use super::access_list::AccessList;
use crate::{keccak256, Bytes, ChainId, Signature, TxKind, TxType, B256, U256};
use alloy_rlp::{length_of_length, Decodable, Encodable, Header};
use bytes::BytesMut;
use reth_codecs::{main_codec, Compact};
use std::mem;

/// Transaction with an [`AccessList`] ([EIP-2930](https://eips.ethereum.org/EIPS/eip-2930)).
#[main_codec]
#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
pub struct TxEip2930 {
    /// Added as EIP-pub 155: Simple replay attack protection
    pub chain_id: ChainId,
    /// A scalar value equal to the number of transactions sent by the sender; formally Tn.
    pub nonce: u64,
    /// A scalar value equal to the number of
    /// Wei to be paid per unit of gas for all computation
    /// costs incurred as a result of the execution of this transaction; formally Tp.
    ///
    /// As ethereum circulation is around 120mil eth as of 2022 that is around
    /// 120000000000000000000000000 wei we are safe to use u128 as its max number is:
    /// 340282366920938463463374607431768211455
    pub gas_price: u128,
    /// A scalar value equal to the maximum
    /// amount of gas that should be used in executing
    /// this transaction. This is paid up-front, before any
    /// computation is done and may not be increased
    /// later; formally Tg.
    pub gas_limit: u64,
    /// The 160-bit address of the message call’s recipient or, for a contract creation
    /// transaction, ∅, used here to denote the only member of B0 ; formally Tt.
    pub to: TxKind,
    /// A scalar value equal to the number of Wei to
    /// be transferred to the message call’s recipient or,
    /// in the case of contract creation, as an endowment
    /// to the newly created account; formally Tv.
    pub value: U256,
    /// The accessList specifies a list of addresses and storage keys;
    /// these addresses and storage keys are added into the `accessed_addresses`
    /// and `accessed_storage_keys` global sets (introduced in EIP-2929).
    /// A gas cost is charged, though at a discount relative to the cost of
    /// accessing outside the list.
    pub access_list: AccessList,
    /// Input has two uses depending if transaction is Create or Call (if `to` field is None or
    /// Some). pub init: An unlimited size byte array specifying the
    /// EVM-code for the account initialisation procedure CREATE,
    /// data: An unlimited size byte array specifying the
    /// input data of the message call, formally Td.
    pub input: Bytes,
}

impl TxEip2930 {
    /// Calculates a heuristic for the in-memory size of the [`TxEip2930`] transaction.
    #[inline]
    pub fn size(&self) -> usize {
        mem::size_of::<ChainId>() + // chain_id
        mem::size_of::<u64>() + // nonce
        mem::size_of::<u128>() + // gas_price
        mem::size_of::<u64>() + // gas_limit
        self.to.size() + // to
        mem::size_of::<U256>() + // value
        self.access_list.size() + // access_list
        self.input.len() // input
    }

    /// Decodes the inner [`TxEip2930`] fields from RLP bytes.
    ///
    /// NOTE: This assumes a RLP header has already been decoded, and _just_ decodes the following
    /// RLP fields in the following order:
    ///
    /// - `chain_id`
    /// - `nonce`
    /// - `gas_price`
    /// - `gas_limit`
    /// - `to`
    /// - `value`
    /// - `data` (`input`)
    /// - `access_list`
    pub(crate) fn decode_inner(buf: &mut &[u8]) -> alloy_rlp::Result<Self> {
        Ok(Self {
            chain_id: Decodable::decode(buf)?,
            nonce: Decodable::decode(buf)?,
            gas_price: Decodable::decode(buf)?,
            gas_limit: Decodable::decode(buf)?,
            to: Decodable::decode(buf)?,
            value: Decodable::decode(buf)?,
            input: Decodable::decode(buf)?,
            access_list: Decodable::decode(buf)?,
        })
    }

    /// Outputs the length of the transaction's fields, without a RLP header.
    pub(crate) fn fields_len(&self) -> usize {
        self.chain_id.length() +
            self.nonce.length() +
            self.gas_price.length() +
            self.gas_limit.length() +
            self.to.length() +
            self.value.length() +
            self.input.0.length() +
            self.access_list.length()
    }

    /// Encodes only the transaction's fields into the desired buffer, without a RLP header.
    pub(crate) fn encode_fields(&self, out: &mut dyn bytes::BufMut) {
        self.chain_id.encode(out);
        self.nonce.encode(out);
        self.gas_price.encode(out);
        self.gas_limit.encode(out);
        self.to.encode(out);
        self.value.encode(out);
        self.input.0.encode(out);
        self.access_list.encode(out);
    }

    /// Inner encoding function that is used for both rlp [`Encodable`] trait and for calculating
    /// hash that for eip2718 does not require rlp header
    ///
    /// This encodes the transaction as:
    /// `rlp(nonce, gas_price, gas_limit, to, value, input, access_list, y_parity, r, s)`
    pub(crate) fn encode_with_signature(
        &self,
        signature: &Signature,
        out: &mut dyn bytes::BufMut,
        with_header: bool,
    ) {
        let payload_length = self.fields_len() + signature.payload_len();
        if with_header {
            Header {
                list: false,
                payload_length: 1 + length_of_length(payload_length) + payload_length,
            }
            .encode(out);
        }
        out.put_u8(self.tx_type() as u8);
        let header = Header { list: true, payload_length };
        header.encode(out);
        self.encode_fields(out);
        signature.encode(out);
    }

    /// Output the length of the RLP signed transaction encoding, _without_ a RLP string header.
    pub(crate) fn payload_len_with_signature_without_header(&self, signature: &Signature) -> usize {
        let payload_length = self.fields_len() + signature.payload_len();
        // 'transaction type byte length' + 'header length' + 'payload length'
        1 + length_of_length(payload_length) + payload_length
    }

    /// Output the length of the RLP signed transaction encoding. This encodes with a RLP header.
    pub(crate) fn payload_len_with_signature(&self, signature: &Signature) -> usize {
        let len = self.payload_len_with_signature_without_header(signature);
        length_of_length(len) + len
    }

    /// Get transaction type
    pub(crate) const fn tx_type(&self) -> TxType {
        TxType::Eip2930
    }

    /// Encodes the EIP-2930 transaction in RLP for signing.
    ///
    /// This encodes the transaction as:
    /// `tx_type || rlp(chain_id, nonce, gas_price, gas_limit, to, value, input, access_list)`
    ///
    /// Note that there is no rlp header before the transaction type byte.
    pub(crate) fn encode_for_signing(&self, out: &mut dyn bytes::BufMut) {
        out.put_u8(self.tx_type() as u8);
        Header { list: true, payload_length: self.fields_len() }.encode(out);
        self.encode_fields(out);
    }

    /// Outputs the length of the signature RLP encoding for the transaction.
    pub(crate) fn payload_len_for_signature(&self) -> usize {
        let payload_length = self.fields_len();
        // 'transaction type byte length' + 'header length' + 'payload length'
        1 + length_of_length(payload_length) + payload_length
    }

    /// Outputs the signature hash of the transaction by first encoding without a signature, then
    /// hashing.
    pub(crate) fn signature_hash(&self) -> B256 {
        let mut buf = BytesMut::with_capacity(self.payload_len_for_signature());
        self.encode_for_signing(&mut buf);
        keccak256(&buf)
    }
}

#[cfg(test)]
mod tests {
    use super::TxEip2930;
    use crate::{
        transaction::{signature::Signature, TxKind},
        Address, Bytes, Transaction, TransactionSigned, U256,
    };
    use alloy_rlp::{Decodable, Encodable};

    #[test]
    fn test_decode_create() {
        // tests that a contract creation tx encodes and decodes properly
        let request = Transaction::Eip2930(TxEip2930 {
            chain_id: 1u64,
            nonce: 0,
            gas_price: 1,
            gas_limit: 2,
            to: TxKind::Create,
            value: U256::from(3),
            input: Bytes::from(vec![1, 2]),
            access_list: Default::default(),
        });
        let signature = Signature { odd_y_parity: true, r: U256::default(), s: U256::default() };
        let tx = TransactionSigned::from_transaction_and_signature(request, signature);

        let mut encoded = Vec::new();
        tx.encode(&mut encoded);
        assert_eq!(encoded.len(), tx.length());

        let decoded = TransactionSigned::decode(&mut &*encoded).unwrap();
        assert_eq!(decoded, tx);
    }

    #[test]
    fn test_decode_call() {
        let request = Transaction::Eip2930(TxEip2930 {
            chain_id: 1u64,
            nonce: 0,
            gas_price: 1,
            gas_limit: 2,
            to: Address::default().into(),
            value: U256::from(3),
            input: Bytes::from(vec![1, 2]),
            access_list: Default::default(),
        });

        let signature = Signature { odd_y_parity: true, r: U256::default(), s: U256::default() };

        let tx = TransactionSigned::from_transaction_and_signature(request, signature);

        let mut encoded = Vec::new();
        tx.encode(&mut encoded);
        assert_eq!(encoded.len(), tx.length());

        let decoded = TransactionSigned::decode(&mut &*encoded).unwrap();
        assert_eq!(decoded, tx);
    }
}
