/// Updating and processing of RPKI data.
///
/// This module provides types and traits implementing validation of RPKI data
/// from a set of trust anchor locators to some output data.
///
/// Data validation is configured through [`Engine`] so that the
/// configuration can be used for multiple validation runs. This includes both
/// a [collector][crate::collector::Collector] and
/// [store][crate::store::Store] to use for validation.
///
/// Individual validation runs are managed through [`Run`]. Such a runner can
/// be obtained from validation via its [`start`][Engine::start] method.
/// It in turn provides the [`process`][Run::process] method which drives the
/// actual validation.
///
/// Engine runs are generic over what exactly should be done with valid
/// RPKI data. The trait [`ProcessRun`] represents a full validation run with
/// the accompanying trait [`ProcessPubPoint`] dealing with individual
/// publication points.

use std::{fmt, fs, thread};
use std::borrow::Cow;
use std::collections::HashMap;
use std::fs::File;
use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};
use std::sync::atomic::{AtomicBool, Ordering};
use bytes::Bytes;
use crossbeam_queue::{ArrayQueue, SegQueue};
use log::{debug, error, info, warn};
use rpki::crypto::keys::KeyIdentifier;
#[allow(unused_imports)]
use rpki::repository::aspa::{Aspa, AsProviderAttestation};
use rpki::repository::cert::{Cert, KeyUsage, ResourceCert};
use rpki::repository::crl::Crl;
use rpki::repository::error::{InspectionError, ValidationError};
use rpki::repository::manifest::{Manifest, ManifestContent, ManifestHash};
use rpki::repository::roa::{Roa, RouteOriginAttestation};
use rpki::repository::sigobj::SignedObject;
use rpki::repository::tal::{Tal, TalInfo, TalUri};
use rpki::repository::x509::{Time, Validity};
use rpki::uri;
use crate::{collector, store, tals};
use crate::config::{Config, FilterPolicy};
use crate::collector::Collector;
use crate::error::Failed;
use crate::metrics::{
    Metrics, PublicationMetrics, RepositoryMetrics, TalMetrics
};
use crate::store::{Store, StoredManifest, StoredObject, StoredPoint};
use crate::utils::str::str_from_ascii;


//------------ Configuration -------------------------------------------------

/// The minimum number of manifest entries that triggers CRL serial caching.
///
/// The value has been determined experimentally with the RPKI repository at
/// a certain state so may or may not be a good one, really.
const CRL_CACHE_LIMIT: usize = 50;


//------------ Engine --------------------------------------------------------

/// The mechanism to update and process RPKI data.
///
/// A validation value can be created from the configuration via
/// [`Engine::new`]. If you don’t actually want to perform a validation run
/// but just initialize everything, [`Engine::init`] will suffice.
///
/// When created, the set of TALs is loaded and kept around. It will only be
/// refreshed explicitly through the [`reload_tals`][Self::reload_tals]
/// method.
///
/// Before starting the very first validation run, you need to call
/// [`ignite`][Self::ignite] at least once. As this may spawn threads, this
/// must happen after a possible fork.
///
/// A run is started via the [`start`][Self::start] method, providing a
/// processor that handles valid data. The method returns a [Run] value that
/// drives the validation run.
#[derive(Debug)]
pub struct Engine {
    /// A list of built-in TALs to use.
    bundled_tals: Vec<Tal>,

    /// An optional directory to load TALs from.
    extra_tals_dir: Option<PathBuf>,

    /// A mapping of TAL file names to TAL labels.
    tal_labels: HashMap<String, String>,

    /// The list of our TALs. 
    tals: Vec<Tal>,

    /// The collector to load updated data from.
    ///
    /// If this is `None`, updates have been disabled.
    collector: Option<Collector>,

    /// The store to load stored data from.
    store: Store,

    /// Should we be strict when decoding data?
    strict: bool,

    /// How do we deal with stale objects?
    stale: FilterPolicy,

    /// Number of validation threads.
    validation_threads: usize,

    /// Should we leave the repository dirty after a valiation run.
    dirty_repository: bool,

    /// Maximum depth of the CA chain.
    max_ca_depth: usize,
}

impl Engine {
    /// Initializes the engine without creating a value.
    ///
    /// This ensures that the TAL directory is present and logs a hint how
    /// to achieve that if not.
    ///
    /// The function is called implicitly by [`new`][Self::new].
    pub fn init(config: &Config) -> Result<(), Failed> {
        Collector::init(config)?;
        Store::init(config)?;
        Ok(())
    }

    /// Creates a new engine.
    ///
    /// Takes all necessary information from `config`.
    /// It also takes over the provided cache and store for use during
    /// validation.
    ///
    /// Loads the initial set of TALs and errors out if that fails.
    pub fn new(
        config: &Config,
        update: bool,
    ) -> Result<Self, Failed> {
        let collector = if update {
            Some(Collector::new(config)?)
        }
        else {
            None
        };
        let store = Store::new(config)?;
        let mut res = Engine {
            bundled_tals: tals::collect_tals(config)?,
            extra_tals_dir: config.extra_tals_dir.clone(),
            tal_labels: config.tal_labels.clone(),
            tals: Vec::new(),
            collector,
            store,
            strict: config.strict,
            stale: config.stale,
            validation_threads: config.validation_threads,
            dirty_repository: config.dirty_repository,
            max_ca_depth: config.max_ca_depth,
        };
        res.reload_tals()?;
        Ok(res)
    }

    /// Reloads the set of TALs.
    ///
    /// Assumes that all regular files with an extension of `tal` in the
    /// TAL directory specified during object creation are TAL files and
    /// tries to load and decode them. Fails if that fails for at least one
    /// of those files.
    ///
    /// It is not considered an error if there are no TAL files in the TAL
    /// directory. However, a warning will be logged in this case.
    pub fn reload_tals(&mut self) -> Result<(), Failed> {
        let mut res = self.bundled_tals.clone();
        if let Some(extra_tals_dir) = self.extra_tals_dir.as_ref() {
            let dir = match fs::read_dir(extra_tals_dir) {
                Ok(dir) => dir,
                Err(err) => {
                    error!("Failed to open TAL directory {}: {}.",
                        extra_tals_dir.display(), err
                    );
                    return Err(Failed)
                }
            };
            for entry in dir {
                let entry = match entry {
                    Ok(entry) => entry,
                    Err(err) => {
                        error!(
                            "Failed to iterate over tal directory: {}",
                            err
                        );
                        return Err(Failed)
                    }
                };

                if !entry.file_type().map(|ft| ft.is_file()).unwrap_or(false) {
                    continue
                }

                let path = entry.path();
                if path.extension().map(|ext| ext != "tal").unwrap_or(true) {
                    continue
                }

                let mut file = match File::open(&path) {
                    Ok(file) => {
                        file
                    }
                    Err(err) => {
                        error!(
                            "Failed to open TAL {}: {}. \n\
                             Aborting.",
                             path.display(), err
                        );
                        return Err(Failed)
                    }
                };
                let mut tal = match Tal::read_named(
                    self.path_to_tal_label(&path),
                    &mut file
                ) {
                    Ok(tal) => tal,
                    Err(err) => {
                        error!(
                            "Failed to read TAL {}: {}. \n\
                             Aborting.",
                            path.display(), err
                        );
                        return Err(Failed)
                    }
                };
                tal.prefer_https();
                res.push(tal);
            }
        }
        if res.is_empty() {
            warn!(
                "No TALs provided. Starting anyway."
            );
        }
        res.sort_by(|left, right| {
            left.info().name().cmp(right.info().name())
        });
        self.tals = res;

        Ok(())
    }

    /// Converts a path into a TAL label.
    ///
    /// This will be an explicitly configured TAL label if the file name
    /// portion of the path is registered in `self.tal_labels` or the file
    /// name without the `tal` extension otherwise.
    fn path_to_tal_label(&self, path: &Path) -> String {
        if let Some(name) = path.file_name().unwrap().to_str() {
            if let Some(label) = self.tal_labels.get(name) {
                return label.clone()
            }
        }
        path.file_stem().unwrap().to_string_lossy().into_owned()
    }

    /// Ignites validation processing.
    ///
    /// This spawns threads and therefore needs to be done after a
    /// possible fork.
    pub fn ignite(&mut self) -> Result<(), Failed> {
        if let Some(collector) = self.collector.as_mut() {
            collector.ignite()?;
        }
        Ok(())
    }

    /// Starts a validation run.
    ///
    /// During the run, `processor` will be responsible for dealing with
    /// valid objects. It must implement the [`ProcessRun`] trait.
    ///
    /// The method returns a [`Run`] that drives the validation run.
    pub fn start<P: ProcessRun>(
        &self, processor: P
    ) -> Result<Run<P>, Failed> {
        info!("Using the following TALs:");
        for tal in &self.tals {
            info!("  * {}", tal.info().name());
        }
        Ok(Run::new(
            self,
            self.collector.as_ref().map(Collector::start),
            self.store.start(),
            processor
        ))
    }

    /// Dumps the content of the collector and store owned by the engine.
    pub fn dump(&self, dir: &Path) -> Result<(), Failed> {
        self.store.dump(dir)?;
        if let Some(collector) = self.collector.as_ref() {
            collector.dump(dir)?;
        }
        Ok(())
    }
}


//------------ Run -----------------------------------------------------------

/// A single validation run.
///
/// The runner is generic over the processor of valid data which must
/// implement the [`ProcessRun`] trait. The actual run is triggered by the
/// [`process`][Self::process] method. Upon completion, metrics of the run
/// can be extracted through [`done`][Self::done].
pub struct Run<'a, P> {
    /// A reference to the underlying validation.
    validation: &'a Engine,

    /// The runner for the collector.
    collector: Option<collector::Run<'a>>,

    /// The runner for the store.
    store: store::Run<'a>,

    /// The processor for valid data.
    processor: P,

    /// The metrics collected during the run.
    metrics: Metrics,
}

impl<'a, P> Run<'a, P> {
    /// Creates a new runner from all the parts.
    fn new(
        validation: &'a Engine,
        collector: Option<collector::Run<'a>>,
        store: store::Run<'a>,
        processor: P,
    ) -> Self {
        Run {
            validation, collector, store, processor,
            metrics: Default::default()
        }
    }

    /// Cleans the collector and store owned by the engine.
    pub fn cleanup(&mut self) -> Result<(), Failed> {
        if self.validation.dirty_repository {
            debug!("Skipping cleanup as configured.");
            return Ok(())
        }

        let mut retain = collector::Cleanup::new();
        self.store.cleanup(&mut retain)?;
        if let Some(collector) = self.collector.as_mut() {
            collector.cleanup(&mut retain)?;
        }
        Ok(())
    }

    /// Finishes the validation run and returns the metrics.
    ///
    /// If you are not interested in the metrics, you can simple drop the
    /// value, instead.
    pub fn done(self) -> Metrics {
        let mut metrics = self.metrics;
        if let Some(collector) = self.collector {
            collector.done(&mut metrics)
        }
        self.store.done(&mut metrics);
        metrics
    }
}

impl<'a, P: ProcessRun> Run<'a, P> {
    /// Performs the validation run.
    pub fn process(&mut self) -> Result<(), Failed> {
        // If we don’t have any TALs, we ain’t got nothing to do.
        if self.validation.tals.is_empty() {
            return Ok(())
        }

        // Initialize our task queue with all the TALs.
        let metrics = RunMetrics::default();
        let tasks = SegQueue::new();
        for (index, tal) in self.validation.tals.iter().enumerate() {
            tasks.push(Task::Tal(TalTask { tal, index }));
            self.metrics.tals.push(TalMetrics::new(tal.info().clone()));
        }

        // And off we trot.

        // Keep a flag to cancel everything if something goes wrong.
        let had_err = AtomicBool::new(false);
        let thread_metrics = ArrayQueue::new(
            self.validation.validation_threads
        );
        thread::scope(|scope| {
            for _ in 0 .. self.validation.validation_threads {
                scope.spawn(|| {
                    let mut metrics = metrics.fork();
                    while let Some(task) = tasks.pop() {
                        if self.process_task(
                            task, &tasks, &mut metrics, &had_err,
                        ).is_err() {
                            break;
                        }
                    }
                    thread_metrics.push(metrics).unwrap();
                });
            }
        });

        if had_err.load(Ordering::Relaxed) {
            return Err(Failed);
        }

        metrics.prepare_final(&mut self.metrics);
        while let Some(metrics) = thread_metrics.pop() {
            metrics.collapse(&mut self.metrics);
        }

        Ok(())
    }

    /// Process a task. Any task.
    fn process_task(
        &self,
        task: Task<P::PubPoint>,
        tasks: &SegQueue<Task<P::PubPoint>>,
        metrics: &mut RunMetrics,
        had_err: &AtomicBool,
    ) -> Result<(), Failed> {
        match task {
            Task::Tal(task) => {
                self.process_tal_task(task, tasks, metrics, had_err)
            }
            Task::Ca(task) => {
                self.process_ca_task(task, tasks, metrics, had_err)
            }
        }
    }

    /// Processes a trust anchor.
    fn process_tal_task(
        &self, task: TalTask,
        tasks: &SegQueue<Task<P::PubPoint>>,
        metrics: &mut RunMetrics,
        had_err: &AtomicBool,
    ) -> Result<(), Failed> {
        for uri in task.tal.uris() {
            let cert = match self.load_ta(uri, task.tal.info())? {
                Some(cert) => cert,
                _ => continue,
            };
            if cert.subject_public_key_info() != task.tal.key_info() {
                warn!(
                    "Trust anchor {}: key doesn’t match TAL.",
                    uri
                );
                continue;
            }
            let cert = match cert.validate_ta(
                task.tal.info().clone(), self.validation.strict
            ) {
                Ok(cert) => CaCert::root(cert, uri.clone(), task.index),
                Err(err) => {
                    warn!("Trust anchor {}: {}.", uri, err);
                    continue;
                }
            };
            let cert = match cert {
                Ok(cert) => cert,
                Err(_) => continue,
            };
            debug!("Found valid trust anchor {}. Processing.", uri);

            match self.processor.process_ta(
                task.tal, uri, &cert, cert.tal
            )? {
                Some(processor) => {
                    return self.process_ca_task(
                        CaTask {
                            cert, processor,
                            repository_index: None,
                            defer: false,
                        },
                        tasks, metrics, had_err
                    )
                }
                None => {
                    debug!("Skipping trust anchor {}.", uri);
                    return Ok(())
                }
            }
        }
        warn!("No valid trust anchor for TAL {}", task.tal.info().name());
        Ok(())
    }

    /// Loads a trust anchor certificate with the given URI.
    ///
    /// Attempts to download the certificate from upstream but falls back to
    /// the version in the store if available.
    fn load_ta(
        &self,
        uri: &TalUri,
        _info: &TalInfo,
    ) -> Result<Option<Cert>, Failed> {
        // Get the new version, store and return it if it decodes.
        if let Some(collector) = self.collector.as_ref() {
            if let Some(bytes) = collector.load_ta(uri) {
                if let Ok(cert) = Cert::decode(bytes.clone()) {
                    self.store.update_ta(uri, &bytes)?;
                    return Ok(Some(cert))
                }
            }
        }

        // Get what we have in store.
        self.store.load_ta(uri).map(|bytes| {
            bytes.and_then(|bytes| Cert::decode(bytes).ok())
        })
    }

    /// Processes a CA.
    fn process_ca_task(
        &self,
        task: CaTask<P::PubPoint>,
        tasks: &SegQueue<Task<P::PubPoint>>,
        metrics: &mut RunMetrics,
        had_err: &AtomicBool,
    ) -> Result<(), Failed> {
        let more_tasks = PubPoint::new(
            self, &task.cert, task.processor, task.repository_index,
        ).and_then(|point| {
            point.process(metrics)
        }).map_err(|_| {
            had_err.store(true, Ordering::Relaxed);
            Failed
        })?;
        for task in more_tasks {
            if had_err.load(Ordering::Relaxed) {
                return Err(Failed)
            }
            if task.defer {
                tasks.push(Task::Ca(task))
            }
            else {
                self.process_ca_task(task, tasks, metrics, had_err)?;
            }
        }
        Ok(())
    }
}


//------------ PubPoint ------------------------------------------------------

/// Validation of a single publication point.
struct PubPoint<'a, P: ProcessRun> {
    /// A reference to the runner.
    run: &'a Run<'a, P>,

    /// A reference to the CA certificate of the publication point.
    cert: &'a Arc<CaCert>,

    /// The processor for valid data at this publication point.
    processor: P::PubPoint,

    /// The index of this point’s repository in the run’s metrics.
    repository_index: Option<usize>,

    /// The base publication metrics for this publication point.
    ///
    /// This one only receives information about the publication point itself,
    /// as well as the manifest and manifest CRL. Everything else will be
    /// collected during object processing via `ValidPointManifest` so we can
    /// drop it if the point gets cancelled.
    metrics: PublicationMetrics,
}

impl<'a, P: ProcessRun> PubPoint<'a, P> {
    /// Creates a new publication point validator based on a CA certificate.
    pub fn new(
        run: &'a Run<'a, P>,
        cert: &'a Arc<CaCert>,
        processor: P::PubPoint,
        repository_index: Option<usize>,
    ) -> Result<Self, Failed> {
        Ok(PubPoint {
            run, cert, processor, repository_index,
            metrics: Default::default(),
        })
    }

    /// Performs validation of the publication point.
    ///
    /// Upon success, returns a list of all the child CAs of this publication
    /// point as CA processing tasks.
    pub fn process(
        self,
        metrics: &mut RunMetrics,
    ) -> Result<Vec<CaTask<P::PubPoint>>, Failed> {
        let mut store = self.run.store.pub_point(self.cert)?;
        if let Some(collector) = self.run.collector.as_ref() {
            if let Some(collector) = collector.repository(self.cert)? {
                match self.process_collected(
                    collector, &mut store, metrics
                )? {
                    Ok(res) => return Ok(res),
                    Err(mut this) => {
                        this.metrics = Default::default();
                        return this.process_stored(store, metrics)
                    }
                }
            }
        }
        self.process_stored(store, metrics)
    }

    /// Tries to update the stored data and validate at the same time.
    ///
    /// Tries to fetch the updated manifest from the collector. If it differs
    /// from the stored manifest, updates the stored manifest and objects if
    /// the manifest is valid and all the objects are present and match their
    /// hashes. While checking, also processes the data so we only need to do
    /// that once.
    ///
    /// Returns a list of the child CAs if it successfully finished or `self`
    /// if there is no update or it is not valid and the store needs to be
    /// consulted.
    #[allow(clippy::type_complexity)] // Yeah, I know ...
    fn process_collected(
        mut self,
        collector: collector::Repository,
        store: &mut StoredPoint,
        metrics: &mut RunMetrics,
    ) -> Result<Result<Vec<CaTask<P::PubPoint>>, Self>, Failed> {
        // Try to load the manifest from the collector. If there isn’t one,
        // we are done, too.
        let collected = match collector.load_object(
            self.cert.rpki_manifest()
        )? {
            Some(collected) => collected,
            None => return Ok(Err(self))
        };

        // If the stored and collected manifests are the same, nothing has
        // changed and we can abort the update. However, we need to check that
        // the stored manifest refers to the same CA repository URI, just to
        // be sure.
        let same = if let Some(mft) = store.manifest() {
            mft.manifest() == &collected
                && mft.ca_repository() == self.cert.ca_repository()
        }
        else {
            false
        };
        if same {
            return Ok(Err(self))
        }

        // Validate the collected manifest. If it is no good, well, you know
        // the drill.
        let mut collected = match self.validate_collected_manifest(
            collected, &collector
        )? {
            Some(collected) => collected,
            None => {
                return Ok(Err(self))
            }
        };

        // The manifest is fine, so we can now look at the objects. The
        // objects are fine if they are present and match the hash. If they
        // don’t we have to cancel the update. We also validate them while we
        // are at it. This also collects all the child CAs that need
        // processing later on in `ca_tasks`. 
        //
        // However, the processor can decide it doesn’t like the publication
        // point at all. This is not an error -- the publication point is
        // correct from a store perspective --, but we must not process te
        // collected `ca_tasks`. We keep track of this through `point_ok` and,
        // if that happens to end up being `false` return an empty list to
        // signal that the publication point was processed successfully but
        // shouldn’t be considered further.
        let mut ca_tasks = Vec::new();
        let mut items = collected.content.iter();
        let mut point_ok = true;
        let update_result = store.update(
            StoredManifest::new(
                collected.ee_cert.validity().not_after(),
                self.cert.rpki_notify().cloned(),
                self.cert.ca_repository().clone(),
                self.cert.rpki_manifest().clone(),
                collected.manifest_bytes.clone(),
                collected.crl_uri.clone(),
                collected.crl_bytes.clone(),
            ),
            || {
                let item = match items.next() {
                    Some(item) => item,
                    None => return Ok(None)
                };

                let file = match str_from_ascii(item.file()) {
                    Ok(file) => file,
                    Err(_) => {
                        warn!("{}: illegal file name '{}'.",
                            self.cert.rpki_manifest(),
                            String::from_utf8_lossy(item.file())
                        );
                        return Err(store::UpdateError::Abort)
                    }
                };
                let uri = self.cert.ca_repository().join(
                    file.as_ref()
                ).unwrap();

                let hash = ManifestHash::new(
                    item.hash().clone(), collected.content.file_hash_alg()
                );

                let content = match collector.load_object(&uri)? {
                    Some(content) => content,
                    None => {
                        warn!("{}: failed to load.", uri);
                        return Err(store::UpdateError::Abort)
                    }
                };

                if hash.verify(&content).is_err() {
                    warn!("{}: file has wrong manifest hash.", uri);
                    return Err(store::UpdateError::Abort)
                }

                if !self.process_object(
                    &uri, content.clone(),
                    &mut collected, &mut ca_tasks
                )? {
                    point_ok = false;
                }

                Ok(Some(StoredObject::new(uri, content, Some(hash))))
            }
        );

        match update_result {
            Ok(()) => {
                // Update was successful. We have to accept whatever result
                // we got.
                if point_ok {
                    self.accept_point(collected, metrics);
                    Ok(Ok(ca_tasks))
                }
                else {
                    self.reject_point(metrics);
                    Ok(Ok(Vec::new()))
                }
            }
            Err(store::UpdateError::Abort) => {
                // Update was aborted. We need to use the store.
                Ok(Err(self))
            }
            Err(store::UpdateError::Fatal) => {
                // We are doomed.
                Err(Failed)
            }
        }
    }

    /// Tries to validate a manifest acquired from the collector.
    ///
    /// Checks that the manifest is correct itself and has been signed by the
    /// publication point’s CA. Tries to load the associated CRL from the
    /// collector, validates that against the CA and checks that the manifest
    /// has not been revoked.
    fn validate_collected_manifest(
        &mut self,
        manifest_bytes: Bytes,
        repository: &collector::Repository,
    ) -> Result<Option<ValidPointManifest>, Failed> {
        let manifest = match Manifest::decode(
            manifest_bytes.clone(), self.run.validation.strict
        ) {
            Ok(manifest) => manifest,
            Err(_) => {
                self.metrics.invalid_manifests += 1;
                warn!(
                    "{}: failed to decode manifest.",
                    self.cert.rpki_manifest()
                );
                return Ok(None)
            }
        };
        let (ee_cert, content) = match manifest.validate(
            self.cert.cert(), self.run.validation.strict
        ) {
            Ok(some) => some,
            Err(err) => {
                self.metrics.invalid_manifests += 1;
                warn!("{}: {}.", self.cert.rpki_manifest(), err);
                return Ok(None)
            }
        };

        if content.this_update() > Time::now() {
            self.metrics.premature_manifests += 1;
            warn!("{}: premature manifest", self.cert.rpki_manifest());
            return Ok(None)
        }

        if content.is_stale() {
            self.metrics.stale_manifests += 1;
            match self.run.validation.stale {
                FilterPolicy::Reject => {
                    warn!("{}: stale manifest", self.cert.rpki_manifest());
                    return Ok(None)
                }
                FilterPolicy::Warn => {
                    warn!("{}: stale manifest", self.cert.rpki_manifest());
                }
                FilterPolicy::Accept => { }
            }
        }

        let (crl_uri, crl, crl_bytes) = match self.validate_collected_crl(
            &ee_cert, &content, repository
        )? {
            Some(some) => some,
            None => return Ok(None)
        };

        self.metrics.valid_manifests += 1;

        Ok(Some(ValidPointManifest {
            ee_cert, content, crl_uri, crl, manifest_bytes, crl_bytes,
            metrics: Default::default(),
        }))
    }

    /// Check the manifest CRL.
    ///
    /// Checks that there is exactly one CRL on the manifest, that it matches
    /// the CRL mentioned in the manifest’s EE certificate, that it matches
    /// its manifest hash, that it is a valid CRL for the CA, and that it does
    /// not revoke the manifest’s EE certificate.
    ///
    /// If all that is true, returns the decoded CRL.
    fn validate_collected_crl(
        &mut self,
        ee_cert: &ResourceCert,
        manifest: &ManifestContent,
        repository: &collector::Repository
    ) -> Result<Option<(uri::Rsync, Crl, Bytes)>, Failed> {
        // Let’s first get the manifest CRL’s name relative to repo_uri. If
        // it ain’t relative at all, this is already invalid.
        let crl_uri = match ee_cert.crl_uri() {
            // RFC 6481: MUST end in .crl.
            Some(some) if some.ends_with(".crl") => some.clone(),
            _ => {
                self.metrics.invalid_manifests += 1;
                warn!("{}: invalid CRL URI.", self.cert.rpki_manifest());
                return Ok(None)
            }
        };
        let crl_name = match crl_uri.relative_to(self.cert.ca_repository()) {
            Some(name) => name,
            None => {
                self.metrics.invalid_manifests += 1;
                warn!(
                    "{}: CRL URI outside repository directory.",
                    self.cert.rpki_manifest()
                );
                return Ok(None)
            }
        };

        // Now we go over the manifest and try to find an entry matching
        // crl_name.
        let mut crl_bytes = None;
        for item in manifest.iter() {
            let (file, hash) = item.into_pair();
            if file == crl_name {
                let bytes = match repository.load_object(&crl_uri)? {
                    Some(bytes) => bytes,
                    None => {
                        self.metrics.invalid_crls += 1;
                        warn!("{}: failed to load.", crl_uri);
                        return Ok(None)
                    }
                };
                let hash = ManifestHash::new(hash, manifest.file_hash_alg());
                if hash.verify(&bytes).is_err() {
                    self.metrics.invalid_crls += 1;
                    warn!("{}: file has wrong hash.", crl_uri);
                    return Ok(None)
                }
                crl_bytes = Some(bytes);
            }
        }
        let crl_bytes = match crl_bytes {
            Some(some) => some,
            None => {
                self.metrics.invalid_crls += 1;
                warn!(
                    "{}: CRL not listed on manifest.",
                    self.cert.rpki_manifest()
                );
                return Ok(None)
            }
        };

        // Decode and validate the CRL.
        let mut crl = match Crl::decode(crl_bytes.clone()) {
            Ok(crl) => crl,
            Err(_) => {
                self.metrics.invalid_crls += 1;
                warn!("{}: failed to decode CRL.", crl_uri);
                return Ok(None)
            }
        };
        if let Err(err) = crl.verify_signature(
            self.cert.cert().subject_public_key_info()
        ) {
            self.metrics.invalid_crls += 1;
            warn!("{}: {}.", crl_uri, err);
            return Ok(None)
        }
        if crl.is_stale() {
            self.metrics.stale_crls += 1;
            match self.run.validation.stale {
                FilterPolicy::Reject => {
                    warn!("{}: stale CRL.", crl_uri);
                    return Ok(None)
                }
                FilterPolicy::Warn => {
                    warn!("{}: stale CRL.", crl_uri);
                }
                FilterPolicy::Accept => { }
            }
        }

        // Turn on serial caching before looking for the first serial.
        if manifest.len() > CRL_CACHE_LIMIT {
            crl.cache_serials()
        }

        // Finally: has the manifest’s cert been revoked?
        if crl.contains(ee_cert.serial_number()) {
            self.metrics.invalid_manifests += 1;
            warn!(
                "{}: certificate has been revoked.",
                self.cert.rpki_manifest()
            );
            return Ok(None)
        }

        // Phew: All good.
        self.metrics.valid_crls += 1;
        Ok(Some((crl_uri, crl, crl_bytes)))
    }

    /// Process the stored version of the publication point.
    ///
    /// Validates the objects of the currently stored version of the
    /// publication point if there is one.
    ///
    /// Returns a list of all child CAs of this publication point.
    fn process_stored(
        mut self,
        mut store: StoredPoint,
        metrics: &mut RunMetrics,
    ) -> Result<Vec<CaTask<P::PubPoint>>, Failed> {
        let manifest = match store.take_manifest() {
            Some(manifest) => manifest,
            None => {
                // We don’t seem to have this point in the store either.
                // Warn and return.
                warn!(
                    "{}: no valid manifest {} found.",
                    self.cert.uri(), self.cert.rpki_manifest()
                );
                self.metrics.missing_manifests += 1;
                self.reject_point(metrics);
                return Ok(Vec::new())
            }
        };

        let mut manifest = match self.validate_stored_manifest(manifest) {
            Ok(manifest) => manifest,
            Err(_) => {
                self.reject_point(metrics);
                return Ok(Vec::new())
            }
        };

        let mut ca_tasks = Vec::new();
        for object in &mut store {
            let object = match object {
                Ok(object) => object,
                Err(err) => {
                    if err.is_fatal() {
                        error!(
                            "Fatal: failed to read from {}: {}",
                            store.path().display(), err
                        );
                        return Err(Failed)
                    }
                    else {
                        info!(
                            "Ignoring invalid stored publication point \
                             at {}: {}",
                            store.path().display(), err
                        );
                        self.reject_point(metrics);
                        return Ok(Vec::new())
                    }
                }
            };
            if !self.process_object(
                object.uri(), object.content().clone(),
                &mut manifest, &mut ca_tasks
            )? {
                self.reject_point(metrics);
                return Ok(Vec::new())
            }
        }

        self.accept_point(manifest, metrics);
        Ok(ca_tasks)
    }

    /// Tries to validate a stored manifest.
    ///
    /// This is similar to
    /// [`validate_collected_manifest`][Self::validate_collected_manifest]
    /// but has less hassle with the CRL because that is actually included in
    /// the stored manifest.
    fn validate_stored_manifest(
        &mut self,
        stored_manifest: StoredManifest,
    ) -> Result<ValidPointManifest, Failed> {
        // Decode and validate the manifest.
        let manifest = match Manifest::decode(
            stored_manifest.manifest().clone(), self.run.validation.strict
        ) {
            Ok(manifest) => manifest,
            Err(_) => {
                warn!(
                    "{}: failed to decode manifest.",
                    self.cert.rpki_manifest(),
                );
                self.metrics.invalid_manifests += 1;
                return Err(Failed);
            }
        };
        let (ee_cert, content) = match manifest.validate(
            self.cert.cert(), self.run.validation.strict
        ) {
            Ok(some) => some,
            Err(err) => {
                warn!("{}: {}.", self.cert.rpki_manifest(), err);
                self.metrics.invalid_manifests += 1;
                return Err(Failed);
            }
        };
        if content.is_stale() {
            self.metrics.stale_manifests += 1;
            match self.run.validation.stale {
                FilterPolicy::Reject => {
                    warn!("{}: stale manifest", self.cert.rpki_manifest());
                    self.metrics.invalid_manifests += 1;
                    return Err(Failed);
                }
                FilterPolicy::Warn => {
                    warn!("{}: stale manifest", self.cert.rpki_manifest());
                }
                FilterPolicy::Accept => { }
            }
        }

        // Get the CRL URI. We actually only need this for error reporting.
        let crl_uri = match ee_cert.crl_uri() {
            Some(uri) => uri.clone(),
            None => {
                // This should have been ruled out in manifest validation.
                warn!(
                    "{}: manifest without CRL URI.",
                    self.cert.rpki_manifest()
                );
                self.metrics.invalid_manifests += 1;
                return Err(Failed)
            }
        };

        // Decode and validate the CRL.
        let mut crl = match Crl::decode(stored_manifest.crl().clone()) {
            Ok(crl) => crl,
            Err(_) => {
                warn!("{}: failed to decode CRL.", crl_uri);
                self.metrics.invalid_manifests += 1;
                self.metrics.invalid_crls += 1;
                return Err(Failed)
            }
        };
        if let Err(err) = crl.verify_signature(
            self.cert.cert().subject_public_key_info()
        ) {
            warn!("{}: {}.", crl_uri, err);
            self.metrics.invalid_manifests += 1;
            self.metrics.invalid_crls += 1;
            return Err(Failed)
        }
        if crl.is_stale() {
            self.metrics.stale_crls += 1;
            match self.run.validation.stale {
                FilterPolicy::Reject => {
                    warn!("{}: stale CRL.", crl_uri);
                    self.metrics.invalid_manifests += 1;
                    self.metrics.invalid_crls += 1;
                    return Err(Failed)
                }
                FilterPolicy::Warn => {
                    warn!("{}: stale CRL.", crl_uri);
                }
                FilterPolicy::Accept => { }
            }
        }

        // Turn on serial caching before looking for the first serial.
        if content.len() > CRL_CACHE_LIMIT {
            crl.cache_serials()
        }

        // Finally: has the manifest’s cert been revoked?
        //
        // XXX This shouldn’t really happen because if it were we would never
        //     have stored this manifest.
        if crl.contains(ee_cert.serial_number()) {
            warn!(
                "{}: certificate has been revoked.",
                self.cert.rpki_manifest()
            );
            self.metrics.invalid_manifests += 1;
            return Err(Failed)
        }

        self.metrics.valid_manifests += 1;
        self.metrics.valid_crls += 1;
        Ok(ValidPointManifest {
            ee_cert, content, crl_uri, crl,
            manifest_bytes: stored_manifest.manifest().clone(),
            crl_bytes: stored_manifest.crl().clone(),
            metrics: Default::default(),
        })
    }

    // XXX Check metrics generation and concentrate at one central point.

    fn accept_point(
        mut self,
        manifest: ValidPointManifest,
        metrics: &mut RunMetrics,
    ) {
        self.metrics.valid_points += 1;
        self.metrics += manifest.metrics;
        self.apply_metrics(metrics);
        self.processor.commit();
    }

    fn reject_point(
        mut self,
        metrics: &mut RunMetrics,
    ) {
        self.metrics.rejected_points += 1;
        self.apply_metrics(metrics);
        self.processor.cancel(self.cert);
    }

    fn apply_metrics(
        &mut self,
        metrics: &mut RunMetrics,
    ) {
        let repository_index = self.repository_index.unwrap_or_else(|| {
            metrics.repository_index(self.cert)
        });
        self.processor.repository_index(repository_index);
        metrics.apply(
            &self.metrics,
            repository_index,
            self.cert.tal
        );
    }

    /// Processes a single object.
    ///
    /// Returns whether processing should continue or whether the entire (!)
    /// publication point should be disregarded.
    fn process_object(
        &mut self,
        uri: &uri::Rsync,
        content: Bytes,
        manifest: &mut ValidPointManifest,
        ca_task: &mut Vec<CaTask<P::PubPoint>>,
    ) -> Result<bool, Failed> {
        if !self.processor.want(uri)? {
            return Ok(true)
        }

        if uri.ends_with(".cer") {
            self.process_cer(uri, content, manifest, ca_task)?;
        }
        else if uri.ends_with(".roa") {
            self.process_roa(uri, content, manifest)?;
        }
        else if uri.ends_with(".asa") {
            self.process_aspa(uri, content, manifest)?;
        }
        else if uri.ends_with(".gbr") {
            self.process_gbr(uri, content, manifest)?;
        }
        else if uri.ends_with(".crl") {
            if *uri != manifest.crl_uri {
                warn!("{}: stray CRL.", uri);
                manifest.metrics.stray_crls += 1;
            }
        }
        else {
            manifest.metrics.others += 1;
            warn!("{}: unknown object type.", uri);
        }
        Ok(true)
    }

    /// Processes a certificate object.
    fn process_cer(
        &mut self,
        uri: &uri::Rsync,
        content: Bytes,
        manifest: &mut ValidPointManifest,
        ca_task: &mut Vec<CaTask<P::PubPoint>>,
    ) -> Result<(), Failed> {
        let cert = match Cert::decode(content) {
            Ok(cert) => cert,
            Err(_) => {
                warn!("{}: failed to decode certificate.", uri);
                manifest.metrics.invalid_certs += 1;
                return Ok(())
            }
        };

        if cert.key_usage() == KeyUsage::Ca {
            self.process_ca_cer(uri, cert, manifest, ca_task)
        }
        else {
            self.process_router_cert(uri, cert, manifest)
        }
    }

    /// Processes a CA certificate.
    #[allow(clippy::too_many_arguments)]
    fn process_ca_cer(
        &mut self, uri: &uri::Rsync, cert: Cert,
        manifest: &mut ValidPointManifest,
        ca_task: &mut Vec<CaTask<P::PubPoint>>,
    ) -> Result<(), Failed> {
        if self.cert.check_loop(&cert).is_err() {
            warn!("{}: certificate loop detected.", uri);
            manifest.metrics.invalid_certs += 1;
            return Ok(())
        }
        let cert = match cert.validate_ca(
            self.cert.cert(), self.run.validation.strict
        ) {
            Ok(cert) => cert,
            Err(err) => {
                warn!("{}: {}.", uri, err);
                manifest.metrics.invalid_certs += 1;
                return Ok(())
            }
        };
        if let Err(err) = manifest.check_crl(&cert) {
            warn!("{}: {}.", uri, err);
            manifest.metrics.invalid_certs += 1;
            return Ok(())
        }

        let cert = match CaCert::chain(
            self.cert, uri.clone(), cert, self.run.validation.max_ca_depth,
        ) {
            Ok(cert) => cert,
            Err(_) => {
                manifest.metrics.invalid_certs += 1;
                return Ok(())
            }
        };

        manifest.metrics.valid_ca_certs += 1;

        let mut processor = match self.processor.process_ca(
            uri, &cert
        )? {
            Some(processor) => processor,
            None => return Ok(())
        };
        processor.update_refresh(cert.cert().validity().not_after());

        // Defer operation if we need to update the repository part where
        // the CA lives.
        let defer = match self.run.collector.as_ref() {
            Some(collector) => !collector.was_updated(&cert),
            None => false,
        };

        // If we switch repositories, we need to apply our metrics.
        let repository_index = if cert.repository_switch() {
            None
        }
        else {
            self.repository_index
        };

        ca_task.push(CaTask {
            cert, processor, repository_index, defer
        });
        Ok(())
    }

    /// Processes a router certificate.
    fn process_router_cert(
        &mut self, uri: &uri::Rsync, cert: Cert,
        manifest: &mut ValidPointManifest,
    ) -> Result<(), Failed> {
        if let Err(err) = cert.validate_router(
            self.cert.cert(), self.run.validation.strict
        ) {
            warn!("{}: {}.", uri, err);
            manifest.metrics.invalid_certs += 1;
            return Ok(())
        };
        if let Err(err) = manifest.check_crl(&cert) {
            warn!("{}: {}.", uri, err);
            manifest.metrics.invalid_certs += 1;
            return Ok(())
        }
        manifest.metrics.valid_router_certs += 1;
        self.processor.process_router_cert(uri, cert, self.cert)?;
        Ok(())
    }

    /// Processes a ROA object.
    fn process_roa(
        &mut self, uri: &uri::Rsync, content: Bytes,
        manifest: &mut ValidPointManifest,
    ) -> Result<(), Failed> {
        let roa = match Roa::decode(
            content, self.run.validation.strict
        ) {
            Ok(roa) => roa,
            Err(_) => {
                warn!("{}: failed to decode ROA.", uri);
                manifest.metrics.invalid_roas += 1;
                return Ok(())
            }
        };
        match roa.process(
            self.cert.cert(),
            self.run.validation.strict,
            |cert| manifest.check_crl(cert)
        ) {
            Ok((cert, route)) => {
                manifest.metrics.valid_roas += 1;
                self.processor.process_roa(uri, cert, route)?
            }
            Err(err) => {
                manifest.metrics.invalid_roas += 1;
                warn!("{}: {}.", uri, err)
            }
        }
        Ok(())
    }

    /// Process an ASPA object.
    #[allow(unused_variables)]
    fn process_aspa(
        &mut self, uri: &uri::Rsync, content: Bytes,
        manifest: &mut ValidPointManifest,
    ) -> Result<(), Failed> {
        #[cfg(feature = "aspa")] {
            let aspa = match Aspa::decode(
                content, self.run.validation.strict
            ) {
                Ok(aspa) => aspa,
                Err(_) => {
                    warn!("{}: failed to decode ASPA.", uri);
                    manifest.metrics.invalid_aspas += 1;
                    return Ok(())
                }
            };
            match aspa.process(
                self.cert.cert(),
                self.run.validation.strict,
                |cert| manifest.check_crl(cert)
            ) {
                Ok((cert, aspa)) => {
                    manifest.metrics.valid_aspas += 1;
                    self.processor.process_aspa(uri, cert, aspa)?
                }
                Err(err) => {
                    manifest.metrics.invalid_aspas += 1;
                    warn!("{}: {}.", uri, err)
                }
            }
        }
        Ok(())
    }

    /// Processes a Ghostbuster Record.
    fn process_gbr(
        &mut self, uri: &uri::Rsync, content: Bytes,
        manifest: &mut ValidPointManifest,
    ) -> Result<(), Failed> {
        let obj = match SignedObject::decode(
            content, self.run.validation.strict
        ) {
            Ok(obj) => obj,
            Err(_) => {
                warn!("{}: failed to decode GBR.", uri);
                manifest.metrics.invalid_gbrs += 1;
                return Ok(())
            }
        };
        match obj.process(
            self.cert.cert(),
            self.run.validation.strict,
            |cert| manifest.check_crl(cert)
        ) {
            Ok((cert, content)) => {
                manifest.metrics.valid_gbrs += 1;
                self.processor.process_gbr(uri, cert, content)?
            }
            Err(err) => {
                manifest.metrics.invalid_gbrs += 1;
                warn!("{}: {}.", uri, err)
            }
        }
        Ok(())
    }
}


//------------ ValidPointManifest --------------------------------------------

/// All information from a validated manifest.
#[derive(Clone, Debug)]
struct ValidPointManifest {
    /// The EE certificate the manifest was signed with.
    ee_cert: ResourceCert,

    /// The payload of the manifest.
    content: ManifestContent,

    /// The CRL distribution point URI of the manifest.
    ///
    /// This is here separately because it may be `None` in a `ResourceCert`
    /// but can’t be in a valid CA cert.
    crl_uri: uri::Rsync,

    /// The CRL.
    crl: Crl,

    /// The raw bytes of the manifest.
    manifest_bytes: Bytes,

    /// The raw bytes of the CRL.
    crl_bytes: Bytes,

    /// The publication metrics collected while processing the manifest.
    ///
    /// We keep them here separatedly, so we can just zero them out if
    /// processor decides to drop the publication point.
    metrics: PublicationMetrics,
}

impl ValidPointManifest {
    /// Checks whether `cert` has been revoked.
    fn check_crl(&self, cert: &Cert) -> Result<(), ValidationError> {
        let crl_uri = match cert.crl_uri() {
            Some(some) => some,
            None => {
                return Err(InspectionError::new(
                    "certificate has no CRL URI"
                ).into())
            }
        };

        if *crl_uri != self.crl_uri {
            return Err(InspectionError::new(
                "certificate's CRL differs from manifest's"
            ).into())
        }

        if self.crl.contains(cert.serial_number()) {
            return Err(InspectionError::new(
                "certificate has been revoked"
            ).into())
        }

        Ok(())
    }
}


//------------ Task ----------------------------------------------------------

/// Any task that can be queued for delayed processing.
enum Task<'a, P> {
    /// The task is to process a trust anchor locator.
    Tal(TalTask<'a>),

    /// The task is to process a CA.
    Ca(CaTask<P>),
}

impl<'a, P> fmt::Debug for Task<'a, P> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Task::Tal(ref inner) => {
                write!(f, "TalTask {{ tal: {} }}", inner.tal.info().name())
            }
            Task::Ca(ref inner) => {
                write!(
                    f, "CaTask {{ ca_repository: {} }}",
                    inner.cert.ca_repository
                )
            }
        }
    }
}


//------------ TalTask ------------------------------------------------------

/// A task for processing a single trust anchor locator.
struct TalTask<'a> {
    /// A reference to the actual TAL.
    tal: &'a Tal,

    /// The index of this TAL in the metrics.
    index: usize,
}


//------------ CaTask --------------------------------------------------------

/// A task for processing a single CA.
struct CaTask<P> {
    /// The CA certificate of the CA.
    cert: Arc<CaCert>,

    /// The processor for this CA.
    processor: P,

    /// The repository index of we know it already.
    repository_index: Option<usize>,

    /// Defer processing?
    ///
    /// Processing is deferred if the CA lives in a different repository than
    /// its issuing CA:
    defer: bool,
}


//------------ CaCert --------------------------------------------------------

/// A CA certificate plus references to all its parents.
#[derive(Clone, Debug)]
pub struct CaCert {
    /// The CA certificate of this CA.
    cert: ResourceCert,

    /// The certificate’s location.
    ///
    /// Don’t be confused by the type – this is a TAL URI because it can be
    /// an HTTPS URI for TAL certificates. But it definitely isn’t the URI
    /// of the TAL this was derived from, it is the actual URI of the actual
    /// certificate.
    uri: TalUri,

    /// The CA repository URI of the certificate.
    ca_repository: uri::Rsync,

    /// The manifest URI of the certificate.
    rpki_manifest: uri::Rsync,

    /// The parent CA.
    /// 
    /// This will be `None` for a trust anchor certificate.
    parent: Option<Arc<CaCert>>,

    /// The length of the chain of certificates from a trust anchor.
    chain_len: usize,

    /// The index of the TAL in the metrics.
    pub(crate) // XXX
    tal: usize,

    /// The combined validity of the certificate.
    ///
    /// This is derived from the validity of all the parents and the
    /// certificate itself.
    combined_validity: Validity,
}

impl CaCert {
    /// Creates a new CA cert for a trust anchor.
    pub fn root(
        cert: ResourceCert, uri: TalUri, tal: usize
    ) -> Result<Arc<Self>, Failed> {
        Self::new(cert, uri, None, 0, tal)
    }

    /// Creates a new CA cert for an issued CA.
    pub fn chain(
        issuer: &Arc<Self>,
        uri: uri::Rsync,
        cert: ResourceCert,
        max_depth: usize,
    ) -> Result<Arc<Self>, Failed> {
        let chain_len = match issuer.chain_len.checked_add(1) {
            Some(chain_len) => chain_len,
            None => {
                error!(
                    "CA {}: CA depth overrun.",
                    uri
                );
                return Err(Failed)
            }
        };
        if chain_len > max_depth {
            error!(
                "CA {}: CA depth overrun.",
                uri
            );
            return Err(Failed)
        }
        Self::new(
            cert, TalUri::Rsync(uri),
            Some(issuer.clone()), chain_len,
            issuer.tal
        )
    }

    /// Creates a new CA cert from its various parts.
    fn new(
        cert: ResourceCert,
        uri: TalUri, 
        parent: Option<Arc<Self>>,
        chain_len: usize,
        tal: usize,
    ) -> Result<Arc<Self>, Failed> {
        let combined_validity = match parent.as_ref() {
            Some(ca) => cert.validity().trim(ca.combined_validity()),
            None => cert.validity()
        };
        let ca_repository = match cert.ca_repository() {
            Some(uri) => uri.clone(),
            None => {
                // This is actually checked during certificate validation,
                // so this should never happen.
                error!(
                    "CA cert {} has no repository URI. \
                     Why has it not been rejected yet?",
                    uri
                );
                return Err(Failed)
            }
        };
        
        let rpki_manifest = match cert.rpki_manifest() {
            Some(uri) => uri.clone(),
            None => {
                // This is actually checked during certificate validation,
                // so this should never happen.
                error!(
                    "CA cert {} has no manifest URI. \
                     Why has it not been rejected yet?",
                    uri
                );
                return Err(Failed)
            }
        };
        Ok(Arc::new(CaCert {
            cert, uri, ca_repository, rpki_manifest, parent, chain_len, tal,
            combined_validity,
        }))
    }

    /// Checks whether a child cert has appeared in the chain already.
    pub fn check_loop(&self, cert: &Cert) -> Result<(), Failed> {
        self._check_loop(cert.subject_key_identifier())
    }

    /// The actual recursive loop test.
    ///
    /// We are comparing certificates by comparing their subject key
    /// identifiers.
    fn _check_loop(&self, key_id: KeyIdentifier) -> Result<(), Failed> {
        if self.cert.subject_key_identifier() == key_id {
            Err(Failed)
        }
        else if let Some(ref parent) = self.parent {
            parent._check_loop(key_id)
        }
        else {
            Ok(())
        }
    }

    /// Returns a reference to the resource certificate.
    pub fn cert(&self) -> &ResourceCert {
        &self.cert
    }

    /// Returns a reference to the certificate’s URI.
    ///
    /// Note that this really is the URI of the certificate itself despite
    /// the type of `TalUri`. This type is used because TAL certificates
    /// (which are CA certificates) are published with an HTTPS URI rather
    /// than an rsync URI.
    pub fn uri(&self) -> &TalUri {
        &self.uri
    }

    /// Returns a reference the caRepository URI of the certificate.
    pub fn ca_repository(&self) -> &uri::Rsync {
        &self.ca_repository
    }

    /// Returns a reference to the rpkiManifest URI of the certificate.
    pub fn rpki_manifest(&self) -> &uri::Rsync {
        &self.rpki_manifest
    }

    /// Returns a reference to the rpkiNotify URI of the certificate.
    pub fn rpki_notify(&self) -> Option<&uri::Https> {
        self.cert.rpki_notify()
    }

    /// Returns the combined validaty of the whole CA.
    pub fn combined_validity(&self) -> Validity {
        self.combined_validity
    }

    /// Returns whether the CA is in a different repository from its parent.
    ///
    /// This is just a quick check and may report a switch when in fact there
    /// isn’t one.
    pub(crate) // XXX
    fn repository_switch(&self) -> bool {
        let parent = match self.parent.as_ref() {
            Some(parent) => parent,
            None => return true,
        };

        match self.rpki_notify() {
            Some(rpki_notify) => {
                Some(rpki_notify) != parent.rpki_notify()
            }
            None => {
                self.ca_repository.module() != parent.ca_repository.module()
            }
        }
    }
} 


//------------ RunMetrics ----------------------------------------------------

/// The metrics collected during a engine run.
#[derive(Debug, Default)]
struct RunMetrics {
    /// The per-TAL metrics.
    tals: Vec<PublicationMetrics>,

    /// The per-repository metrics.
    repositories: Vec<PublicationMetrics>,

    /// The overall metrics.
    publication: PublicationMetrics,

    /// The indexes of repositories in the repository metrics vec.
    ///
    /// The key is the string representation of the rpkiNotify or rsync
    /// module URI.
    repository_indexes: Arc<Mutex<HashMap<String, usize>>>,
}

impl RunMetrics {
    /// Creates a new value that shares indexes with the current one.
    pub fn fork(&self) -> Self {
        RunMetrics {
            tals: Default::default(),
            repositories: Default::default(),
            publication: Default::default(),
            repository_indexes: self.repository_indexes.clone(),
        }
    }

    /// Returns the index of a repository in the metrics.
    ///
    /// Adds a new repository if necessary.
    pub fn repository_index(&self, cert: &CaCert) -> usize {
        let uri = cert.rpki_notify().map(|uri| {
            Cow::Borrowed(uri.as_str())
        }).unwrap_or_else(|| {
            cert.ca_repository.canonical_module()
        });

        let mut repository_indexes = self.repository_indexes.lock().unwrap();
        if let Some(index) = repository_indexes.get(uri.as_ref()) {
            return *index
        }

        let index = repository_indexes.len();
        repository_indexes.insert(uri.into_owned(), index);
        index
    }

    /// Apply publication metrics.
    pub fn apply(
        &mut self, metrics: &PublicationMetrics,
        repository_index: usize, tal_index: usize
    ) {
        while self.repositories.len() <= repository_index {
            self.repositories.push(Default::default())
        }
        self.repositories[repository_index] += metrics;

        while self.tals.len() <= tal_index {
            self.tals.push(Default::default())
        }
        self.tals[tal_index] += metrics;

        self.publication += metrics;
    }

    /// Prepares the final metrics.
    pub fn prepare_final(&self, target: &mut Metrics) {
        let mut indexes: Vec<_>
            = self.repository_indexes.lock().unwrap().iter().map(|item| {
                (item.0.clone(), *item.1)
            }).collect();
        indexes.sort_by_key(|(_, idx)| *idx);
        target.repositories = indexes.into_iter().map(|(uri, _)| {
            RepositoryMetrics::new(uri)
        }).collect();
    }

    /// Collapse into the final metrics.
    ///
    /// Assumes that the target has been extended to fit all TALs and
    /// repositories.
    ///
    /// This only collapses the publication metrics since those are the ones
    /// collected by the engine.
    pub fn collapse(self, target: &mut Metrics) {
        for (target, metric) in target.tals.iter_mut().zip(self.tals) {
            target.publication += metric
        }
        for (target, metric) in target.repositories.iter_mut().zip(
            self.repositories
        ) {
            target.publication += metric
        }
        target.publication += self.publication;
    }
}


//------------ ProcessRun ----------------------------------------------------

/// A type that can process the valid data from the RPKI.
pub trait ProcessRun: Send + Sync {
    /// The type processing the valid data of a single publication point.
    type PubPoint: ProcessPubPoint;

    /// Processes the given trust anchor.
    ///
    /// If the method wants the content of this trust anchor to be validated
    /// and processed, it returns a processor for it as some success value.
    /// If it rather wishes to skip this trust anchor, it returns `Ok(None)`.
    /// If it wishes to abort processing, it returns an error.
    ///
    /// The `tal_index` argument indicates the index of the TAL in the
    /// metrics produced by the processing run. Similarly, the
    /// `repository_index` argument refers to the index of the repository 
    /// publishing the trust anchor CA’s publication point in the metrics.
    fn process_ta(
        &self, tal: &Tal, uri: &TalUri, cert: &CaCert, tal_index: usize
    ) -> Result<Option<Self::PubPoint>, Failed>;
}


//------------ ProcessPubPoint -----------------------------------------------

/// A type that can process the valid data from an RPKI publication point.
pub trait ProcessPubPoint: Sized + Send + Sync {
    /// Sets the index of repository in the processing run metrics.
    fn repository_index(&mut self, repository_index: usize) {
        let _ = repository_index;
    }

    /// Updates the refresh time for this publication poont.
    fn update_refresh(&mut self, not_after: Time) {
        let _ = not_after;
    }

    /// Determines whether an object with the given URI should be processed.
    ///
    /// The object will only be processed if the method returns `Ok(true)`.
    /// If it returns `Ok(false)`, the object will be skipped quietly. If it
    /// returns an error, the entire processing run will be aborted.
    fn want(&self, uri: &uri::Rsync) -> Result<bool, Failed>;
   
    /// Process the content of a validated CA.
    ///
    /// The method can choose how to proceed. If it chooses to process the CA,
    /// it returns `Ok(Some(value))` with a new processor to be used for this
    /// CA. If it wishes to skip this CA, it returns `Ok(None)`. And if it
    /// wishes to abort processing, it returns an error.
    ///
    /// The `repository_index` argument indicates the index of the repository
    /// publishing the CA’s publication point in the metrics produced by the
    /// processing run.
    fn process_ca(
        &mut self, uri: &uri::Rsync, cert: &CaCert,
    ) -> Result<Option<Self>, Failed>;

    /// Process the content of a validated router certificate.
    ///
    /// The method is given both the URI and the certificate. If it
    /// returns an error, the entire processing run will be aborted.
    fn process_router_cert(
        &mut self, uri: &uri::Rsync, cert: Cert, ca_cert: &CaCert,
    ) -> Result<(), Failed> {
        let _ = (uri, cert, ca_cert);
        Ok(())
    }
 
    /// Process the content of a validated ROA.
    ///
    /// The method is given both the URI and the content of the ROA. If it
    /// returns an error, the entire processing run will be aborted.
    fn process_roa(
        &mut self,
        uri: &uri::Rsync,
        cert: ResourceCert,
        route: RouteOriginAttestation
    ) -> Result<(), Failed> {
        let _ = (uri, cert, route);
        Ok(())
    }

    /// Process the content of a validated ASPA object.
    ///
    /// The method is given both the URI and the content of the ASPA object.
    /// If it returns an error, the entire processing run will be aborted.
    fn process_aspa(
        &mut self,
        uri: &uri::Rsync,
        cert: ResourceCert,
        aspa: AsProviderAttestation,
    ) -> Result<(), Failed> {
        let _ = (uri, cert, aspa);
        Ok(())
    }
 
    /// Process the content of a Ghostbuster Record.
    ///
    /// The method is given both the URI and the raw content of the object
    /// as we currently don’t support parsing of these records.
    ///
    /// If the method returns an error, the entire processing run will be
    /// aborted.
    fn process_gbr(
        &mut self,
        uri: &uri::Rsync,
        cert: ResourceCert,
        content: Bytes
    ) -> Result<(), Failed> {
        let _ = (uri, cert, content);
        Ok(())
    }

    /// Restart processing with an empty data set.
    ///
    /// The method is called if processing has to switch to a different
    /// object set for a publication point. An implementation must drop all
    /// data collected so far and start with an empty set again.
    ///
    /// The method does not indicate whether processing has succeeded or
    /// failed.
    fn restart(&mut self) -> Result<(), Failed>;

    /// Completes processing of the CA.
    ///
    /// The method is called when all objects of the CA have been processed
    /// successfully or have been actively ignored and no error has happend.
    fn commit(self);

    /// Completes processing of an invalid CA.
    ///
    /// The method is called when at least one of the objects published by the
    /// CA is invalid.
    ///
    /// The default implementation does nothing at all.
    fn cancel(self, _cert: &CaCert) {
    }
}


//============ Tests =========================================================

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn dump_empty_cache() {
        let _ = crate::process::Process::init(); // May be inited already.
        let src = tempfile::tempdir().unwrap();
        let target = tempfile::tempdir().unwrap();
        let target = target.path().join("dump");
        let mut config = Config::default_with_paths(src.path().into());
        config.rsync_command = "echo".into();
        config.rsync_args = Some(vec!["some".into()]);
        let engine = Engine::new(&config, true).unwrap();
        engine.dump(&target).unwrap();
    }
}