use crate::event::{Event, Fields, Level};
use crate::event_matcher::{Count, EventMatcher, Events};
use anyhow::{anyhow, Context, Result};
use cargo_metadata::{Metadata, MetadataCommand};
use itertools::Itertools;
use nix::sys::signal::Signal;
use nix::unistd::Pid;
use nu_ansi_term::Color;
use once_cell::sync::Lazy;
use std::collections::HashSet;
use std::env;
use std::path::Path;
use std::process::Stdio;
use std::sync::Mutex;
use subprocess::{Exec, Redirection};
use tokio::sync::mpsc;
use tokio::{
    io::{AsyncBufReadExt, BufReader},
    process::{Child, ChildStdout, Command},
};

struct CargoCache {
    metadata: Option<Metadata>,
    built_binaries: HashSet<BuiltBinary>,
}

#[derive(Hash, PartialEq, Eq)]
struct BuiltBinary {
    name: String,
    profile: String,
}

// It is actually quite expensive to invoke `cargo build` even when there is nothing to build.
// On my machine, on a specific project, it takes 170ms.
// To avoid this cost for every call to start_with_args we use this global to keep track of which packages have been built by a BinProcess for the lifetime of the test run.
//
// Unfortunately this doesnt work when running each test in its own process. e.g. when using nextest
// But worst case it just unnecessarily reruns `cargo build`.
// TODO: we might be able to use CARGO_TARGET_TMPDIR to fix for nextest
static CARGO_CACHE: Lazy<Mutex<CargoCache>> = Lazy::new(|| {
    Mutex::new(CargoCache {
        metadata: None,
        built_binaries: HashSet::new(),
    })
});

/// A running process of a binary.
///
/// All `tracing` events emitted by your binary in JSON over stdout will be processed by `BinProcess` and then emitted to the tests stdout in the default human readable tracing format.
/// To ensure any WARN/ERROR's from your test logic are visible, `BinProcess` will setup its own subscriber that outputs to the tests stdout in the default human readable format.
/// If you set your own subscriber before constructing a [`BinProcess`] that will take preference instead.
///
/// Dropping the BinProcess will trigger a panic unless [`BinProcess::shutdown_and_then_consume_events`] or [`BinProcess::consume_remaining_events`] has been called.
/// This is done to avoid missing important assertions run by those methods.
///
/// ## Which constructor to use:
/// A guide to constructing `BinProcess` based on your use case:
///
/// ### You are writing an integration test or bench and the binary you want to run is defined in the same package as the test or bench you are writing.
///
/// Use [`BinProcess::start_binary`] like this:
/// ```rust
/// # use tokio_bin_process::BinProcess;
/// # // hack to make the doc test compile
/// # macro_rules! bin_path {
/// #     ($bin_name:expr) => {
/// #         &std::path::Path::new("foo")
/// #     };
/// # }
/// # async {
/// BinProcess::start_binary(
///     bin_path!("cooldb"),
///     "cooldb",
///     &["--log-format", "json"],
/// ).await;
/// # };
/// ```
/// Using `start_binary` instead of `start_binary_name` here is faster and more robust as `BinProcess` does not need to invoke Cargo.
///
/// ### You are writing an integration test or bench and the binary you want to test is in the same workspace but in a different package to the test or bench you are writing.
/// Use [`BinProcess::start_binary_name`] like this:
/// ```rust
/// # use tokio_bin_process::BinProcess;
/// # async {
/// BinProcess::start_binary_name(
///     "cooldb",
///     "cooldb",
///     &["--log-format", "json"],
///     None
/// ).await;
/// # };
/// ```
///
/// ### You are writing an example or other binary within a package
/// Use [`BinProcess::start_binary_name`] like this:
/// ```rust
/// # use tokio_bin_process::BinProcess;
/// # async {
/// BinProcess::start_binary_name(
///     "cooldb",
///     "cooldb",
///     &["--log-format", "json"],
///     None
/// ).await;
/// # };
/// ```
///
/// ### You need to compile the binary with an arbitrary profile
/// Use [`BinProcess::start_binary_name`] like this:
/// ```rust
/// # use tokio_bin_process::BinProcess;
/// # async {
/// BinProcess::start_binary_name(
///     "cooldb",
///     "cooldb",
///     &["--log-format", "json"],
///     Some("profilename")
/// ).await;
/// # };
/// ```
///
/// ### You have an arbitrary pre-compiled binary to run
/// Use [`BinProcess::start_binary`] like this:
/// ```rust
/// # use tokio_bin_process::BinProcess;
/// # use std::path::Path;
/// # async {
/// BinProcess::start_binary(
///     Path::new("some/path/to/precompiled/cooldb"),
///     "cooldb",
///     &["--log-format", "json"],
/// ).await;
/// # };
/// ```
pub struct BinProcess {
    /// Always Some while BinProcess is owned
    child: Option<Child>,
    event_rx: mpsc::UnboundedReceiver<Event>,
}

impl Drop for BinProcess {
    fn drop(&mut self) {
        if self.child.is_some() && !std::thread::panicking() {
            panic!("Need to call either wait or shutdown_and_assert_success method on BinProcess before dropping it.");
        }
    }
}

impl BinProcess {
    /// Prefer [`BinProcess::start_binary`] where possible as it is faster and more robust.
    ///
    /// Start the binary named `cargo_bin_name` in the current workspace in a new process.
    /// A `BinProcess` is returned which can be used to interact with the process.
    ///
    /// `log_name` is prepended to the logs that `BinProcess` forwards to stdout.
    /// This helps to differentiate between `tracing` logs generated by the test itself and the process under test.
    ///
    /// The `binary_args` will be used as the args to the binary.
    /// The args should give the desired setup for the given integration test and should also enable the `tracing` JSON logger to stdout if that is not the default.
    ///
    /// The crate will be compiled with the Cargo profile specified in `cargo_profile`.
    /// * When it is `Some(_)` the value specified is used.
    /// * When it is `None` it will use "release" if `tokio-bin-process` was compiled in a release derived profile or "dev" if it was compiled in a dev derived profile.
    ///
    /// The reason `None` will only ever result in a "release" or "dev" profile is due to a limitation on what profile information Cargo exposes to us.
    pub async fn start_binary_name(
        cargo_bin_name: &str,
        log_name: &str,
        binary_args: &[&str],
        cargo_profile: Option<&str>,
    ) -> BinProcess {
        // PROFILE is set in build.rs from PROFILE listed in https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts
        let profile = cargo_profile.unwrap_or(if env!("PROFILE") == "release" {
            "release"
        } else {
            "dev"
        });

        // First build the binary if its not yet built
        let target_dir = {
            let mut cargo_cache = CARGO_CACHE.lock().unwrap();
            if cargo_cache.metadata.is_none() {
                cargo_cache.metadata = Some(MetadataCommand::new().exec().unwrap());
            }
            let built_package = BuiltBinary {
                name: cargo_bin_name.to_owned(),
                profile: profile.to_owned(),
            };
            if !cargo_cache.built_binaries.contains(&built_package) {
                let all_args = vec![
                    "build",
                    "--all-features",
                    "--profile",
                    profile,
                    "--bin",
                    cargo_bin_name,
                ];
                let metadata = cargo_cache.metadata.as_ref().unwrap();
                run_command(
                    metadata.workspace_root.as_std_path(),
                    env!("CARGO"),
                    &all_args,
                )
                .unwrap();
                cargo_cache.built_binaries.insert(built_package);
            }

            cargo_cache
                .metadata
                .as_ref()
                .unwrap()
                .target_directory
                .clone()
        };

        let target_profile_name = match profile {
            // dev is mapped to debug for legacy reasons
            "dev" => "debug",
            // test and bench are hardcoded to reuse dev and release directories
            "test" => "debug",
            "bench" => "release",
            profile => profile,
        };
        let bin_path = target_dir.join(target_profile_name).join(cargo_bin_name);
        BinProcess::start_binary(
            bin_path.into_std_path_buf().as_path(),
            log_name,
            binary_args,
        )
        .await
    }

    /// Start the binary specified in `bin_path`.
    ///
    /// `log_name` is prepended to the logs that `BinProcess` forwards to stdout.
    /// This helps to differentiate between `tracing` logs generated by the test itself and the process under test.
    ///
    /// The `binary_args` will be used as the args to the binary.
    /// The args should give the desired setup for the given integration test and should also enable the `tracing` JSON logger to stdout if that is not the default.
    pub async fn start_binary(bin_path: &Path, log_name: &str, binary_args: &[&str]) -> BinProcess {
        let log_name = if log_name.len() > 10 {
            panic!("In order to line up in log outputs, argument log_name to BinProcess::start_with_args must be of length <= 10 but the value was: {log_name}");
        } else {
            format!("{log_name: <10}") // pads log_name up to 10 chars so that it lines up properly when included in log output.
        };

        let mut child = Command::new(bin_path)
            .args(binary_args)
            .stdout(Stdio::piped())
            .stderr(Stdio::piped())
            .kill_on_drop(true)
            .spawn()
            .context(format!("Failed to run {bin_path:?}"))
            .unwrap();

        let (event_tx, event_rx) = tokio::sync::mpsc::unbounded_channel();
        let stdout_reader = BufReader::new(child.stdout.take().unwrap()).lines();
        let mut stderr_reader = BufReader::new(child.stderr.take().unwrap()).lines();
        tokio::spawn(async move {
            if let Err(err) = process_stdout_events(stdout_reader, &event_tx, log_name).await {
                // Because we are in a task, panicking is likely to be ignored.
                // Instead we generate a fake error event, which is possibly a bit confusing for the user but will at least cause the test to fail.
                event_tx
                    .send(Event {
                        timestamp: "".to_owned(),
                        level: Level::Error,
                        target: "tokio-bin-process".to_owned(),
                        fields: Fields {
                            message: err.to_string(),
                            fields: Default::default(),
                        },
                        span: Default::default(),
                        spans: Default::default(),
                    })
                    .ok();
            }
        });
        tokio::spawn(async move {
            while let Some(line) = stderr_reader.next_line().await.expect("An IO error occured while reading stderr from the application, I'm not actually sure when this happens?") {
                tracing::error!("stderr from process: {line}");
            }
        });

        BinProcess {
            child: Some(child),
            event_rx,
        }
    }

    /// Return the PID of
    /// TODO: when nix crate is 1.0 this method should return a `nix::unistd::Pid` instead of an i32
    pub fn pid(&self) -> i32 {
        self.child.as_ref().unwrap().id().unwrap() as i32
    }

    /// TODO: make this public when nix crate goes 1.0
    ///       Additionally reexport the Signal enum so that the user doesnt need to manually add nix crate to their Cargo.toml
    fn send_signal(&self, signal: Signal) {
        nix::sys::signal::kill(Pid::from_raw(self.pid()), signal).unwrap();
    }

    /// Send SIGTERM to the process
    /// TODO: This will be replaced with a `send_signal` method when nix crate is 1.0
    pub fn send_sigterm(&self) {
        self.send_signal(Signal::SIGTERM)
    }

    /// Send SIGINT to the process
    /// TODO: This will be replaced with a `send_signal` method when nix crate is 1.0
    pub fn send_sigint(&self) {
        self.send_signal(Signal::SIGINT)
    }

    /// Waits for the `ready` `EventMatcher` to match on an incoming event.
    /// All events that were encountered while waiting are returned.
    pub async fn wait_for(
        &mut self,
        ready: &EventMatcher,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> Events {
        let mut events = vec![];
        while let Some(event) = self.event_rx.recv().await {
            let ready_match = ready.matches(&event);
            events.push(event);
            if ready_match {
                BinProcess::assert_no_errors_or_warnings(&events, expected_errors_and_warnings);
                return Events { events };
            }
        }
        panic!("bin process shutdown before an event was found matching {ready:?}")
    }

    /// Await `event_count` messages to be emitted from the process.
    /// The emitted events are returned.
    pub async fn consume_events(
        &mut self,
        event_count: usize,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> Events {
        let mut events = vec![];
        for _ in 0..event_count {
            match self.event_rx.recv().await {
                Some(event) => events.push(event),
                None => {
                    if events.is_empty() {
                        panic!("The process was terminated before the expected count of {event_count} events occured. No events received so far");
                    } else {
                        let events_received = events.iter().map(|x| format!("{x}")).join("\n");
                        panic!("The process was terminated before the expected count of {event_count} events occured. Events received so far:\n{events_received}");
                    }
                }
            }
        }
        BinProcess::assert_no_errors_or_warnings(&events, expected_errors_and_warnings);
        Events { events }
    }

    /// Issues SIGTERM to the process and then awaits its shutdown.
    /// All remaining events will be returned.
    pub async fn shutdown_and_then_consume_events(
        self,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> Events {
        self.send_signal(nix::sys::signal::Signal::SIGTERM);
        self.consume_remaining_events(expected_errors_and_warnings)
            .await
    }

    /// prefer `shutdown_and_then_consume_events`.
    /// This method will not return until the process has terminated.
    /// It is useful when you need to test a shutdown method other than SIGTERM.
    pub async fn consume_remaining_events(
        mut self,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> Events {
        let (events, status) = self
            .consume_remaining_events_inner(expected_errors_and_warnings)
            .await;

        if status != 0 {
            panic!("The bin process exited with {status} but expected 0 exit code (Success).\nevents:\n{events}");
        }

        events
    }

    /// Identical to `consume_remaining_events` but asserts that the process exited with failure code instead of success
    pub async fn consume_remaining_events_expect_failure(
        mut self,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> Events {
        let (events, status) = self
            .consume_remaining_events_inner(expected_errors_and_warnings)
            .await;

        if status == 0 {
            panic!("The bin process exited with {status} but expected non 0 exit code (Failure).\nevents:\n{events}");
        }

        events
    }

    fn assert_no_errors_or_warnings(
        events: &[Event],
        expected_errors_and_warnings: &[EventMatcher],
    ) {
        let mut error_count = vec![0; expected_errors_and_warnings.len()];
        for event in events {
            if let Level::Error | Level::Warn = event.level {
                let mut matched = false;
                for (matcher, count) in expected_errors_and_warnings
                    .iter()
                    .zip(error_count.iter_mut())
                {
                    if matcher.matches(event) {
                        *count += 1;
                        matched = true;
                    }
                }
                if !matched {
                    panic!("Unexpected event {event}\nAny ERROR or WARN events that occur in integration tests must be explicitly allowed by adding an appropriate EventMatcher to the method call.")
                }
            }
        }

        // TODO: move into Events::contains
        for (matcher, count) in expected_errors_and_warnings.iter().zip(error_count.iter()) {
            match matcher.count {
                Count::Any => {}
                Count::Times(matcher_count) => {
                    if matcher_count != *count {
                        panic!("Expected to find matches for {matcher:?}, {matcher_count} times but actually matched {count} times")
                    }
                }
            }
        }
    }

    async fn consume_remaining_events_inner(
        &mut self,
        expected_errors_and_warnings: &[EventMatcher],
    ) -> (Events, i32) {
        // Take the child before we wait for the process to terminate.
        // This ensures that the drop bomb wont go off if the future is dropped partway through.
        // e.g. the user might have run BinProcess through `tokio::time::timeout`
        let child = self.child.take().unwrap();

        let mut events = vec![];
        while let Some(event) = self.event_rx.recv().await {
            events.push(event);
        }

        BinProcess::assert_no_errors_or_warnings(&events, expected_errors_and_warnings);

        use std::os::unix::process::ExitStatusExt;
        let output = child.wait_with_output().await.unwrap();
        let status = output.status.code().unwrap_or_else(|| {
            panic!(
                r#"Failed to get exit status.
The signal that killed the process was {:?}.
Possible causes:
* a SIGKILL was issued, something is going very wrong.
* a SIGINT or SIGTERM was issued but the aplications handler aborted without returning an exit value. (The default handler does this)
  If you are building a long running application you should handle SIGKILL and SIGTERM such that your application cleanly shutsdown and returns an exit value.
  Consider referring to how the tokio-bin-process example uses https://docs.rs/tokio/latest/tokio/signal/unix/struct.Signal.html
* a SIGINT or SIGTERM was issued and the aplication has an appropriate handler but the process was killed before the handler could be setup.
"#,
                output.status.signal()
            )
        });

        (Events { events }, status)
    }
}

async fn process_stdout_events(
    mut reader: tokio::io::Lines<BufReader<ChildStdout>>,
    event_tx: &mpsc::UnboundedSender<Event>,
    name: String,
) -> Result<()> {
    while let Some(line) = reader.next_line().await.context("An IO error occured while reading stdout from the application, I'm not actually sure when this happens?")? {
        let event = Event::from_json_str(&line).context(format!(
            "The application emitted a line that was not a valid event encoded in json: {}",
            line
        ))?;
        println!("{} {event}", Color::Default.dimmed().paint(&name));
        if event_tx.send(event).is_err() {
            // BinProcess is no longer interested in events
            return Ok(());
        }
    }
    Ok(())
}

/// Runs a command and returns the output as a string.
/// Both stderr and stdout are returned in the result.
fn run_command(working_dir: &Path, command: &str, args: &[&str]) -> Result<String> {
    let data = Exec::cmd(command)
        .args(args)
        .cwd(working_dir)
        .stdout(Redirection::Pipe)
        .stderr(Redirection::Merge)
        .capture()?;

    if data.exit_status.success() {
        Ok(data.stdout_str())
    } else {
        Err(anyhow!(
            "command {} {:?} exited with {:?} and output:\n{}",
            command,
            args,
            data.exit_status,
            data.stdout_str()
        ))
    }
}