parsers: Add support for XEP-0335: JSON Containers

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

parsers/src/json_containers.rs

@@ -0,0 +1,62 @@
+// Copyright (c) 2025 Maxime “pep” Buquet <pep@bouah.net>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::ns;
+
+use xso::{AsXml, FromXml};
+
+/// Structure representing a `<json xmlns='urn:xmpp:json:0'/>` element.
+#[derive(FromXml, AsXml, Debug, Clone, PartialEq)]
+#[xml(namespace = ns::JSON_CONTAINERS, name = "json")]
+pub struct JsonContainer(#[xml(text)] serde_json::Value);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use minidom::Element;
+
+    use crate::Error::TextParseError;
+    use xso::error::FromElementError;
+
+    #[cfg(target_pointer_width = "32")]
+    #[test]
+    fn test_size() {
+        assert_size!(JsonContainer, 16);
+    }
+
+    #[cfg(target_pointer_width = "64")]
+    #[test]
+    fn test_size() {
+        assert_size!(JsonContainer, 32);
+    }
+
+    #[test]
+    fn test_empty() {
+        let elem: Element = "<json xmlns='urn:xmpp:json:0'/>".parse().unwrap();
+        let error = JsonContainer::try_from(elem.clone()).unwrap_err();
+        match error {
+            FromElementError::Invalid(TextParseError(err)) => {
+                assert_eq!(
+                    err.to_string(),
+                    "EOF while parsing a value at line 1 column 0"
+                );
+            }
+            _ => panic!(),
+        }
+    }
+
+    #[test]
+    fn test_simple() {
+        let elem: Element = "<json xmlns='urn:xmpp:json:0'>{\"a\": 1}</json>"
+            .parse()
+            .unwrap();
+        let result: serde_json::Value = "{\"a\": 1}".parse().unwrap();
+        match JsonContainer::try_from(elem.clone()) {
+            Ok(json) => assert_eq!(json.0, result),
+            _ => panic!(),
+        };
+    }
+}