;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10 -*-
;;;; *************************************************************************
;;;;
;;;; The CLSQL Object Oriented Data Manipulation Language (OODML).
;;;;
;;;; This file is part of CLSQL.
;;;;
;;;; 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 find-normalized-key (obj)
  "Find the first / primary key of a normalized object"
  (find-slot-if obj #'key-slot-p T T))

(defun normalized-key-value (obj)
  "Normalized classes share a single key for all their key slots"
  (when (normalizedp (class-of obj))
    (easy-slot-value obj (find-normalized-key obj))))

(defun key-qualifier-for-instance (obj &key (database *default-database*) this-class)
  "Generate a boolean sql-expression that identifies an object by its keys"
  (let* ((obj-class (or this-class (class-of obj)))
         (keys (keyslots-for-class obj-class))
         (normal-db-value (normalized-key-value obj)))
    (when keys
      (labels ((db-value (k)
                 (or normal-db-value
                     (db-value-from-slot
                      k
                      (easy-slot-value obj k)
                      database)))
               (key-equal-exp (k)
                 (sql-operation '== (generate-attribute-reference obj-class k database)
                                (db-value k))))
        (clsql-ands (mapcar #'key-equal-exp keys))))))

(defun generate-attribute-reference (vclass slotdef &optional (database *default-database*))
  "Turns key class and slot-def into a sql-expression representing the
   table and column it comes from

   used by things like generate-selection-list, update-slot-from-record"
  (when (key-or-base-slot-p slotdef)
    (sql-expression :attribute (database-identifier slotdef database)
                    :table (database-identifier vclass database))))

;;
;; Function used by 'find-all'
;;

(defun generate-selection-list (vclass)
  (let* ((sels nil)
         (this-class vclass)
         (slots (if (normalizedp vclass)
                    (labels ((getdslots ()
                               (let ((sl (ordered-class-direct-slots this-class)))
                                 (cond (sl)
                                       (t
                                        (setf this-class
                                              (car (class-direct-superclasses this-class)))
                                        (getdslots))))))
                      (getdslots))
                    (ordered-class-slots this-class))))
    (dolist (slotdef slots)
      (let ((res (generate-attribute-reference this-class slotdef)))
        (when res
          (push (cons slotdef res) sels))))
    (if sels
        sels
        (error "No slots of type :base in view-class ~A" (class-name vclass)))))



(defun generate-retrieval-joins-list (vclass retrieval-method)
  "Returns list of immediate join slots for a class."
  (let ((join-slotdefs nil))
    (dolist (slotdef (ordered-class-slots vclass) join-slotdefs)
      (when (and (eq :join (view-class-slot-db-kind slotdef))
                 (eq retrieval-method (gethash :retrieval (view-class-slot-db-info slotdef))))
        (push slotdef join-slotdefs)))))

(defun generate-immediate-joins-selection-list (vclass)
  "Returns list of immediate join slots for a class."
  (let (sels)
    (dolist (joined-slot (generate-retrieval-joins-list vclass :immediate) sels)
      (let* ((join-class-name (gethash :join-class (view-class-slot-db-info joined-slot)))
             (join-class (when join-class-name (find-class join-class-name))))
        (dolist (slotdef (ordered-class-slots join-class))
          (let ((res (generate-attribute-reference join-class slotdef)))
            (when res
              (push (cons slotdef res) sels))))))
    sels))

(defun immediate-join-slots (class)
  (generate-retrieval-joins-list class :immediate))

(defmethod choose-database-for-instance ((obj standard-db-object) &optional database)
  "Determine which database connection to use for a standard-db-object.
        Errs if none is available."
  (or (find-if #'(lambda (db)
                   (and db (is-database-open db)))
               (list (view-database obj)
                     database
                     *default-database*))
      (signal-no-database-error nil)))



(defmethod update-slot-with-null ((object standard-db-object) slotdef)
  "sets a slot to the void value of the slot-def (usually nil)"
  (setf (easy-slot-value object slotdef)
        (slot-value slotdef 'void-value)))

(defmethod update-slot-from-db-value ((instance standard-db-object) slotdef value)
  "This gets a value from the database and turns it itno a lisp value
   based on the slot's slot-db-reader or baring that read-sql-value"
  (declare (optimize (speed 3) #+cmu (extensions:inhibit-warnings 3)))
  (let* ((slot-reader (view-class-slot-db-reader slotdef))
         (slot-type   (specified-type slotdef)))
    (cond
      ((null value) (update-slot-with-null instance slotdef))
      ((null slot-reader)
       (setf (easy-slot-value instance slotdef)
             (read-sql-value value (delistify slot-type)
                             (choose-database-for-instance instance)
                             (database-underlying-type
                              (choose-database-for-instance instance)))))
      (t (etypecase slot-reader
           ((or symbol function)
            (setf (easy-slot-value instance slotdef)
                  (apply slot-reader (list value))))
           (string
            (setf (easy-slot-value instance slotdef)
                  (format nil slot-reader value))))))))

(defmethod key-value-from-db (slotdef value database)
  "TODO: is this deprecated? there are no uses anywhere in clsql"
  (declare (optimize (speed 3) #+cmu (extensions:inhibit-warnings 3)))
  (let ((slot-reader (view-class-slot-db-reader slotdef))
        (slot-type (specified-type slotdef)))
    (cond ((and value (null slot-reader))
           (read-sql-value value (delistify slot-type) database
                           (database-underlying-type database)))
          ((null value)
           nil)
          ((typep slot-reader 'string)
           (format nil slot-reader value))
          ((typep slot-reader '(or symbol function))
           (apply slot-reader (list value)))
          (t
           (error "Slot reader is of an unusual type.")))))

(defun db-value-from-slot (slotdef val database)
  (let ((dbwriter (view-class-slot-db-writer slotdef))
        (dbtype (specified-type slotdef)))
    (typecase dbwriter
      (string (format nil dbwriter val))
      ((and (or symbol function) (not null)) (apply dbwriter (list val)))
      (t
       (database-output-sql-as-type
        (typecase dbtype
          (cons (car dbtype))
          (t dbtype))
        val database (database-underlying-type database))))))

(defun check-slot-type (slotdef val)
  (let* ((slot-type (specified-type slotdef))
         (basetype (if (listp slot-type) (car slot-type) slot-type)))
    (when (and slot-type val)
      (unless (typep val basetype)
        (error 'sql-user-error
               :message
               (format nil "Invalid value ~A in slot ~A, not of type ~A."
                       val (slot-definition-name slotdef) slot-type))))))

(defmethod get-slot-values-from-view (obj slotdeflist values)
  "Used to copy values from the database into the object
   used by things like find-all and select"
  (loop for slot in slotdeflist
        for value in values
        do (update-slot-from-db-value obj slot value))
  obj)

(defclass class-and-slots ()
  ((view-class :accessor view-class :initarg :view-class :initform nil)
   (slot-defs :accessor slot-defs :initarg :slot-defs :initform nil))
  (:documentation "A helper class to keep track of which slot-defs from a
   table need to be updated, a normalized class might have many of these
   because each of its parent classes might represent some other table and we
   need to match which slots came from which parent class/table"))

(defun make-class-and-slots (c &optional s)
  "Create a new class-and-slots object"
  (make-instance 'class-and-slots :view-class c :slot-defs (listify s) ))

(defmethod view-table ((o class-and-slots))
  "get the view-table of the view-class of o"
  (view-table (view-class o)))

(defmethod view-table-exp ((o class-and-slots))
  (sql-expression :table (view-table o)))

(defmethod view-table-exp ((o standard-db-class))
  (sql-expression :table (view-table o)))

(defmethod attribute-references ((o class-and-slots))
  "build sql-ident-attributes for a given class-and-slots"
  (loop
    with class = (view-class o)
    for sd in (slot-defs o)
    collect (generate-attribute-reference class sd)))

(defmethod attribute-value-pairs ((def class-and-slots) (o standard-db-object)
                                  database)
  "for a given class-and-slots and object, create the sql-expression & value pairs
   that need to be sent to the database"
  (loop for s in (slot-defs def)
        for n = (to-slot-name s)
        when (slot-boundp o n)
        collect (make-attribute-value-pair s (slot-value o n) database)))

(defmethod view-classes-and-slots-by-name ((obj standard-db-object) slots-to-match)
  "If it's normalized, find the class that actually contains
   the slot that's tied to the db,

   otherwise just search the current class
  "
  (let* ((view-class (class-of obj))
         (normalizedp (normalizedp view-class))
         rtns)
    (labels ((get-c&s-obj (class)
               (or (find class rtns :key #'view-class)
                   (first (push (make-class-and-slots class) rtns))))
             (associate-slot-with-class (class slot)
               "Find the best class to associate with the slot. If it is
                normalized then it needs to be a direct slot otherwise it just
                needs to be on the class."
               (let ((sd (find-slot-by-name class slot normalizedp nil)))
                 (if sd
                     ;;we found it directly or it's (not normalized)
                     (pushnew sd (slot-defs (get-c&s-obj class)))
                     (when normalizedp
                       (loop for parent in (class-direct-superclasses class)
                             until (associate-slot-with-class parent slot))))
                 sd)))
      (loop
        for in-slot in (listify slots-to-match)
        do (associate-slot-with-class view-class in-slot)))
    rtns))

(defun update-auto-increments-keys (class obj database)
  " handle pulling any autoincrement values into the object
   if normalized and we now that all the "
  (let ((pk-slots (keyslots-for-class class))
        (table (view-table class))
        new-pk-value)
    (labels ((do-update (slot)
               (when (and (null (easy-slot-value obj slot))
                          (auto-increment-column-p slot database))
                 (update-slot-from-db-value
                  obj slot
                  (or new-pk-value
                      (setf new-pk-value
                            (database-last-auto-increment-id
                             database table slot))))))
             (chain-primary-keys (in-class)
               "This seems kindof wrong, but this is mostly how it was working, so
                  its here to keep the normalized code path working"
               (when (typep in-class 'standard-db-class)
                 (loop for slot in (ordered-class-slots in-class)
                       when (key-slot-p slot)
                       do (do-update slot)))))
      (loop for slot in pk-slots do (do-update slot))
      (let ((direct-class (to-class obj)))
        (when (and new-pk-value (normalizedp direct-class))
          (chain-primary-keys direct-class)))
      new-pk-value)))

(defmethod %update-instance-helper
    (class-and-slots obj database
     &aux (avps (attribute-value-pairs class-and-slots obj database)))
  "A function to help us update a given table (based on class-and-slots)
   with values from an object"
  ;; we dont actually need to update anything on this particular
  ;; class / parent class
  (unless avps (return-from %update-instance-helper))

  (let* ((view-class (view-class class-and-slots))
         (table (view-table view-class))
         (table-sql (sql-expression :table table)))

    ;; view database is the flag we use to tell it was pulled from a database
    ;; and thus probably needs an update instead of an insert
    (cond ((view-database obj)
           (let ((where (key-qualifier-for-instance
                         obj :database database :this-class view-class)))
             (unless where
               (error "update-record-from-*: could not generate a where clause for ~a using ~A"
                      obj view-class))
             (update-records table-sql
                             :av-pairs avps
                             :where where
                             :database database)))
          (T ;; was not pulled from the db so insert it
           ;; avps MUST contain any primary key slots set
           ;; by previous inserts of the same object into different
           ;; tables (ie: normalized stuff)
           (insert-records :into table-sql
                           :av-pairs avps
                           :database database)
           (update-auto-increments-keys view-class obj database)
           ;; we dont set view database here, because there could be
           ;; N of these for each call to update-record-from-* because
           ;; of normalized classes
           ))
    (update-slot-default-values obj class-and-slots)))

(defmethod update-record-from-slots ((obj standard-db-object) slots
                                     &key (database *default-database*))
  "For a given list of slots, update all records associated with those slots
   and classes.

   Generally this will update the single record associated with this object,
   but for normalized classes might update as many records as there are
   inheritances "
  (setf slots (listify slots))
  (let* ((classes-and-slots (view-classes-and-slots-by-name obj slots))
         (database (choose-database-for-instance obj database)))
    (loop for class-and-slots in classes-and-slots
          do (%update-instance-helper class-and-slots obj database))
    (setf (slot-value obj 'view-database) database))
  (values))

(defmethod update-record-from-slot
    ((obj standard-db-object) slot &key (database *default-database*))
  "just call update-records-from-slots which now handles this.

   This function is only here to maintain backwards compatibility in
   the public api"
  (update-record-from-slots obj slot :database database))

(defun view-classes-and-storable-slots (class)
  "Get a list of all the tables we need to update and the slots on them

   for non normalized classes we return the class and all its storable slots

   for normalized classes we return a list of direct slots and the class they
   came from for each normalized view class
  "
  (setf class (to-class class))
  (let* (rtns)
    (labels ((storable-slots (class)
               (loop for sd in (slots-for-possibly-normalized-class class)
                     when (key-or-base-slot-p sd)
                     collect sd))
             (get-classes-and-slots (class &aux (normalizedp (normalizedp class)))
               (let ((slots (storable-slots class)))
                 (when slots
                   (push (make-class-and-slots class slots) rtns)))
               (when normalizedp
                 (loop for new-class in (class-direct-superclasses class)
                       do (when (typep new-class 'standard-db-class)
                            (get-classes-and-slots new-class))))))
      (get-classes-and-slots class))
    rtns))

(defmethod primary-key-slot-values ((obj standard-db-object)
                                    &key class slots )
  "Returns the values of all key-slots for a given class"
  (defaulting class (class-of obj)
              slots (keyslots-for-class class))
  (loop for slot in slots
        collect (easy-slot-value obj slot)))

(defmethod update-slot-default-values ((obj standard-db-object)
                                       classes-and-slots)
  "Makes sure that if a class has unfilled slots that claim to have a default,
   that we retrieve those defaults from the database

   TODO: use update slots-from-record instead to batch this!"
  (loop for class-and-slots in (listify classes-and-slots)
        do (loop for slot in (slot-defs class-and-slots)
                 do (when (and (slot-has-default-p slot)
                               (not (easy-slot-value obj slot)))
                      (update-slot-from-record obj (to-slot-name slot))))))

(defmethod update-records-from-instance ((obj standard-db-object)
                                         &key (database *default-database*))
  "Updates the records in the database associated with this object if
   view-database slot on the object is nil then the object is assumed to be
   new and is inserted"
  (let ((database (choose-database-for-instance obj database))
        (classes-and-slots (view-classes-and-storable-slots obj)))
    (loop for class-and-slots in classes-and-slots
          do (%update-instance-helper class-and-slots obj database))
    (setf (slot-value obj 'view-database) database)
    (primary-key-slot-values obj)))

(defmethod delete-instance-records ((instance standard-db-object) &key database)
  "Removes the records associated with a given instance
   (as determined by key-qualifier-for-instance)

   TODO: Doesnt handle normalized classes at all afaict"
  (let ((database (choose-database-for-instance instance database))
        (vt (sql-expression :table (view-table (class-of instance)))))
    (if database
        (let ((qualifier (key-qualifier-for-instance instance :database database)))
          (delete-records :from vt :where qualifier :database database)
          (setf (record-caches database) nil)
          (setf (slot-value instance 'view-database) nil)
          (values))
        (signal-no-database-error database))))

(defmethod update-instance-from-records ((instance standard-db-object)
                                         &key (database *default-database*)
                                         this-class)
  (let* ((view-class (or this-class (class-of instance)))
         (pclass (car (class-direct-superclasses view-class)))
         (pres nil))
    (when (normalizedp view-class)
      (setf pres (update-instance-from-records instance :database database
                                               :this-class pclass)))
    (let* ((view-table (sql-expression :table (view-table view-class)))
           (vd (choose-database-for-instance instance database))
           (view-qual (key-qualifier-for-instance instance :database vd
                                                           :this-class view-class))
           (sels (generate-selection-list view-class))
           (res nil))
      (cond (view-qual
             (setf res (apply #'select (append (mapcar #'cdr sels)
                                               (list :from  view-table
                                                     :where view-qual
                                                     :result-types nil
                                                     :database vd))))
             (when res
	       (setf (slot-value instance 'view-database) vd)
               (get-slot-values-from-view instance (mapcar #'car sels) (car res))))
            (pres)
            (t nil)))))


(defmethod get-slot-value-from-record ((instance standard-db-object)
                                       slot &key (database *default-database*))
  (let* ((class-and-slot
           (first
            (view-classes-and-slots-by-name instance slot)))
         (view-class (view-class class-and-slot))
         (slot-def (first (slot-defs class-and-slot)))
         (vd (choose-database-for-instance instance database))
         (att-ref (first (attribute-references class-and-slot)))
         (res (first
               (select att-ref
                 :from (view-table-exp class-and-slot)
                 :where (key-qualifier-for-instance
                         instance
                         :database vd
                         :this-class view-class)
                 :result-types nil
                 :flatp T))))
    (values res slot-def)))

(defmethod update-slot-from-record ((instance standard-db-object)
                                    slot &key (database *default-database*))
  "Pulls the value of a given slot form the database and stores that in the
   appropriate slot on instance"
  (multiple-value-bind (res slot-def)
      (get-slot-value-from-record instance slot :database database)
    (let ((vd (choose-database-for-instance instance database)))
      (setf (slot-value instance 'view-database) vd)
      (update-slot-from-db-value instance slot-def res))))


(defvar +no-slot-value+ '+no-slot-value+)

(defsql sql-slot-value (:symbol "slot-value") (classname slot &optional (value +no-slot-value+) (database *default-database*))
        (let* ((class (find-class classname))
               (sld (slotdef-for-slot-with-class slot class)))
          (if sld
              (if (eq value +no-slot-value+)
                  (sql-expression :attribute (database-identifier sld database)
                                  :table (view-table class))
                  (db-value-from-slot
                   sld
                   value
                   database))
              (error "Unknown slot ~A for class ~A" slot classname))))

(defsql sql-view-class (:symbol "view-class") (classname &optional (database *default-database*))
        (declare (ignore database))
        (let* ((class (find-class classname)))
          (unless (view-table class)
            (error "No view-table for class ~A"  classname))
          (sql-expression :table (view-table class))))


(defmethod database-get-type-specifier (type args database db-type)
  (declare (ignore type args database db-type))
  (format nil "VARCHAR(~D)" *default-string-length*))

(defmethod database-get-type-specifier ((type (eql 'integer)) args database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "INT(~A)" (car args))
      "INT"))

(deftype tinyint ()
  "An 8-bit integer, this width may vary by SQL implementation."
  'integer)

(defmethod database-get-type-specifier ((type (eql 'tinyint)) args database db-type)
  (declare (ignore args database db-type))
  "INT")

(deftype smallint ()
  "An integer smaller than a 32-bit integer. this width may vary by SQL implementation."
  'integer)

(defmethod database-get-type-specifier ((type (eql 'smallint)) args database db-type)
  (declare (ignore args database db-type))
  "INT")

(deftype mediumint ()
  "An integer smaller than a 32-bit integer, but may be larger than a smallint. This width may vary by SQL implementation."
  'integer)

(defmethod database-get-type-specifier ((type (eql 'mediumint)) args database db-type)
  (declare (ignore args database db-type))
  "INT")

(deftype bigint ()
  "An integer larger than a 32-bit integer, this width may vary by SQL implementation."
  'integer)

(defmethod database-get-type-specifier ((type (eql 'bigint)) args database db-type)
  (declare (ignore args database db-type))
  "BIGINT")

(deftype varchar (&optional size)
  "A variable length string for the SQL varchar type."
  (declare (ignore size))
  'string)

(defmethod database-get-type-specifier ((type (eql 'varchar)) args
                                        database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "VARCHAR(~A)" (car args))
      (format nil "VARCHAR(~D)" *default-string-length*)))

(defmethod database-get-type-specifier ((type (eql 'string)) args database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "CHAR(~A)" (car args))
      (format nil "VARCHAR(~D)" *default-string-length*)))

(deftype universal-time ()
  "A positive integer as returned by GET-UNIVERSAL-TIME."
  '(integer 1 *))

(defmethod database-get-type-specifier ((type (eql 'universal-time)) args database db-type)
  (declare (ignore args database db-type))
  "BIGINT")

(defmethod database-get-type-specifier ((type (eql 'wall-time)) args database db-type)
  (declare (ignore args database db-type))
  "TIMESTAMP")

(defmethod database-get-type-specifier ((type (eql 'date)) args database db-type)
  (declare (ignore args database db-type))
  "DATE")

(defmethod database-get-type-specifier ((type (eql 'duration)) args database db-type)
  (declare (ignore database args db-type))
  "VARCHAR")

(defmethod database-get-type-specifier ((type (eql 'money)) args database db-type)
  (declare (ignore database args db-type))
  "INT8")

#+ignore
(deftype char (&optional len)
  "A lisp type for the SQL CHAR type."
  `(string ,len))

(defmethod database-get-type-specifier ((type (eql 'float)) args database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "FLOAT(~A)" (car args))
      "FLOAT"))

(defmethod database-get-type-specifier ((type (eql 'long-float)) args database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "FLOAT(~A)" (car args))
      "FLOAT"))

(deftype generalized-boolean ()
  "A type which outputs a SQL boolean value, though any lisp type can be stored in the slot."
  t)

(defmethod database-get-type-specifier ((type (eql 'boolean)) args database db-type)
  (declare (ignore args database db-type))
  "BOOL")

(defmethod database-get-type-specifier ((type (eql 'generalized-boolean)) args database db-type)
  (declare (ignore args database db-type))
  "BOOL")

(defmethod database-get-type-specifier ((type (eql 'number)) args database db-type)
  (declare (ignore database db-type))
  (cond
    ((and (consp args) (= (length args) 2))
     (format nil "NUMBER(~D,~D)" (first args) (second args)))
    ((and (consp args) (= (length args) 1))
     (format nil "NUMBER(~D)" (first args)))
    (t
     "NUMBER")))

(defmethod database-get-type-specifier ((type (eql 'char)) args database db-type)
  (declare (ignore database db-type))
  (if args
      (format nil "CHAR(~D)" (first args))
      "CHAR(1)"))


(defmethod database-output-sql-as-type (type val database db-type)
  (declare (ignore type database db-type))
  val)

(defmethod database-output-sql-as-type ((type (eql 'list)) val database db-type)
  (declare (ignore database db-type))
  (progv '(*print-circle* *print-array*) '(t t)
    (let ((escaped (prin1-to-string val)))
      (substitute-char-string
       escaped #\Null " "))))

(defmethod database-output-sql-as-type ((type (eql 'symbol)) val database db-type)
  (declare (ignore database db-type))
  (if val
      (concatenate 'string
                   (package-name (symbol-package val))
                   "::"
                   (symbol-name val))
      ""))

(defmethod database-output-sql-as-type ((type (eql 'keyword)) val database db-type)
  (declare (ignore database db-type))
  (if val
      (symbol-name val)
      ""))

(defmethod database-output-sql-as-type ((type (eql 'vector)) val database db-type)
  (declare (ignore database db-type))
  (progv '(*print-circle* *print-array*) '(t t)
    (prin1-to-string val)))

(defmethod database-output-sql-as-type ((type (eql 'array)) val database db-type)
  (declare (ignore database db-type))
  (progv '(*print-circle* *print-array*) '(t t)
    (prin1-to-string val)))

(defmethod database-output-sql-as-type ((type (eql 'boolean)) val database db-type)
  (declare (ignore database db-type))
  (if val "t" "f"))

(defmethod database-output-sql-as-type ((type (eql 'generalized-boolean)) val database db-type)
  (declare (ignore database db-type))
  (if val "t" "f"))

(defmethod database-output-sql-as-type ((type (eql 'string)) val database db-type)
  (declare (ignore database db-type))
  val)

(defmethod database-output-sql-as-type ((type (eql 'char)) val database db-type)
  (declare (ignore database db-type))
  (etypecase val
    (character (write-to-string val))
    (string val)))

(defmethod database-output-sql-as-type ((type (eql 'float)) val database db-type)
  (declare (ignore database db-type))
  (if (eq (type-of val) 'null)
      nil
      (let ((*read-default-float-format* (type-of val)))
       (format nil "~F" val))))

(defmethod read-sql-value (val type database db-type)
  (declare (ignore database db-type))
  (cond
    ((null type) val) ;;we have no desired type, just give the value
    ((typep val type) val) ;;check that it hasn't already been converted.
    ((typep val 'string) (read-from-string val)) ;;maybe read will just take care of it?
    (T (error "Unable to read-sql-value ~a as type ~a" val type))))

(defmethod read-sql-value (val (type (eql 'string)) database db-type)
  (declare (ignore database db-type))
  val)

(defmethod read-sql-value (val (type (eql 'varchar)) database db-type)
  (declare (ignore database db-type))
  val)

(defmethod read-sql-value (val (type (eql 'char)) database db-type)
  (declare (ignore database db-type))
  (schar val 0))

(defmethod read-sql-value (val (type (eql 'keyword)) database db-type)
  (declare (ignore database db-type))
  (when (< 0 (length val))
    (intern (symbol-name-default-case val)
            (find-package '#:keyword))))

(defmethod read-sql-value (val (type (eql 'symbol)) database db-type)
  (declare (ignore database db-type))
  (when (< 0 (length val))
    (unless (string= val (symbol-name-default-case "NIL"))
      (read-from-string val))))

(defmethod read-sql-value (val (type (eql 'integer)) database db-type)
  (declare (ignore database db-type))
  (etypecase val
    (string
     (unless (string-equal "NIL" val)
       (parse-integer val)))
    (number val)))

(defmethod read-sql-value (val (type (eql 'smallint)) database db-type)
  (declare (ignore database db-type))
  (etypecase val
    (string
     (unless (string-equal "NIL" val)
       (parse-integer val)))
    (number val)))

(defmethod read-sql-value (val (type (eql 'bigint)) database db-type)
  (declare (ignore database db-type))
  (etypecase val
    (string
     (unless (string-equal "NIL" val)
       (parse-integer val)))
    (number val)))

(defmethod read-sql-value (val (type (eql 'float)) database db-type)
  (declare (ignore database db-type))
  ;; writing 1.0 writes 1, so we we *really* want a float, must do (float ...)
  (etypecase val
    (string (float (read-from-string val)))
    (float val)))

(defmethod read-sql-value (val (type (eql 'double-float)) database db-type)
  (declare (ignore database db-type))
  ;; writing 1.0 writes 1, so if we *really* want a float, must do (float ...)
  (etypecase val
    (string (float
	     (let ((*read-default-float-format* 'double-float))
	       (read-from-string val))
	     1.0d0))
    (double-float val)
    (float (coerce val 'double-float))))

(defmethod read-sql-value (val (type (eql 'boolean)) database db-type)
  (declare (ignore database db-type))
  (equal "t" val))

(defmethod read-sql-value (val (type (eql 'generalized-boolean)) database db-type)
  (declare (ignore database db-type))
  (equal "t" val))

(defmethod read-sql-value (val (type (eql 'number)) database db-type)
  (declare (ignore database db-type))
  (etypecase val
    (string
     (unless (string-equal "NIL" val)
       (read-from-string val)))
    (number val)))

(defmethod read-sql-value (val (type (eql 'universal-time)) database db-type)
  (declare (ignore database db-type))
  (unless (eq 'NULL val)
    (etypecase val
      (string
       (parse-integer val))
      (number val))))

(defmethod read-sql-value (val (type (eql 'wall-time)) database db-type)
  (declare (ignore database db-type))
  (unless (eq 'NULL val)
    (parse-timestring val)))

(defmethod read-sql-value (val (type (eql 'date)) database db-type)
  (declare (ignore database db-type))
  (unless (eq 'NULL val)
    (parse-datestring val)))

(defmethod read-sql-value (val (type (eql 'duration)) database db-type)
  (declare (ignore database db-type))
  (unless (or (eq 'NULL val)
              (equal "NIL" val))
    (parse-timestring val)))

;; ------------------------------------------------------------
;; Logic for 'faulting in' :join slots

;; this works, but is inefficient requiring (+ 1 n-rows)
;; SQL queries
#+ignore
(defun fault-join-target-slot (class object slot-def)
  (let* ((res (fault-join-slot-raw class object slot-def))
         (dbi (view-class-slot-db-info slot-def))
         (target-name (gethash :target-slot dbi))
         (target-class (find-class target-name)))
    (when res
      (mapcar (lambda (obj)
                (list
                 (car
                  (fault-join-slot-raw
                   target-class
                   obj
                   (find target-name (class-slots (class-of obj))
                         :key #'slot-definition-name)))
                 obj))
              res)
      #+ignore ;; this doesn't work when attempting to call slot-value
      (mapcar (lambda (obj)
                (cons obj (slot-value obj ts))) res))))

(defun fault-join-target-slot (class object slot-def)
  (let* ((dbi (view-class-slot-db-info slot-def))
         (ts (gethash :target-slot dbi))
         (jc  (gethash :join-class dbi))
         (jc-view-table (view-table (find-class jc)))
         (tdbi (view-class-slot-db-info
                (find ts (class-slots (find-class jc))
                      :key #'slot-definition-name)))
         (retrieval (gethash :retrieval tdbi))
         (tsc (gethash :join-class tdbi))
         (ts-view-table (view-table (find-class tsc)))
         (jq (join-qualifier class object slot-def))
         (key (slot-value object (gethash :home-key dbi))))

    (when jq
      (ecase retrieval
        (:immediate
         (let ((res
                (find-all (list tsc)
                          :inner-join (sql-expression :table jc-view-table)
                          :on (sql-operation
                               '==
                               (sql-expression
                                :attribute (gethash :foreign-key tdbi)
                                :table ts-view-table)
                               (sql-expression
                                :attribute (gethash :home-key tdbi)
                                :table jc-view-table))
                          :where jq
                          :result-types :auto
                          :database (choose-database-for-instance object))))
           (mapcar #'(lambda (i)
                       (let* ((instance (car i))
                              (jcc (make-instance jc :view-database (choose-database-for-instance instance))))
                         (setf (slot-value jcc (gethash :foreign-key dbi))
                               key)
                         (setf (slot-value jcc (gethash :home-key tdbi))
                               (slot-value instance (gethash :foreign-key tdbi)))
                         (list instance jcc)))
                   res)))
        (:deferred
         ;; just fill in minimal slots
         (mapcar
          #'(lambda (k)
              (let ((instance (make-instance tsc :view-database (choose-database-for-instance object)))
                    (jcc (make-instance jc :view-database (choose-database-for-instance object)))
                    (fk (car k)))
                (setf (slot-value instance (gethash :home-key tdbi)) fk)
                (setf (slot-value jcc (gethash :foreign-key dbi))
                      key)
                (setf (slot-value jcc (gethash :home-key tdbi))
                      fk)
                (list instance jcc)))
          (select (sql-expression :attribute (gethash :foreign-key tdbi) :table jc-view-table)
                  :from (sql-expression :table jc-view-table)
                  :where jq
                  :database (choose-database-for-instance object))))))))


;;; Remote Joins

(defvar *default-update-objects-max-len* nil
  "The default value to use for the MAX-LEN keyword argument to
  UPDATE-OBJECT-JOINS.")

(defun update-objects-joins (objects &key (slots t) (force-p t)
                             class-name (max-len
                                         *default-update-objects-max-len*))
  "Updates from the records of the appropriate database tables
the join slots specified by SLOTS in the supplied list of View
Class instances OBJECTS.  SLOTS is t by default which means that
all join slots with :retrieval :immediate are updated. CLASS-NAME
is used to specify the View Class of all instance in OBJECTS and
default to nil which means that the class of the first instance
in OBJECTS is used. FORCE-P is t by default which means that all
join slots are updated whereas a value of nil means that only
unbound join slots are updated. MAX-LEN defaults to
*DEFAULT-UPDATE-OBJECTS-MAX-LEN* and when non-nil specifies that
UPDATE-OBJECT-JOINS may issue multiple database queries with a
maximum of MAX-LEN instances updated in each query."
  (assert (or (null max-len) (plusp max-len)))
  (when objects
    (unless class-name
      (setq class-name (class-name (class-of (first objects)))))
    (let* ((class (find-class class-name))
           (class-slots (ordered-class-slots class))
           (slotdefs
            (if (eq t slots)
                (generate-retrieval-joins-list class :deferred)
                (remove-if #'null
                           (mapcar #'(lambda (name)
                                       (let ((slotdef (find name class-slots :key #'slot-definition-name)))
                                         (unless slotdef
                                           (warn "Unable to find slot named ~S in class ~S." name class))
                                         slotdef))
                                   slots)))))
      (dolist (slotdef slotdefs)
        (let* ((dbi (view-class-slot-db-info slotdef))
               (slotdef-name (slot-definition-name slotdef))
               (foreign-key (gethash :foreign-key dbi))
               (home-key (gethash :home-key dbi))
               (object-keys
                (remove-duplicates
                 (if force-p
                     (mapcar #'(lambda (o) (slot-value o home-key)) objects)
                     (remove-if #'null
                                (mapcar
                                 #'(lambda (o) (if (slot-boundp o slotdef-name)
                                                   nil
                                                   (slot-value o home-key)))
                                 objects)))))
               (n-object-keys (length object-keys))
               (query-len (or max-len n-object-keys)))

          (do ((i 0 (+ i query-len)))
              ((>= i n-object-keys))
            (let* ((keys (if max-len
                             (subseq object-keys i (min (+ i query-len) n-object-keys))
                             object-keys))
                   (results (unless (gethash :target-slot dbi)
                              (find-all (list (gethash :join-class dbi))
                                        :where (make-instance 'sql-relational-exp
                                                              :operator 'in
                                                              :sub-expressions (list (sql-expression :attribute foreign-key)
                                                                                     keys))
                                        :result-types :auto
                                        :flatp t)) ))

              (dolist (object objects)
                (when (or force-p (not (slot-boundp object slotdef-name)))
                  (let ((res (if results
                                 (remove-if-not #'(lambda (obj)
                                                    (equal obj (slot-value
                                                                object
                                                                home-key)))
                                                results
                                                :key #'(lambda (res)
                                                         (slot-value res
                                                                     foreign-key)))

                                 (progn
                                   (when (gethash :target-slot dbi)
                                     (fault-join-target-slot class object slotdef))))))
                    (when res
                      (setf (slot-value object slotdef-name)
                            (if (gethash :set dbi) res (car res)))))))))))))
  (values))

(defun fault-join-slot-raw (class object slot-def)
  (let* ((dbi (view-class-slot-db-info slot-def))
         (jc (gethash :join-class dbi)))
    (let ((jq (join-qualifier class object slot-def)))
      (when jq
        (select jc :where jq :flatp t :result-types nil
                :database (choose-database-for-instance object))))))



(defun fault-join-slot (class object slot-def)
  (let* ((dbi (view-class-slot-db-info slot-def))
         (ts (gethash :target-slot dbi))
         (dbi-set (gethash :set dbi)))
    (if (and ts dbi-set)
        (fault-join-target-slot class object slot-def)
        (let ((res (fault-join-slot-raw class object slot-def)))
          (when res
            (cond
              ((and ts (not dbi-set))
               (mapcar (lambda (obj) (slot-value obj ts)) res))
              ((and (not ts) (not dbi-set))
               (car res))
              ((and (not ts) dbi-set)
               res)))))))

(defun update-fault-join-normalized-slot (class object slot-def)
  (if (and (normalizedp class) (key-slot-p slot-def))
      (setf (easy-slot-value object slot-def)
            (normalized-key-value object))
      (update-slot-from-record object slot-def)))

(defun all-home-keys-have-values-p (object slot-def)
  "Do all of the home-keys have values ?"
  (let ((home-keys (join-slot-info-value slot-def :home-key)))
    (loop for key in (listify home-keys)
          always (easy-slot-value object key))))

(defun join-qualifier (class object slot-def)
  "Builds the join where clause based on the keys of the join slot and values
   of the object"
  (declare (ignore class))
  (let* ((jc (join-slot-class slot-def))
         ;;(ts (gethash :target-slot dbi))
         ;;(tsdef (if ts (slotdef-for-slot-with-class ts jc)))
         (foreign-keys (listify (join-slot-info-value slot-def :foreign-key)))
         (home-keys (listify (join-slot-info-value slot-def :home-key))))
    (when (all-home-keys-have-values-p object slot-def)
      (clsql-ands
       (loop for hk in home-keys
             for fk in foreign-keys
             for fksd = (slotdef-for-slot-with-class fk jc)
             for fk-sql = (typecase fk
                            (symbol
                             (sql-expression
                              :attribute (database-identifier fksd nil)
                              :table (database-identifier jc nil)))
                            (t fk))
             for hk-val = (typecase hk
                            ((or symbol
                                 view-class-effective-slot-definition
                                 view-class-direct-slot-definition)
                             (easy-slot-value object hk))
                            (t hk))
             collect (sql-operation '== fk-sql hk-val))))))

(defmethod select-table-sql-expr ((table T))
  "Turns an object representing a table into the :from part of the sql expression that will be executed "
  (sql-expression :table (view-table table)))

(defun select-reference-equal (r1 r2)
  "determines if two sql select references are equal
   using database identifier equal"
  (flet ((id-of (r)
           (etypecase r
             (cons (cdr r))
             (sql-ident-attribute r))))
    (database-identifier-equal (id-of r1) (id-of r2))))

(defun join-slot-qualifier (class join-slot)
  "Creates a sql-expression expressing the join between the home-key on the table
   and its respective key on the joined-to-table"
  (sql-operation
   '==
   (sql-expression
    :attribute (join-slot-info-value join-slot :foreign-key)
    :table (view-table (join-slot-class join-slot)))
   (sql-expression
    :attribute (join-slot-info-value join-slot :home-key)
    :table (view-table class))))

(defun all-immediate-join-classes-for (classes)
  "returns a list of all join-classes needed for a list of classes"
  (loop for class in (listify classes)
        appending (loop for slot in (immediate-join-slots class)
                        collect (join-slot-class slot))))

(defun %tables-for-query (classes from where inner-joins)
  "Given lists of classes froms wheres and inner-join compile a list
   of tables that should appear in the FROM section of the query.

   This includes any immediate join classes from each of the classes"
  (let ((inner-join-tables (collect-table-refs (listify inner-joins))))
    (loop for tbl in (append
                      (mapcar #'select-table-sql-expr classes)
                      (mapcar #'select-table-sql-expr
                              (all-immediate-join-classes-for classes))
                      (collect-table-refs (listify where))
                      (collect-table-refs (listify from)))
          when (and tbl
                    (not (find tbl rtn :test #'database-identifier-equal))
                    ;; TODO: inner-join is currently hacky as can be
                    (not (find tbl inner-join-tables :test #'database-identifier-equal)))
          collect tbl into rtn
          finally (return rtn))))

(defun full-select-list ( classes )
  "Returns a list of sql-ref of things to select for the given classes

   THIS NEEDS TO MATCH THE ORDER OF build-objects

   TODO: this used to include order-by and distinct as more things to select.
    distinct seems to always be used in a boolean context, so it doesnt seem
    like appending it to the select makes any sense

    We also used to remove duplicates, but that seems like it would make
    filling/building objects much more difficult so skipping for now...
  "
  (setf classes (mapcar #'to-class (listify classes)))
  (mapcar
   #'cdr
   (loop for class in classes
         appending (generate-selection-list class)
         appending
            (loop for join-slot in (immediate-join-slots class)
                  for join-class = (join-slot-class-name join-slot)
                  appending (generate-selection-list join-class)))))

(defun build-objects (classes row database &optional existing-instances)
  "Used by find-all to build objects.

   THIS NEEDS TO MATCH THE ORDER OF FULL-SELECT-LIST

   TODO: this caching scheme seems bad for a number of reasons
    * order is not guaranteed so references being held by one object
      might change to represent a different database row (seems HIGHLY
      suspect)
    * also join objects are overwritten rather than refreshed

   TODO: the way we handle immediate joins seems only valid if it is a single
      object.  I suspect that making a :set :immediate join column would result
      in an invalid number of objects returned from the database, because there
      would be multiple rows per object, but we would return an object per row
   "
  (setf existing-instances (listify existing-instances))
  (loop for class in classes
        for existing = (pop existing-instances)
        for object = (or existing
                         (make-instance class :view-database database))
        do (loop for (slot . _) in (generate-selection-list class)
                 do (update-slot-from-db-value object slot (pop row)))
        do (loop for join-slot in (immediate-join-slots class)
                 for join-class = (join-slot-class-name join-slot)
                 for join-object =
                     (setf
                      (easy-slot-value object join-slot)
                      (make-instance join-class))
                 do (loop for (slot . _) in (generate-selection-list join-class)
                          do (update-slot-from-db-value join-object slot (pop row))))
        do (when existing (instance-refreshed object))
        collect object))

(defun find-all (view-classes
                 &rest args
                 &key all set-operation distinct from where group-by having
                 order-by offset limit refresh flatp result-types
                 inner-join on
                 (database *default-database*)
                 instances parameters)
  "Called by SELECT to generate object query results when the
  View Classes VIEW-CLASSES are passed as arguments to SELECT.

   TODO: the caching scheme of passing in instances and overwriting their
         values seems bad for a number of reasons
    * order is not guaranteed so references being held by one object
      might change to represent a different database row (seems HIGHLY
      suspect)

   TODO: the way we handle immediate joins seems only valid if it is a single
      object.  I suspect that making a :set :immediate join column would result
      in an invalid number of objects returned from the database, because there
      would be multiple objects returned from the database
  "
  (declare (ignore all set-operation group-by having offset limit on parameters
                   distinct order-by)
           (dynamic-extent args))
  (let* ((args (filter-plist
                args :from :where :flatp :additional-fields :result-types :instances))
         (*db-deserializing* t)
         (sclasses (mapcar #'to-class view-classes))
         (tables (%tables-for-query sclasses from where inner-join))
         (join-where
           (loop for class in sclasses
                 appending (loop for slot in (immediate-join-slots class)
                                 collect (join-slot-qualifier class slot))))
         (full-select-list (full-select-list sclasses))
         (where (clsql-ands (append (listify where) (listify join-where))))
         #|
          (_ (format t "~&sclasses: ~W~%ijc: ~W~%tables: ~W~%"
                    sclasses immediate-join-classes tables))
         |#
         (rows (apply #'select
                      (append full-select-list
                              (list :from tables
                                    :result-types result-types
                                    :where where)
                              args)))
         (return-objects
           (loop for row in rows
                 for old-objs = (pop instances)
                 for objs = (build-objects sclasses row database
                                           (when refresh old-objs))
                 collecting (if flatp
                                (delist-if-single objs)
                                objs))))
    return-objects))

(defmethod instance-refreshed ((instance standard-db-object)))

(defvar *default-caching* t
  "Controls whether SELECT caches objects by default. The CommonSQL
specification states caching is on by default.")

(defun select (&rest select-all-args)
  "Executes a query on DATABASE, which has a default value of
*DEFAULT-DATABASE*, specified by the SQL expressions supplied
using the remaining arguments in SELECT-ALL-ARGS. The SELECT
argument can be used to generate queries in both functional and
object oriented contexts.

In the functional case, the required arguments specify the
columns selected by the query and may be symbolic SQL expressions
or strings representing attribute identifiers. Type modified
identifiers indicate that the values selected from the specified
column are converted to the specified lisp type. The keyword
arguments ALL, DISTINCT, FROM, GROUP-by, HAVING, ORDER-BY,
SET-OPERATION and WHERE are used to specify, using the symbolic
SQL syntax, the corresponding components of the SQL query
generated by the call to SELECT. RESULT-TYPES is a list of
symbols which specifies the lisp type for each field returned by
the query. If RESULT-TYPES is nil all results are returned as
strings whereas the default value of :auto means that the lisp
types are automatically computed for each field. FIELD-NAMES is t
by default which means that the second value returned is a list
of strings representing the columns selected by the query. If
FIELD-NAMES is nil, the list of column names is not returned as a
second value.

In the object oriented case, the required arguments to SELECT are
symbols denoting View Classes which specify the database tables
to query. In this case, SELECT returns a list of View Class
instances whose slots are set from the attribute values of the
records in the specified table. Slot-value is a legal operator
which can be employed as part of the symbolic SQL syntax used in
the WHERE keyword argument to SELECT. REFRESH is nil by default
which means that the View Class instances returned are retrieved
from a cache if an equivalent call to SELECT has previously been
issued. If REFRESH is true, the View Class instances returned are
updated as necessary from the database and the generic function
INSTANCE-REFRESHED is called to perform any necessary operations
on the updated instances.

In both object oriented and functional contexts, FLATP has a
default value of nil which means that the results are returned as
a list of lists. If FLATP is t and only one result is returned
for each record selected in the query, the results are returned
as elements of a list."
  (multiple-value-bind (target-args qualifier-args)
      (query-get-selections select-all-args)
    (unless (or *default-database* (getf qualifier-args :database))
      (signal-no-database-error nil))

    (let ((caching (getf qualifier-args :caching *default-caching*))
          (result-types (getf qualifier-args :result-types :auto))
          (refresh (getf qualifier-args :refresh nil))
          (database (getf qualifier-args :database *default-database*)))

      (cond
        ((and target-args
              (every #'(lambda (arg)
                         (and (symbolp arg)
                              (find-class arg nil)))
                     target-args))

         (setf qualifier-args (filter-plist qualifier-args :caching :refresh :result-types))

         ;; Add explicity table name to order-by if not specified and only
         ;; one selected table. This is required so FIND-ALL won't duplicate
         ;; the field
         (let ((order-by (getf qualifier-args :order-by)))
           (when (and order-by (= 1 (length target-args)))
             (let ((table-name (view-table (find-class (car target-args))))
                   (order-by-list (copy-seq (listify order-by))))
               (labels ((sv (val name) (ignore-errors (slot-value val name)))
                        (set-table-if-needed (val)
                          (typecase val
                            (sql-ident-attribute
                             (handler-case
                                 (if (sv val 'qualifier)
                                     val
                                     (make-instance 'sql-ident-attribute
                                                    :name (sv val 'name)
                                                    :qualifier table-name))
                               (simple-error ()
                                 ;; TODO: Check for a specific error we expect
                                 )))
                            (cons (cons (set-table-if-needed (car val))
                                        (cdr val)))
                            (t val))))
                 (setf order-by-list
                       (loop for i from 0 below (length order-by-list)
                             for id in order-by-list
                             collect (set-table-if-needed id))))
               (setf (getf qualifier-args :order-by) order-by-list))))

         (cond
           ((null caching)
            (apply #'find-all target-args :result-types result-types :refresh refresh qualifier-args))
           (t
            (let ((cached (records-cache-results target-args qualifier-args database)))
              (if (and cached (not refresh))
                  cached
                  (let ((results (apply #'find-all target-args
                                        :result-types :auto :refresh refresh
                                        :instances cached
                                        qualifier-args)))
                    (setf (records-cache-results target-args qualifier-args database) results)

                    results))))))
        (t
         (let* ((expr (apply #'make-query select-all-args))
                (parameters (second (member :parameters select-all-args)))
                (specified-types
                  (mapcar #'(lambda (attrib)
                              (if (typep attrib 'sql-ident-attribute)
                                  (let ((type (slot-value attrib 'type)))
                                    (if type
                                        type
                                        t))
                                  t))
                          (slot-value expr 'selections)))
                (flatp (getf qualifier-args :flatp))
                (field-names (getf qualifier-args :field-names t)))

           (when parameters
             (setf expr (command-object (sql-output expr database) parameters)))
           (query expr :flatp flatp
                       :result-types
                       ;; specifying a type for an attribute overrides result-types
                       (if (some #'(lambda (x) (not (eq t x))) specified-types)
                           specified-types
                           result-types)
                       :field-names field-names
                       :database database)))))))

(defun compute-records-cache-key (targets qualifiers)
  (list targets
        (do ((args *select-arguments* (cdr args))
             (results nil))
            ((null args) results)
          (let* ((arg (car args))
                 (value (getf qualifiers arg)))
            (when value
              (push (list arg
                          (typecase value
                            (cons (cons (sql (car value)) (cdr value)))
                            (%sql-expression (sql value))
                            (t value)))
                    results))))))

(defun records-cache-results (targets qualifiers database)
  (when (record-caches database)
    (gethash (compute-records-cache-key targets qualifiers) (record-caches database))))

(defun (setf records-cache-results) (results targets qualifiers database)
  (unless (record-caches database)
    (setf (record-caches database)
          (make-weak-hash-table :test 'equal)))
  (setf (gethash (compute-records-cache-key (copy-list targets) qualifiers)
                 (record-caches database)) results)
  results)



;;; Serialization functions

(defun write-instance-to-stream (obj stream)
  "Writes an instance to a stream where it can be later be read.
NOTE: an error will occur if a slot holds a value which can not be written readably."
  (let* ((class (class-of obj))
         (alist '()))
    (dolist (slot (ordered-class-slots (class-of obj)))
      (let ((name (slot-definition-name slot)))
        (when (and (not (eq 'view-database name))
                   (slot-boundp obj name))
          (push (cons name (slot-value obj name)) alist))))
    (setq alist (reverse alist))
    (write (cons (class-name class) alist) :stream stream :readably t))
  obj)

(defun read-instance-from-stream (stream)
  (let ((raw (read stream nil nil)))
    (when raw
      (let ((obj (make-instance (car raw))))
        (dolist (pair (cdr raw))
          (setf (slot-value obj (car pair)) (cdr pair)))
        obj))))