nornir 0.4.4

//! Pure-Rust git helpers (via `gix`). The single home for read-side
//! git inspection so the rest of the crate never shells out to the
//! `git` binary. No `std::process::Command`, no libgit2/C — matches
//! nornir's pure-Rust ethos (gix over libgit2, like `ureq` over curl).
//!
//! Write/network release operations (commit-on-release, push) live in
//! [`crate::release::publish`]. The write helpers here — [`init`] and
//! [`commit_all`] — exist only to build *new* repositories from scratch
//! (test fixtures and the synthetic-repo generator) without ever
//! shelling out; they use a fixed, deterministic identity so fixtures
//! are reproducible and need no ambient git config.

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

use anyhow::{anyhow, Context, Result};

/// Full 40-char hex SHA of the commit `HEAD` points at.
pub fn head_sha(root: &Path) -> Result<String> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    let id = repo
        .head()
        .context("read HEAD")?
        .id()
        .ok_or_else(|| anyhow!("HEAD has no commit (unborn?) in {}", root.display()))?;
    Ok(id.to_string())
}

/// Short branch name for `HEAD`, or `"(detached)"` when detached.
pub fn head_branch(root: &Path) -> Result<String> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    Ok(match repo.head_name().context("read HEAD name")? {
        Some(name) => name.shorten().to_string(),
        None => "(detached)".to_string(),
    })
}

/// `(sha, branch)` for `HEAD` in one open. Branch falls back to
/// `"(detached)"` when `HEAD` is not on a branch.
pub fn head_sha_and_branch(root: &Path) -> Result<(String, String)> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    let sha = repo
        .head()
        .context("read HEAD")?
        .id()
        .ok_or_else(|| anyhow!("HEAD has no commit (unborn?) in {}", root.display()))?
        .to_string();
    let branch = match repo.head_name().context("read HEAD name")? {
        Some(name) => name.shorten().to_string(),
        None => "(detached)".to_string(),
    };
    Ok((sha, branch))
}

/// Commit SHA the tag `refs/tags/<tag>` resolves to, peeling annotated
/// tags down to their target commit. `Ok(None)` if the tag is absent.
pub fn tag_commit_sha(root: &Path, tag: &str) -> Result<Option<String>> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    let full = format!("refs/tags/{tag}");
    let Some(reference) = repo
        .try_find_reference(full.as_str())
        .with_context(|| format!("look up {full}"))?
    else {
        return Ok(None);
    };
    let id = reference
        .into_fully_peeled_id()
        .with_context(|| format!("peel {full}"))?;
    Ok(Some(id.to_string()))
}

/// True iff `refs/tags/<tag>` exists and (after peeling) points at the
/// same commit as `HEAD`.
pub fn tag_points_at_head(root: &Path, tag: &str) -> Result<bool> {
    match tag_commit_sha(root, tag)? {
        Some(tag_sha) => Ok(tag_sha == head_sha(root)?),
        None => Ok(false),
    }
}

/// Fixed identity for fixture/generated commits — deterministic so test
/// repos hash reproducibly and require no ambient `git` config.
const FIXTURE_NAME: &str = "Nornir Fixture";
const FIXTURE_EMAIL: &str = "fixtures@nornir.invalid";
const FIXTURE_TIME: &str = "1700000000 +0000";

/// Initialise a fresh git repository at `root` (pure-Rust via `gix`).
/// The directory is created if missing. Used by test fixtures and the
/// synthetic-repo generator so setup code is also free of `git`
/// subprocesses.
pub fn init(root: &Path) -> Result<()> {
    std::fs::create_dir_all(root).with_context(|| format!("mkdir {}", root.display()))?;
    gix::init(root).with_context(|| format!("gix init {}", root.display()))?;
    Ok(())
}

/// Snapshot the entire working tree (every file except those under
/// `.git/`) into a new commit on `HEAD`, returning the commit SHA.
///
/// Works for the initial commit (unborn `HEAD`, no parent) and for
/// subsequent commits (parent = current `HEAD`). Because the tree is
/// rebuilt from the filesystem each call, additions, modifications and
/// deletions are all captured — a faithful `git add -A && git commit`
/// for synthetic repos that have no `.gitattributes` content filters.
pub fn commit_all(root: &Path, message: &str) -> Result<String> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    let empty = gix::ObjectId::empty_tree(repo.object_hash());
    let mut editor = repo.edit_tree(empty).context("seed empty tree editor")?;

    add_dir_recursive(&repo, &mut editor, root, root)?;
    let tree = editor.write().context("write fixture tree")?.detach();

    let parents: Vec<gix::ObjectId> = repo.head_commit().ok().map(|c| c.id).into_iter().collect();
    let sig = gix::actor::SignatureRef {
        name: gix::bstr::BStr::new(FIXTURE_NAME),
        email: gix::bstr::BStr::new(FIXTURE_EMAIL),
        time: FIXTURE_TIME,
    };
    let id = repo
        .commit_as(sig, sig, "HEAD", message, tree, parents)
        .context("create fixture commit")?;

    // Write the index from the new tree so the freshly-built repo reads
    // clean (gix::init leaves no index; without this the whole worktree
    // would look untracked to a subsequent status check).
    let mut index = repo
        .index_from_tree(&tree)
        .context("rebuild index from fixture tree")?;
    index
        .write(gix::index::write::Options::default())
        .context("persist fixture index")?;

    Ok(id.to_string())
}

/// Create a lightweight tag `refs/tags/<name>` pointing at `target_sha`.
/// Pure-gix (no shell). Fails if the tag already exists.
pub fn tag_lightweight(root: &Path, name: &str, target_sha: &str) -> Result<()> {
    let repo = gix::open(root).with_context(|| format!("gix::open {}", root.display()))?;
    let target = gix::ObjectId::from_hex(target_sha.as_bytes())
        .with_context(|| format!("parse target sha `{target_sha}`"))?;
    repo.tag_reference(name, target, gix::refs::transaction::PreviousValue::MustNotExist)
        .with_context(|| format!("create tag `{name}` -> {target_sha}"))?;
    Ok(())
}

// ── Network (server-monitored poll/fetch) ───────────────────────────────────
//
// Pure-Rust git, no `git`/`ssh` subprocess, no C:
// - HTTPS: gix + rustls (clone/fetch).
// - SSH:   `russh` runs `git-upload-pack` over an authenticated channel and gix
//          drives the wire protocol + pack indexing over it (see [`ssh_sync`]).
//          gix's *own* SSH transport execs `ssh`, which we avoid.

/// `true` for SSH-style remotes (`git@host:…` or `ssh://…`).
pub fn is_ssh_url(url: &str) -> bool {
    url.starts_with("ssh://") || (url.contains('@') && !url.contains("://"))
}

/// Clone `url` into `dest` (full worktree). Pure Rust over HTTPS.
fn clone_repo(url: &str, dest: &Path) -> Result<()> {
    std::fs::create_dir_all(dest).with_context(|| format!("create {}", dest.display()))?;
    let mut prepare = gix::prepare_clone(url, dest)
        .with_context(|| format!("prepare clone {url} → {}", dest.display()))?;
    let (mut checkout, _) = prepare
        .fetch_then_checkout(gix::progress::Discard, &gix::interrupt::IS_INTERRUPTED)
        .with_context(|| format!("clone-fetch {url}"))?;
    checkout
        .main_worktree(gix::progress::Discard, &gix::interrupt::IS_INTERRUPTED)
        .with_context(|| format!("checkout worktree for {url}"))?;
    Ok(())
}

/// Fetch the default remote of an existing HTTPS clone at `dest`.
fn fetch_repo(dest: &Path) -> Result<()> {
    let repo = gix::open(dest).with_context(|| format!("gix::open {}", dest.display()))?;
    let remote = repo
        .find_default_remote(gix::remote::Direction::Fetch)
        .ok_or_else(|| anyhow!("{} has no fetch remote", dest.display()))?
        .context("resolve default remote")?;
    remote
        .connect(gix::remote::Direction::Fetch)
        .context("connect to remote")?
        .prepare_fetch(gix::progress::Discard, Default::default())
        .context("prepare fetch")?
        .receive(gix::progress::Discard, &gix::interrupt::IS_INTERRUPTED)
        .context("fetch")?;
    Ok(())
}

/// Resolve the deploy-key path the server uses for git-over-SSH. Mirrors the
/// CLI's `nornir key` resolution: honors `NORNIR_SSH_DIR`, else the `nornir`
/// system user's home (`/home/nornir/.ssh`), else a per-user dev location that
/// never touches the operator's own `~/.ssh`. Returns the private key path only
/// if it exists.
pub fn nornir_ssh_key_path() -> Option<PathBuf> {
    let dir = if let Some(d) = std::env::var_os("NORNIR_SSH_DIR") {
        PathBuf::from(d)
    } else {
        let sys = Path::new("/home/nornir/.ssh");
        if sys.exists() {
            sys.to_path_buf()
        } else if let Some(home) = std::env::var_os("HOME") {
            Path::new(&home).join(".nornir/ssh")
        } else {
            return None;
        }
    };
    let key = dir.join("id_ed25519");
    key.exists().then_some(key)
}

/// Clone-or-fetch `url` into `dest` over SSH with the deploy key at `key_path`,
/// returning the fetched `HEAD` SHA.
///
/// `russh` opens an authenticated `git-upload-pack` channel; gix's blocking git
/// transport (`ConnectMode::Process`) negotiates and receives the pack over it,
/// writing objects + `refs/remotes/origin/*` into the repo. We then point HEAD
/// at the fetched commit and materialize the worktree from its tree.
fn ssh_sync(url: &str, dest: &Path, key_path: &Path) -> Result<String> {
    use gix::protocol::transport::client::git::blocking_io::Connection as GitConnection;
    use gix::protocol::transport::client::git::ConnectMode;
    use gix::protocol::transport::Protocol;

    let loc = crate::ssh::parse_ssh_url(url)?;

    // 1. Cheap ref advertisement: HEAD's SHA + the branch it points at.
    let refs = crate::ssh::ls_remote_blocking(url, key_path)
        .with_context(|| format!("ssh ls-remote {url}"))?;
    let head_sha = refs
        .iter()
        .find(|(_, name)| name == "HEAD")
        .map(|(sha, _)| sha.clone())
        .ok_or_else(|| anyhow!("remote {url} advertised no HEAD"))?;
    // GitHub advertises HEAD's branch too; match by SHA to learn its name.
    let branch = refs
        .iter()
        .find(|(sha, name)| sha == &head_sha && name.starts_with("refs/heads/"))
        .map(|(_, name)| name.clone())
        .unwrap_or_else(|| "refs/heads/main".to_string());

    // Cheap change-detection (ls-remote's purpose): if the worktree is already at
    // this commit, there's nothing to fetch — the common steady-state poll.
    if dest.join(".git").exists()
        && crate::gitio::head_sha(dest).ok().as_deref() == Some(head_sha.as_str())
    {
        return Ok(head_sha);
    }
    eprintln!("nornir-ssh: {url} HEAD={head_sha} changed; fetching pack…");

    // 2. Repo: open if present, else init a fresh non-bare one.
    let mut repo = if dest.join(".git").exists() {
        gix::open(dest).with_context(|| format!("gix::open {}", dest.display()))?
    } else {
        std::fs::create_dir_all(dest).with_context(|| format!("create {}", dest.display()))?;
        gix::init(dest).with_context(|| format!("gix::init {}", dest.display()))?
    };
    // A freshly init'd repo has no user identity; gix needs a committer to write
    // reflogs for the fetched ref updates (and our HEAD update below). Inject the
    // generic in-memory fallback so those succeed without ambient git config.
    let _ = repo.committer_or_set_generic_fallback();

    // 3. Fetch the pack over the russh channel. gix's blocking fetch runs on
    //    THIS thread; the upload-pack runtime's workers handle the socket I/O.
    let mut up = crate::ssh::connect_upload_pack(&loc, key_path)
        .with_context(|| format!("ssh upload-pack {url}"))?;
    let transport = GitConnection::new(
        &mut up.reader,
        &mut up.writer,
        Protocol::V2,
        loc.path.clone(),
        Option::<(String, Option<u16>)>::None,
        ConnectMode::Process,
        false,
    );
    let remote = repo
        .remote_at(url)
        .context("build in-memory remote")?
        .with_refspecs(
            Some("+refs/heads/*:refs/remotes/origin/*"),
            gix::remote::Direction::Fetch,
        )
        .context("set fetch refspecs")?;
    remote
        .to_connection_with_transport(transport)
        .prepare_fetch(gix::progress::Discard, Default::default())
        .context("prepare ssh fetch")?
        .receive(gix::progress::Discard, &gix::interrupt::IS_INTERRUPTED)
        .context("ssh fetch (pack transfer)")?;
    drop(up); // close the ssh channel before touching the worktree

    // 4. Point HEAD at the fetched commit and materialize the worktree.
    set_head(&repo, &branch, &head_sha)?;
    materialize_worktree(&repo, &head_sha, dest)
        .with_context(|| format!("checkout {head_sha} into {}", dest.display()))?;
    eprintln!("nornir-ssh: {url} synced {head_sha} → {}", dest.display());
    Ok(head_sha)
}

/// Create/update `branch` → `sha` (a direct ref) and point `HEAD` at `branch`.
fn set_head(repo: &gix::Repository, branch: &str, sha: &str) -> Result<()> {
    use gix::refs::transaction::{Change, LogChange, PreviousValue, RefEdit, RefLog};
    use gix::refs::{FullName, Target};

    let oid = gix::ObjectId::from_hex(sha.as_bytes()).with_context(|| format!("parse sha {sha}"))?;
    let branch_name: FullName = branch
        .try_into()
        .map_err(|e| anyhow!("invalid branch ref `{branch}`: {e}"))?;
    let log = LogChange {
        mode: RefLog::AndReference,
        force_create_reflog: false,
        message: "nornir: ssh fetch".into(),
    };
    let edits = vec![
        RefEdit {
            change: Change::Update {
                log: log.clone(),
                expected: PreviousValue::Any,
                new: Target::Object(oid),
            },
            name: branch_name.clone(),
            deref: false,
        },
        RefEdit {
            change: Change::Update {
                log,
                expected: PreviousValue::Any,
                new: Target::Symbolic(branch_name),
            },
            name: "HEAD".try_into().expect("HEAD is a valid ref name"),
            deref: false,
        },
    ];
    repo.edit_references(edits).context("set HEAD + branch")?;
    Ok(())
}

/// Materialize the worktree at `dest` from the tree of commit `sha`, using only
/// public gix APIs (no `gix-worktree-state`): clear everything but `.git`, then
/// write each index blob. Handles regular/executable files and symlinks; skips
/// submodule gitlinks. Sufficient for the read-only scans the monitor runs.
fn materialize_worktree(repo: &gix::Repository, sha: &str, dest: &Path) -> Result<()> {
    use gix::index::entry::Mode;

    let oid = gix::ObjectId::from_hex(sha.as_bytes()).with_context(|| format!("parse sha {sha}"))?;
    let tree_id = repo
        .find_commit(oid)
        .with_context(|| format!("find commit {sha}"))?
        .tree_id()
        .context("commit tree")?
        .detach();
    let index = repo
        .index_from_tree(&tree_id)
        .with_context(|| format!("index from tree {tree_id}"))?;

    // Clear the worktree (keep `.git`) so deletions upstream are reflected.
    for entry in std::fs::read_dir(dest).with_context(|| format!("read {}", dest.display()))? {
        let path = entry?.path();
        if path.file_name().map(|n| n == ".git").unwrap_or(false) {
            continue;
        }
        if path.is_dir() {
            std::fs::remove_dir_all(&path).ok();
        } else {
            std::fs::remove_file(&path).ok();
        }
    }

    for entry in index.entries() {
        if entry.mode == Mode::COMMIT {
            continue; // submodule gitlink — no blob to write
        }
        let rel = gix::path::from_bstr(entry.path(&index));
        let full = dest.join(rel.as_ref());
        if let Some(parent) = full.parent() {
            std::fs::create_dir_all(parent)
                .with_context(|| format!("mkdir {}", parent.display()))?;
        }
        let blob = repo
            .find_object(entry.id)
            .with_context(|| format!("blob {} for {}", entry.id, full.display()))?;

        if entry.mode == Mode::SYMLINK {
            #[cfg(unix)]
            {
                use std::os::unix::ffi::OsStrExt;
                let target = std::ffi::OsStr::from_bytes(&blob.data);
                std::fs::remove_file(&full).ok();
                std::os::unix::fs::symlink(target, &full)
                    .with_context(|| format!("symlink {}", full.display()))?;
            }
            #[cfg(not(unix))]
            std::fs::write(&full, &blob.data).with_context(|| format!("write {}", full.display()))?;
        } else {
            std::fs::write(&full, &blob.data).with_context(|| format!("write {}", full.display()))?;
            #[cfg(unix)]
            if entry.mode == Mode::FILE_EXECUTABLE {
                use std::os::unix::fs::PermissionsExt;
                std::fs::set_permissions(&full, std::fs::Permissions::from_mode(0o755)).ok();
            }
        }
    }
    Ok(())
}

/// Ensure `dest` is an up-to-date clone of `url`: clone if absent, else fetch.
/// Returns the resulting `HEAD` SHA. SSH remotes use the deploy key at
/// `ssh_key` (resolved via [`nornir_ssh_key_path`] when `None`).
pub fn clone_or_fetch(url: &str, dest: &Path, ssh_key: Option<&Path>) -> Result<String> {
    if is_ssh_url(url) {
        let resolved;
        let key = match ssh_key {
            Some(k) => k,
            None => {
                resolved = nornir_ssh_key_path().ok_or_else(|| {
                    anyhow!(
                        "SSH remote `{url}` needs a deploy key, but none was found \
                         (set NORNIR_SSH_DIR or install the service so the key lives \
                         at /home/nornir/.ssh/id_ed25519 — see `nornir key show`)"
                    )
                })?;
                resolved.as_path()
            }
        };
        return ssh_sync(url, dest, key);
    }
    if dest.join(".git").exists() {
        fetch_repo(dest)?;
    } else {
        clone_repo(url, dest)?;
    }
    head_sha(dest)
}

/// Recursively upsert every file under `dir` into `editor`, keyed by its
/// path relative to `repo_root`. Skips the `.git` directory.
fn add_dir_recursive(
    repo: &gix::Repository,
    editor: &mut gix::object::tree::Editor<'_>,
    repo_root: &Path,
    dir: &Path,
) -> Result<()> {
    use gix::object::tree::EntryKind;

    let mut entries: Vec<_> = std::fs::read_dir(dir)
        .with_context(|| format!("read_dir {}", dir.display()))?
        .collect::<std::io::Result<Vec<_>>>()
        .with_context(|| format!("iterate {}", dir.display()))?;
    // Deterministic order keeps generated history reproducible.
    entries.sort_by_key(|e| e.file_name());

    for entry in entries {
        let path = entry.path();
        let name = entry.file_name();
        if name == ".git" {
            continue;
        }
        let meta = std::fs::symlink_metadata(&path)
            .with_context(|| format!("stat {}", path.display()))?;
        let ft = meta.file_type();
        if ft.is_dir() {
            add_dir_recursive(repo, editor, repo_root, &path)?;
            continue;
        }
        let rela = path
            .strip_prefix(repo_root)
            .expect("path is under repo_root");
        let rela = gix::path::into_bstr(rela).into_owned();

        let (bytes, kind): (Vec<u8>, EntryKind) = if ft.is_symlink() {
            let target = std::fs::read_link(&path)
                .with_context(|| format!("readlink {}", path.display()))?;
            (gix::path::into_bstr(target).into_owned().into(), EntryKind::Link)
        } else {
            let bytes = std::fs::read(&path).with_context(|| format!("read {}", path.display()))?;
            #[cfg(unix)]
            let kind = {
                use std::os::unix::fs::PermissionsExt;
                if meta.permissions().mode() & 0o111 != 0 {
                    EntryKind::BlobExecutable
                } else {
                    EntryKind::Blob
                }
            };
            #[cfg(not(unix))]
            let kind = EntryKind::Blob;
            (bytes, kind)
        };

        let blob = repo.write_blob(&bytes).context("write blob")?;
        editor
            .upsert(rela.as_ref() as &gix::bstr::BStr, kind, blob.detach())
            .with_context(|| format!("tree upsert {rela}"))?;
    }
    Ok(())
}