Add support for JSON POJOs

sop-java/src/main/kotlin/sop/Verification.kt

@@ -17,6 +17,7 @@ data class Verification(
     val signatureMode: Optional<SignatureMode>,
     val jsonOrDescription: Optional<String>
 ) {
+
     @JvmOverloads
     constructor(
         creationTime: Date,
@@ -31,11 +32,44 @@ data class Verification(
         Optional.ofNullable(signatureMode),
         Optional.ofNullable(description?.trim()))
 
+    @JvmOverloads
+    constructor(
+        creationTime: Date,
+        signingKeyFingerprint: String,
+        signingCertFingerprint: String,
+        signatureMode: SignatureMode? = null,
+        json: JSON,
+        jsonSerializer: JSONSerializer
+    ) : this(
+        creationTime,
+        signingKeyFingerprint,
+        signingCertFingerprint,
+        Optional.ofNullable(signatureMode),
+        Optional.of(jsonSerializer.serialize(json)))
+
     @Deprecated("Replaced by jsonOrDescription",
         replaceWith = ReplaceWith("jsonOrDescription")
     )
     val description = jsonOrDescription
 
+    /**
+     * Attempt to parse the [jsonOrDescription] field using the provided [JSONParser] and return the result.
+     * This method returns `null` if parsing fails.
+     *
+     * @param parser [JSONParser] implementation
+     * @return successfully parsed [JSON] POJO or `null`.
+     */
+    fun getJson(parser: JSONParser): JSON? {
+        return jsonOrDescription.get()
+            ?.let {
+                try {
+                    parser.parse(it)
+                } catch (e: ParseException) {
+                    null
+                }
+            }
+    }
+
     override fun toString(): String =
         "${UTCUtil.formatUTCDate(creationTime)} $signingKeyFingerprint $signingCertFingerprint" +
             (if (signatureMode.isPresent) " mode:${signatureMode.get()}" else "") +
@@ -78,4 +112,48 @@ data class Verification(
             }
         }
     }
+
+    /**
+     * POJO data class representing JSON metadata.
+     *
+     * @param signers list of supplied CERTS objects that could have issued the signature, identified by
+     * the name given on the command line.
+     * @param comment a freeform UTF-8 encoded text describing the verification
+     * @param ext an extension object containing arbitrary, implementation-specific data
+     */
+    data class JSON(
+        val signers: List<String>,
+        val comment: String?,
+        val ext: Any?)
+
+    /**
+     * Interface abstracting a JSON parser that parses [JSON] POJOs from single-line strings.
+     */
+    fun interface JSONParser {
+        /**
+         * Parse a [JSON] POJO from the given single-line [string].
+         * If the string does not represent a JSON object matching the [JSON] definition,
+         * this method throws a [ParseException].
+         *
+         * @param string [String] representation of the [JSON] object.
+         * @return parsed [JSON] POJO
+         * @throws ParseException if the [string] is not a JSON string representing the [JSON] object.
+         */
+        @Throws(ParseException::class)
+        fun parse(string: String): JSON
+    }
+
+    /**
+     * Interface abstracting a JSON serializer that converts [JSON] POJOs into single-line JSON strings.
+     */
+    fun interface JSONSerializer {
+
+        /**
+         * Serialize the given [JSON] object into a single-line JSON string.
+         *
+         * @param json JSON POJO
+         * @return JSON string
+         */
+        fun serialize(json: JSON): String
+    }
 }