Add initial implementation of json-records

These behave like normal records, but with an added procedure to convert from a JSON string.

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/zambyte/meta/json.sld b/lib/zambyte/meta/json.sld
index b6e681d..6d18d88 100644
--- a/lib/zambyte/meta/json.sld
+++ b/lib/zambyte/meta/json.sld
@@ -1,6 +1,7 @@
 (define-library (zambyte meta json)
   ;; portable
   (export json
+	  define-json-record-type
 	  json-ref
 	  json-value?
 
@@ -41,6 +42,51 @@
 	     value
 	     (error "json: not a json value" value)))))
 
+    ;; TODO: implement this
+    (define (json-object-set! . args) #f)
+
+    (define-syntax handle-field-declarations
+      (syntax-rules ()
+	((_ (field accessor))
+	 (define (accessor obj)
+	   (json-object-ref obj 'field)))
+	((_ (field accessor mutator))
+	 (begin
+	   (define (accessor obj)
+	     (json-object-ref obj 'field))
+	   (define (mutator obj value)
+	     (json-object-set! obj 'field value))))))
+
+    (define-syntax define-json-record-type
+      (syntax-rules ()
+	((_ type
+	    (constructor fields ...)
+	    from-json-string
+	    predicate
+	    field-declarations ...)
+	 (begin
+	   (define (constructor fields ...)
+	     (make-json-record 'type
+			       (json-object `(fields . ,fields) ...)
+			       from-json-string))
+
+	   (define (predicate obj)
+	     (and (json-record? obj)
+		  (eq? (json-record->name obj) 'type)))
+
+	   (define (from-json-string str)
+	     (let ((json (string->json str)))
+	       (constructor (json-ref json 'fields) ...)))
+
+	   (handle-field-declarations field-declarations) ...))))
+
+    (define-record-type <json-record>
+      (make-json-record name fields from-json-string)
+      json-record?
+      (name json-record->name)
+      (fields json-record->fields)
+      (from-json-string json-record->from-json-string))
+
     (define (json-ref json key . keys)
       (let ((ref (cond ((json-object? json) json-object-ref)
 		       ((json-list? json) json-list-ref)