Added validation.lisp

darcs-hash:20051122061905-5417e-f23fa0abcb18e9d248ebac25b657029d12390c0d.gz

diff --git a/src/validation.lisp b/src/validation.lisp
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+(in-package :lisp-on-lines)
+
+;;;; Validation Conditions
+
+(define-condition validation-condition ()
+  ((message :accessor message :initarg :message :initform "Invalid value")
+   (value :accessor value :initarg :value :initform (warn "condition was not given a value"))))
+
+
+;;;; ** Attributes
+(define-condition attribute-validation-condition (validation-condition)
+  ((attribute :accessor attribute :initarg :attribute :initform nil)))
+
+(defgeneric validate-attribute (instance attribute)
+  (:documentation "
+Returns T if the ATTRIBUTE-VALUE in INSTANCE passes all the validation functions. Otherwise, returns (values nil conditions) where CONDITIONS is a list of conditions representing the validation errors the slot.")
+  (:method (instance attribute)
+      (let (conditions)
+       (handler-bind ((attribute-validation-condition
+                       #'(lambda (c)
+                           (setf conditions (cons c conditions))
+                           (signal c))))
+             (dolist (f (find-validation-functions instance attribute))
+                      (funcall f instance attribute)))
+       (if conditions
+           (values nil conditions)
+           t)))
+  (:method (instance (attribute symbol))
+    (validate-attribute instance (find-attribute instance attribute))))
+
+
+(defmethod find-validation-functions (instance (attribute standard-attribute))
+  (getf (attribute.plist attribute) :validate-using))
+
+
+;;;; ** Instances
+(define-condition instance-validation-condition (validation-condition)
+  ((instance :accessor instance :initarg instance :initform nil)
+   (conditions :accessor conditions :initarg :conditions :initform nil)))
+
+(defmethod invalid-instance-p (instance attributes)
+  (let (condition)
+    (handler-bind ((instance-validation-condition
+                 #'(lambda (c)
+                     (setf condition c))))
+      (validate-instance instance attributes))
+    condition))
+  
+(defmethod validate-instance (instance attributes)
+  (let (all-conditions)
+    (dolist (att attributes)
+      (multiple-value-bind (is-valid-p conditions)
+         (validate-attribute instance att)
+       (unless is-valid-p
+         (setf all-conditions (nconc conditions all-conditions)))))
+    (if all-conditions
+       (progn (signal 'instance-validation-condition
+                      :message "Invalid Instance"
+                      :instance instance
+                      :conditions all-conditions)
+              (values nil all-conditions))
+       
+       t)))
+
+;;;; Attribute Validation Functions
+;;;; I have not quite figured all this out yet.
+;;;; A generic validation system needs more thought than i've given it, but this is a start.
+
+(defun validate-string-exists (instance attribute)
+  (let ((value (lol::attribute-value instance attribute)))
+    (if (or
+        (not (stringp value))
+        (not (< 0 (length value))))
+       (signal 'attribute-validation-condition
+               :message (format nil "You must enter a value for ~A."
+                             (getf (attribute.plist attribute) :label))
+               :attribute attribute))))
+
+
+
+
+
+
+