// Copyright 2019-2022 Parity Technologies (UK) Ltd.
// This file is part of subxt.
//
// subxt 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.
//
// subxt 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 subxt.  If not, see <http://www.gnu.org/licenses/>.

use sp_keyring::AccountKeyring;
use std::{
    ffi::{
        OsStr,
        OsString,
    },
    net::TcpListener,
    process,
    thread,
    time,
};
use subxt::{
    Client,
    ClientBuilder,
    Config,
};

/// Spawn a local substrate node for testing subxt.
pub struct TestNodeProcess<R: Config> {
    proc: process::Child,
    client: Client<R>,
}

impl<R> Drop for TestNodeProcess<R>
where
    R: Config,
{
    fn drop(&mut self) {
        let _ = self.kill();
    }
}

impl<R> TestNodeProcess<R>
where
    R: Config,
{
    /// Construct a builder for spawning a test node process.
    pub fn build<S>(program: S) -> TestNodeProcessBuilder
    where
        S: AsRef<OsStr> + Clone,
    {
        TestNodeProcessBuilder::new(program)
    }

    /// Attempt to kill the running substrate process.
    pub fn kill(&mut self) -> Result<(), String> {
        log::info!("Killing node process {}", self.proc.id());
        if let Err(err) = self.proc.kill() {
            let err = format!("Error killing node process {}: {}", self.proc.id(), err);
            log::error!("{}", err);
            return Err(err)
        }
        Ok(())
    }

    /// Returns the subxt client connected to the running node.
    pub fn client(&self) -> &Client<R> {
        &self.client
    }
}

/// Construct a test node process.
pub struct TestNodeProcessBuilder {
    node_path: OsString,
    authority: Option<AccountKeyring>,
    scan_port_range: bool,
}

impl TestNodeProcessBuilder {
    pub fn new<P>(node_path: P) -> TestNodeProcessBuilder
    where
        P: AsRef<OsStr>,
    {
        Self {
            node_path: node_path.as_ref().into(),
            authority: None,
            scan_port_range: false,
        }
    }

    /// Set the authority dev account for a node in validator mode e.g. --alice.
    pub fn with_authority(&mut self, account: AccountKeyring) -> &mut Self {
        self.authority = Some(account);
        self
    }

    /// Enable port scanning to scan for open ports.
    ///
    /// Allows spawning multiple node instances for tests to run in parallel.
    pub fn scan_for_open_ports(&mut self) -> &mut Self {
        self.scan_port_range = true;
        self
    }

    /// Spawn the substrate node at the given path, and wait for rpc to be initialized.
    pub async fn spawn<R>(&self) -> Result<TestNodeProcess<R>, String>
    where
        R: Config,
    {
        let mut cmd = process::Command::new(&self.node_path);
        cmd.env("RUST_LOG", "error").arg("--dev").arg("--tmp");

        if let Some(authority) = self.authority {
            let authority = format!("{:?}", authority);
            let arg = format!("--{}", authority.as_str().to_lowercase());
            cmd.arg(arg);
        }

        let ws_port = if self.scan_port_range {
            let (p2p_port, http_port, ws_port) = next_open_port()
                .ok_or_else(|| "No available ports in the given port range".to_owned())?;

            cmd.arg(format!("--port={}", p2p_port));
            cmd.arg(format!("--rpc-port={}", http_port));
            cmd.arg(format!("--ws-port={}", ws_port));
            ws_port
        } else {
            // the default Websockets port
            9944
        };

        let ws_url = format!("ws://127.0.0.1:{}", ws_port);

        let mut proc = cmd.spawn().map_err(|e| {
            format!(
                "Error spawning substrate node '{}': {}",
                self.node_path.to_string_lossy(),
                e
            )
        })?;
        // wait for rpc to be initialized
        const MAX_ATTEMPTS: u32 = 6;
        let mut attempts = 1;
        let mut wait_secs = 1;
        let client = loop {
            thread::sleep(time::Duration::from_secs(wait_secs));
            log::info!(
                "Connecting to contracts enabled node, attempt {}/{}",
                attempts,
                MAX_ATTEMPTS
            );
            let result = ClientBuilder::new().set_url(ws_url.clone()).build().await;
            match result {
                Ok(client) => break Ok(client),
                Err(err) => {
                    if attempts < MAX_ATTEMPTS {
                        attempts += 1;
                        wait_secs *= 2; // backoff
                        continue
                    }
                    break Err(err)
                }
            }
        };
        match client {
            Ok(client) => Ok(TestNodeProcess { proc, client }),
            Err(err) => {
                let err = format!(
                    "Failed to connect to node rpc at {} after {} attempts: {}",
                    ws_url, attempts, err
                );
                log::error!("{}", err);
                proc.kill().map_err(|e| {
                    format!("Error killing substrate process '{}': {}", proc.id(), e)
                })?;
                Err(err)
            }
        }
    }
}

/// Returns the next set of 3 open ports.
///
/// Returns None if there are not 3 open ports available.
fn next_open_port() -> Option<(u16, u16, u16)> {
    // Ask the kernel to allocate a port.
    let next_port = || {
        match TcpListener::bind(("127.0.0.1", 0)) {
            Ok(listener) => {
                if let Ok(address) = listener.local_addr() {
                    Some(address.port())
                } else {
                    None
                }
            }
            Err(_) => None,
        }
    };

    // The ports allocated should be different, unless in
    // the unlikely case that the system has less than 3 available ports.
    Some((next_port()?, next_port()?, next_port()?))
}