//! Cylinder, step C1 (docs/cylinder.md §4.1): an **artifact** is an

//! immutable, content-addressed object naming a tree of files, each kept as

//! an ordinary Oxygen blob of FastCDC BLAKE3 chunks. An image rebuilt with

//! one changed file moves only that file's changed chunks, and a binary in

//! a release archive and in a runner image is the same chunks.

//!

//! The model is oxy-core's ([`oxy_core::artifact`]): an `artifact` object

//! in canonical CBOR, named by its object hash, whose tree is a blob. This

//! crate packs a directory into one, opens, verifies and unpacks it, and

//! keeps it: `.oxy/artifacts/NAME` records each artifact this repository

//! keeps, which garbage collection keeps with its tree and files

//! ([`roots`]).

use oxy_core::hash::{ObjectRef, ObjectType};

use oxy_core::repo::Repo;

use std::collections::BTreeMap;

use std::path::{Path, PathBuf};

pub use oxy_core::artifact::{

    Artifact, DirTree, Entry, Kind, MODE_EXEC, MODE_FILE, MODE_LINK, VERSION,

};

#[derive(Debug, thiserror::Error)]

pub enum Error {

    #[error(transparent)]

    Repo(#[from] oxy_core::repo::RepoError),

    #[error("io: {0}")]

    Io(#[from] std::io::Error),

    #[error("not an artifact: {0}")]

    Object(#[from] oxy_core::objects::ObjectError),

    #[error("store: {0}")]

    Store(#[from] oxy_core::store::StoreError),

    #[error("{0}")]

    Bad(String),

}

pub type Result<T> = std::result::Result<T, Error>;

fn bad<T>(msg: impl Into<String>) -> Result<T> {

    Err(Error::Bad(msg.into()))

}

/// What to pack a directory as.

#[derive(Clone, Debug)]

pub struct Spec {

    pub kind: Kind,

    pub arch: Option<String>,

    pub os: Option<String>,

    pub entrypoint: Option<Vec<String>>,

    pub env: BTreeMap<String, String>,

    pub labels: BTreeMap<String, String>,

}

impl Spec {

    pub fn new(kind: Kind) -> Spec {

        Spec {

            kind,

            arch: None,

            os: None,

            entrypoint: None,

            env: BTreeMap::new(),

            labels: BTreeMap::new(),

        }

    }

}

/// An artifact kept in a repository, with its name.

#[derive(Clone, Debug)]

pub struct Kept {

    pub name: String,

    pub artifact: Artifact,

    /// Its object (its name, as a reference).

    pub object: ObjectRef,

}

fn kept_dir(repo: &Repo) -> PathBuf {

    repo.oxy_dir().join("artifacts")

}

/// Every file under `dir`, by relative path: regular files and links, in

/// path order. `.oxy` and `.git` directories are not part of an artifact.

fn walk(dir: &Path) -> Result<Vec<(String, PathBuf, std::fs::Metadata)>> {

    let mut out = Vec::new();

    let mut stack = vec![(dir.to_path_buf(), String::new())];

    while let Some((d, rel)) = stack.pop() {

        for e in std::fs::read_dir(&d)? {

            let e = e?;

            let name = e

                .file_name()

                .into_string()

                .map_err(|n| Error::Bad(format!("{n:?} is not UTF-8")))?;

            let path = if rel.is_empty() {

                name.clone()

            } else {

                format!("{rel}/{name}")

            };

            let md = std::fs::symlink_metadata(e.path())?;

            if md.is_dir() {

                if name != ".oxy" && name != ".git" {

                    stack.push((e.path(), path));

                }

            } else if md.is_file() || md.file_type().is_symlink() {

                out.push((path, e.path(), md));

            }

        }

    }

    out.sort_by(|a, b| a.0.cmp(&b.0));

    Ok(out)

}

#[cfg(unix)]

fn mode_of(md: &std::fs::Metadata) -> u32 {

    use std::os::unix::fs::PermissionsExt;

    if md.file_type().is_symlink() {

        MODE_LINK

    } else if md.permissions().mode() & 0o111 != 0 {

        MODE_EXEC

    } else {

        MODE_FILE

    }

}

#[cfg(not(unix))]

fn mode_of(md: &std::fs::Metadata) -> u32 {

    if md.file_type().is_symlink() {

        MODE_LINK

    } else {

        MODE_FILE

    }

}

/// Pack the files under `dir` into an artifact of `spec`'s kind in

/// `repo`'s store: each file a blob, so files and chunks the store holds

/// already cost nothing; then its tree and its encoding, kept under its

/// name.

pub fn pack(repo: &Repo, dir: &Path, spec: &Spec) -> Result<Kept> {

    if !dir.is_dir() {

        return bad(format!("{} is not a directory", dir.display()));

    }

    let mut tree = DirTree::default();

    for (path, full, md) in walk(dir)? {

        let mode = mode_of(&md);

        let bytes = if mode == MODE_LINK {

            std::fs::read_link(&full)?

                .to_string_lossy()

                .into_owned()

                .into_bytes()

        } else {

            std::fs::read(&full)?

        };

        let blob = repo.store_blob(&bytes)?;

        tree.entries.push(Entry {

            path,

            mode,

            blob,

            size: bytes.len() as u64,

        });

    }

    let artifact = Artifact {

        kind: spec.kind,

        arch: spec.arch.clone(),

        os: spec.os.clone(),

        tree: repo.store_blob(&tree.encode())?,

        entrypoint: spec.entrypoint.clone(),

        env: spec.env.clone(),

        labels: spec.labels.clone(),

        total_size: tree.entries.iter().map(|e| e.size).sum(),

        receipt: None,

    };

    let object = repo.store().put(ObjectType::Artifact, &artifact.encode())?;

    let name = object.to_hex();

    std::fs::create_dir_all(kept_dir(repo))?;

    std::fs::write(kept_dir(repo).join(&name), b"")?;

    Ok(Kept {

        name,

        artifact,

        object,

    })

}

/// The names of the artifacts kept in `repo`, sorted.

pub fn list(repo: &Repo) -> Result<Vec<String>> {

    let mut out = Vec::new();

    match std::fs::read_dir(kept_dir(repo)) {

        Ok(rd) => {

            for e in rd {

                let n = e?.file_name().to_string_lossy().into_owned();

                if n.len() == 64 && n.bytes().all(|b| b.is_ascii_hexdigit()) {

                    out.push(n);

                }

            }

        }

        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}

        Err(e) => return Err(e.into()),

    }

    out.sort();

    Ok(out)

}

/// The kept artifact `name` names, or a unique prefix of it (at least six

/// characters), read from the store, which checks it against its name.

pub fn open(repo: &Repo, name: &str) -> Result<Kept> {

    let name = name.to_ascii_lowercase();

    if name.len() < 6 {

        return bad("name an artifact by at least six characters of its name");

    }

    let found: Vec<String> = list(repo)?

        .into_iter()

        .filter(|n| n.starts_with(&name))

        .collect();

    let full = match found.as_slice() {

        [one] => one.clone(),

        [] => {

            return bad(format!(

                "no artifact {name} here; `oxy artifact list` shows them"

            ))

        }

        _ => {

            return bad(format!(

                "{name} names {} artifacts: give more of the name",

                found.len()

            ))

        }

    };

    let object = ObjectRef::from_hex(&full).map_or_else(

        || bad(format!("artifact {full}: its record is damaged")),

        Ok,

    )?;

    // The store checks the bytes against the object's name as it reads.

    let bytes = repo.store().get_typed(&object, ObjectType::Artifact)?;

    Ok(Kept {

        name: full,

        artifact: Artifact::decode(&bytes)?,

        object,

    })

}

/// An artifact's tree.

pub fn tree(repo: &Repo, a: &Artifact) -> Result<DirTree> {

    Ok(DirTree::decode(&repo.read_blob(&a.tree)?)?)

}

/// Check that every file of `k` is in the store whole: its bytes read, at

/// the size its tree says. Answers how many files were read.

pub fn verify(repo: &Repo, k: &Kept) -> Result<usize> {

    let t = tree(repo, &k.artifact)?;

    let mut total = 0;

    for e in &t.entries {

        let n = repo.read_blob(&e.blob)?.len() as u64;

        if n != e.size {

            return bad(format!(

                "{}: {n} bytes, but the tree says {}",

                e.path, e.size

            ));

        }

        total += n;

    }

    if total != k.artifact.total_size {

        return bad(format!(

            "the files are {total} bytes together, but the artifact says {}",

            k.artifact.total_size

        ));

    }

    Ok(t.entries.len())

}

/// Write `k`'s files under `dest`, which must not exist or be empty.

pub fn unpack(repo: &Repo, k: &Kept, dest: &Path) -> Result<usize> {

    if dest.exists() && std::fs::read_dir(dest)?.next().is_some() {

        return bad(format!("{} is not empty", dest.display()));

    }

    let t = tree(repo, &k.artifact)?;

    for e in &t.entries {

        let out = dest.join(&e.path);

        if let Some(p) = out.parent() {

            std::fs::create_dir_all(p)?;

        }

        let bytes = repo.read_blob(&e.blob)?;

        if e.mode == MODE_LINK {

            #[cfg(unix)]

            std::os::unix::fs::symlink(String::from_utf8_lossy(&bytes).as_ref(), &out)?;

            #[cfg(not(unix))]

            std::fs::write(&out, &bytes)?;

            continue;

        }

        std::fs::write(&out, &bytes)?;

        #[cfg(unix)]

        if e.mode == MODE_EXEC {

            use std::os::unix::fs::PermissionsExt;

            std::fs::set_permissions(&out, std::fs::Permissions::from_mode(0o755))?;

        }

    }

    Ok(t.entries.len())

}

/// The blobs garbage collection must keep for the kept artifacts: each

/// one's encoding, its tree and its files (`Repo::gc_keeping`).

pub fn roots(repo: &Repo) -> Result<Vec<ObjectRef>> {

    let mut out = Vec::new();

    for name in list(repo)? {

        let k = open(repo, &name)?;

        out.push(k.object);

        out.push(k.artifact.tree);

        out.extend(tree(repo, &k.artifact)?.entries.iter().map(|e| e.blob));

    }

    Ok(out)

}

#[cfg(test)]

mod tests {

    use super::*;

    use oxy_core::cbor::{self, Value};

    fn repo(dir: &Path) -> Repo {

        Repo::init(&dir.join("repo")).unwrap()

    }

    #[test]

    fn a_directory_packs_into_an_artifact_and_back() {

        let t = tempfile::tempdir().unwrap();

        let r = repo(t.path());

        let src = t.path().join("out");

        std::fs::create_dir_all(src.join("bin")).unwrap();

        std::fs::write(src.join("README"), b"hello\n").unwrap();

        std::fs::write(src.join("bin/tool"), vec![7u8; 300_000]).unwrap();

        #[cfg(unix)]

        {

            use std::os::unix::fs::PermissionsExt;

            std::fs::set_permissions(src.join("bin/tool"), std::fs::Permissions::from_mode(0o755))

                .unwrap();

            std::os::unix::fs::symlink("bin/tool", src.join("tool")).unwrap();

        }

        let mut spec = Spec::new(Kind::Archive);

        spec.arch = Some("x86_64".into());

        spec.labels.insert("version".into(), "0.1.0".into());

        let k = pack(&r, &src, &spec).unwrap();

        assert_eq!(k.name, k.artifact.name().to_hex());

        assert_eq!(

            k.artifact.total_size,

            300_006 + if cfg!(unix) { 8 } else { 0 }

        );

        assert_eq!(list(&r).unwrap(), vec![k.name.clone()]);

        let again = open(&r, &k.name[..10]).unwrap();

        assert_eq!(again.artifact, k.artifact);

        let paths: Vec<(String, u32)> = tree(&r, &again.artifact)

            .unwrap()

            .entries

            .into_iter()

            .map(|e| (e.path, e.mode))

            .collect();

        assert_eq!(paths[0], ("README".into(), MODE_FILE));

        assert_eq!(

            paths[1],

            (

                "bin/tool".into(),

                if cfg!(unix) { MODE_EXEC } else { MODE_FILE }

            )

        );

        assert_eq!(verify(&r, &again).unwrap(), paths.len());

        let dest = t.path().join("back");

        unpack(&r, &again, &dest).unwrap();

        assert_eq!(

            std::fs::read(dest.join("bin/tool")).unwrap(),

            vec![7u8; 300_000]

        );

        #[cfg(unix)]

        assert_eq!(

            std::fs::read_link(dest.join("tool")).unwrap(),

            Path::new("bin/tool")

        );

        assert!(unpack(&r, &again, &dest)

            .unwrap_err()

            .to_string()

            .contains("not empty"));

        // The same files pack to the same name; garbage collection keeps it.

        assert_eq!(pack(&r, &src, &spec).unwrap().name, k.name);

        let keep = roots(&r).unwrap();

        assert!(keep.contains(&k.object) && keep.contains(&k.artifact.tree));

        r.gc_keeping(true, &keep, &mut |_| {}).unwrap();

        // An artifact is an object of its own, which fsck reads and accepts.

        let report = r.fsck().unwrap();

        let errors: Vec<_> = report

            .problems

            .iter()

            .filter(|p| p.severity == oxy_core::repo::Severity::Error)

            .collect();

        assert!(errors.is_empty(), "{errors:?}");

        assert_eq!(

            verify(&r, &open(&r, &k.name).unwrap()).unwrap(),

            paths.len()

        );

    }

    #[test]

    fn encodings_are_canonical_and_checked() {

        let a = Artifact {

            kind: Kind::RunnerImage,

            arch: Some("riscv64".into()),

            os: Some("linux".into()),

            tree: ObjectRef([1; 32]),

            entrypoint: Some(vec!["/sbin/init".into()]),

            env: [("PATH".to_string(), "/bin".to_string())].into(),

            labels: BTreeMap::new(),

            total_size: 42,

            receipt: Some(ObjectRef([2; 32])),

        };

        let bytes = a.encode();

        assert_eq!(Artifact::decode(&bytes).unwrap(), a);

        assert_eq!(

            a.name(),

            oxy_core::hash::hash_object(ObjectType::Artifact, &bytes)

        );

        assert!(Kind::parse("tarball")

            .unwrap_err()

            .to_string()

            .contains("runner-image"));

        let wrong = |v: Value| Artifact::decode(&cbor::encode(&v)).unwrap_err().to_string();

        assert!(wrong(Value::map([(0, Value::Uint(2))])).contains("version"));

        assert!(wrong(Value::map([(0, Value::Uint(1)), (10, Value::Null)])).contains("key 10"));

        let t = DirTree {

            entries: vec![Entry {

                path: "a".into(),

                mode: MODE_FILE,

                blob: ObjectRef([3; 32]),

                size: 1,

            }],

        };

        assert_eq!(DirTree::decode(&t.encode()).unwrap(), t);

        let entry = |p: &str, mode: u32| {

            Value::Array(vec![

                Value::Text(p.into()),

                Value::Uint(mode as u64),

                Value::Bytes(vec![0; 32]),

                Value::Uint(0),

            ])

        };

        let tree = |items: Vec<Value>| {

            DirTree::decode(&cbor::encode(&Value::map([

                (0, Value::Uint(1)),

                (1, Value::Array(items)),

            ])))

            .unwrap_err()

            .to_string()

        };

        assert!(tree(vec![entry("../x", MODE_FILE)]).contains("clean"));

        assert!(tree(vec![entry("b", MODE_FILE), entry("a", MODE_FILE)]).contains("order"));

        assert!(tree(vec![entry("a", 0o040000)]).contains("mode"));

    }

}