Add support for json schema string with format metadata (#13)

Dedicated transform-string function to handle various string formats

Both StringSchema and JsonSchema (with "string" type) use a new transform-string helper. This enables structured handling of formats like uuid, date, and email, while preserving support for maxLength, pattern, and enumerations.

Author: JohanCodinha

src/navi/transform.clj

@@ -66,17 +66,35 @@
          (map p/transform)
          (into [compose-as]))))
 
-(extend-protocol p/Transformable
-  StringSchema
-  (p/transform [schema]
-    (let [content-fn string?
-          max-length (.getMaxLength schema)
-          min-length (.getMinLength schema)
-          properties (cond-> nil
-                       max-length (assoc :max max-length)
-                       min-length (assoc :min min-length))
-          pattern (some-> schema .getPattern re-pattern)
-          enums (into [:enum] (.getEnum schema))]
+(defn format->malli-predicate
+  "Given an OpenAPI string format, return a suitable Malli predicate for basic validation."
+  [fmt]
+  (case fmt
+    "uuid"      uuid?
+    "binary"    string?
+    "byte"      string?
+    "date"      string?
+    "date-time" string?
+    "password"  string?
+    "email"     string?
+    "uri"       string?
+    "hostname"  string?
+    "ipv4"      string?
+    "ipv6"      string?
+    string?))
+
+(defn transform-string
+  "Given a StringSchema or a JsonSchema that we know is string-typed,
+   return a Malli schema that respects format, length constraints, pattern, and enum."
+  [^Schema schema]
+  (let [content-fn (format->malli-predicate (.getFormat schema))
+        max-length (.getMaxLength schema)
+        min-length (.getMinLength schema)
+        properties (cond-> nil
+                     max-length (assoc :max max-length)
+                     min-length (assoc :min min-length))
+        pattern (some-> schema .getPattern re-pattern)
+        enums (into [:enum] (.getEnum schema))]
       (cond
         (and properties pattern)
         [:and content-fn [:string properties] pattern]
@@ -93,6 +111,11 @@
         :else
         content-fn)))
 
+(extend-protocol p/Transformable
+  StringSchema
+  (p/transform [schema]
+    (transform-string schema))
+
   DateSchema
   (p/transform [_] inst?)
 
@@ -133,7 +156,7 @@
                    "null" nil?
                    "number" number?
                    "object" (transform-object schema)
-                   "string" string?
+                   "string" (transform-string schema)
                    (throw (IllegalArgumentException. (format "Unsupported type %s for schema %s" typ schema)))))
           types (.getTypes schema)]
       (case (count types)