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A Scala ORM and DSL for talking with Databases using minimum verbosity and maximum type safety
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/*******************************************************************************
 * Copyright 2010 Maxime Lévesque
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ***************************************************************************** */
package org.squeryl

import dsl.ast.ViewExpressionNode
import dsl.{TypedExpression, QueryDsl}
import internals._
import java.sql.ResultSet

/**
 * This class can be used for read only tables or (database) views
 * for an updatable view, or table use Table[T] 
 */
class View[T] private [squeryl](_name: String, private[squeryl] val classOfT: Class[T], schema: Schema, _prefix: Option[String], val ked: Option[KeyedEntityDef[T,_]]) extends Queryable[T] {


//2.9.x approach for LyfeCycle events :
//  private [squeryl] var _callbacks: PosoLifecycleEventListener = NoOpPosoLifecycleEventListener

////2.8.x approach for LyfeCycle events :
  private [squeryl] lazy val _callbacks =
    schema._callbacks.get(this).getOrElse(NoOpPosoLifecycleEventListener)


  def name = schema.tableNameFromClassName(_name)

  def prefix: Option[String] =
    if(_prefix != None)
      _prefix
    else
      schema.name

  def prefixedName =
    if(prefix != None)
      prefix.get + "." + name
    else
      name

  /**
   * Suppose you have : prefix.MyTable
   * myTable.prefixedPrefixedName("z") will yield : prefix.zMyTable
   * used for creating names for objects derived from a table, ex.: a sequence 
   */
  def prefixedPrefixedName(s: String) =
    if(prefix != None)
      prefix.get + "." + s + name
    else
      s + name
  
  private [squeryl] def findFieldMetaDataForProperty(name: String) = posoMetaData.findFieldMetaDataForProperty(name)

  val posoMetaData = new PosoMetaData(classOfT, schema, this)

  private [squeryl] def allFieldsMetaData: Iterable[FieldMetaData] = posoMetaData.fieldsMetaData

  protected val _setPersisted =
    if(classOf[PersistenceStatus].isAssignableFrom(classOfT))
      (t:T) => t.asInstanceOf[PersistenceStatus]._isPersisted = true
    else
      (t:T) => {}

  private val _posoFactory =
    FieldMetaData.factory.createPosoFactory(posoMetaData)
  
  private [squeryl] def _createInstanceOfRowObject =
    _posoFactory()
  
  private [squeryl] def give(resultSetMapper: ResultSetMapper, resultSet: ResultSet) : T  = {

    var o = _callbacks.create

    if(o == null)
      o = _createInstanceOfRowObject
    
    resultSetMapper.map(o, resultSet);
    val t = o.asInstanceOf[T]
    _setPersisted(t)
    _callbacks.afterSelect(t.asInstanceOf[AnyRef]).asInstanceOf[T]
  }

  def lookup[K](k: K)(implicit ked: KeyedEntityDef[T,K], dsl: QueryDsl, toCanLookup: K => CanLookup): Option[T] = {
    //TODO: find out why scalac won't let dsl be passed to another method
    import dsl._

    val q = from(this)(a => dsl.where {
      FieldReferenceLinker.createEqualityExpressionWithLastAccessedFieldReferenceAndConstant(ked.getId(a), k, toCanLookup(k))
    } select(a))

    val it = q.iterator

    if(it.hasNext) {
      val ret = Some(it.next)
      // Forces statement to be closed.
      it.hasNext
      ret
    }
    else
      None
  }
  
  /**
   * Will throw an exception if the given key (k) returns no row.
   */
  def get[K](k: K)(implicit ked: KeyedEntityDef[T,K], dsl: QueryDsl, toCanLookup: K => CanLookup): T = 
     lookup(k).getOrElse(throw new NoSuchElementException("Found no row with key '"+ k + "' in " + name + "."))
  
  def allRows(implicit dsl: QueryDsl): Iterable[T] = {
    import dsl._
    dsl.queryToIterable(from(this)(a=> select(a)))
  }

  def viewExpressionNode: ViewExpressionNode[T] = new ViewExpressionNode[T](this)
}

sealed trait CanLookup

private [squeryl] case object CompositeKeyLookup extends CanLookup

private [squeryl] case object UnknownCanLookup extends CanLookup

private [squeryl] case class SimpleKeyLookup[T](convert: T => TypedExpression[T, _]) extends CanLookup