imagegen-bridge-artifacts 0.1.0

//! Atomic, collision-safe artifact publication.

use std::{
    fs,
    io::Write,
    path::{Path, PathBuf},
    time::{Duration, SystemTime, UNIX_EPOCH},
};

use imagegen_bridge_core::{ArtifactCollisionPolicy, BridgeError, ErrorCode, OutputFormat};
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use tempfile::NamedTempFile;
use uuid::Uuid;

use crate::{ImageLimits, ImageMetadata, inspect_image};

const OWNERSHIP_DIRECTORY: &str = ".imagegen-bridge-ownership";
const MAX_MARKER_BYTES: u64 = 4 * 1024;
const MAX_SIDECAR_BYTES: u64 = 1024 * 1024;

/// Bridge-owned artifact returned to the runtime.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StoredArtifact {
    /// Opaque public identifier.
    pub id: String,
    /// Safe single-component filename.
    pub name: String,
    /// Internal absolute path; never expose this directly to remote clients.
    pub path: PathBuf,
    /// Verified image metadata.
    pub metadata: ImageMetadata,
}

/// Portable reference to an attached generation-metadata sidecar.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StoredSidecar {
    /// Safe relative name below the artifact root.
    pub name: String,
}

/// Verified bridge-owned artifact bytes for trusted delivery code.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StoredArtifactContent {
    /// Opaque artifact identifier.
    pub id: String,
    /// Portable relative artifact name.
    pub name: String,
    /// Independently verified encoded image bytes.
    pub bytes: Vec<u8>,
    /// Verified image properties and checksum.
    pub metadata: ImageMetadata,
}

/// Per-request artifact placement below the configured owned root.
#[derive(Debug, Clone, Copy, Default)]
pub struct ArtifactPublication<'a> {
    /// Portable relative directory, or the root when absent.
    pub directory: Option<&'a str>,
    /// Exact single-image filename, or a generated UUID name when absent.
    pub filename: Option<&'a str>,
    /// Behavior when the explicit filename exists.
    pub collision: ArtifactCollisionPolicy,
}

/// Publishes verified images beneath one owned output root.
#[derive(Debug, Clone)]
pub struct ArtifactStore {
    root: PathBuf,
    ownership_root: PathBuf,
    limits: ImageLimits,
}

/// Bounded policy for deleting bridge-owned artifacts.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct RetentionPolicy {
    /// Delete artifacts at least this old.
    pub max_age: Duration,
    /// Optional maximum retained artifact count, keeping newest valid records.
    pub max_artifacts: Option<usize>,
    /// Hard bound on ownership records inspected per cleanup pass.
    pub max_scan_entries: usize,
}

impl Default for RetentionPolicy {
    fn default() -> Self {
        Self {
            max_age: Duration::from_secs(7 * 24 * 60 * 60),
            max_artifacts: None,
            max_scan_entries: 100_000,
        }
    }
}

/// Safe aggregate result from one retention pass.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct CleanupReport {
    /// Ownership entries inspected.
    pub scanned: usize,
    /// Verified owned artifacts and markers removed.
    pub deleted: usize,
    /// Invalid, changed, missing, or otherwise non-deletable records.
    pub skipped: usize,
    /// Whether the scan stopped at its configured entry bound.
    pub scan_limit_reached: bool,
}

/// Aggregate result from one bounded ownership repair pass.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct ArtifactRepairReport {
    /// Ownership entries inspected.
    pub scanned: usize,
    /// Fully valid artifact records requiring no repair.
    pub healthy: usize,
    /// Valid ownership records whose artifact file is absent.
    pub orphaned_records: usize,
    /// Valid artifacts whose recorded metadata sidecar is absent.
    pub missing_sidecars: usize,
    /// Orphan records removed or sidecar references cleared.
    pub repaired: usize,
    /// Invalid, changed, or otherwise unsafe records left untouched.
    pub skipped: usize,
    /// Whether the scan stopped at its configured entry bound.
    pub scan_limit_reached: bool,
}

/// Selects whether an orphan-repair pass only reports or also applies repairs.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ArtifactRepairMode {
    /// Inspect storage without mutating it.
    Audit,
    /// Apply only repairs that can be proven safe from ownership records.
    Apply,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
struct OwnershipRecord {
    version: u8,
    id: String,
    name: String,
    created_at: u64,
    sha256: String,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    sidecar_name: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    sidecar_sha256: Option<String>,
}

struct OwnedCandidate {
    marker: PathBuf,
    artifact: PathBuf,
    sidecar: Option<PathBuf>,
    record: OwnershipRecord,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum SidecarState {
    None,
    Missing,
    Valid,
    Invalid,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum OwnedPathState {
    Missing,
    Regular(u64),
    Invalid,
}

impl ArtifactStore {
    /// Creates or opens an artifact root.
    pub fn new(root: impl Into<PathBuf>, limits: ImageLimits) -> Result<Self, BridgeError> {
        let root = root.into();
        fs::create_dir_all(&root)
            .map_err(|error| artifact_error(format!("could not create artifact root: {error}")))?;
        let root = fs::canonicalize(root)
            .map_err(|error| artifact_error(format!("could not open artifact root: {error}")))?;
        if !root.is_dir() {
            return Err(artifact_error("artifact root is not a directory"));
        }
        let ownership_path = root.join(OWNERSHIP_DIRECTORY);
        fs::create_dir_all(&ownership_path).map_err(|error| {
            artifact_error(format!("could not create artifact ownership root: {error}"))
        })?;
        if fs::symlink_metadata(&ownership_path)
            .map_err(|error| {
                artifact_error(format!(
                    "could not inspect artifact ownership root: {error}"
                ))
            })?
            .file_type()
            .is_symlink()
        {
            return Err(artifact_error(
                "artifact ownership root must not be a symbolic link",
            ));
        }
        let ownership_root = fs::canonicalize(ownership_path).map_err(|error| {
            artifact_error(format!("could not open artifact ownership root: {error}"))
        })?;
        if !ownership_root.is_dir()
            || ownership_root.parent() != Some(root.as_path())
            || !ownership_root.starts_with(&root)
            || ownership_root.file_name().and_then(|value| value.to_str())
                != Some(OWNERSHIP_DIRECTORY)
        {
            return Err(artifact_error(
                "artifact ownership root must be a real child directory",
            ));
        }
        Ok(Self {
            root,
            ownership_root,
            limits,
        })
    }

    /// Verifies and atomically publishes one image without overwriting a file.
    pub fn publish(
        &self,
        bytes: &[u8],
        filename_prefix: Option<&str>,
        expected_format: Option<OutputFormat>,
    ) -> Result<StoredArtifact, BridgeError> {
        self.publish_with_options(
            bytes,
            filename_prefix,
            expected_format,
            ArtifactPublication::default(),
        )
    }

    /// Verifies and atomically publishes one image at a constrained relative location.
    pub fn publish_with_options(
        &self,
        bytes: &[u8],
        filename_prefix: Option<&str>,
        expected_format: Option<OutputFormat>,
        publication: ArtifactPublication<'_>,
    ) -> Result<StoredArtifact, BridgeError> {
        let metadata = inspect_image(bytes, self.limits).map_err(|error| BridgeError {
            code: ErrorCode::Artifact,
            ..error
        })?;
        if expected_format.is_some_and(|expected| expected != metadata.format) {
            return Err(artifact_error(
                "generated image format does not match the effective request",
            ));
        }

        let id = Uuid::now_v7().to_string();
        let (directory, portable_directory) = self.publication_directory(publication.directory)?;
        if let Some(filename) = publication.filename
            && !safe_filename(filename, metadata.format)
        {
            return Err(artifact_error(
                "output filename must be a safe component with a matching image extension",
            ));
        }
        let requested_name = publication.filename.map_or_else(
            || {
                let prefix = sanitize_prefix(filename_prefix.unwrap_or("image"));
                format!("{prefix}-{id}.{}", extension(metadata.format))
            },
            |filename| filename_with_extension(filename, metadata.format),
        );
        let (destination, filename) = publish_noclobber(
            &directory,
            &requested_name,
            bytes,
            publication.collision,
            publication.filename.is_some(),
        )?;
        if let Err(error) = sync_directory(&directory) {
            let _ = fs::remove_file(&destination);
            return Err(error);
        }

        let name = portable_directory.map_or_else(
            || filename.clone(),
            |directory| format!("{directory}/{filename}"),
        );

        let record = OwnershipRecord {
            version: 1,
            id: id.clone(),
            name: name.clone(),
            created_at: unix_timestamp(SystemTime::now())?,
            sha256: metadata.sha256.clone(),
            sidecar_name: None,
            sidecar_sha256: None,
        };
        if let Err(error) = self.publish_ownership(&record) {
            let _ = fs::remove_file(&destination);
            let _ = sync_directory(&self.root);
            return Err(error);
        }

        Ok(StoredArtifact {
            id,
            name,
            path: destination,
            metadata,
        })
    }

    /// Atomically attaches bounded JSON metadata to an owned artifact.
    pub fn attach_metadata(
        &self,
        artifact_id: &str,
        artifact_name: &str,
        encoded: &[u8],
    ) -> Result<StoredSidecar, BridgeError> {
        if Uuid::parse_str(artifact_id).is_err() || !safe_relative(artifact_name) {
            return Err(artifact_error("artifact identity is invalid"));
        }
        if encoded.is_empty()
            || u64::try_from(encoded.len()).unwrap_or(u64::MAX) > MAX_SIDECAR_BYTES
            || !matches!(
                serde_json::from_slice::<serde_json::Value>(encoded),
                Ok(serde_json::Value::Object(_))
            )
        {
            return Err(artifact_error(
                "artifact metadata must be a bounded JSON object",
            ));
        }
        let marker = self.ownership_root.join(format!("{artifact_id}.json"));
        let mut candidate = self
            .read_candidate(&marker)
            .map_err(|()| artifact_error("artifact ownership record is invalid"))?;
        if candidate.record.name != artifact_name
            || candidate.record.sidecar_name.is_some()
            || candidate.record.sidecar_sha256.is_some()
            || self.verify_candidate(&candidate).is_err()
        {
            return Err(artifact_error(
                "artifact metadata cannot be attached to this artifact",
            ));
        }
        let directory = candidate
            .artifact
            .parent()
            .ok_or_else(|| artifact_error("artifact directory is invalid"))?;
        let filename = format!("metadata-{artifact_id}.json");
        let destination = directory.join(&filename);
        let mut temporary = NamedTempFile::new_in(directory)
            .map_err(|_| artifact_error("could not create metadata sidecar"))?;
        temporary
            .write_all(encoded)
            .and_then(|()| temporary.as_file().sync_all())
            .map_err(|_| artifact_error("could not write metadata sidecar"))?;
        temporary
            .persist_noclobber(&destination)
            .map_err(|_| artifact_error("could not publish metadata sidecar without overwrite"))?;
        sync_directory(directory)?;

        let portable_name = Path::new(artifact_name)
            .parent()
            .filter(|parent| !parent.as_os_str().is_empty())
            .and_then(Path::to_str)
            .map_or_else(|| filename.clone(), |parent| format!("{parent}/{filename}"));
        candidate.record.sidecar_name = Some(portable_name.clone());
        candidate.record.sidecar_sha256 =
            Some(base16ct::lower::encode_string(&Sha256::digest(encoded)));
        if let Err(error) = self.replace_ownership(&candidate.record) {
            let _ = fs::remove_file(&destination);
            let _ = sync_directory(directory);
            return Err(error);
        }
        Ok(StoredSidecar {
            name: portable_name,
        })
    }

    /// Reads one ownership-verified artifact without exposing its filesystem path.
    pub fn read(&self, artifact_id: &str) -> Result<StoredArtifactContent, BridgeError> {
        if Uuid::parse_str(artifact_id).is_err() {
            return Err(artifact_error("artifact identity is invalid"));
        }
        let marker = self.ownership_root.join(format!("{artifact_id}.json"));
        let candidate = self
            .read_candidate(&marker)
            .map_err(|()| artifact_error("artifact was not found or is invalid"))?;
        self.verify_candidate(&candidate)
            .map_err(|()| artifact_error("artifact was not found or is invalid"))?;
        let bytes = fs::read(&candidate.artifact)
            .map_err(|_| artifact_error("artifact could not be read"))?;
        let metadata = inspect_image(&bytes, self.limits)
            .map_err(|_| artifact_error("artifact failed delivery verification"))?;
        Ok(StoredArtifactContent {
            id: candidate.record.id,
            name: candidate.record.name,
            bytes,
            metadata,
        })
    }

    fn publication_directory(
        &self,
        relative: Option<&str>,
    ) -> Result<(PathBuf, Option<String>), BridgeError> {
        let Some(relative) = relative else {
            return Ok((self.root.clone(), None));
        };
        if !safe_relative(relative) {
            return Err(artifact_error(
                "output directory is not a safe relative path",
            ));
        }
        let mut directory = self.root.clone();
        for component in relative.split('/') {
            directory.push(component);
            match fs::symlink_metadata(&directory) {
                Ok(metadata) if metadata.file_type().is_dir() => {}
                Ok(_) => {
                    return Err(artifact_error(
                        "output directory component must not be a file or symlink",
                    ));
                }
                Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
                    fs::create_dir(&directory).map_err(|_| {
                        artifact_error("could not create output directory component")
                    })?;
                }
                Err(_) => return Err(artifact_error("could not inspect output directory")),
            }
        }
        let canonical = fs::canonicalize(&directory)
            .map_err(|_| artifact_error("could not open output directory"))?;
        if !canonical.starts_with(&self.root) || canonical == self.ownership_root {
            return Err(artifact_error("output directory escapes the artifact root"));
        }
        Ok((canonical, Some(relative.to_owned())))
    }

    /// Returns the private artifact root for trusted runtime code.
    #[must_use]
    pub fn root(&self) -> &Path {
        &self.root
    }

    /// Deletes only verified artifacts with bridge-created ownership records.
    pub fn cleanup(
        &self,
        policy: RetentionPolicy,
        now: SystemTime,
    ) -> Result<CleanupReport, BridgeError> {
        if policy.max_scan_entries == 0 {
            return Err(artifact_error(
                "retention scan limit must be greater than zero",
            ));
        }
        self.verify_ownership_root()?;
        let now = unix_timestamp(now)?;
        let cutoff = now.saturating_sub(policy.max_age.as_secs());
        let mut report = CleanupReport::default();
        let mut candidates = Vec::new();
        for entry in fs::read_dir(&self.ownership_root)
            .map_err(|error| artifact_error(format!("could not scan ownership records: {error}")))?
        {
            if report.scanned >= policy.max_scan_entries {
                report.scan_limit_reached = true;
                break;
            }
            report.scanned += 1;
            let Ok(entry) = entry else {
                report.skipped += 1;
                continue;
            };
            match self.read_candidate(&entry.path()) {
                Ok(candidate) if self.verify_candidate(&candidate).is_ok() => {
                    candidates.push(candidate);
                }
                Err(()) | Ok(_) => report.skipped += 1,
            }
        }

        candidates.sort_by(|left, right| {
            right
                .record
                .created_at
                .cmp(&left.record.created_at)
                .then_with(|| right.record.id.cmp(&left.record.id))
        });
        for (index, candidate) in candidates.into_iter().enumerate() {
            let exceeds_count = policy.max_artifacts.is_some_and(|maximum| index >= maximum);
            let expired = candidate.record.created_at <= cutoff;
            if !expired && !exceeds_count {
                continue;
            }
            if self.remove_verified(&candidate).is_ok() {
                report.deleted += 1;
            } else {
                report.skipped += 1;
            }
        }
        Ok(report)
    }

    /// Audits or repairs only unambiguous ownership-record orphans.
    ///
    /// Audit mode is non-mutating. Apply mode
    /// removes a valid marker only when its artifact is absent, optionally
    /// removing an unchanged owned sidecar, or clears a missing-sidecar
    /// reference from an otherwise valid artifact. Invalid or changed content
    /// is always left untouched.
    pub fn repair_orphans(
        &self,
        max_scan_entries: usize,
        mode: ArtifactRepairMode,
    ) -> Result<ArtifactRepairReport, BridgeError> {
        if max_scan_entries == 0 {
            return Err(artifact_error(
                "artifact repair scan limit must be greater than zero",
            ));
        }
        self.verify_ownership_root()?;
        let mut report = ArtifactRepairReport::default();
        for entry in fs::read_dir(&self.ownership_root)
            .map_err(|error| artifact_error(format!("could not scan ownership records: {error}")))?
        {
            if report.scanned >= max_scan_entries {
                report.scan_limit_reached = true;
                break;
            }
            report.scanned += 1;
            let Ok(entry) = entry else {
                report.skipped += 1;
                continue;
            };
            let Ok(candidate) = self.read_candidate(&entry.path()) else {
                report.skipped += 1;
                continue;
            };
            if self.verify_artifact(&candidate).is_ok() {
                match self.sidecar_state(&candidate) {
                    SidecarState::None | SidecarState::Valid => report.healthy += 1,
                    SidecarState::Missing => {
                        report.missing_sidecars += 1;
                        if mode == ArtifactRepairMode::Apply {
                            if self.clear_missing_sidecar(&candidate).is_ok() {
                                report.repaired += 1;
                            } else {
                                report.skipped += 1;
                            }
                        }
                    }
                    SidecarState::Invalid => report.skipped += 1,
                }
            } else if self.owned_path_state(&candidate.artifact) == OwnedPathState::Missing {
                report.orphaned_records += 1;
                match self.sidecar_state(&candidate) {
                    SidecarState::None | SidecarState::Missing | SidecarState::Valid => {
                        if mode == ArtifactRepairMode::Apply {
                            if self.remove_orphaned_record(&candidate).is_ok() {
                                report.repaired += 1;
                            } else {
                                report.skipped += 1;
                            }
                        }
                    }
                    SidecarState::Invalid => report.skipped += 1,
                }
            } else {
                report.skipped += 1;
            }
        }
        Ok(report)
    }

    fn publish_ownership(&self, record: &OwnershipRecord) -> Result<(), BridgeError> {
        self.verify_ownership_root()?;
        let encoded = serde_json::to_vec(record)
            .map_err(|_| artifact_error("could not encode artifact ownership record"))?;
        if u64::try_from(encoded.len()).unwrap_or(u64::MAX) > MAX_MARKER_BYTES {
            return Err(artifact_error("artifact ownership record is too large"));
        }
        let destination = self.ownership_root.join(format!("{}.json", record.id));
        let mut temporary = NamedTempFile::new_in(&self.ownership_root).map_err(|error| {
            artifact_error(format!("could not create ownership record: {error}"))
        })?;
        temporary
            .write_all(&encoded)
            .and_then(|()| temporary.as_file().sync_all())
            .map_err(|error| {
                artifact_error(format!("could not write ownership record: {error}"))
            })?;
        temporary.persist_noclobber(destination).map_err(|error| {
            artifact_error(format!("could not publish ownership record: {error}"))
        })?;
        sync_directory(&self.ownership_root)
    }

    fn replace_ownership(&self, record: &OwnershipRecord) -> Result<(), BridgeError> {
        self.verify_ownership_root()?;
        let encoded = serde_json::to_vec(record)
            .map_err(|_| artifact_error("could not encode artifact ownership record"))?;
        if u64::try_from(encoded.len()).unwrap_or(u64::MAX) > MAX_MARKER_BYTES {
            return Err(artifact_error("artifact ownership record is too large"));
        }
        let destination = self.ownership_root.join(format!("{}.json", record.id));
        let mut temporary = NamedTempFile::new_in(&self.ownership_root)
            .map_err(|_| artifact_error("could not create ownership record"))?;
        temporary
            .write_all(&encoded)
            .and_then(|()| temporary.as_file().sync_all())
            .map_err(|_| artifact_error("could not write ownership record"))?;
        temporary
            .persist(&destination)
            .map_err(|_| artifact_error("could not replace ownership record"))?;
        sync_directory(&self.ownership_root)
    }

    fn read_candidate(&self, marker: &Path) -> Result<OwnedCandidate, ()> {
        if marker.parent() != Some(self.ownership_root.as_path())
            || self.verify_ownership_root().is_err()
        {
            return Err(());
        }
        let marker_metadata = fs::symlink_metadata(marker).map_err(|_| ())?;
        if !marker_metadata.file_type().is_file() || marker_metadata.len() > MAX_MARKER_BYTES {
            return Err(());
        }
        let marker_name = marker
            .file_name()
            .and_then(|value| value.to_str())
            .ok_or(())?;
        let encoded = fs::read(marker).map_err(|_| ())?;
        let record: OwnershipRecord = serde_json::from_slice(&encoded).map_err(|_| ())?;
        let sidecar_valid = match (&record.sidecar_name, &record.sidecar_sha256) {
            (None, None) => true,
            (Some(name), Some(sha256)) => {
                safe_relative(name)
                    && sha256.len() == 64
                    && sha256.bytes().all(|byte| byte.is_ascii_hexdigit())
            }
            _ => false,
        };
        if record.version != 1
            || marker_name != format!("{}.json", record.id)
            || Uuid::parse_str(&record.id).is_err()
            || !safe_relative(&record.name)
            || record.sha256.len() != 64
            || !record.sha256.bytes().all(|byte| byte.is_ascii_hexdigit())
            || !sidecar_valid
        {
            return Err(());
        }
        Ok(OwnedCandidate {
            marker: marker.to_owned(),
            artifact: self.root.join(&record.name),
            sidecar: record
                .sidecar_name
                .as_deref()
                .map(|name| self.root.join(name)),
            record,
        })
    }

    fn remove_verified(&self, candidate: &OwnedCandidate) -> Result<(), ()> {
        self.verify_candidate(candidate)?;
        if let Some(sidecar) = &candidate.sidecar {
            fs::remove_file(sidecar).map_err(|_| ())?;
        }
        fs::remove_file(&candidate.artifact).map_err(|_| ())?;
        fs::remove_file(&candidate.marker).map_err(|_| ())?;
        sync_directory(&self.root).map_err(|_| ())?;
        sync_directory(&self.ownership_root).map_err(|_| ())
    }

    fn clear_missing_sidecar(&self, expected: &OwnedCandidate) -> Result<(), ()> {
        let mut candidate = self.read_candidate(&expected.marker)?;
        if candidate.record != expected.record
            || self.verify_artifact(&candidate).is_err()
            || self.sidecar_state(&candidate) != SidecarState::Missing
        {
            return Err(());
        }
        candidate.record.sidecar_name = None;
        candidate.record.sidecar_sha256 = None;
        self.replace_ownership(&candidate.record).map_err(|_| ())
    }

    fn remove_orphaned_record(&self, expected: &OwnedCandidate) -> Result<(), ()> {
        let candidate = self.read_candidate(&expected.marker)?;
        if candidate.record != expected.record
            || self.owned_path_state(&candidate.artifact) != OwnedPathState::Missing
        {
            return Err(());
        }
        match self.sidecar_state(&candidate) {
            SidecarState::Valid => {
                let sidecar = candidate.sidecar.as_ref().ok_or(())?;
                fs::remove_file(sidecar).map_err(|_| ())?;
                sync_directory(sidecar.parent().ok_or(())?).map_err(|_| ())?;
            }
            SidecarState::None | SidecarState::Missing => {}
            SidecarState::Invalid => return Err(()),
        }
        fs::remove_file(&candidate.marker).map_err(|_| ())?;
        sync_directory(&self.ownership_root).map_err(|_| ())
    }

    fn verify_candidate(&self, candidate: &OwnedCandidate) -> Result<(), ()> {
        self.verify_artifact(candidate)?;
        if !matches!(
            self.sidecar_state(candidate),
            SidecarState::None | SidecarState::Valid
        ) {
            return Err(());
        }
        Ok(())
    }

    fn verify_artifact(&self, candidate: &OwnedCandidate) -> Result<(), ()> {
        let OwnedPathState::Regular(length) = self.owned_path_state(&candidate.artifact) else {
            return Err(());
        };
        if length > self.limits.max_encoded_bytes {
            return Err(());
        }
        let bytes = fs::read(&candidate.artifact).map_err(|_| ())?;
        let digest = base16ct::lower::encode_string(&Sha256::digest(&bytes));
        if digest != candidate.record.sha256 || inspect_image(&bytes, self.limits).is_err() {
            return Err(());
        }
        Ok(())
    }

    fn sidecar_state(&self, candidate: &OwnedCandidate) -> SidecarState {
        let (Some(sidecar), Some(expected)) =
            (&candidate.sidecar, &candidate.record.sidecar_sha256)
        else {
            return SidecarState::None;
        };
        match self.owned_path_state(sidecar) {
            OwnedPathState::Missing => SidecarState::Missing,
            OwnedPathState::Invalid => SidecarState::Invalid,
            OwnedPathState::Regular(length) => {
                if length > MAX_SIDECAR_BYTES {
                    return SidecarState::Invalid;
                }
                let Ok(encoded) = fs::read(sidecar) else {
                    return SidecarState::Invalid;
                };
                if base16ct::lower::encode_string(&Sha256::digest(&encoded)) != *expected
                    || !matches!(
                        serde_json::from_slice::<serde_json::Value>(&encoded),
                        Ok(serde_json::Value::Object(_))
                    )
                {
                    SidecarState::Invalid
                } else {
                    SidecarState::Valid
                }
            }
        }
    }

    fn owned_path_state(&self, path: &Path) -> OwnedPathState {
        owned_path_state_beneath(&self.root, path)
    }

    fn verify_ownership_root(&self) -> Result<(), BridgeError> {
        let metadata = fs::symlink_metadata(&self.ownership_root)
            .map_err(|_| artifact_error("artifact ownership root is unavailable"))?;
        if !metadata.file_type().is_dir()
            || self.ownership_root.parent() != Some(self.root.as_path())
        {
            return Err(artifact_error("artifact ownership root is invalid"));
        }
        Ok(())
    }
}

fn owned_path_state_beneath(root: &Path, path: &Path) -> OwnedPathState {
    let Ok(relative) = path.strip_prefix(root) else {
        return OwnedPathState::Invalid;
    };
    let mut components = relative.components().peekable();
    if components.peek().is_none() {
        return OwnedPathState::Invalid;
    }
    let mut current = root.to_owned();
    while let Some(component) = components.next() {
        let std::path::Component::Normal(component) = component else {
            return OwnedPathState::Invalid;
        };
        current.push(component);
        let metadata = match fs::symlink_metadata(&current) {
            Ok(metadata) => metadata,
            Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
                return OwnedPathState::Missing;
            }
            Err(_) => return OwnedPathState::Invalid,
        };
        if metadata.file_type().is_symlink() {
            return OwnedPathState::Invalid;
        }
        if components.peek().is_some() {
            if !metadata.file_type().is_dir() {
                return OwnedPathState::Invalid;
            }
        } else if metadata.file_type().is_file() {
            return OwnedPathState::Regular(metadata.len());
        } else {
            return OwnedPathState::Invalid;
        }
    }
    OwnedPathState::Invalid
}

fn safe_relative(value: &str) -> bool {
    !value.is_empty()
        && value.len() <= 512
        && value.split('/').all(|component| {
            !component.is_empty()
                && component != "."
                && component != ".."
                && component.len() <= 160
                && !component.starts_with('.')
                && component
                    .bytes()
                    .all(|byte| byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_' | b'.'))
        })
}

fn safe_filename(value: &str, format: OutputFormat) -> bool {
    if value.is_empty()
        || value.len() > 160
        || value.starts_with('.')
        || value.contains(['/', '\\'])
        || !value
            .bytes()
            .all(|byte| byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_' | b'.'))
    {
        return false;
    }
    let Some((_, extension)) = value.rsplit_once('.') else {
        return true;
    };
    match format {
        OutputFormat::Png => extension.eq_ignore_ascii_case("png"),
        OutputFormat::Jpeg => {
            extension.eq_ignore_ascii_case("jpg") || extension.eq_ignore_ascii_case("jpeg")
        }
        OutputFormat::Webp => extension.eq_ignore_ascii_case("webp"),
    }
}

fn filename_with_extension(filename: &str, format: OutputFormat) -> String {
    if Path::new(filename).extension().is_some() {
        filename.to_owned()
    } else {
        format!("{filename}.{}", extension(format))
    }
}

fn publish_noclobber(
    directory: &Path,
    requested_name: &str,
    bytes: &[u8],
    collision: ArtifactCollisionPolicy,
    explicit_filename: bool,
) -> Result<(PathBuf, String), BridgeError> {
    let attempts = if explicit_filename && collision == ArtifactCollisionPolicy::Suffix {
        10_000
    } else {
        1
    };
    for attempt in 0..attempts {
        let name = if attempt == 0 {
            requested_name.to_owned()
        } else {
            suffixed_filename(requested_name, attempt + 1)
        };
        let destination = directory.join(&name);
        let mut temporary = NamedTempFile::new_in(directory)
            .map_err(|_| artifact_error("could not create temporary artifact"))?;
        temporary
            .write_all(bytes)
            .and_then(|()| temporary.as_file().sync_all())
            .map_err(|_| artifact_error("could not write artifact"))?;
        match temporary.persist_noclobber(&destination) {
            Ok(_) => return Ok((destination, name)),
            Err(error) if error.error.kind() == std::io::ErrorKind::AlreadyExists => {}
            Err(_) => {
                return Err(artifact_error(
                    "could not publish artifact without overwrite",
                ));
            }
        }
    }
    Err(artifact_error(
        "artifact collision suffix limit was reached",
    ))
}

fn suffixed_filename(filename: &str, suffix: usize) -> String {
    let path = Path::new(filename);
    let stem = path
        .file_stem()
        .and_then(|value| value.to_str())
        .unwrap_or("image");
    path.extension()
        .and_then(|value| value.to_str())
        .map_or_else(
            || format!("{stem}-{suffix}"),
            |extension| format!("{stem}-{suffix}.{extension}"),
        )
}

fn unix_timestamp(time: SystemTime) -> Result<u64, BridgeError> {
    time.duration_since(UNIX_EPOCH)
        .map(|duration| duration.as_secs())
        .map_err(|_| artifact_error("system time is before the Unix epoch"))
}

fn sanitize_prefix(value: &str) -> String {
    let sanitized: String = value
        .chars()
        .filter_map(|character| {
            if character.is_ascii_alphanumeric() || matches!(character, '-' | '_') {
                Some(character.to_ascii_lowercase())
            } else if character.is_whitespace() {
                Some('-')
            } else {
                None
            }
        })
        .take(64)
        .collect();
    let sanitized = sanitized.trim_matches('-');
    if sanitized.is_empty() {
        "image".to_owned()
    } else {
        sanitized.to_owned()
    }
}

const fn extension(format: OutputFormat) -> &'static str {
    match format {
        OutputFormat::Png => "png",
        OutputFormat::Jpeg => "jpg",
        OutputFormat::Webp => "webp",
    }
}

#[cfg(unix)]
fn sync_directory(path: &Path) -> Result<(), BridgeError> {
    fs::File::open(path)
        .and_then(|directory| directory.sync_all())
        .map_err(|error| artifact_error(format!("could not sync artifact directory: {error}")))
}

#[cfg(not(unix))]
fn sync_directory(_path: &Path) -> Result<(), BridgeError> {
    Ok(())
}

fn artifact_error(message: impl Into<String>) -> BridgeError {
    BridgeError::new(ErrorCode::Artifact, message)
}

#[cfg(test)]
mod tests {
    #![allow(clippy::unwrap_used)]

    use std::fs;

    use super::*;
    use crate::inspect::test_png;

    #[test]
    fn publishes_verified_artifacts_without_name_reuse() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let bytes = test_png(2, 2);
        let first = store
            .publish(&bytes, Some("My portrait"), Some(OutputFormat::Png))
            .unwrap();
        let second = store
            .publish(&bytes, Some("My portrait"), Some(OutputFormat::Png))
            .unwrap();
        assert_ne!(first.name, second.name);
        assert!(first.name.starts_with("my-portrait-"));
        assert_eq!(fs::read(first.path).unwrap(), bytes);
    }

    #[test]
    fn rejects_mismatched_effective_format_before_write() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let error = store
            .publish(&test_png(1, 1), None, Some(OutputFormat::Jpeg))
            .unwrap_err();
        assert_eq!(error.code, ErrorCode::Artifact);
        assert_eq!(
            fs::read_dir(root.path())
                .unwrap()
                .filter_map(Result::ok)
                .filter(|entry| entry.file_name() != OWNERSHIP_DIRECTORY)
                .count(),
            0
        );
    }

    #[test]
    fn cleanup_deletes_only_verified_bridge_owned_artifacts() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), Some("owned"), Some(OutputFormat::Png))
            .unwrap();
        let unowned = root.path().join("unowned.png");
        fs::write(&unowned, test_png(2, 2)).unwrap();
        let report = store
            .cleanup(
                RetentionPolicy {
                    max_age: Duration::ZERO,
                    ..RetentionPolicy::default()
                },
                SystemTime::now() + Duration::from_secs(1),
            )
            .unwrap();
        assert_eq!(report.deleted, 1);
        assert!(!owned.path.exists());
        assert!(unowned.exists());
    }

    #[test]
    fn reads_only_matching_owned_artifacts() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let published = store
            .publish(&test_png(2, 3), Some("owned"), Some(OutputFormat::Png))
            .unwrap();
        let content = store.read(&published.id).unwrap();
        assert_eq!(content.id, published.id);
        assert_eq!(content.name, published.name);
        assert_eq!((content.metadata.width, content.metadata.height), (2, 3));
        assert!(store.read("019f0000-0000-7000-8000-000000000000").is_err());
    }

    #[test]
    fn cleanup_does_not_delete_an_owned_path_after_content_replacement() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), None, Some(OutputFormat::Png))
            .unwrap();
        fs::write(&owned.path, test_png(3, 3)).unwrap();
        let report = store
            .cleanup(
                RetentionPolicy {
                    max_age: Duration::ZERO,
                    ..RetentionPolicy::default()
                },
                SystemTime::now() + Duration::from_secs(1),
            )
            .unwrap();
        assert_eq!(report.deleted, 0);
        assert_eq!(report.skipped, 1);
        assert!(owned.path.exists());
    }

    #[test]
    fn cleanup_scan_is_bounded() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        for index in 0..3 {
            fs::write(
                store.ownership_root.join(format!("invalid-{index}.json")),
                b"{}",
            )
            .unwrap();
        }
        let report = store
            .cleanup(
                RetentionPolicy {
                    max_scan_entries: 2,
                    ..RetentionPolicy::default()
                },
                SystemTime::now(),
            )
            .unwrap();
        assert_eq!(report.scanned, 2);
        assert_eq!(report.skipped, 2);
        assert!(report.scan_limit_reached);
    }

    #[test]
    fn orphan_repair_is_auditable_and_removes_only_verified_owned_state() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), Some("orphan"), Some(OutputFormat::Png))
            .unwrap();
        let sidecar = store
            .attach_metadata(&owned.id, &owned.name, br#"{"prompt":"test"}"#)
            .unwrap();
        let marker = store.ownership_root.join(format!("{}.json", owned.id));
        let sidecar = root.path().join(sidecar.name);
        let unowned = root.path().join("unowned.png");
        fs::write(&unowned, test_png(1, 1)).unwrap();
        fs::remove_file(&owned.path).unwrap();

        let audit = store.repair_orphans(10, ArtifactRepairMode::Audit).unwrap();
        assert_eq!(audit.scanned, 1);
        assert_eq!(audit.orphaned_records, 1);
        assert_eq!(audit.repaired, 0);
        assert!(marker.exists());
        assert!(sidecar.exists());

        let repaired = store.repair_orphans(10, ArtifactRepairMode::Apply).unwrap();
        assert_eq!(repaired.orphaned_records, 1);
        assert_eq!(repaired.repaired, 1);
        assert!(!marker.exists());
        assert!(!sidecar.exists());
        assert!(unowned.exists());
    }

    #[test]
    fn orphan_repair_clears_only_an_absent_sidecar_reference() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), Some("sidecar"), Some(OutputFormat::Png))
            .unwrap();
        let sidecar = store
            .attach_metadata(&owned.id, &owned.name, br#"{"prompt":"test"}"#)
            .unwrap();
        fs::remove_file(root.path().join(sidecar.name)).unwrap();
        assert!(store.read(&owned.id).is_err());

        let audit = store.repair_orphans(10, ArtifactRepairMode::Audit).unwrap();
        assert_eq!(audit.missing_sidecars, 1);
        assert_eq!(audit.repaired, 0);
        let repaired = store.repair_orphans(10, ArtifactRepairMode::Apply).unwrap();
        assert_eq!(repaired.missing_sidecars, 1);
        assert_eq!(repaired.repaired, 1);
        assert_eq!(store.read(&owned.id).unwrap().name, owned.name);
        assert_eq!(
            store
                .repair_orphans(10, ArtifactRepairMode::Audit)
                .unwrap()
                .healthy,
            1
        );
    }

    #[test]
    fn orphan_repair_never_modifies_changed_or_invalid_content() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), Some("changed"), Some(OutputFormat::Png))
            .unwrap();
        let sidecar = store
            .attach_metadata(&owned.id, &owned.name, br#"{"prompt":"test"}"#)
            .unwrap();
        let sidecar = root.path().join(sidecar.name);
        fs::write(&sidecar, br#"{"prompt":"changed"}"#).unwrap();
        fs::remove_file(&owned.path).unwrap();

        let report = store.repair_orphans(10, ArtifactRepairMode::Apply).unwrap();
        assert_eq!(report.repaired, 0);
        assert_eq!(report.orphaned_records, 1);
        assert_eq!(report.skipped, 1);
        assert!(sidecar.exists());
        assert!(
            store
                .ownership_root
                .join(format!("{}.json", owned.id))
                .exists()
        );
        assert!(store.repair_orphans(0, ArtifactRepairMode::Audit).is_err());
    }

    #[cfg(unix)]
    #[test]
    fn reads_cleanup_and_repair_reject_replaced_parent_symlinks() {
        use std::os::unix::fs::symlink;

        let root = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let bytes = test_png(2, 2);
        let owned = store
            .publish_with_options(
                &bytes,
                None,
                Some(OutputFormat::Png),
                ArtifactPublication {
                    directory: Some("gallery"),
                    ..ArtifactPublication::default()
                },
            )
            .unwrap();
        fs::remove_file(&owned.path).unwrap();
        fs::remove_dir(root.path().join("gallery")).unwrap();
        fs::write(outside.path().join(owned.path.file_name().unwrap()), &bytes).unwrap();
        symlink(outside.path(), root.path().join("gallery")).unwrap();

        assert!(store.read(&owned.id).is_err());
        let cleanup = store
            .cleanup(
                RetentionPolicy {
                    max_age: Duration::ZERO,
                    ..RetentionPolicy::default()
                },
                SystemTime::now() + Duration::from_secs(1),
            )
            .unwrap();
        assert_eq!(cleanup.deleted, 0);
        assert_eq!(cleanup.skipped, 1);
        let repair = store.repair_orphans(10, ArtifactRepairMode::Apply).unwrap();
        assert_eq!(repair.repaired, 0);
        assert_eq!(repair.skipped, 1);
        assert!(
            outside
                .path()
                .join(owned.path.file_name().unwrap())
                .exists()
        );
    }

    #[cfg(unix)]
    #[test]
    fn ownership_operations_reject_a_replaced_ownership_root() {
        use std::os::unix::fs::symlink;

        let root = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), Some("owned"), Some(OutputFormat::Png))
            .unwrap();
        let marker_name = format!("{}.json", owned.id);
        fs::copy(
            store.ownership_root.join(&marker_name),
            outside.path().join(&marker_name),
        )
        .unwrap();
        fs::rename(
            &store.ownership_root,
            root.path().join("original-ownership"),
        )
        .unwrap();
        symlink(outside.path(), &store.ownership_root).unwrap();

        assert!(store.read(&owned.id).is_err());
        assert!(
            store
                .cleanup(RetentionPolicy::default(), SystemTime::now())
                .is_err()
        );
        assert!(store.repair_orphans(10, ArtifactRepairMode::Apply).is_err());
        assert!(outside.path().join(marker_name).is_file());
        assert!(owned.path.is_file());
    }

    #[test]
    fn publishes_nested_exact_names_and_cleans_them_up() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let bytes = test_png(2, 2);
        let owned = store
            .publish_with_options(
                &bytes,
                None,
                Some(OutputFormat::Png),
                ArtifactPublication {
                    directory: Some("portraits/people"),
                    filename: Some("alice"),
                    collision: ArtifactCollisionPolicy::Error,
                },
            )
            .unwrap();
        assert_eq!(owned.name, "portraits/people/alice.png");
        assert_eq!(fs::read(&owned.path).unwrap(), bytes);
        let sidecar = store
            .attach_metadata(&owned.id, &owned.name, br#"{"prompt":"test"}"#)
            .unwrap();
        assert!(root.path().join(&sidecar.name).is_file());

        let report = store
            .cleanup(
                RetentionPolicy {
                    max_age: Duration::ZERO,
                    ..RetentionPolicy::default()
                },
                SystemTime::now() + Duration::from_secs(1),
            )
            .unwrap();
        assert_eq!(report.deleted, 1);
        assert!(!owned.path.exists());
        assert!(!root.path().join(sidecar.name).exists());
    }

    #[test]
    fn explicit_collision_can_error_or_select_a_suffix() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let bytes = test_png(2, 2);
        let exact = ArtifactPublication {
            filename: Some("portrait.png"),
            ..ArtifactPublication::default()
        };
        store
            .publish_with_options(&bytes, None, Some(OutputFormat::Png), exact)
            .unwrap();
        assert!(
            store
                .publish_with_options(&bytes, None, Some(OutputFormat::Png), exact)
                .is_err()
        );
        let suffixed = store
            .publish_with_options(
                &bytes,
                None,
                Some(OutputFormat::Png),
                ArtifactPublication {
                    collision: ArtifactCollisionPolicy::Suffix,
                    ..exact
                },
            )
            .unwrap();
        assert_eq!(suffixed.name, "portrait-2.png");
    }

    #[test]
    fn direct_store_calls_reject_filename_traversal_and_symlink_directories() {
        let root = tempfile::tempdir().unwrap();
        let outside = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let bytes = test_png(2, 2);
        assert!(
            store
                .publish_with_options(
                    &bytes,
                    None,
                    Some(OutputFormat::Png),
                    ArtifactPublication {
                        filename: Some("../escape.png"),
                        ..ArtifactPublication::default()
                    },
                )
                .is_err()
        );
        #[cfg(unix)]
        {
            std::os::unix::fs::symlink(outside.path(), root.path().join("linked")).unwrap();
            assert!(
                store
                    .publish_with_options(
                        &bytes,
                        None,
                        Some(OutputFormat::Png),
                        ArtifactPublication {
                            directory: Some("linked"),
                            ..ArtifactPublication::default()
                        },
                    )
                    .is_err()
            );
        }
    }

    #[test]
    fn metadata_attachment_rejects_non_json_and_duplicate_sidecars() {
        let root = tempfile::tempdir().unwrap();
        let store = ArtifactStore::new(root.path(), ImageLimits::default()).unwrap();
        let owned = store
            .publish(&test_png(2, 2), None, Some(OutputFormat::Png))
            .unwrap();
        assert!(
            store
                .attach_metadata(&owned.id, &owned.name, b"not-json")
                .is_err()
        );
        store
            .attach_metadata(&owned.id, &owned.name, br#"{"version":1}"#)
            .unwrap();
        assert!(
            store
                .attach_metadata(&owned.id, &owned.name, br#"{"version":2}"#)
                .is_err()
        );
    }
}