Make subxt-core ready for publishing (#1508)

* Move Extrinsic decoding things to subxt_core and various tidy-ups

* A couple more fixes and fmt

* first pass moving tx logic to subxt_core

* cargo fmt

* fix wasm example

* clippy

* more clippy

* WIP Adding examples and such

* Move storage functionality more fully to subxt_core and nice examples for storage and txs

* Add example for events

* consistify how addresses/payloads are exposed in subxt-core and add runtime API fns

* Add runtime API core example

* fmt

* remove scale-info patch

* Add a little to the top level docs

* swap args around

* clippy

* cargo fmt and fix wasm-example

* doc fixes

* no-std-ise new subxt-core additions

* alloc, not core

* more no-std fixes

* A couple more fixes

* Add back extrinsic decode test

core/src/tx/payload.rs

@@ -0,0 +1,178 @@
+// Copyright 2019-2024 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! This module contains the trait and types used to represent
+//! transactions that can be submitted.
+
+use crate::error::MetadataError;
+use crate::metadata::Metadata;
+use crate::Error;
+use alloc::borrow::{Cow, ToOwned};
+use alloc::string::String;
+
+use alloc::vec::Vec;
+use codec::Encode;
+use scale_encode::EncodeAsFields;
+use scale_value::{Composite, Value, ValueDef, Variant};
+
+/// This represents a transaction payload that can be submitted
+/// to a node.
+pub trait PayloadT {
+    /// Encode call data to the provided output.
+    fn encode_call_data_to(&self, metadata: &Metadata, out: &mut Vec<u8>) -> Result<(), Error>;
+
+    /// Encode call data and return the output. This is a convenience
+    /// wrapper around [`PayloadT::encode_call_data_to`].
+    fn encode_call_data(&self, metadata: &Metadata) -> Result<Vec<u8>, Error> {
+        let mut v = Vec::new();
+        self.encode_call_data_to(metadata, &mut v)?;
+        Ok(v)
+    }
+
+    /// Returns the details needed to validate the call, which
+    /// include a statically generated hash, the pallet name,
+    /// and the call name.
+    fn validation_details(&self) -> Option<ValidationDetails<'_>> {
+        None
+    }
+}
+
+/// Details required to validate the shape of a transaction payload against some metadata.
+pub struct ValidationDetails<'a> {
+    /// The pallet name.
+    pub pallet_name: &'a str,
+    /// The call name.
+    pub call_name: &'a str,
+    /// A hash (this is generated at compile time in our codegen)
+    /// to compare against the runtime code.
+    pub hash: [u8; 32],
+}
+
+/// A transaction payload containing some generic `CallData`.
+#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub struct Payload<CallData> {
+    pallet_name: Cow<'static, str>,
+    call_name: Cow<'static, str>,
+    call_data: CallData,
+    validation_hash: Option<[u8; 32]>,
+}
+
+/// The type of a payload typically used for dynamic transaction payloads.
+pub type DynamicPayload = Payload<Composite<()>>;
+
+impl<CallData> Payload<CallData> {
+    /// Create a new [`Payload`].
+    pub fn new(
+        pallet_name: impl Into<String>,
+        call_name: impl Into<String>,
+        call_data: CallData,
+    ) -> Self {
+        Payload {
+            pallet_name: Cow::Owned(pallet_name.into()),
+            call_name: Cow::Owned(call_name.into()),
+            call_data,
+            validation_hash: None,
+        }
+    }
+
+    /// Create a new [`Payload`] using static strings for the pallet and call name.
+    /// This is only expected to be used from codegen.
+    #[doc(hidden)]
+    pub fn new_static(
+        pallet_name: &'static str,
+        call_name: &'static str,
+        call_data: CallData,
+        validation_hash: [u8; 32],
+    ) -> Self {
+        Payload {
+            pallet_name: Cow::Borrowed(pallet_name),
+            call_name: Cow::Borrowed(call_name),
+            call_data,
+            validation_hash: Some(validation_hash),
+        }
+    }
+
+    /// Do not validate this call prior to submitting it.
+    pub fn unvalidated(self) -> Self {
+        Self {
+            validation_hash: None,
+            ..self
+        }
+    }
+
+    /// Returns the call data.
+    pub fn call_data(&self) -> &CallData {
+        &self.call_data
+    }
+
+    /// Returns the pallet name.
+    pub fn pallet_name(&self) -> &str {
+        &self.pallet_name
+    }
+
+    /// Returns the call name.
+    pub fn call_name(&self) -> &str {
+        &self.call_name
+    }
+}
+
+impl Payload<Composite<()>> {
+    /// Convert the dynamic `Composite` payload into a [`Value`].
+    /// This is useful if you want to use this as an argument for a
+    /// larger dynamic call that wants to use this as a nested call.
+    pub fn into_value(self) -> Value<()> {
+        let call = Value {
+            context: (),
+            value: ValueDef::Variant(Variant {
+                name: self.call_name.into_owned(),
+                values: self.call_data,
+            }),
+        };
+
+        Value::unnamed_variant(self.pallet_name, [call])
+    }
+}
+
+impl<CallData: EncodeAsFields> PayloadT for Payload<CallData> {
+    fn encode_call_data_to(&self, metadata: &Metadata, out: &mut Vec<u8>) -> Result<(), Error> {
+        let pallet = metadata.pallet_by_name_err(&self.pallet_name)?;
+        let call = pallet
+            .call_variant_by_name(&self.call_name)
+            .ok_or_else(|| MetadataError::CallNameNotFound((*self.call_name).to_owned()))?;
+
+        let pallet_index = pallet.index();
+        let call_index = call.index;
+
+        pallet_index.encode_to(out);
+        call_index.encode_to(out);
+
+        let mut fields = call
+            .fields
+            .iter()
+            .map(|f| scale_encode::Field::new(&f.ty.id, f.name.as_deref()));
+
+        self.call_data
+            .encode_as_fields_to(&mut fields, metadata.types(), out)
+            .expect("The fields are valid types from the metadata, qed;");
+        Ok(())
+    }
+
+    fn validation_details(&self) -> Option<ValidationDetails<'_>> {
+        self.validation_hash.map(|hash| ValidationDetails {
+            pallet_name: &self.pallet_name,
+            call_name: &self.call_name,
+            hash,
+        })
+    }
+}
+
+/// Construct a transaction at runtime; essentially an alias to [`Payload::new()`]
+/// which provides a [`Composite`] value for the call data.
+pub fn dynamic(
+    pallet_name: impl Into<String>,
+    call_name: impl Into<String>,
+    call_data: impl Into<Composite<()>>,
+) -> DynamicPayload {
+    Payload::new(pallet_name, call_name, call_data.into())
+}