<?php
class LedgerEntry extends AppModel {

	var $name = 'LedgerEntry';
	var $validate = array(
		'id' => array('numeric'),
		'transaction_id' => array('numeric'),
		'amount' => array('money')
	);

	var $belongsTo = array(
		'MonetarySource',
		'Transaction',

		'DebitLedger' => array(
			'className' => 'Ledger',
			'foreignKey' => 'debit_ledger_id',
		),
		'CreditLedger' => array(
			'className' => 'Ledger',
			'foreignKey' => 'credit_ledger_id',
		),
	);


  /**************************************************************************
   **************************************************************************
   **************************************************************************
   * function: conditionEntryAsCreditOrDebit
   *  - returns the condition necessary to match a set of
   *    Ledgers to all related LedgerEntries
   */
  function conditionEntryAsCreditOrDebit($ledger_ids) {
    return array('OR' =>
		 array(array('debit_ledger_id'  => $ledger_ids),
		       array('credit_ledger_id' => $ledger_ids)));
  }

    
  /**************************************************************************
   **************************************************************************
   **************************************************************************
   * function: ledgerContext query helpers
   *  - Returns parameters necessary to generate a query which
   *    puts ledger entries into the context of a ledger.  Since
   *    debit/credit depends on the account type, it is required
   *    as an argument for each function to avoid having to
   *    query the ledger/account to find it out.
   */
  function ledgerContextFields($ledger_id, $account_type) {
    if (in_array($account_type, array('ASSET', 'EXPENSE')))
      $ledger_type = 'debit';
    else
      $ledger_type = 'credit';

    return array
      ('id', 'name', 'comment',
       "IF(LedgerEntry.debit_ledger_id = $ledger_id," .
       "   LedgerEntry.amount, NULL) AS debit",
       "IF(LedgerEntry.credit_ledger_id = $ledger_id," .
       "   LedgerEntry.amount, NULL) AS credit",
       "(IF(LedgerEntry.{$ledger_type}_ledger_id = $ledger_id, 1, -1)" .
       " * LedgerEntry.amount) AS balance",
       );
  }

  function ledgerContextConditions($ledger_id, $account_type) {
    return array
      ('OR' =>
       array(array('LedgerEntry.debit_ledger_id' => $ledger_id),
	     array('LedgerEntry.credit_ledger_id' => $ledger_id)),
       );
  }      

  /**************************************************************************
   **************************************************************************
   **************************************************************************
   * function: findInLedgerContext
   *  - Returns an array of ledger entries that belong to a given ledger.
   *    There is extra logic to also figure out whether the ledger_entry
   *    amount is either a credit, or a debit, depending on how it was
   *    written into the ledger, as well as whether the amount increases or
   *    decreases the balance depending on the particular account type of
   *    the ledger.
   */
  function findInLedgerContext($ledger_id, $account_type, $cond = null, $link = null) {
    if (!isset($link))
      $link = array('Transaction');

    if (!isset($cond))
      $cond = array();

    $fields = $this->ledgerContextFields($ledger_id, $account_type);
    $cond[] = $this->ledgerContextConditions($ledger_id, $account_type);
    $order  = array('Transaction.stamp');

    $entries = $this->find
      ('all',
       array('link'       => $link,
	     'fields'     => $fields,
	     'conditions' => $cond,
	     'order'      => $order,
	     ));

    return $entries;
  }
}

?>