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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
use sp_core::H256;
use sp_io::hashing::keccak_256;
use sp_std::prelude::*;

use snowbridge_ethereum::{mpt, Receipt};

pub fn verify_receipt_proof(
	receipts_root: H256,
	proof: &[Vec<u8>],
) -> Option<Result<Receipt, rlp::DecoderError>> {
	match apply_merkle_proof(proof) {
		Some((root, data)) if root == receipts_root => Some(rlp::decode(&data)),
		Some((_, _)) => None,
		None => None,
	}
}

fn apply_merkle_proof(proof: &[Vec<u8>]) -> Option<(H256, Vec<u8>)> {
	let mut iter = proof.iter().rev();
	let first_bytes = match iter.next() {
		Some(b) => b,
		None => return None,
	};
	let item_to_prove: mpt::ShortNode = rlp::decode(first_bytes).ok()?;

	let final_hash: Option<[u8; 32]> = iter.try_fold(keccak_256(first_bytes), |acc, x| {
		let node: Box<dyn mpt::Node> = x.as_slice().try_into().ok()?;
		if (*node).contains_hash(acc.into()) {
			return Some(keccak_256(x))
		}
		None
	});

	final_hash.map(|hash| (hash.into(), item_to_prove.value))
}

#[cfg(test)]
mod tests {
	use super::*;
	use hex_literal::hex;

	#[test]
	fn test_verify_receipt_proof() {
		let root: H256 =
			hex!("fd5e397a84884641f53c496804f24b5276cbb8c5c9cfc2342246be8e3ce5ad02").into();

		// Valid proof
		let proof_receipt5 = vec!(
			hex!("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").to_vec(),
			hex!("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").to_vec(),
			hex!("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").to_vec(),
		);
		assert!(verify_receipt_proof(root, &proof_receipt5).is_some());

		// Various invalid proofs
		let proof_empty: Vec<Vec<u8>> = vec![];
		let proof_missing_full_node = vec![proof_receipt5[0].clone(), proof_receipt5[2].clone()];
		let proof_missing_short_node1 = vec![proof_receipt5[0].clone(), proof_receipt5[1].clone()];
		let proof_missing_short_node2 = vec![proof_receipt5[0].clone()];
		let proof_invalid_encoding = vec![proof_receipt5[2][2..].to_vec()];
		let proof_no_full_node = vec![proof_receipt5[2].clone(), proof_receipt5[2].clone()];
		assert!(verify_receipt_proof(root, &proof_empty).is_none());
		assert!(verify_receipt_proof(root, &proof_missing_full_node).is_none());

		assert_eq!(
			verify_receipt_proof(root, &proof_missing_short_node1),
			Some(Err(rlp::DecoderError::Custom("Unsupported receipt type")))
		);

		assert_eq!(
			verify_receipt_proof(root, &proof_missing_short_node2),
			Some(Err(rlp::DecoderError::Custom("Unsupported receipt type")))
		);

		assert!(verify_receipt_proof(root, &proof_invalid_encoding).is_none());
		assert!(verify_receipt_proof(root, &proof_no_full_node).is_none());
	}

	#[test]
	fn test_verify_receipt_proof_with_intermediate_short_node() {
		let root: H256 =
			hex!("d128e3a57142d2bf15bc0cbcac7ad54f40750d571b5c3097e425882c10c9ba66").into();

		let proof_receipt263 = vec![
			hex!("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").to_vec(),
			hex!("f871a0246de222036ee6a03329b0105da0a6b3f916fc95a9ed5a403a581a0c4d74242ca0ac108a49a88b57a05ac34a108b39f1e45f6f167f2b9fbc8d52fb58e2e5a6af1ea0fcfe07ac2ccd3c28b6eab68d1bce112f6f6dbd9023e4ec3c05b96615aa803d798080808080808080808080808080").to_vec(),
			hex!("e4820001a04fff54398cad4d05ea6abfd8b0f3b4fe14c04d7ff5f5211c5b927d9cf72ac1d8").to_vec(),
			hex!("f851a096d010643ca2d47412ca66898286b5f2412963b9ec051b33e570d575914c9c5ca028cd24c652989542fe89479ec6388eac4592432242af5ba97563b3ac7c71c019808080808080808080808080808080").to_vec(),
			hex!("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").to_vec(),
			hex!("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").to_vec(),
		];
		assert!(verify_receipt_proof(root, &proof_receipt263).is_some());
	}
}