[feat] Add metadata v15 class

Cargo.toml

@@ -27,3 +27,4 @@ codec = { package = "parity-scale-codec", version = "3.2.2", default-features =
 	"derive",
 ] }
 scale-info = { version = "2.11.2", default-features = false }
+serde_json = { version = "1.0.127", default-features = false }

bt_decode.pyi

@@ -218,3 +218,34 @@ class DelegateInfo:
     @staticmethod
     def decode_delegated(encoded: bytes) -> List[Tuple["DelegateInfo", int]]:
         pass
+
+class MetadataV15:
+    """
+    MetadataV15 is the 15th version-style of metadata for the chain.
+    It contains information about all the chain types, including the type signatures
+    of the Runtime API functions.
+
+    Example:
+    >>> import bittensor, bt_decode, scalecodec
+    >>> sub = bittensor.subtensor()
+    >>> v15_int = scalecodec.U32()
+    >>> v15_int.value = 15
+    >>> metadata_rpc_result = sub.substrate.rpc_request("state_call", [
+    ...     "Metadata_metadata_at_version",
+    ...     v15_int.encode().to_hex(),
+    ...     sub.substrate.get_chain_finalised_head()
+    ])
+    >>> metadata_hex_str = metadata_rpc_result['result']
+    >>> metadata_bytes = bytes.fromhex(metadata_hex_str[2:])
+    >>> metadata_v15 = bt_decode.MetadataV15.decode_from_metadata(encoded_metadata)
+    >>> print(metadata_v15.to_json())
+    """
+
+    @staticmethod
+    def decode_from_metadata_option(encoded_metadata_v15: bytes) -> "MetadataV15":
+        pass
+    def to_json(self) -> str:
+        """
+        Returns a JSON representation of the metadata.
+        """
+        pass

src/lib.rs

@@ -1,5 +1,6 @@
 use codec::{Decode, Encode};
 use custom_derive::pydecode;
+use serde_json;
 
 use pyo3::prelude::*;
 
@@ -26,6 +27,8 @@ type AccountId = [u8; 32];
 
 #[pymodule(name = "bt_decode")]
 mod bt_decode {
+    use frame_metadata::v15::RuntimeMetadataV15;
+
     use super::*;
 
     #[pyclass(name = "AxonInfo", get_all)]
@@ -291,6 +294,35 @@ mod bt_decode {
         }
     }
 
+    #[pyclass(name = "MetadataV15")]
+    struct PyMetadataV15 {
+        metadata: RuntimeMetadataV15,
+    }
+
+    #[pymethods]
+    impl PyMetadataV15 {
+        fn to_json(&self) -> String {
+            serde_json::to_string(&self.metadata).unwrap().into()
+        }
+
+        #[staticmethod]
+        fn decode_from_metadata_option(encoded_metadata_v15: &[u8]) -> Self {
+            let option_vec = Option::<Vec<u8>>::decode(&mut &encoded_metadata_v15[..])
+                .ok()
+                .flatten()
+                .expect("Failed to Option metadata");
+
+            let metadata_v15 = RuntimeMetadataPrefixed::decode(&mut &option_vec[..])
+                .expect("Failed to decode metadata")
+                .1;
+
+            match metadata_v15 {
+                RuntimeMetadata::V15(metadata) => PyMetadataV15 { metadata },
+                _ => panic!("Invalid metadata version"),
+            }
+        }
+    }
+
     // #[pyfunction(name = "decode")]
     // fn py_decode(
     //     type_string: &str,