import fschmidt.db.DbObject;
import fschmidt.db.DbKey;
import fschmidt.db.DbRecord;
import fschmidt.db.extend.DbRecordExt;
import fschmidt.db.extend.DbTableExt;
import fschmidt.db.extend.DbDatabaseExt;
import fschmidt.db.extend.DbTransaction;
import fschmidt.db.extend.FilterTable;


final class DbTableImpl<K extends DbKey,V extends DbObject<K,V>> extends FilterTable<K,V> {
	private static final DbObject NULL0 = new DbObject(){
		public DbRecord getDbRecord() { throw new RuntimeException(); }
	};

	@SuppressWarnings("unchecked")
	private final V NULL = (V)NULL0;  // hack

	private static class CacheKey {
		private final DbTableImpl table;
		final Object key;

		CacheKey(DbTableImpl table,Object key) {
			this.table = table;
			this.key = key;
		}

		@Override public boolean equals(Object obj) {
			if( obj == this )
				return true;
			if( !(obj instanceof DbTableImpl.CacheKey) )
				return false;
			CacheKey ck = (CacheKey)obj;
			return ck.table == table && ck.key.equals(key);
		}

		@Override public int hashCode() {
			return table.hashCode() + key.hashCode();
		}

	}

	private static final Map<CacheKey,DbObject> cache0 = Collections.synchronizedMap(new WeakCacheMap<CacheKey,DbObject>());
	private final Unique<K> unique = new Unique<K>();
	private final DbDatabaseImpl database;

	DbTableImpl(DbTableExt<K,V> table,DbDatabaseImpl database) {
		super(database,table);
		this.database = database;
	}

	private Map<CacheKey,DbObject> transCache() {
		Map<String,Object> transMap = database.transactionMap();
		@SuppressWarnings("unchecked")
		Map<CacheKey,DbObject> transCache = (Map<CacheKey,DbObject>)transMap.get("transCache");
		if( transCache == null ) {
			transCache = new WeakCacheMap<CacheKey,DbObject>();
			transMap.put( "transCache", transCache );
		}
		return transCache;
	}

	private final boolean isStale(DbObject obj) {
		if( obj==null )
			return true;
		if( obj==NULL )
			return false;
/*
		if( database.isInTransaction() ) {
			return transCache().containsKey(obj.getDbRecord().getPrimaryKey());
		} else {
			return obj.getDbRecord().isStale();
		}
*/
		return obj.getDbRecord().isStale();
	}

	public final V findByPrimaryKey(K key) {
		CacheKey ck = new CacheKey(this,key);
		if( database.isInTransaction() ) {
			Map<CacheKey,DbObject> cache = transCache();
			@SuppressWarnings("unchecked")
			V obj = (V)cache.get(ck);
			if( obj==null ) {
				obj = table.findByPrimaryKey(key);
				if( obj==null )
					obj = NULL;
				cache.put(ck,obj);
			}
			return obj==NULL ? null : obj;
		}
		Map<CacheKey,DbObject> cache = cache0;
		key = unique.get(key);
		try {
			synchronized(key) {
				@SuppressWarnings("unchecked")
				V obj = (V)cache.get(ck);
				if( !isStale(obj) )
					return obj==NULL ? null : obj;
				obj = table.findByPrimaryKey(key);
				if( !isStale( cache.put( ck, obj==null ? NULL : obj ) ) )
					throw new RuntimeException();
				return obj;
			}
		} finally {
			unique.free(key);
		}
	}

	public final Map<K,V> findByPrimaryKey(Collection<K> keys) {
		Map<K,V> map = new HashMap<K,V>();
		Set<K> set = new HashSet<K>();
		Map<CacheKey,DbObject> cache = database.isInTransaction() ? transCache() : cache0;
		boolean inTrans = database.isInTransaction();
		for( K key : keys ) {
			CacheKey ck = new CacheKey(this,key);
			@SuppressWarnings("unchecked")
			V obj = (V)cache.get(ck);
			if( obj==null || !inTrans && isStale(obj) ) {
				set.add(key);
			} else {
				map.put( key, obj==NULL ? null : obj );
			}
		}
		if( !set.isEmpty() ) {
			Map<K,V> objs = table.findByPrimaryKey(set);
			for( K key : set ) {
				CacheKey ck = new CacheKey(this,key);
				if( inTrans ) {
					if( cache.get(ck) != null )
						throw new RuntimeException();
					V obj = table.findByPrimaryKey(key);
					if( obj==null )
						obj = NULL;
					cache.put(ck,obj);
					map.put( key, obj==NULL ? null : obj );
				} else {
					key = unique.get(key);
					try {
						synchronized(key) {
							@SuppressWarnings("unchecked")
							V obj = (V)cache.get(ck);
							if( isStale(obj) ) {
								obj = objs.get(key);
								if( obj == null )
									obj = NULL;
								if( !isStale( cache.put(ck,obj) ) )
									throw new RuntimeException();
							}
							map.put( key, obj==NULL ? null : obj );
						}
					} finally {
						unique.free(key);
					}
				}
			}
		}
		return map;
	}

	public V getDbObject(K key,ResultSet rs,String tableName)
		throws SQLException
	{
		CacheKey ck = new CacheKey(this,key);
		if( database.isInTransaction() ) {
			Map<CacheKey,DbObject> cache = transCache();
			@SuppressWarnings("unchecked")
			V obj = (V)cache.get(ck);
			if( obj==null ) {
				obj = table.getDbObject(key,rs,tableName);
				if( obj==null )
					obj = NULL;
				cache.put(ck,obj);
			}
			return obj==NULL ? null : obj;
		}
		Map<CacheKey,DbObject> cache = cache0;
		key = unique.get(key);
		try {
			synchronized(key) {
				@SuppressWarnings("unchecked")
				V obj = (V)cache.get(ck);
				if( !isStale(obj) )
					return obj==NULL ? null : obj;
				obj = table.getDbObject(key,rs,tableName);
				if( !isStale( cache.put( ck, obj==null ? NULL : obj ) ) )
					throw new RuntimeException();
				return obj;
			}
		} finally {
			unique.free(key);
		}
	}

	public void uncache(final K key) {
		if( key == null )
			return;
		final CacheKey ck = new CacheKey(this,key);
		if( database.isInTransaction() ) {
			doUncache(ck,transCache());
		}
		database.runJustAfterCommit( new Runnable() {
			public void run() {
				doUncache(ck,cache0);
			}
		} );
	}

	private static void doUncache(CacheKey ck,Map<CacheKey,DbObject> cache) {
		DbObject obj = cache.remove(ck);
		if( obj!=null && obj!=NULL0 ) {
			DbRecordExt rec = (DbRecordExt)obj.getDbRecord();
			rec.makeStale();
		}
	}

	static void clearCache() {
		while( !cache0.isEmpty() ) {
			CacheKey[] a = cache0.keySet().toArray(new CacheKey[0]);
			for( CacheKey ck : a ) {
				doUncache( ck, cache0 );
			}
		}
	}

}