// Copyright 2020-2021 Parity Technologies (UK) Ltd.
// This file is part of Cumulus.

// Cumulus is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Cumulus is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.

use codec::Encode;
use sc_chain_spec::ChainSpec;
use sp_runtime::traits::{Block as BlockT, Hash as HashT, Header as HeaderT, Zero};

/// Generate the genesis block from a given ChainSpec.
pub fn generate_genesis_block<Block: BlockT>(
	chain_spec: &Box<dyn ChainSpec>,
) -> Result<Block, String> {
	let storage = chain_spec.build_storage()?;

	let child_roots = storage.children_default.iter().map(|(sk, child_content)| {
		let state_root = <<<Block as BlockT>::Header as HeaderT>::Hashing as HashT>::trie_root(
			child_content.data.clone().into_iter().collect(),
		);
		(sk.clone(), state_root.encode())
	});
	let state_root = <<<Block as BlockT>::Header as HeaderT>::Hashing as HashT>::trie_root(
		storage.top.clone().into_iter().chain(child_roots).collect(),
	);

	let extrinsics_root =
		<<<Block as BlockT>::Header as HeaderT>::Hashing as HashT>::trie_root(Vec::new());

	Ok(Block::new(
		<<Block as BlockT>::Header as HeaderT>::new(
			Zero::zero(),
			extrinsics_root,
			state_root,
			Default::default(),
			Default::default(),
		),
		Default::default(),
	))
}