girt 0.7.2

use std::io;
use std::sync::atomic::{AtomicBool, Ordering};

use super::{
    ExpireFailure, ExpireReport, MaintenanceIsolation, PruneFailure, PruneReport, RepackLimits,
    RetentionPolicy, RetireFailure, RetireReport,
};
use crate::Repository;

/// Known completed phases of one isolated maintenance attempt.
#[derive(Clone, Debug, Default)]
pub struct MaintenanceReport {
    /// Reflog expiry completed; an empty report means no records qualified.
    pub expired: Option<ExpireReport>,
    /// A replacement pack was verified and eligible old packs were retired.
    pub retired: Option<RetireReport>,
    /// Old unreachable primary loose objects were swept.
    pub pruned: Option<PruneReport>,
}

/// Why maintenance stopped; a phase error carries that phase's partial effects.
#[derive(Debug, thiserror::Error)]
pub enum MaintenanceCause {
    /// A pinned pack/index changed or a content read found damage before this mutation boundary.
    #[error(transparent)]
    PackChanged(Box<crate::ObjectReadError>),
    /// The caller could not hold a repository-wide exclusion boundary.
    #[error("maintenance isolation unavailable")]
    Isolation(#[source] io::Error),
    /// Directory durability for destructive publication is not established on this platform.
    #[error("composed maintenance is unsupported on this platform")]
    UnsupportedPlatform,
    /// Cancellation was observed before a phase began.
    #[error("maintenance cancelled")]
    Cancelled,
    /// A bounded plan or input observation was incomplete; no phase has started.
    #[error("retention scan incomplete: {0}")]
    Incomplete(String),
    /// An input changed after planning; retry with a fresh isolated plan.
    #[error("maintenance inputs changed")]
    Changed,
    /// Reflog expiry stopped; inspect its partial report and uncertain source or stack.
    #[error(transparent)]
    Expire(Box<ExpireFailure>),
    /// Pack retirement stopped; inspect its visible publication and old-artifact removals.
    #[error(transparent)]
    Retire(Box<RetireFailure>),
    /// Loose pruning stopped; inspect its completed removals and uncertain target.
    #[error(transparent)]
    Prune(Box<PruneFailure>),
}

/// Failure with completed earlier phases and a partial current phase in its cause.
#[derive(Debug, thiserror::Error)]
#[error("maintenance failed")]
pub struct MaintenanceFailure {
    /// The phase that stopped.
    #[source]
    pub cause: MaintenanceCause,
    /// Phases completed before the failure.
    pub report: Box<MaintenanceReport>,
}

impl Repository {
    /// Expires reflogs, replaces old packs, then prunes old unreachable loose objects.
    ///
    /// The caller's [`MaintenanceIsolation`] guard must exclude external Git and girt writers,
    /// old readers and alternate-store dependents for the entire sequence. One bounded retention
    /// plan serves all phases. Input fingerprints are revalidated before mutation, with exact
    /// phase outputs advancing the observation. An external change refuses the attempt; a new
    /// isolated call re-plans. The graph is not re-walked per phase.
    /// Expiry uses the policy cutoffs; pack retirement then retains every remaining history,
    /// protected pack and alternate, regardless of those cutoffs. Loose pruning also retains all
    /// remaining histories. An earlier phase's success does not authorize a later deletion by
    /// itself. A failed phase stops the sequence and reports known earlier effects plus that
    /// phase's partial effects. Retry with a new isolation guard and fresh scans. On non-Unix
    /// platforms the sequence refuses before any publication or deletion.
    ///
    /// # Errors
    ///
    /// Isolation refusal, unsupported platform, cancellation and any phase failure preserve the
    /// completed-phase report and the current phase's partial result when applicable.
    pub fn run_maintenance<I: MaintenanceIsolation>(
        &self,
        isolation: &mut I,
        policy: &RetentionPolicy,
        limits: RepackLimits,
        cancel: &AtomicBool,
    ) -> Result<MaintenanceReport, MaintenanceFailure> {
        if cancel.load(Ordering::Relaxed) {
            return Err(failed(
                MaintenanceCause::Cancelled,
                MaintenanceReport::default(),
            ));
        }
        let _guard = isolation.acquire(self).map_err(|error| {
            failed(
                MaintenanceCause::Isolation(error),
                MaintenanceReport::default(),
            )
        })?;
        #[cfg(not(unix))]
        {
            let _ = (policy, limits);
            Err(failed(
                MaintenanceCause::UnsupportedPlatform,
                MaintenanceReport::default(),
            ))
        }
        #[cfg(unix)]
        self.run_maintenance_exclusive(policy, limits, cancel, || {})
    }

    /// Expires reflogs and prunes old unreachable loose objects under one isolation guard.
    ///
    /// Builds one bounded retention plan. Before either phase mutates storage, fingerprints of
    /// refs, histories, worktree metadata, indexes, shallow state, loose generations, packs and
    /// alternate topology must still match. Expiry advances the observation only for its exact
    /// outputs; pruning uses the plan's post-expiry required closure. Pack files stay untouched.
    /// External changes refuse the attempt; retry under a new guard to re-plan.
    ///
    /// # Errors
    ///
    /// Returns isolation, incomplete/changed input, cancellation or phase errors, preserving any
    /// completed expiry and partial pruning. Non-Unix hosts refuse before mutation.
    pub fn collect_garbage<I: MaintenanceIsolation>(
        &self,
        isolation: &mut I,
        policy: &RetentionPolicy,
        cancel: &AtomicBool,
    ) -> Result<MaintenanceReport, MaintenanceFailure> {
        self.collect_garbage_with_checkpoint(isolation, policy, cancel, || {})
    }

    /// Collects garbage with an observation checkpoint after planning and before mutation.
    ///
    /// `after_plan` runs synchronously while the caller's isolation guard is held. It may inspect
    /// progress or coordinate a deterministic race test. Any input changes it causes refuse the
    /// attempt before mutation. All other contracts are those of [`Self::collect_garbage`].
    ///
    /// # Errors
    ///
    /// Returns the errors and completed effects described by [`Self::collect_garbage`].
    pub fn collect_garbage_with_checkpoint<I: MaintenanceIsolation>(
        &self,
        isolation: &mut I,
        policy: &RetentionPolicy,
        cancel: &AtomicBool,
        after_plan: impl FnOnce(),
    ) -> Result<MaintenanceReport, MaintenanceFailure> {
        if cancel.load(Ordering::Relaxed) {
            return Err(failed(
                MaintenanceCause::Cancelled,
                MaintenanceReport::default(),
            ));
        }
        let _guard = isolation.acquire(self).map_err(|error| {
            failed(
                MaintenanceCause::Isolation(error),
                MaintenanceReport::default(),
            )
        })?;
        #[cfg(not(unix))]
        {
            let _ = (policy, after_plan);
            Err(failed(
                MaintenanceCause::UnsupportedPlatform,
                MaintenanceReport::default(),
            ))
        }
        #[cfg(unix)]
        self.maintain_exclusive(policy, None, cancel, after_plan, || {}, || {})
    }

    #[cfg(unix)]
    fn run_maintenance_exclusive(
        &self,
        policy: &RetentionPolicy,
        limits: RepackLimits,
        cancel: &AtomicBool,
        after_expiry: impl FnOnce(),
    ) -> Result<MaintenanceReport, MaintenanceFailure> {
        self.maintain_exclusive(policy, Some(limits), cancel, || {}, after_expiry, || {})
    }

    #[cfg(unix)]
    fn maintain_exclusive(
        &self,
        policy: &RetentionPolicy,
        repack: Option<RepackLimits>,
        cancel: &AtomicBool,
        after_plan: impl FnOnce(),
        after_expiry: impl FnOnce(),
        after_retirement: impl FnOnce(),
    ) -> Result<MaintenanceReport, MaintenanceFailure> {
        let _headers = crate::pack::HeaderScope::new();
        let mut report = MaintenanceReport::default();
        let mut session = super::inputs::Session::new(self, policy, cancel).map_err(|reason| {
            failed(
                if cancel.load(Ordering::Relaxed) {
                    MaintenanceCause::Cancelled
                } else {
                    MaintenanceCause::Incomplete(reason)
                },
                report.clone(),
            )
        })?;
        after_plan();
        if cancel.load(Ordering::Relaxed) {
            return Err(failed(MaintenanceCause::Cancelled, report));
        }
        session
            .plan
            .check_packs_unchanged(cancel)
            .map_err(|error| {
                failed(
                    MaintenanceCause::PackChanged(Box::new(error)),
                    report.clone(),
                )
            })?;
        session.validate(self, policy, cancel).map_err(|_| {
            failed(
                if cancel.load(Ordering::Relaxed) {
                    MaintenanceCause::Cancelled
                } else {
                    MaintenanceCause::Changed
                },
                report.clone(),
            )
        })?;
        let expired = self
            .expire_reflogs_planned(policy, cancel, &mut session)
            .map_err(|error| failed(MaintenanceCause::Expire(Box::new(error)), report.clone()))?;
        report.expired = Some(expired);
        session.plan.reachable = session.plan.required.clone();
        session.plan.roots = session.plan.strong_roots.clone();
        session.plan.reflog_expiry_candidates.clear();
        after_expiry();
        if cancel.load(Ordering::Relaxed) {
            return Err(failed(MaintenanceCause::Cancelled, report));
        }
        if let Some(limits) = repack {
            let retired = self
                .retire_planned(policy, limits, cancel, &mut session)
                .map_err(|error| {
                    failed(MaintenanceCause::Retire(Box::new(error)), report.clone())
                })?;
            let changes: Vec<_> = retired
                .removed
                .iter()
                .map(|path| (path.clone(), None))
                .collect();
            report.retired = Some(retired);
            after_retirement();
            if cancel.load(Ordering::Relaxed) {
                return Err(failed(MaintenanceCause::Cancelled, report));
            }
            let observed =
                super::inputs::Inputs::observe(self, policy, cancel).map_err(|reason| {
                    failed(
                        if cancel.load(Ordering::Relaxed) {
                            MaintenanceCause::Cancelled
                        } else {
                            MaintenanceCause::Incomplete(reason)
                        },
                        report.clone(),
                    )
                })?;
            session.inputs.accept(observed, &changes).map_err(|_| {
                failed(
                    if cancel.load(Ordering::Relaxed) {
                        MaintenanceCause::Cancelled
                    } else {
                        MaintenanceCause::Changed
                    },
                    report.clone(),
                )
            })?;
        }
        if cancel.load(Ordering::Relaxed) {
            return Err(failed(MaintenanceCause::Cancelled, report));
        }
        let pruned = self
            .prune_planned(policy, cancel, &session)
            .map_err(|error| failed(MaintenanceCause::Prune(Box::new(error)), report.clone()))?;
        report.pruned = Some(pruned);
        Ok(report)
    }
}

fn failed(cause: MaintenanceCause, report: MaintenanceReport) -> MaintenanceFailure {
    MaintenanceFailure {
        cause,
        report: Box::new(report),
    }
}

#[cfg(all(test, unix))]
mod tests {
    use std::process::Command;

    use super::*;

    #[test]
    fn cancellation_after_expiry_reports_completed_prefix() {
        let root = tempfile::tempdir().unwrap();
        assert!(
            Command::new("git")
                .args([
                    "init",
                    "--bare",
                    "--initial-branch=main",
                    "--template=",
                    root.path().to_str().unwrap(),
                ])
                .output()
                .unwrap()
                .status
                .success()
        );
        let repository = Repository::open(root.path()).unwrap();
        let cancel = AtomicBool::new(false);
        let error = repository
            .run_maintenance_exclusive(
                &RetentionPolicy::default(),
                RepackLimits::default(),
                &cancel,
                || cancel.store(true, Ordering::Relaxed),
            )
            .unwrap_err();
        assert!(matches!(error.cause, MaintenanceCause::Cancelled));
        assert!(error.report.expired.is_some());
        assert!(error.report.retired.is_none());
        assert!(error.report.pruned.is_none());
    }
    #[rstest::rstest]
    #[case::sha1("sha1")]
    #[case::sha256("sha256")]
    fn ref_change_after_expiry_refuses_prune(#[case] format: &str) {
        let root = tempfile::tempdir().unwrap();
        let output = isolated_git(root.path())
            .args([
                "init",
                "--bare",
                "--template=",
                &format!("--object-format={format}"),
                root.path().to_str().unwrap(),
            ])
            .output()
            .unwrap();
        assert!(output.status.success());
        let repository = Repository::open(root.path()).unwrap();
        let blob = repository
            .loose_objects()
            .write_blob(b"old orphan")
            .unwrap();
        let error = repository
            .maintain_exclusive(
                &RetentionPolicy {
                    recent_cutoff: std::time::SystemTime::now()
                        + std::time::Duration::from_secs(60),
                    ..Default::default()
                },
                None,
                &AtomicBool::new(false),
                || {},
                || {
                    assert!(
                        isolated_git(root.path())
                            .current_dir(root.path())
                            .args(["update-ref", "refs/tags/saved", &blob.to_string()])
                            .output()
                            .unwrap()
                            .status
                            .success()
                    );
                },
                || {},
            )
            .unwrap_err();
        assert!(
            matches!(error.cause, MaintenanceCause::Prune(ref failure) if matches!(failure.cause, super::super::PruneCause::Changed))
        );
        assert!(error.report.expired.is_some());
        assert!(error.report.pruned.is_none());
        assert!(
            isolated_git(root.path())
                .current_dir(root.path())
                .args(["cat-file", "-e", &blob.to_string()])
                .output()
                .unwrap()
                .status
                .success()
        );
    }
    #[test]
    fn cancellation_after_retirement_keeps_completed_report() {
        let root = tempfile::tempdir().unwrap();
        assert!(
            isolated_git(root.path())
                .args(["init", "--bare", "--template=", "."])
                .output()
                .unwrap()
                .status
                .success()
        );
        let repository = Repository::open(root.path()).unwrap();
        let cancel = AtomicBool::new(false);
        let error = repository
            .maintain_exclusive(
                &RetentionPolicy::default(),
                Some(RepackLimits::default()),
                &cancel,
                || {},
                || {},
                || cancel.store(true, Ordering::Relaxed),
            )
            .unwrap_err();
        assert!(matches!(error.cause, MaintenanceCause::Cancelled));
        assert!(error.report.expired.is_some());
        assert!(error.report.retired.as_ref().unwrap().durable);
        assert!(error.report.pruned.is_none());
    }

    fn isolated_git(root: &std::path::Path) -> Command {
        let mut command = Command::new("git");
        for (key, _) in std::env::vars_os() {
            if key.to_string_lossy().starts_with("GIT_") {
                command.env_remove(key);
            }
        }
        command
            .current_dir(root)
            .env("GIT_CONFIG_NOSYSTEM", "1")
            .env("GIT_CONFIG_GLOBAL", root.join("absent-config"));
        command
    }
    #[rstest::rstest]
    #[case::truncate(true)]
    #[case::overwrite(false)]
    fn warmed_pack_change_refuses_maintenance(#[case] truncate: bool) {
        let (_root, repo, policy, pack) = super::super::walk_tests::header_fixture();
        let before = std::fs::read_dir(repo.object_dir().join("pack"))
            .unwrap()
            .count();
        let error = repo
            .maintain_exclusive(
                &policy,
                Some(RepackLimits::trusted()),
                &AtomicBool::new(false),
                || super::super::walk_tests::change_pack(&pack, truncate),
                || {},
                || {},
            )
            .unwrap_err();
        assert!(matches!(&error.cause, MaintenanceCause::PackChanged(source)
            if matches!(source.as_ref(), crate::ObjectReadError::PackChanged { path } if path == &pack)));
        assert!(error.report.expired.is_none());
        assert!(error.report.retired.is_none());
        assert!(error.report.pruned.is_none());
        assert_eq!(
            std::fs::read_dir(repo.object_dir().join("pack"))
                .unwrap()
                .count(),
            before
        );
    }
}