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    #![deny(missing_docs)]
    //! This library provides basically two functions for querying Minecraft
    //! servers. For increased stability, an extra function for handshakes
    //! is not provided.
    //!
    //! ## Usage
    //! To perform a query, call [`Query::get_basic`] or [`Query::get_full`].
    //! The returned response will either be a [`BasicQueryResponse`] or a
    //! [`FullQueryResponse`] respectively.
    //!
    //! ## Development resources
    //! Thank you to the [Tokio project] and the [Minecraft Developer Wiki] for
    //! providing a great asynchronous runtime and useful documentation!
    //!
    //! Without them, this crate wouldn't be possible.
    //!
    //! [Tokio project]: https://tokio.rs/
    //! [Minecraft Developer Wiki]: https://wiki.vg/

    use std::{
        collections::HashMap,
        io,
        time::Duration
    };
    use tokio::{
        net::{ ToSocketAddrs, UdpSocket },
        time::timeout as tokioTimeout,
    };

    /// Bitmask to validate a session ID
    ///
    /// Usually you don't need this.
    ///
    /// # Example
    /// ```
    /// use mcquery::SESSION_ID_MASK;
    ///
    /// # #[allow(unused_variables)]
    /// # fn main() {
    /// let session_id = 0x12345678_u32;
    /// let valid_session_id = session_id & SESSION_ID_MASK;
    /// # }
    /// ```
    pub const SESSION_ID_MASK: u32 = 0x0F0F0F0F;
    const REQUEST_HEADER: [u8; 2] = [0xFE, 0xFD];

    static mut SESSION_ID_COUNTER: u16 = 0;

    fn gen_session_id() -> u32 {
        unsafe {
            SESSION_ID_COUNTER = SESSION_ID_COUNTER.wrapping_add(1);
        }

        let mut session_id_bytes = [0; 4];
        for (i, b) in unsafe { SESSION_ID_COUNTER }.to_be_bytes().iter().enumerate() {
            session_id_bytes[i * 2] = b >> 4;
            session_id_bytes[i * 2 + 1] = b & 0x0F;
        }
        u32::from_be_bytes(session_id_bytes)
    }

    /// Encountered when the buffer is full.
    ///
    /// # Desciption
    /// The response may be incomplete, if the buffer has been filled up,
    /// because excess bytes that don't fit into it are discarded.
    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
    pub struct MaybeIncompleteDataError(usize);

    impl std::error::Error for MaybeIncompleteDataError {}

    impl core::fmt::Display for MaybeIncompleteDataError {
        fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
            write!(f, "Buffer filled up")
        }
    }

    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
    enum PacketType {
        Handshake = 0x09,
        Query = 0x00,
    }

    #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
    struct HandshakeRequest {
        session_id: u32,
    }

    impl HandshakeRequest {
        const PACKET_TYPE: PacketType = PacketType::Handshake;

        fn bytes(&self) -> Vec<u8> {
            let mut vec = Vec::new();
            vec.extend_from_slice(&REQUEST_HEADER);
            vec.push(Self::PACKET_TYPE as u8);
            vec.extend_from_slice(&self.session_id.to_be_bytes());

            vec
        }

        async fn send(&self, socket: &UdpSocket, timeout: Duration) -> io::Result<HandshakeResponse> {
            // Sending
            tokioTimeout(timeout, socket.send(self.bytes().as_slice())).await??;

            // Receiving
            let mut response_buffer = [0; 16];
            let bytes_read = tokioTimeout(timeout, socket.recv(&mut response_buffer)).await??;

            // Parsing
            let mut response_buffer = response_buffer[..bytes_read].to_owned();
            let res_packet_type = response_buffer.remove(0);
            let mut res_session_id = [0; 4];

            for (i, b) in response_buffer.drain(..4).enumerate() {
                res_session_id[i] = b;
            }

            let res_session_id = u32::from_be_bytes(res_session_id);
            let res_challenge_token =
                String::from_utf8(
                    response_buffer
                        .into_iter()
                        .take_while(|x| x != &0x00)
                        .collect()
                ).map_err(|_| io::ErrorKind::InvalidData)?
                .parse()
                .map_err(|_| io::ErrorKind::InvalidData)?;

            if res_packet_type != Self::PACKET_TYPE as u8 || res_session_id != self.session_id {
                Err(io::ErrorKind::InvalidData.into())
            } else {
                Ok(HandshakeResponse {
                    session_id: res_session_id,
                    challenge_token: res_challenge_token,
                })
            }
        }
    }

    #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
    struct HandshakeResponse {
        session_id: u32,
        challenge_token: i32,
    }

    impl From<HandshakeResponse> for BasicQueryRequest {
        fn from(res: HandshakeResponse) -> Self {
            BasicQueryRequest {
                session_id: res.session_id,
                challenge_token: res.challenge_token,
            }
        }
    }

    impl From<HandshakeResponse> for FullQueryRequest {
        fn from(res: HandshakeResponse) -> Self {
            FullQueryRequest {
                session_id: res.session_id,
                challenge_token: res.challenge_token,
            }
        }
    }

    #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
    struct BasicQueryRequest {
        session_id: u32,
        challenge_token: i32,
    }

    impl BasicQueryRequest {
        const PACKET_TYPE: PacketType = PacketType::Query;

        fn bytes(&self) -> Vec<u8> {
            let mut vec = Vec::new();
            vec.extend_from_slice(&REQUEST_HEADER);
            vec.push(Self::PACKET_TYPE as u8);
            vec.extend_from_slice(&self.session_id.to_be_bytes());
            vec.extend_from_slice(&self.challenge_token.to_be_bytes());

            vec
        }

        async fn send(&self, socket: &UdpSocket, timeout: Duration, buffer: &mut [u8]) -> io::Result<BasicQueryResponse> {
            // Sending
            tokioTimeout(timeout, socket.send(self.bytes().as_slice())).await??;

            // Receiving
            let bytes_read = tokioTimeout(timeout, socket.recv(buffer)).await??;
            if bytes_read == buffer.len() {
                return Err(io::Error::new(io::ErrorKind::Other, MaybeIncompleteDataError(bytes_read)));
            }

            // Parsing
            let mut response_buffer: String = buffer[0..bytes_read].iter().map(|b| *b as char).collect();

            // Packet type
            let res_packet_type = response_buffer.remove(0) as u8;

            // Session ID
            let mut res_session_id = [0; 4];
            for (i, b) in response_buffer.drain(..4).enumerate() {
                res_session_id[i] = b as u8;
            }
            let res_session_id = u32::from_be_bytes(res_session_id);

            let (
                res_motd,
                res_gametype,
                res_map,
                res_num_players,
                res_max_players,
                mut res_address
            ) = {
                let mut i = 0;
                let vec: Vec<_> = response_buffer
                    .split_terminator(|c| {
                        if i < 5 {
                            if c == '\0' {
                                i += 1;
                            }
                            c == '\0'
                        } else {
                            i += 1;
                            i > 7 && c == '\0'
                        }
                    })
                    .collect();
                (
                    vec[0].clone(),
                    vec[1].clone(),
                    vec[2].clone(),
                    vec[3].clone(),
                    vec[4].clone(),
                    vec[5].chars().map(|c| c as u8).collect::<Vec<_>>(),
                )
            };

            // Number of players
            let res_num_players = res_num_players.parse().map_err(|_| io::ErrorKind::InvalidData)?;

            // Max number of players
            let res_max_players = res_max_players.parse().map_err(|_| io::ErrorKind::InvalidData)?;

            // Host port
            let mut res_port = [0; 2];
            for (i, b) in res_address.drain(..2).enumerate() {
                res_port[i] = b;
            }
            let res_port = u16::from_le_bytes(res_port);

            // Host IP
            let res_ip = String::from_utf8(res_address).map_err(|_| io::ErrorKind::InvalidData)?;

            if res_packet_type != Self::PACKET_TYPE as u8 || res_session_id != self.session_id {
                Err(io::ErrorKind::InvalidData.into())
            } else {
                Ok(BasicQueryResponse {
                    session_id: res_session_id,
                    motd: res_motd.to_owned(),
                    gametype: res_gametype.to_owned(),
                    map: res_map.to_owned(),
                    num_players: res_num_players,
                    max_players: res_max_players,
                    port: res_port,
                    ip: res_ip,
                })
            }
        }
    }

    /// Response to a basic query
    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
    pub struct BasicQueryResponse {
        session_id: u32,
        /// The Motto of the Day
        pub motd: String,
        /// Should always be `"SMP"`
        pub gametype: String,
        /// The default map
        pub map: String,
        /// Number of players currently online
        pub num_players: u32,
        /// Maximum player capacity
        pub max_players: u32,
        /// The host port. Default is `25565`
        pub port: u16,
        /// The host ip. This is the localhost by default
        pub ip: String,
    }

    struct FullQueryRequest {
        session_id: u32,
        challenge_token: i32,
    }

    impl FullQueryRequest {
        const PACKET_TYPE: PacketType = PacketType::Query;

        fn bytes(&self) -> Vec<u8> {
            let mut vec = Vec::new();
            vec.extend_from_slice(&REQUEST_HEADER);
            vec.push(Self::PACKET_TYPE as u8);
            vec.extend_from_slice(&self.session_id.to_be_bytes());
            vec.extend_from_slice(&self.challenge_token.to_be_bytes());
            vec.extend_from_slice(&[0; 4]);

            vec
        }

        async fn send(&self, socket: &UdpSocket, timeout: Duration, buffer: &mut [u8]) -> io::Result<FullQueryResponse> {
            // Sending
            tokioTimeout(timeout, socket.send(self.bytes().as_slice())).await??;

            // Receiving
            let bytes_read = tokioTimeout(timeout, socket.recv(buffer)).await??;
            if bytes_read == buffer.len() {
                return Err(io::Error::new(io::ErrorKind::Other, MaybeIncompleteDataError(bytes_read)));
            }

            // Parsing
            let mut response_buffer = buffer[0..bytes_read].to_vec();

            // Packet type
            let res_packet_type = response_buffer.remove(0);

            // Session ID
            let mut res_session_id = [0; 4];
            for (i, b) in response_buffer.drain(..4).enumerate() {
                res_session_id[i] = b
            }
            let res_session_id = u32::from_be_bytes(res_session_id);

            // Key value section
            let mut res_kv = HashMap::<String, String>::new();
            loop {
                let key: Vec<u8> = response_buffer.iter()
                    .take_while(|b| **b != 0x00)
                    .map(|&b| b)
                    .collect();
                response_buffer.drain(0..key.len() + 1);
                if key.len() == 0 {
                    break;
                }

                let value: Vec<u8> = response_buffer.iter()
                    .take_while(|b| **b != 0x00)
                    .map(|&b| b)
                    .collect();
                response_buffer.drain(0..value.len() + 1);

                res_kv.insert(
                    key.iter()
                        .map(|b| *b as char)
                        .collect(),
                    value.iter()
                        .map(|b| *b as char)
                        .collect()
                );
            }
            res_kv.remove("splitnum").ok_or(io::ErrorKind::InvalidData)?;

            // Plugins and server software
            let (
                res_software,
                res_plugins
            ) = if let Some(mut plugins) = res_kv.get("plugins")
                .map(|s| s.clone())
            {
                res_kv.remove("plugins");
                // let mut plugin_string = plugin_string;
                let software: String = plugins.chars().take_while(|c| *c != ':').collect();
                plugins.drain(0..software.len() + 1);

                let plugins = if plugins.len() > 0 {
                    Some(plugins.split(';').map(|s| s.trim().to_owned()).collect())
                } else {
                    None
                };

                (Some(software), plugins)
            } else {
                (None, None)
            };

            // Players
            {
                let player_header = "\x01player_\0\0";
                if !response_buffer.starts_with(player_header.as_bytes()) {
                    return Err(io::ErrorKind::InvalidData.into());
                } else {
                    response_buffer.drain(0..player_header.len());
                }
            }
            let mut res_players = Vec::new();
            loop {
                let player: Vec<u8> = response_buffer.iter()
                    .take_while(|b| **b != 0x00)
                    .map(|&b| b)
                    .collect();
                response_buffer.drain(0..player.len());
                if player.len() == 0 {
                    break;
                }

                res_players.push(
                    player.iter()
                        .map(|b| *b as char)
                        .collect()
                );
            }

            if res_packet_type != Self::PACKET_TYPE as u8 || res_session_id != self.session_id {
                Err(io::ErrorKind::InvalidData.into())
            } else {
                Ok(FullQueryResponse {
                    session_id: res_session_id,
                    kv: res_kv,
                    players: res_players,
                    software: res_software,
                    plugins: res_plugins,
                })
            }
        }
    }

    /// Response to a full query
    #[derive(Debug, Clone, PartialEq, Eq)]
    pub struct FullQueryResponse {
        session_id: u32,
        /// Additional server information
        pub kv: HashMap<String, String>,
        /// Names of players currently online
        pub players: Vec<String>,
        /// The software string. Empty if vanilla server or not supported
        pub software: Option<String>,
        /// Plugins used on the server. Empty if vanilla server or not supported
        pub plugins: Option<Vec<String>>
    }

    /// The main data structure in this crate
    ///
    /// # Description
    /// Basic queries are enabled by default. They can be diabled in the server's
    /// `server.properties` with `enable-status=true`. This is what is used in the
    /// server list inside Minecraft.
    ///
    /// Full queries are diabled by default. They can be enabled in the server's
    /// `server.properties` with `enable-query=true`.
    #[derive(Debug, Clone, PartialEq, Eq)]
    pub enum Query {
        /// Response to a basic query. Can be obtained with [`Query::get_basic()`]
        ///
        /// See [`BasicQueryResponse`] for more
        Basic(BasicQueryResponse),
        /// Response to a full query. Can be obtained with [`Query::get_full()`]
        ///
        /// See [`FullQueryResponse`] for more
        Full(FullQueryResponse),
    }

    impl Query {
        /// Connects with the Minecraft server at `address` and performs a basic query.
        /// `timeout` is used as a response timeout. The specified buffer needs to be big
        /// enough to hold all response bytes, else this function will return a
        /// [`MaybeIncompleteDataError`] wrapped in an [`std::io::Error`]. The [`Ok`] value
        /// will be [`Query::Basic`].
        pub async fn get_basic<A: ToSocketAddrs>(address: A, timeout: Duration, buffer: &mut [u8]) -> io::Result<Self> {
            let socket = UdpSocket::bind("0.0.0.0:0").await?;
            socket.connect(address).await?;

            let handshake_req = HandshakeRequest {
                session_id: gen_session_id(),
            };

            let handshake_res = handshake_req.send(&socket, timeout).await?;

            let query_req: BasicQueryRequest = handshake_res.into();

            buffer.iter_mut().for_each(|b| *b = 0);
            let query_res = query_req.send(&socket, timeout, buffer).await?;

            Ok(Query::Basic(query_res))
        }

        /// Connects with the Minecraft server at `address` and performs a full query.
        /// `timeout` is used as a response timeout. The specified buffer needs to be big
        /// enough to hold all response bytes, else this function will return a
        /// [`MaybeIncompleteDataError`] wrapped in an [`std::io::Error`]. The [`Ok`] vlaue
        /// will be [`Query::Full`].
        pub async fn get_full<A: ToSocketAddrs>(address: A, timeout: Duration, buffer: &mut [u8]) -> io::Result<Self> {
            let socket = UdpSocket::bind("0.0.0.0:0").await?;
            socket.connect(address).await?;

            let handshake_req = HandshakeRequest {
                session_id: gen_session_id(),
            };

            let handshake_res = handshake_req.send(&socket, timeout).await?;

            let query_req: FullQueryRequest = handshake_res.into();

            buffer.iter_mut().for_each(|b| *b = 0);
            let query_res = query_req.send(&socket, timeout, buffer).await?;

            Ok(Query::Full(query_res))
        }
    }