/*
  This file is part of TALER
  Copyright (C) 2022 Taler Systems SA

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

  TALER 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 Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
//! This is a very simple RPC client designed only for a specific geth version
//! and to use on an secure unix domain socket to a trusted node
//!
//! We only parse the thing we actually use, this reduce memory usage and
//! make our code more compatible with future deprecation

use common::{log::log::error, password, reconnect::AutoReconnect, url::Url};
use ethereum_types::{Address, H256, U256, U64};
use serde::de::DeserializeOwned;
use serde_json::error::Category;
use std::{
    fmt::Debug,
    io::{self, BufWriter, ErrorKind, Read, Write},
    os::unix::net::UnixStream,
    path::{Path, PathBuf},
};

use self::hex::Hex;

pub type AutoRpcWallet = AutoReconnect<(PathBuf, Address), Rpc>;

/// Create a reconnecting rpc connection with an unlocked wallet
pub fn auto_rpc_wallet(ipc_path: PathBuf, address: Address) -> AutoRpcWallet {
    AutoReconnect::new(
        (ipc_path, address),
        |(path, address)| {
            let mut rpc = Rpc::new(path)
                .map_err(|err| error!("connect RPC: {}", err))
                .ok()?;
            rpc.unlock_account(address, &password())
                .map_err(|err| error!("connect RPC: {}", err))
                .ok()?;
            Some(rpc)
        },
        |client| client.node_info().is_err(),
    )
}

pub type AutoRpcCommon = AutoReconnect<PathBuf, Rpc>;

/// Create a reconnecting rpc connection
pub fn auto_rpc_common(ipc_path: PathBuf) -> AutoRpcCommon {
    AutoReconnect::new(
        ipc_path,
        |path| {
            Rpc::new(path)
                .map_err(|err| error!("connect RPC: {}", err))
                .ok()
        },
        |client| client.node_info().is_err(),
    )
}
#[derive(Debug, serde::Serialize)]
struct RpcRequest<'a, T: serde::Serialize> {
    method: &'a str,
    id: u64,
    params: &'a T,
}

#[derive(Debug, serde::Deserialize)]
struct RpcResponse<T> {
    result: Option<T>,
    error: Option<RpcErr>,
    id: u64,
}

#[derive(Debug, serde::Deserialize)]
struct RpcErr {
    code: i64,
    message: String,
}

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("{0:?}")]
    Transport(#[from] std::io::Error),
    #[error("{code:?} - {msg}")]
    RPC { code: i64, msg: String },
    #[error("JSON: {0}")]
    Json(#[from] serde_json::Error),
    #[error("Null rpc, no result or error")]
    Null,
}

pub type Result<T> = std::result::Result<T, Error>;

const EMPTY: [(); 0] = [];

/// Ethereum RPC connection
pub struct Rpc {
    id: u64,
    conn: BufWriter<UnixStream>,
    read_buf: Vec<u8>,
    cursor: usize,
}

impl Rpc {
    /// Start a RPC connection, path can be datadir or ipc path
    pub fn new(path: impl AsRef<Path>) -> io::Result<Self> {
        let path = path.as_ref();

        let conn = if path.is_dir() {
            UnixStream::connect(path.join("geth.ipc"))
        } else {
            UnixStream::connect(path)
        }?;

        Ok(Self {
            id: 0,
            conn: BufWriter::new(conn),
            read_buf: vec![0u8; 8 * 1024],
            cursor: 0,
        })
    }

    fn send(&mut self, method: &str, params: &impl serde::Serialize) -> Result<()> {
        let request = RpcRequest {
            method,
            id: self.id,
            params,
        };

        // Send request
        serde_json::to_writer(&mut self.conn, &request)?;
        self.conn.flush()?;
        Ok(())
    }

    fn receive<T>(&mut self) -> Result<T>
    where
        T: serde::de::DeserializeOwned + Debug,
    {
        loop {
            // Double buffer size if full
            if self.cursor == self.read_buf.len() {
                self.read_buf.resize(self.cursor * 2, 0);
            }
            match self.conn.get_mut().read(&mut self.read_buf[self.cursor..]) {
                Ok(0) => Err(std::io::Error::new(
                    ErrorKind::UnexpectedEof,
                    "RPC EOF".to_string(),
                ))?,
                Ok(nb) => {
                    self.cursor += nb;
                    let mut de: serde_json::StreamDeserializer<_, T> =
                        serde_json::Deserializer::from_slice(&self.read_buf[..self.cursor])
                            .into_iter();

                    if let Some(result) = de.next() {
                        match result {
                            Ok(response) => {
                                let read = de.byte_offset();
                                self.read_buf.copy_within(read..self.cursor, 0);
                                self.cursor -= read;
                                return Ok(response);
                            }
                            Err(err) if err.classify() == Category::Eof => {
                                if nb == 0 {
                                    Err(std::io::Error::new(
                                        ErrorKind::UnexpectedEof,
                                        "Stream EOF",
                                    ))?;
                                }
                            }
                            Err(e) => Err(e)?,
                        }
                    }
                }
                Err(e) if e.kind() == ErrorKind::Interrupted => {}
                Err(e) => Err(e)?,
            }
        }
    }

    pub fn subscribe_new_head(&mut self) -> Result<RpcStream<Nothing>> {
        let id: String = self.call("eth_subscribe", &["newHeads"])?;
        Ok(RpcStream::new(self, id))
    }

    fn handle_response<T>(&mut self, response: RpcResponse<T>) -> Result<T> {
        assert_eq!(self.id, response.id);
        self.id += 1;
        if let Some(ok) = response.result {
            Ok(ok)
        } else {
            Err(match response.error {
                Some(err) => Error::RPC {
                    code: err.code,
                    msg: err.message,
                },
                None => Error::Null,
            })
        }
    }
}

impl RpcClient for Rpc {
    fn call<T>(&mut self, method: &str, params: &impl serde::Serialize) -> Result<T>
    where
        T: serde::de::DeserializeOwned + Debug,
    {
        self.send(method, params)?;
        let response = self.receive()?;
        self.handle_response(response)
    }
}

#[derive(Debug, serde::Deserialize)]
pub struct NotificationContent<T> {
    subscription: String,
    result: T,
}

#[derive(Debug, serde::Deserialize)]

struct Notification<T> {
    params: NotificationContent<T>,
}

#[derive(Debug, serde::Deserialize)]
#[serde(untagged)]
enum NotificationOrResponse<T, N> {
    Notification(Notification<N>),
    Response(RpcResponse<T>),
}

/// A notification stream wrapping an rpc client
pub struct RpcStream<'a, N: Debug + DeserializeOwned> {
    rpc: &'a mut Rpc,
    id: String,
    buff: Vec<N>,
}

impl<'a, N: Debug + DeserializeOwned> RpcStream<'a, N> {
    fn new(rpc: &'a mut Rpc, id: String) -> Self {
        Self {
            rpc,
            id,
            buff: vec![],
        }
    }

    /// Block until next notification
    pub fn next(&mut self) -> Result<N> {
        match self.buff.pop() {
            // Consume buffered notifications
            Some(prev) => Ok(prev),
            // Else read next one
            None => {
                let notification: Notification<N> = self.rpc.receive()?;
                let notification = notification.params;
                assert_eq!(self.id, notification.subscription);
                Ok(notification.result)
            }
        }
    }
}

impl<N: Debug + DeserializeOwned> Drop for RpcStream<'_, N> {
    fn drop(&mut self) {
        let Self { rpc, id, .. } = self;
        // Request unsubscription, ignoring error
        rpc.send("eth_unsubscribe", &[id]).ok();
        // Ignore all buffered notification until subscription response
        while let Ok(response) = rpc.receive::<NotificationOrResponse<bool, N>>() {
            match response {
                NotificationOrResponse::Notification(_) => { /* Ignore */ }
                NotificationOrResponse::Response(_) => return,
            }
        }
    }
}

impl<N: Debug + DeserializeOwned> RpcClient for RpcStream<'_, N> {
    fn call<T>(&mut self, method: &str, params: &impl serde::Serialize) -> Result<T>
    where
        T: serde::de::DeserializeOwned + Debug,
    {
        self.rpc.send(method, params)?;
        loop {
            // Buffer notifications until response
            let response: NotificationOrResponse<T, N> = self.rpc.receive()?;
            match response {
                NotificationOrResponse::Notification(n) => {
                    let n = n.params;
                    assert_eq!(self.id, n.subscription);
                    self.buff.push(n.result);
                }
                NotificationOrResponse::Response(response) => {
                    return self.rpc.handle_response(response)
                }
            }
        }
    }
}

pub trait RpcClient {
    fn call<T>(&mut self, method: &str, params: &impl serde::Serialize) -> Result<T>
    where
        T: serde::de::DeserializeOwned + Debug;

    /* ----- Account management ----- */

    /// List registered account
    fn list_accounts(&mut self) -> Result<Vec<Address>> {
        self.call("personal_listAccounts", &EMPTY)
    }

    /// Create a new encrypted account
    fn new_account(&mut self, passwd: &str) -> Result<Address> {
        self.call("personal_newAccount", &[passwd])
    }

    /// Unlock an existing account
    fn unlock_account(&mut self, account: &Address, passwd: &str) -> Result<bool> {
        self.call("personal_unlockAccount", &(account, passwd, 0))
    }

    /* ----- Getter ----- */

    /// Get a transaction by hash
    fn get_transaction(&mut self, hash: &H256) -> Result<Option<Transaction>> {
        match self.call("eth_getTransactionByHash", &[hash]) {
            Err(Error::Null) => Ok(None),
            r => r,
        }
    }

    /// Get a transaction receipt by hash
    fn get_transaction_receipt(&mut self, hash: &H256) -> Result<Option<TransactionReceipt>> {
        match self.call("eth_getTransactionReceipt", &[hash]) {
            Err(Error::Null) => Ok(None),
            r => r,
        }
    }

    /// Get block by hash
    fn block(&mut self, hash: &H256) -> Result<Option<Block>> {
        match self.call("eth_getBlockByHash", &(hash, &true)) {
            Err(Error::Null) => Ok(None),
            r => r,
        }
    }

    /// Get pending transactions
    fn pending_transactions(&mut self) -> Result<Vec<Transaction>> {
        self.call("eth_pendingTransactions", &EMPTY)
    }

    /// Get latest block
    fn latest_block(&mut self) -> Result<Block> {
        self.call("eth_getBlockByNumber", &("latest", &true))
    }

    /// Get earliest block (genesis if not pruned)
    fn earliest_block(&mut self) -> Result<Block> {
        self.call("eth_getBlockByNumber", &("earliest", &true))
    }

    /// Get latest account balance
    fn get_balance_latest(&mut self, addr: &Address) -> Result<U256> {
        self.call("eth_getBalance", &(addr, "latest"))
    }

    /// Get pending account balance
    fn get_balance_pending(&mut self, addr: &Address) -> Result<U256> {
        self.call("eth_getBalance", &(addr, "pending"))
    }

    /// Get node info
    fn node_info(&mut self) -> Result<NodeInfo> {
        self.call("admin_nodeInfo", &EMPTY)
    }

    /* ----- Transactions ----- */

    /// Fill missing options from transaction request with default values
    fn fill_transaction(&mut self, req: &TransactionRequest) -> Result<Filled> {
        self.call("eth_fillTransaction", &[req])
    }

    /// Send ethereum transaction
    fn send_transaction(&mut self, req: &TransactionRequest) -> Result<H256> {
        self.call("eth_sendTransaction", &[req])
    }

    /* ----- Miner ----- */

    /// Start mining
    fn miner_start(&mut self) -> Result<()> {
        match self.call("miner_start", &[8]) {
            Err(Error::Null) => Ok(()),
            i => i,
        }
    }

    /// Stop mining
    fn miner_stop(&mut self) -> Result<()> {
        match self.call("miner_stop", &EMPTY) {
            Err(Error::Null) => Ok(()),
            i => i,
        }
    }

    /* ----- Peer management ----- */

    fn export_chain(&mut self, path: &str) -> Result<bool> {
        self.call("admin_exportChain", &[path])
    }

    fn import_chain(&mut self, path: &str) -> Result<bool> {
        self.call("admin_importChain", &[path])
    }
}

#[derive(Debug, Clone, serde::Deserialize)]
pub struct Block {
    pub hash: Option<H256>,
    /// Block number (None if pending)
    pub number: Option<U64>,
    #[serde(rename = "parentHash")]
    pub parent_hash: H256,
    pub transactions: Vec<Transaction>,
}

#[derive(Debug, serde::Deserialize)]
pub struct Nothing {}

/// Description of a Transaction, pending or in the chain.
#[derive(Debug, Clone, serde::Deserialize)]
pub struct Transaction {
    pub hash: H256,
    pub nonce: U256,
    /// Sender address (None when coinbase)
    pub from: Option<Address>,
    /// Recipient address (None when contract creation)
    pub to: Option<Address>,
    /// Transferred value
    pub value: U256,
    /// Input data
    pub input: Hex,
}

/// Description of a Transaction, pending or in the chain.
#[derive(Debug, Clone, serde::Deserialize)]
pub struct TransactionReceipt {
    /// Gas used by this transaction alone.
    #[serde(rename = "gasUsed")]
    pub gas_used: U256,
    /// Effective gas price
    #[serde(rename = "effectiveGasPrice")]
    pub effective_gas_price: Option<U256>,
}

/// Fill result
#[derive(Debug, serde::Deserialize)]
pub struct Filled {
    pub tx: FilledGas,
}

/// Filles gas
#[derive(Debug, serde::Deserialize)]
pub struct FilledGas {
    /// Supplied gas
    pub gas: U256,
    #[serde(rename = "gasPrice")]
    pub gas_price: Option<U256>,
    #[serde(rename = "maxFeePerGas")]
    pub max_fee_per_gas: Option<U256>,
}

/// Send Transaction Parameters
#[derive(Debug, serde::Serialize)]
pub struct TransactionRequest {
    /// Sender address
    pub from: Address,
    /// Recipient address
    pub to: Address,
    /// Transferred value
    pub value: U256,
    /// Gas price (None for sensible default)
    #[serde(rename = "gasPrice")]
    pub gas_price: Option<U256>,
    /// Transaction data
    pub data: Hex,
    /// Transaction nonce (None for next available nonce)
    #[serde(skip_serializing_if = "Option::is_none")]
    pub nonce: Option<U256>,
}

#[derive(Debug, serde::Deserialize)]
pub struct NodeInfo {
    pub enode: Url,
}

pub mod hex {
    use std::{
        fmt,
        ops::{Deref, DerefMut},
    };

    use serde::{
        de::{Error, Unexpected, Visitor},
        Deserialize, Deserializer, Serialize, Serializer,
    };

    /// Raw bytes wrapper
    #[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
    pub struct Hex(pub Vec<u8>);

    impl Deref for Hex {
        type Target = Vec<u8>;

        fn deref(&self) -> &Self::Target {
            &self.0
        }
    }

    impl DerefMut for Hex {
        fn deref_mut(&mut self) -> &mut Self::Target {
            &mut self.0
        }
    }

    impl Serialize for Hex {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: Serializer,
        {
            serializer.serialize_str(&hex::encode_prefixed(&self.0))
        }
    }

    impl<'a> Deserialize<'a> for Hex {
        fn deserialize<D>(deserializer: D) -> Result<Hex, D::Error>
        where
            D: Deserializer<'a>,
        {
            deserializer.deserialize_identifier(BytesVisitor)
        }
    }

    struct BytesVisitor;

    impl<'a> Visitor<'a> for BytesVisitor {
        type Value = Hex;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            write!(formatter, "a 0x-prefixed hex-encoded vector of bytes")
        }

        fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
        where
            E: Error,
        {
            if value.len() >= 2 && &value[0..2] == "0x" {
                let bytes = hex::decode(&value[2..])
                    .map_err(|e| Error::custom(format!("Invalid hex: {}", e)))?;
                Ok(Hex(bytes))
            } else {
                Err(Error::invalid_value(Unexpected::Str(value), &"0x prefix"))
            }
        }

        fn visit_string<E>(self, value: String) -> Result<Self::Value, E>
        where
            E: Error,
        {
            self.visit_str(value.as_ref())
        }
    }
}