//! A small TCP server to handle collection of diagnostics information in a
//! cross-platform way for the `cargo fix` command.

use std::collections::HashSet;
use std::env;
use std::io::{BufReader, Read, Write};
use std::net::{Shutdown, SocketAddr, TcpListener, TcpStream};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::thread::{self, JoinHandle};

use anyhow::{Context, Error};
use cargo_util::ProcessBuilder;
use log::warn;
use serde::{Deserialize, Serialize};

use crate::core::Edition;
use crate::util::errors::CargoResult;
use crate::util::Config;

const DIAGNOSTICS_SERVER_VAR: &str = "__CARGO_FIX_DIAGNOSTICS_SERVER";
const PLEASE_REPORT_THIS_BUG: &str =
    "This likely indicates a bug in either rustc or cargo itself,\n\
     and we would appreciate a bug report! You're likely to see \n\
     a number of compiler warnings after this message which cargo\n\
     attempted to fix but failed. If you could open an issue at\n\
     https://github.com/rust-lang/rust/issues\n\
     quoting the full output of this command we'd be very appreciative!\n\
     Note that you may be able to make some more progress in the near-term\n\
     fixing code with the `--broken-code` flag\n\n\
     ";

#[derive(Deserialize, Serialize, Hash, Eq, PartialEq, Clone)]
pub enum Message {
    Migrating {
        file: String,
        from_edition: Edition,
        to_edition: Edition,
    },
    Fixing {
        file: String,
    },
    Fixed {
        file: String,
        fixes: u32,
    },
    FixFailed {
        files: Vec<String>,
        krate: Option<String>,
        errors: Vec<String>,
        abnormal_exit: Option<String>,
    },
    ReplaceFailed {
        file: String,
        message: String,
    },
    EditionAlreadyEnabled {
        message: String,
        edition: Edition,
    },
}

impl Message {
    pub fn post(&self) -> Result<(), Error> {
        let addr =
            env::var(DIAGNOSTICS_SERVER_VAR).context("diagnostics collector misconfigured")?;
        let mut client =
            TcpStream::connect(&addr).context("failed to connect to parent diagnostics target")?;

        let s = serde_json::to_string(self).context("failed to serialize message")?;
        client
            .write_all(s.as_bytes())
            .context("failed to write message to diagnostics target")?;
        client
            .shutdown(Shutdown::Write)
            .context("failed to shutdown")?;

        client
            .read_to_end(&mut Vec::new())
            .context("failed to receive a disconnect")?;

        Ok(())
    }
}

pub struct DiagnosticPrinter<'a> {
    config: &'a Config,
    dedupe: HashSet<Message>,
}

impl<'a> DiagnosticPrinter<'a> {
    pub fn new(config: &'a Config) -> DiagnosticPrinter<'a> {
        DiagnosticPrinter {
            config,
            dedupe: HashSet::new(),
        }
    }

    pub fn print(&mut self, msg: &Message) -> CargoResult<()> {
        match msg {
            Message::Migrating {
                file,
                from_edition,
                to_edition,
            } => {
                if !self.dedupe.insert(msg.clone()) {
                    return Ok(());
                }
                self.config.shell().status(
                    "Migrating",
                    &format!("{} from {} edition to {}", file, from_edition, to_edition),
                )
            }
            Message::Fixing { file } => self
                .config
                .shell()
                .verbose(|shell| shell.status("Fixing", file)),
            Message::Fixed { file, fixes } => {
                let msg = if *fixes == 1 { "fix" } else { "fixes" };
                let msg = format!("{} ({} {})", file, fixes, msg);
                self.config.shell().status("Fixed", msg)
            }
            Message::ReplaceFailed { file, message } => {
                let msg = format!("error applying suggestions to `{}`\n", file);
                self.config.shell().warn(&msg)?;
                write!(
                    self.config.shell().err(),
                    "The full error message was:\n\n> {}\n\n",
                    message,
                )?;
                write!(self.config.shell().err(), "{}", PLEASE_REPORT_THIS_BUG)?;
                Ok(())
            }
            Message::FixFailed {
                files,
                krate,
                errors,
                abnormal_exit,
            } => {
                if let Some(ref krate) = *krate {
                    self.config.shell().warn(&format!(
                        "failed to automatically apply fixes suggested by rustc \
                         to crate `{}`",
                        krate,
                    ))?;
                } else {
                    self.config
                        .shell()
                        .warn("failed to automatically apply fixes suggested by rustc")?;
                }
                if !files.is_empty() {
                    writeln!(
                        self.config.shell().err(),
                        "\nafter fixes were automatically applied the compiler \
                         reported errors within these files:\n"
                    )?;
                    for file in files {
                        writeln!(self.config.shell().err(), "  * {}", file)?;
                    }
                    writeln!(self.config.shell().err())?;
                }
                write!(self.config.shell().err(), "{}", PLEASE_REPORT_THIS_BUG)?;
                if !errors.is_empty() {
                    writeln!(
                        self.config.shell().err(),
                        "The following errors were reported:"
                    )?;
                    for error in errors {
                        write!(self.config.shell().err(), "{}", error)?;
                        if !error.ends_with('\n') {
                            writeln!(self.config.shell().err())?;
                        }
                    }
                }
                if let Some(exit) = abnormal_exit {
                    writeln!(
                        self.config.shell().err(),
                        "rustc exited abnormally: {}",
                        exit
                    )?;
                }
                writeln!(
                    self.config.shell().err(),
                    "Original diagnostics will follow.\n"
                )?;
                Ok(())
            }
            Message::EditionAlreadyEnabled { message, edition } => {
                if !self.dedupe.insert(msg.clone()) {
                    return Ok(());
                }
                // Don't give a really verbose warning if it has already been issued.
                if self.dedupe.insert(Message::EditionAlreadyEnabled {
                    message: "".to_string(), // Dummy, so that this only long-warns once.
                    edition: *edition,
                }) {
                    self.config.shell().warn(&format!("\
{}

If you are trying to migrate from the previous edition ({prev_edition}), the
process requires following these steps:

1. Start with `edition = \"{prev_edition}\"` in `Cargo.toml`
2. Run `cargo fix --edition`
3. Modify `Cargo.toml` to set `edition = \"{this_edition}\"`
4. Run `cargo build` or `cargo test` to verify the fixes worked

More details may be found at
https://doc.rust-lang.org/edition-guide/editions/transitioning-an-existing-project-to-a-new-edition.html
",
                        message, this_edition=edition, prev_edition=edition.previous().unwrap()
                    ))
                } else {
                    self.config.shell().warn(message)
                }
            }
        }
    }
}

#[derive(Debug)]
pub struct RustfixDiagnosticServer {
    listener: TcpListener,
    addr: SocketAddr,
}

pub struct StartedServer {
    addr: SocketAddr,
    done: Arc<AtomicBool>,
    thread: Option<JoinHandle<()>>,
}

impl RustfixDiagnosticServer {
    pub fn new() -> Result<Self, Error> {
        let listener = TcpListener::bind("127.0.0.1:0")
            .with_context(|| "failed to bind TCP listener to manage locking")?;
        let addr = listener.local_addr()?;

        Ok(RustfixDiagnosticServer { listener, addr })
    }

    pub fn configure(&self, process: &mut ProcessBuilder) {
        process.env(DIAGNOSTICS_SERVER_VAR, self.addr.to_string());
    }

    pub fn start<F>(self, on_message: F) -> Result<StartedServer, Error>
    where
        F: Fn(Message) + Send + 'static,
    {
        let addr = self.addr;
        let done = Arc::new(AtomicBool::new(false));
        let done2 = done.clone();
        let thread = thread::spawn(move || {
            self.run(&on_message, &done2);
        });

        Ok(StartedServer {
            addr,
            thread: Some(thread),
            done,
        })
    }

    fn run(self, on_message: &dyn Fn(Message), done: &AtomicBool) {
        while let Ok((client, _)) = self.listener.accept() {
            if done.load(Ordering::SeqCst) {
                break;
            }
            let mut client = BufReader::new(client);
            let mut s = String::new();
            if let Err(e) = client.read_to_string(&mut s) {
                warn!("diagnostic server failed to read: {}", e);
            } else {
                match serde_json::from_str(&s) {
                    Ok(message) => on_message(message),
                    Err(e) => warn!("invalid diagnostics message: {}", e),
                }
            }
            // The client should be kept alive until after `on_message` is
            // called to ensure that the client doesn't exit too soon (and
            // Message::Finish getting posted before Message::FixDiagnostic).
            drop(client);
        }
    }
}

impl Drop for StartedServer {
    fn drop(&mut self) {
        self.done.store(true, Ordering::SeqCst);
        // Ignore errors here as this is largely best-effort
        if TcpStream::connect(&self.addr).is_err() {
            return;
        }
        drop(self.thread.take().unwrap().join());
    }
}