// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
//! Helper types to work with Ethereum's Merkle Patricia Trie nodes

use ethereum_types::H256;
use sp_std::prelude::*;

pub trait Node {
	fn contains_hash(&self, hash: H256) -> bool;
}

impl TryFrom<&[u8]> for Box<dyn Node> {
	type Error = rlp::DecoderError;

	fn try_from(bytes: &[u8]) -> Result<Box<dyn Node>, Self::Error> {
		let rlp = rlp::Rlp::new(bytes);
		match rlp.item_count()? {
			2 => {
				let node: ShortNode = rlp.as_val()?;
				Ok(Box::new(node))
			},
			17 => {
				let node: FullNode = rlp.as_val()?;
				Ok(Box::new(node))
			},
			_ => Err(rlp::DecoderError::Custom("Invalid number of list elements")),
		}
	}
}

/// Intermediate trie node with children (refers to node with same name in Geth).
/// This struct only handles the proof representation, i.e. a child is either empty
/// or a 32-byte hash of its subtree.
pub struct FullNode {
	pub children: Vec<Option<H256>>,
}

impl rlp::Decodable for FullNode {
	fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
		let children: Vec<Option<H256>> = rlp
			.iter()
			.map(|item| {
				let v: Vec<u8> = item.as_val()?;
				match v.len() {
					0 => Ok(None),
					32 => {
						let mut bytes = [0u8; 32];
						bytes.copy_from_slice(&v);
						Ok(Some(bytes.into()))
					},
					_ => Err(rlp::DecoderError::Custom("Expected 32-byte hash or empty child")),
				}
			})
			.collect::<Result<_, rlp::DecoderError>>()?;

		Ok(Self { children })
	}
}

impl Node for FullNode {
	fn contains_hash(&self, hash: H256) -> bool {
		self.children.iter().any(|h| Some(hash) == *h)
	}
}

/// Trie node where `value` is either the RLP-encoded item we're
/// proving or an intermediate hash (refers to node with same name in Geth)
/// Proof verification should return `value`. `key` is an implementation
/// detail of the trie.
pub struct ShortNode {
	pub key: Vec<u8>,
	pub value: Vec<u8>,
}

impl rlp::Decodable for ShortNode {
	fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
		let mut iter = rlp.iter();

		let key: Vec<u8> = match iter.next() {
			Some(data) => data.as_val()?,
			None => return Err(rlp::DecoderError::Custom("Expected key bytes")),
		};

		let value: Vec<u8> = match iter.next() {
			Some(data) => data.as_val()?,
			None => return Err(rlp::DecoderError::Custom("Expected value bytes")),
		};

		Ok(Self { key, value })
	}
}

impl Node for ShortNode {
	fn contains_hash(&self, hash: H256) -> bool {
		self.value == hash.0
	}
}

#[cfg(test)]
mod tests {

	use super::*;
	use hex_literal::hex;

	const RAW_PROOF: [&[u8]; 3] = [
        &hex!("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"),
        &hex!("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"),
        &hex!("f904de20b904daf904d701830652f0b9010004200000000000000000000080020000000000010000000000010000000000000000000000000000000000000000000002000000080000000000000000200000000000000000000000000008000000220000000000400010000000000000000000000000000000000000000000000000000000000000040000000010000100000000000800000000004000000000000000000000000000080000004000000000020000000000020000000000000000000000000000000000000000000004000000000002000000000100000000000000000000000000001000000002000020000010200000000000010000000000000000000000000000000000000010000000f903ccf89b9421130f34829b4c343142047a28ce96ec07814b15f863a0ddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3efa00000000000000000000000007d843005c7433c16b27ff939cb37471541561ebda0000000000000000000000000e9c1281aae66801fa35ec404d5f2aea393ff6988a000000000000000000000000000000000000000000000000000000005d09b7380f89b9421130f34829b4c343142047a28ce96ec07814b15f863a08c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925a00000000000000000000000007d843005c7433c16b27ff939cb37471541561ebda00000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488da0ffffffffffffffffffffffffffffffffffffffffffffffffffffffcc840c6920f89b94c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2f863a0ddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3efa0000000000000000000000000e9c1281aae66801fa35ec404d5f2aea393ff6988a00000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488da000000000000000000000000000000000000000000000000003e973b5a5d1078ef87994e9c1281aae66801fa35ec404d5f2aea393ff6988e1a01c411e9a96e071241c2f21f7726b17ae89e3cab4c78be50e062b03a9fffbbad1b840000000000000000000000000000000000000000000000000000001f1420ad1d40000000000000000000000000000000000000000000000014ad400879d159a38f8fc94e9c1281aae66801fa35ec404d5f2aea393ff6988f863a0d78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822a00000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488da00000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488db88000000000000000000000000000000000000000000000000000000005d415f3320000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003e973b5a5d1078ef87a94c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2f842a07fcf532c15f0a6db0bd6d0e038bea71d30d808c7d98cb3bf7268a95bf5081b65a00000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488da000000000000000000000000000000000000000000000000003e973b5a5d1078e"),
    ];

	#[test]
	fn decode_full_node() {
		let node1: FullNode = rlp::decode(RAW_PROOF[0]).unwrap();
		let node2: FullNode = rlp::decode(RAW_PROOF[1]).unwrap();
		assert_eq!(node1.children.len(), 17);
		assert_eq!(node2.children.len(), 17);
		assert_eq!(node1.children.iter().filter(|c| c.is_none()).count(), 8);
		assert_eq!(node2.children.iter().filter(|c| c.is_none()).count(), 2);

		let result: Result<FullNode, rlp::DecoderError> = rlp::decode(RAW_PROOF[2]);
		assert!(result.is_err());
	}

	#[test]
	fn decode_short_node() {
		// key + item value
		let node: ShortNode = rlp::decode(RAW_PROOF[2]).unwrap();
		assert_eq!(node.key, vec![32]);
		assert!(!node.value.is_empty());

		// key + item hash
		let node: ShortNode = rlp::decode(&hex!(
			"e4820001a04fff54398cad4d05ea6abfd8b0f3b4fe14c04d7ff5f5211c5b927d9cf72ac1d8"
		))
		.unwrap();
		assert_eq!(node.key, vec![0, 1]);
		assert_eq!(
			node.value,
			hex!("4fff54398cad4d05ea6abfd8b0f3b4fe14c04d7ff5f5211c5b927d9cf72ac1d8").to_vec()
		);
	}
}