//! Code to watch configuration files for any changes.

use std::sync::Weak;

use std::time::Duration;

use anyhow::Context;

use arti_client::config::Reconfigure;

use arti_client::TorClient;

use futures::{select_biased, FutureExt as _, Stream};

use tor_config::file_watcher::{self, FileWatcherBuilder, FileEventSender, FileWatcher};

use tor_config::{sources::FoundConfigFiles, ConfigurationSource, ConfigurationSources};

use tor_rtcompat::Runtime;

use tracing::{debug, error, info, instrument, warn};

use tor_rtcompat::SpawnExt;

use futures::StreamExt;

#[cfg(target_family = "unix")]

use crate::process::sighup_stream;

#[cfg(not(target_family = "unix"))]

use futures::stream;

use crate::{ArtiCombinedConfig, ArtiConfig};

/// How long to wait after an event got received, before we try to process it.

const DEBOUNCE_INTERVAL: Duration = Duration::from_secs(1);

/// An object that can be reconfigured when our configuration changes.

///

/// We use this trait so that we can represent abstract modules in our

/// application, and pass the configuration to each of them.

//

// TODO: It is very likely we will want to refactor this even further once we

// have a notion of what our modules truly are.

#[cfg_attr(feature = "experimental-api", visibility::make(pub))]

pub(crate) trait ReconfigurableModule: Send + Sync {

    /// Try to reconfigure this module according to a newly loaded configuration.

    ///

    /// By convention, this should only return fatal errors; any such error

    /// should cause the program to exit.  For other cases, we should just warn.

    //

    // TODO: This should probably take "how: Reconfigure" as an argument, and

    // pass it down as appropriate. See issue #1156.

    fn reconfigure(&self, new: &ArtiCombinedConfig) -> anyhow::Result<()>;

}

/// Launch a thread to reload our configuration files.

///

/// If current configuration requires it, watch for changes in `sources`

/// and try to reload our configuration. On unix platforms, also watch

/// for SIGHUP and reload configuration then.

///

/// The modules are `Weak` references to prevent this background task

/// from keeping them alive.

///

/// See the [`FileWatcher`](FileWatcher#Limitations) docs for limitations.

    cfg_if::cfg_if! {

        if #[cfg(target_family = "unix")] {

        } else {

            let sighup_stream = stream::pending();

        }

    }

            // TODO: warn_report does not work on anyhow::Error.

        }

/// Start watching for configuration changes.

///

/// Spawned from `watch_for_config_changes`.

#[allow(clippy::cognitive_complexity)] // TODO: Refactor? Partly due to tracing.

#[instrument(level = "trace", skip_all)]

    let (tx, mut rx) = file_watcher::channel();

    let mut watcher = if watch_file {

        let mut watcher = FileWatcher::builder(runtime.clone());

        prepare(&mut watcher, &sources)?;

        Some(watcher.start_watching(tx.clone())?)

    } else {

        None

    };

    debug!("Entering FS event loop");

    loop {

        select_biased! {

            event = sighup_stream.next().fuse() => {

                let Some(()) = event else {

                    break;

                };

                info!("Received SIGHUP");

                watcher = reload_configuration(

                    runtime.clone(),

                    watcher,

                    &sources,

                    &modules,

                    tx.clone()

                ).await?;

            },

            event = rx.next().fuse() => {

                    runtime.sleep(debounce_interval).await;

                }

                while let Some(_ignore) = rx.try_recv() {

                    // Discard other events, so that we only reload once.

                    //

                    // We can afford to treat both error cases from try_recv [Empty

                    // and Disconnected] as meaning that we've discarded other

                    // events: if we're disconnected, we'll notice it when we next

                    // call recv() in the outer loop.

                }

                debug!("Config reload event {:?}: reloading configuration.", event);

                watcher = reload_configuration(

                    runtime.clone(),

                    watcher,

                    &sources,

                    &modules,

                    tx.clone()

                ).await?;

            },

        }

    }

    Ok(())

/// Reload the configuration.

#[allow(clippy::cognitive_complexity)] // TODO: Refactor? Partly due to tracing.

#[instrument(level = "trace", skip_all)]

    let found_files = if watcher.is_some() {

        let mut new_watcher = FileWatcher::builder(runtime.clone());

        let found_files = prepare(&mut new_watcher, sources)

            .context("FS watch: failed to rescan config and re-establish watch")?;

        let new_watcher = new_watcher

            .start_watching(tx.clone())

            .context("FS watch: failed to start watching config")?;

        watcher = Some(new_watcher);

        found_files

    } else {

        sources

            .scan()

            .context("FS watch: failed to rescan config")?

    };

    match reconfigure(found_files, modules) {

        Ok(watch) => {

            info!("Successfully reloaded configuration.");

            if watch && watcher.is_none() {

                info!("Starting watching over configuration.");

                let mut new_watcher = FileWatcher::builder(runtime.clone());

                let _found_files = prepare(&mut new_watcher, sources).context(

                    "FS watch: failed to rescan config and re-establish watch: {}",

                )?;

                let new_watcher = new_watcher.start_watching(tx.clone()).context(

                    "FS watch: failed to rescan config and re-establish watch: {}",

                )?;

                watcher = Some(new_watcher);

            } else if !watch && watcher.is_some() {

                info!("Stopped watching over configuration.");

                watcher = None;

            }

        }

        // TODO: warn_report does not work on anyhow::Error.

        Err(e) => warn!("Couldn't reload configuration: {}", tor_error::Report(e)),

    }

    Ok(watcher)

impl<R: Runtime> ReconfigurableModule for TorClient<R> {

    #[instrument(level = "trace", skip_all)]

}

/// Internal type to represent the Arti application as a `ReconfigurableModule`.

pub(crate) struct Application {

    /// The configuration that Arti had at startup.

    ///

    /// We use this to check whether the user is asking for any impermissible

    /// transitions.

    original_config: ArtiConfig,

}

impl Application {

    /// Construct a new `Application` to receive configuration changes for the

    /// arti application.

}

impl ReconfigurableModule for Application {

    // TODO: This should probably take "how: Reconfigure" as an argument, and

    // pass it down as appropriate. See issue #1156.

    #[allow(clippy::cognitive_complexity)]

    #[instrument(level = "trace", skip_all)]

        #[cfg(feature = "rpc")]

        // Note that this is the only config transition we actually perform so far.

            #[cfg(feature = "harden")]

}

/// Find the configuration files and prepare the watcher

        }

    }

/// Reload the configuration files, apply the runtime configuration, and

/// reconfigure the client as much as we can.

///

/// Return true if we should be watching for configuration changes.

//

// TODO: This should probably take "how: Reconfigure" as an argument, and

// pass it down as appropriate. See issue #1156.

#[instrument(level = "trace", skip_all)]

    // Filter out the modules that have been dropped

    // If there are no more modules, we should exit.

    }

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use crate::ArtiConfigBuilder;

    use super::*;

    use futures::channel::mpsc;

    use futures::SinkExt as _;

    use tor_config::sources::MustRead;

    use std::path::PathBuf;

    use std::sync::{Arc, Mutex};

    use test_temp_dir::{test_temp_dir, TestTempDir};

    use postage::watch;

    use tor_async_utils::PostageWatchSenderExt;

    /// Filename for config1

    const CONFIG_NAME1: &str = "config1.toml";

    /// Filename for config2

    const CONFIG_NAME2: &str = "config2.toml";

    /// Filename for config3

    const CONFIG_NAME3: &str = "config3.toml";

    struct TestModule {

        // A sender for sending the new config to the test function

        tx: Arc<Mutex<watch::Sender<ArtiCombinedConfig>>>,

    }

    impl ReconfigurableModule for TestModule {

        fn reconfigure(&self, new: &ArtiCombinedConfig) -> anyhow::Result<()> {

            let config = new.clone();

            self.tx.lock().unwrap().maybe_send(|_| config);

            Ok(())

        }

    }

    /// Create a test reconfigurable module.

    ///

    /// Returns the module and a channel on which the new configs received by the module are sent.

    async fn create_module(

    ) -> (Arc<dyn ReconfigurableModule>, watch::Receiver<ArtiCombinedConfig>) {

        let (tx, mut rx) = watch::channel();

        // Read the initial value from the postage::watch stream

        // (the first observed value on this test stream is always the default config)

        let _: ArtiCombinedConfig = rx.next().await.unwrap();

        (Arc::new(TestModule { tx: Arc::new(Mutex::new(tx)) }), rx)

    }

    /// Write `data` to file `name` within `dir`.

    fn write_file(dir: &TestTempDir, name: &str, data: &[u8]) -> PathBuf {

        let tmp = dir.as_path_untracked().join("tmp");

        std::fs::write(&tmp, data).unwrap();

        let path = dir.as_path_untracked().join(name);

        // Atomically write the config file

        std::fs::rename(tmp, &path).unwrap();

        path

    }

    /// Write an `ArtiConfigBuilder` to a file within `dir`.

    fn write_config(dir: &TestTempDir, name: &str, config: &ArtiConfigBuilder) -> PathBuf {

        let s = toml::to_string(&config).unwrap();

        write_file(dir, name, s.as_bytes())

    }

    #[test]

    fn watch_single_file() {

        tor_rtcompat::test_with_one_runtime!(|rt| async move {

            let temp_dir = test_temp_dir!();

            let mut config_builder =  ArtiConfigBuilder::default();

            config_builder.application().watch_configuration(true);

            let cfg_file = write_config(&temp_dir, CONFIG_NAME1, &config_builder);

            let mut cfg_sources = ConfigurationSources::new_empty();

            cfg_sources.push_source(ConfigurationSource::File(cfg_file), MustRead::MustRead);

            let (module, mut rx) = create_module().await;

            config_builder.logging().log_sensitive_information(true);

            let _: PathBuf = write_config(&temp_dir, CONFIG_NAME1, &config_builder);

            // Use a fake sighup stream to wait until run_watcher()'s select_biased!

            // loop is entered

            let (mut sighup_tx, sighup_rx) = mpsc::unbounded();

            let runtime = rt.clone();

            let () = rt.spawn(async move {

                run_watcher(

                    runtime,

                    cfg_sources,

                    vec![Arc::downgrade(&module)],

                    true,

                    sighup_rx,

                    None,

                ).await.unwrap();

            }).unwrap();

            sighup_tx.send(()).await.unwrap();

            // The reconfigurable modules should've been reloaded in response to sighup

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder.build().unwrap());

            // Overwrite the config

            config_builder.logging().log_sensitive_information(false);

            let _: PathBuf = write_config(&temp_dir, CONFIG_NAME1, &config_builder);

            // The reconfigurable modules should've been reloaded in response to the config change

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder.build().unwrap());

        });

    }

    // TODO: Ignored until #1607 is fixed

    #[test]

    #[ignore]

    fn watch_multiple() {

        tor_rtcompat::test_with_one_runtime!(|rt| async move {

            let temp_dir = test_temp_dir!();

            let mut config_builder1 =  ArtiConfigBuilder::default();

            config_builder1.application().watch_configuration(true);

            let _: PathBuf = write_config(&temp_dir, CONFIG_NAME1, &config_builder1);

            let mut cfg_sources = ConfigurationSources::new_empty();

            cfg_sources.push_source(

                ConfigurationSource::Dir(temp_dir.as_path_untracked().to_path_buf()),

                MustRead::MustRead

            );

            let (module, mut rx) = create_module().await;

            // Use a fake sighup stream to wait until run_watcher()'s select_biased!

            // loop is entered

            let (mut sighup_tx, sighup_rx) = mpsc::unbounded();

            let runtime = rt.clone();

            let () = rt.spawn(async move {

                run_watcher(

                    runtime,

                    cfg_sources,

                    vec![Arc::downgrade(&module)],

                    true,

                    sighup_rx,

                    None,

                ).await.unwrap();

            }).unwrap();

            config_builder1.logging().log_sensitive_information(true);

            let _: PathBuf = write_config(&temp_dir, CONFIG_NAME1, &config_builder1);

            sighup_tx.send(()).await.unwrap();

            // The reconfigurable modules should've been reloaded in response to sighup

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder1.build().unwrap());

            let mut config_builder2 =  ArtiConfigBuilder::default();

            config_builder2.application().watch_configuration(true);

            // Write another config file...

            config_builder2.system().max_files(0_u64);

            let _: PathBuf = write_config(&temp_dir, CONFIG_NAME2, &config_builder2);

            // Check that the 2 config files are merged

            let mut config_builder_combined = config_builder1.clone();

            config_builder_combined.system().max_files(0_u64);

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder_combined.build().unwrap());

            // Now write a new config file to the watched dir

            config_builder2.logging().console("foo".to_string());

            let mut config_builder_combined2 = config_builder_combined.clone();

            config_builder_combined2.logging().console("foo".to_string());

            let config3: PathBuf = write_config(&temp_dir, CONFIG_NAME3, &config_builder2);

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder_combined2.build().unwrap());

            // Removing the file should also trigger an event

            std::fs::remove_file(config3).unwrap();

            let config = rx.next().await.unwrap();

            assert_eq!(config.0, config_builder_combined.build().unwrap());

        });

    }

}