;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10 -*-
;;;; *************************************************************************
;;;; FILE IDENTIFICATION
;;;;
;;;; Name:          pool.lisp
;;;; Purpose:       Support function for connection pool
;;;; Programmers:   Kevin M. Rosenberg, Marc Battyani
;;;; Date Started:  Apr 2002
;;;;
;;;; $Id$
;;;;
;;;; This file, part of CLSQL, is Copyright (c) 2002-2003 by Kevin M. Rosenberg
;;;;
;;;; CLSQL users are granted the rights to distribute and use this software
;;;; as governed by the terms of the Lisp Lesser GNU Public License
;;;; (http://opensource.franz.com/preamble.html), also known as the LLGPL.
;;;; *************************************************************************

(in-package clsql-sys)

(defun make-process-lock (name) 
  #+allegro (mp:make-process-lock :name name)
  #+scl (thread:make-lock name)
  #+lispworks (mp:make-lock :name name)
  #-(or allegro scl lispworks) (declare (ignore name))
  #-(or allegro scl lispworks) nil)

(defmacro with-process-lock ((lock desc) &body body)
  #+scl `(thread:with-lock-held (,lock ,desc) ,@body)
  #+(or allegro lispworks)
  (declare (ignore desc))
  #+(or allegro lispworks)
  (let ((l (gensym)))
    `(let ((,l ,lock))
       #+allegro (mp:with-process-lock (,l) ,@body)
       #+lispworks (mp:with-lock (,l) ,@body)))
  #-(or scl allegro lispworks) (declare (ignore lock desc))
  #-(or scl allegro lispworks) `(progn ,@body))

(defvar *db-pool* (make-hash-table :test #'equal))
(defvar *db-pool-lock* (make-process-lock "DB Pool lock"))

(defclass conn-pool ()
  ((connection-spec :accessor connection-spec :initarg :connection-spec)
   (database-type :accessor database-type :initarg :database-type)
   (free-connections :accessor free-connections
		     :initform (make-array 5 :fill-pointer 0 :adjustable t))
   (all-connections :accessor all-connections
		    :initform (make-array 5 :fill-pointer 0 :adjustable t))
   (lock :accessor conn-pool-lock
	 :initform (make-process-lock "Connection pool"))))

(defun acquire-from-conn-pool (pool)
  (or (with-process-lock ((conn-pool-lock pool) "Acquire from pool")
	(and (plusp (length (free-connections pool)))
	     (vector-pop (free-connections pool))))
      (let ((conn (connect (connection-spec pool)
			   :database-type (database-type pool)
			   :if-exists :new)))
	(with-process-lock ((conn-pool-lock pool) "Acquire from pool")
	  (vector-push-extend conn (all-connections pool))
	  (setf (conn-pool conn) pool))
	conn)))

(defun release-to-conn-pool (conn)
  (let ((pool (conn-pool conn)))
    (with-process-lock ((conn-pool-lock pool) "Release to pool")
      (vector-push-extend conn (free-connections pool)))))

(defun clear-conn-pool (pool)
  (with-process-lock ((conn-pool-lock pool) "Clear pool")
    (loop for conn across (all-connections pool)
	  do (setf (conn-pool conn) nil)
	  (disconnect :database conn))
    (setf (fill-pointer (free-connections pool)) 0)
    (setf (fill-pointer (all-connections pool)) 0))
  nil)

(defun find-or-create-connection-pool (connection-spec database-type)
  "Find connection pool in hash table, creates a new connection pool if not found"
  (with-process-lock (*db-pool-lock* "Find-or-create connection")
    (let* ((key (list connection-spec database-type))
	   (conn-pool (gethash key *db-pool*)))
      (unless conn-pool
	(setq conn-pool (make-instance 'conn-pool
				       :connection-spec connection-spec
				       :database-type database-type))
	(setf (gethash key *db-pool*) conn-pool))
      conn-pool)))

(defun acquire-from-pool (connection-spec database-type &optional pool)
  (unless (typep pool 'conn-pool)
    (setf pool (find-or-create-connection-pool connection-spec database-type)))
  (acquire-from-conn-pool pool))

(defun release-to-pool (database)
  (release-to-conn-pool database))

(defun disconnect-pooled (&optional clear)
  "Disconnects all connections in the pool"
  (with-process-lock (*db-pool-lock* "Disconnect pooled")
    (maphash
     #'(lambda (key conn-pool)
	 (declare (ignore key))
	 (clear-conn-pool conn-pool))
     *db-pool*)
    (when clear (clrhash *db-pool*)))
  t)