use crate::fetch::command::Feature;use git_transport::{client, Protocol};use quick_error::quick_error;use std::io; quick_error! {    /// The error used in the [response module][crate::fetch::response].    #[derive(Debug)]    #[allow(missing_docs)]    pub enum Error {        Io(err: io::Error) {            display("Failed to read from line reader")            from()            source(err)        }        Transport(err: client::Error) {            display("An error occurred when decoding a line")            from()            source(err)        }        MissingServerCapability(feature: &'static str) {            display("Currently we require feature '{}', which is not supported by the server", feature)        }        UnknownLineType(line: String) {            display("Encountered an unknown line prefix in '{}'", line)        }        UnknownSectionHeader(header: String) {            display("Unknown or unsupported header: '{}'", header)        }    }} /// An 'ACK' line received from the server.#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]pub enum Acknowledgement {    /// The contained `id` is in common.    Common(git_hash::ObjectId),    /// The server is ready to receive more lines.    Ready,    /// The server isn't ready yet.    Nak,} /// A shallow line received from the server.#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]pub enum ShallowUpdate {    /// Shallow the given `id`.    Shallow(git_hash::ObjectId),    /// Don't shallow the given `id` anymore.    Unshallow(git_hash::ObjectId),} impl ShallowUpdate {    /// Parse a `ShallowUpdate` from a `line` as received to the server.    fn from_line(line: &str) -> Result<ShallowUpdate, Error> {        let mut tokens = line.trim_end().splitn(2, ' ');        match (tokens.next(), tokens.next()) {            (Some(prefix), Some(id)) => {                let id =                    git_hash::ObjectId::from_hex(id.as_bytes()).map_err(|_| Error::UnknownLineType(line.to_owned()))?;                Ok(match prefix {                    "shallow" => ShallowUpdate::Shallow(id),                    "unshallow" => ShallowUpdate::Unshallow(id),                    _ => return Err(Error::UnknownLineType(line.to_owned())),                })            }            _ => unreachable!("cannot have an entirely empty line"),        }    }} impl Acknowledgement {    /// Parse an `Acknowledgement` from a `line` as received to the server.    fn from_line(line: &str) -> Result<Acknowledgement, Error> {        let mut tokens = line.trim_end().splitn(3, ' ');        Ok(match (tokens.next(), tokens.next(), tokens.next()) {            (Some(first), id, description) => match first {                "ready" => Acknowledgement::Ready, // V2                "NAK" => Acknowledgement::Nak,     // V1                "ACK" => {                    let id = match id {                        Some(id) => git_hash::ObjectId::from_hex(id.as_bytes())                            .map_err(|_| Error::UnknownLineType(line.to_owned()))?,                        None => return Err(Error::UnknownLineType(line.to_owned())),                    };                    if let Some(description) = description {                        match description {                            "common" => {}                            "ready" => return Ok(Acknowledgement::Ready),                            _ => return Err(Error::UnknownLineType(line.to_owned())),                        }                    }                    Acknowledgement::Common(id)                }                _ => return Err(Error::UnknownLineType(line.to_owned())),            },            (None, _, _) => unreachable!("cannot have an entirely empty line"),        })    }    /// Returns the hash of the acknowledged object if this instance acknowledges a common one.    pub fn id(&self) -> Option<&git_hash::ObjectId> {        match self {            Acknowledgement::Common(id) => Some(id),            _ => None,        }    }} /// A representation of a complete fetch responsepub struct Response {    acks: Vec<Acknowledgement>,    shallows: Vec<ShallowUpdate>,    has_pack: bool,} impl Response {    /// Return true if the response has a pack which can be read next.    pub fn has_pack(&self) -> bool {        self.has_pack    }     /// Return an error if the given `features` don't contain the required ones for the given `version` of the protocol.    ///    /// Even though technically any set of features supported by the server could work, we only implement the ones that    /// make it easy to maintain all versions with a single code base that aims to be and remain maintainable.    pub fn check_required_features(version: Protocol, features: &[Feature]) -> Result<(), Error> {        match version {            Protocol::V1 => {                let has = |name: &str| features.iter().any(|f| f.0 == name);                // Let's focus on V2 standards, and simply not support old servers to keep our code simpler                if !has("multi_ack_detailed") {                    return Err(Error::MissingServerCapability("multi_ack_detailed"));                }                // It's easy to NOT do sideband for us, but then again, everyone supports it.                // CORRECTION: If side-band is off, it would send the packfile without packet line encoding,                // which is nothing we ever want to deal with (despite it being more efficient). In V2, this                // is not even an option anymore, sidebands are always present.                if !has("side-band") && !has("side-band-64k") {                    return Err(Error::MissingServerCapability("side-band OR side-band-64k"));                }            }            Protocol::V2 => {}        }        Ok(())    }    /// Parse a response of the given `version` of the protocol from `reader`.    pub fn from_line_reader(version: Protocol, reader: &mut impl client::ExtendedBufRead) -> Result<Response, Error> {        match version {            Protocol::V1 => {                let mut line = String::new();                let mut acks = Vec::<Acknowledgement>::new();                let mut shallows = Vec::<ShallowUpdate>::new();                let has_pack = 'lines: loop {                    line.clear();                    let peeked_line = match reader.peek_data_line() {                        Some(Ok(Ok(line))) => String::from_utf8_lossy(line),                        // This special case (hang/block forver) deals with a single NAK being a legitimate EOF sometimes                        // Note that this might block forever in stateful connections as there it's not really clear                        // if something will be following or not by just looking at the response. Instead you have to know                        // the arguments sent to the server and count response lines based on intricate knowledge on how the                        // server works.                        // For now this is acceptable, as V2 can be used as a workaround, which also is the default.                        Some(Err(err)) if err.kind() == io::ErrorKind::UnexpectedEof => break 'lines false,                        Some(Err(err)) => return Err(err.into()),                        Some(Ok(Err(err))) => return Err(err.into()),                        None => {                            // maybe we saw a shallow flush packet, let's reset and retry                            reader.read_line(&mut line)?;                            reader.reset(Protocol::V1);                            match reader.peek_data_line() {                                Some(Ok(Ok(line))) => String::from_utf8_lossy(line),                                Some(Err(err)) => return Err(err.into()),                                Some(Ok(Err(err))) => return Err(err.into()),                                None => break 'lines false, // EOF                            }                        }                    };                     // with a friendly server, we just assume that a non-ack line is a pack line                    // which is our hint to stop here.                    match Acknowledgement::from_line(&peeked_line) {                        Ok(ack) => match ack.id() {                            Some(id) => {                                if !acks.iter().any(|a| a.id() == Some(id)) {                                    acks.push(ack);                                }                            }                            None => acks.push(ack),                        },                        Err(_) => match ShallowUpdate::from_line(&peeked_line) {                            Ok(shallow) => {                                shallows.push(shallow);                            }                            Err(_) => break 'lines true,                        },                    };                    assert_ne!(reader.read_line(&mut line)?, 0, "consuming a peeked line works");                };                Ok(Response {                    acks,                    shallows,                    has_pack,                })            }            Protocol::V2 => {                // NOTE: We only read acknowledgements and scrub to the pack file, until we have use for the other features                let mut line = String::new();                reader.reset(Protocol::V2);                let mut acks = Vec::<Acknowledgement>::new();                let mut shallows = Vec::<ShallowUpdate>::new();                let has_pack = 'section: loop {                    line.clear();                    if reader.read_line(&mut line)? == 0 {                        return Err(Error::Io(io::Error::new(                            io::ErrorKind::UnexpectedEof,                            "Could not read message headline",                        )));                    };                     match line.trim_end() {                        "acknowledgments" => {                            if parse_section(&mut line, reader, &mut acks, Acknowledgement::from_line)? {                                break 'section false;                            }                        }                        "shallow-info" => {                            if parse_section(&mut line, reader, &mut shallows, ShallowUpdate::from_line)? {                                break 'section false;                            }                        }                        "packfile" => {                            // what follows is the packfile itself, which can be read with a sideband enabled reader                            break 'section true;                        }                        _ => return Err(Error::UnknownSectionHeader(line)),                    }                };                Ok(Response {                    acks,                    shallows,                    has_pack,                })            }        }    }     /// Return all acknowledgements [parsed previously][Response::from_line_reader()].    pub fn acknowledgements(&self) -> &[Acknowledgement] {        &self.acks    }     /// Return all shallow update lines [parsed previously][Response::from_line_reader()].    pub fn shallow_updates(&self) -> &[ShallowUpdate] {        &self.shallows    }} fn parse_section<T>(    line: &mut String,    reader: &mut impl client::ExtendedBufRead,    res: &mut Vec<T>,    parse: impl Fn(&str) -> Result<T, Error>,) -> Result<bool, Error> {    line.clear();    while reader.read_line(line)? != 0 {        res.push(parse(line)?);        line.clear();    }    // End of message, or end of section?    Ok(if reader.stopped_at() == Some(client::MessageKind::Delimiter) {        // try reading more sections        reader.reset(Protocol::V2);        false    } else {        // we are done, there is no pack        true    })}