ac-node-api 1.21.0

// Copyright 2019-2023 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

//! This file is based on
//! https://github.com/paritytech/subxt/blob/8413c4d2dd625335b9200dc2289670accdf3391a/metadata/src/utils/variant_index.rs

use alloc::{borrow::ToOwned, collections::BTreeMap, string::String};
use scale_info::{form::PortableForm, PortableRegistry, TypeDef, Variant};

/// Given some type ID and type registry, build a couple of
/// indexes to look up variants by index or name. If the ID provided
/// is not a variant, the index will be empty.
///
/// API optimized for dealing with the `Option<u32>` variant type IDs
/// that we get in metadata pallets.
#[derive(Debug, Clone)]
pub struct VariantIndex {
	by_name: BTreeMap<String, usize>,
	by_index: BTreeMap<u8, usize>,
}

impl VariantIndex {
	/// Build indexes from the optional variant ID.
	pub fn build(variant_id: Option<u32>, types: &PortableRegistry) -> Self {
		let Some(variants) = Self::get(variant_id, types) else { return Self::empty() };

		let mut by_name = BTreeMap::new();
		let mut by_index = BTreeMap::new();
		for (pos, variant) in variants.iter().enumerate() {
			by_name.insert(variant.name.to_owned(), pos);
			by_index.insert(variant.index, pos);
		}

		Self { by_name, by_index }
	}

	/// Build an empty index.
	pub fn empty() -> Self {
		Self { by_name: Default::default(), by_index: Default::default() }
	}

	/// Get the variants we're pointing at; None if this isn't possible.
	pub fn get(
		variant_id: Option<u32>,
		types: &PortableRegistry,
	) -> Option<&[Variant<PortableForm>]> {
		let variant_id = variant_id?;
		let TypeDef::Variant(v) = &types.resolve(variant_id)?.type_def else { return None };
		Some(&v.variants)
	}

	/// Lookup a variant by name; `None` if the type is not a variant or name isn't found.
	pub fn lookup_by_name<'a, K>(
		&self,
		name: &K,
		variant_id: Option<u32>,
		types: &'a PortableRegistry,
	) -> Option<&'a Variant<PortableForm>>
	where
		String: alloc::borrow::Borrow<K>,
		K: core::hash::Hash + Eq + ?Sized + Ord,
	{
		let pos = *self.by_name.get(name)?;
		let variants = Self::get(variant_id, types)?;
		variants.get(pos)
	}

	/// Lookup a variant by index; `None` if the type is not a variant or index isn't found.
	pub fn lookup_by_index<'a>(
		&self,
		index: u8,
		variant_id: Option<u32>,
		types: &'a PortableRegistry,
	) -> Option<&'a Variant<PortableForm>> {
		let pos = *self.by_index.get(&index)?;
		let variants = Self::get(variant_id, types)?;
		variants.get(pos)
	}
}