Implement `FromJava` for `Constraint`

1 files changed, 46 insertions, 1 deletions

diff --git a/mullvad-jni/src/from_java.rs b/mullvad-jni/src/from_java.rs
index 11b98ad753..7a87e10884 100644
--- a/mullvad-jni/src/from_java.rs
+++ b/mullvad-jni/src/from_java.rs
@@ -1,8 +1,10 @@
+use crate::get_class;
 use jni::{
     objects::{JObject, JString},
     JNIEnv,
 };
-use std::ops::Deref;
+use mullvad_types::relay_constraints::Constraint;
+use std::{fmt::Debug, ops::Deref};
 
 pub trait FromJava<'env> {
     type JavaType: 'env;
@@ -36,3 +38,46 @@ impl<'env> FromJava<'env> for String {
         )
     }
 }
+
+impl<'env, T> FromJava<'env> for Constraint<T>
+where
+    T: Clone + Debug + Eq + FromJava<'env>,
+    T::JavaType: From<JObject<'env>>,
+{
+    type JavaType = JObject<'env>;
+
+    fn from_java(env: &JNIEnv<'env>, source: Self::JavaType) -> Self {
+        if is_instance_of(env, source, "net/mullvad/mullvadvpn/model/Constraint$Any") {
+            Constraint::Any
+        } else if is_instance_of(env, source, "net/mullvad/mullvadvpn/model/Constraint$Only") {
+            let value = get_object_field(env, source, "value", "Ljava/lang/Object;");
+
+            Constraint::Only(T::from_java(env, T::JavaType::from(value)))
+        } else {
+            panic!("Invalid Constraint Java sub-class");
+        }
+    }
+}
+
+fn is_instance_of<'env>(
+    env: &JNIEnv<'env>,
+    object: JObject<'env>,
+    class_name: &'static str,
+) -> bool {
+    let class = get_class(class_name);
+
+    env.is_instance_of(object, &class)
+        .expect("Failed to check if an object is an instance of a specified class")
+}
+
+fn get_object_field<'env>(
+    env: &JNIEnv<'env>,
+    object: JObject<'env>,
+    field_name: &str,
+    field_type: &str,
+) -> JObject<'env> {
+    env.get_field(object, field_name, field_type)
+        .expect("Failed to get field from object")
+        .l()
+        .expect("Field has incorrect Java type")
+}