//! A job's workspace: the files of the state being built, written to a

//! scratch directory and packed into an ext4 image for the microVM

//! (docs/m0.md §2). Returns each file's content hash for the scope hash.

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

use flow_core::Hash;

use oxy_core::hash::ChangeHash;

use oxy_core::objects::NodeKind;

use oxy_core::repo::Repo;

use oxy_core::state::FileContent;

use std::path::Path;

pub type Files = Vec<(String, Hash)>;

/// Write the state `heads` of `repo` under `dir`.

pub fn export_state(repo: &Repo, heads: &[ChangeHash], dir: &Path) -> Result<Files> {

    let snapshot = repo.load_state(heads).context("load the state")?.materialize();

    let mut files = Vec::new();

    for (path, f) in &snapshot.files {

        if path.split('/').any(|p| p.is_empty() || p == "." || p == ".." || p == ".oxy") {

            continue;

        }

        let target = dir.join(path);

        match (&f.kind, &f.content) {

            (NodeKind::Dir, _) | (_, FileContent::Dir) => std::fs::create_dir_all(&target)?,

            (NodeKind::Subrepo, _) => {}

            (kind, content) => {

                let bytes = match content {

                    FileContent::Text { bytes, .. } => bytes.clone(),

                    FileContent::Opaque { blobs } => match blobs.first() {

                        Some(b) => repo.read_blob(b)?,

                        None => Vec::new(),

                    },

                    FileContent::Dir => unreachable!(),

                };

                if let Some(parent) = target.parent() {

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

                }

                if *kind == NodeKind::Symlink {

                    let to = String::from_utf8_lossy(&bytes).into_owned();

                    std::os::unix::fs::symlink(&to, &target).with_context(|| format!("symlink {path}"))?;

                } else {

                    std::fs::write(&target, &bytes).with_context(|| format!("write {path}"))?;

                    if f.mode.exec {

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

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

                    }

                }

                files.push((path.clone(), *blake3::hash(&bytes).as_bytes()));

            }

        }

    }

    Ok(files)

}

/// Copy a working directory (without `.oxy` and what `.oxyignore` and

/// `.gitignore` exclude) under `dir`, for `flow run`.

pub fn copy_tree(src: &Path, dir: &Path) -> Result<Files> {

    let mut files = Vec::new();

    let walk = ignore::WalkBuilder::new(src)

        .hidden(false)

        .git_ignore(true)

        .require_git(false)

        .add_custom_ignore_filename(".oxyignore")

        .filter_entry(|e| e.file_name() != ".oxy" && e.file_name() != ".git")

        .build();

    for entry in walk {

        let entry = entry?;

        let rel = entry.path().strip_prefix(src)?;

        if rel.as_os_str().is_empty() {

            continue;

        }

        let rel_s = rel.to_string_lossy().replace('\\', "/");

        let target = dir.join(rel);

        let ft = entry.file_type().context("file type")?;

        if ft.is_dir() {

            std::fs::create_dir_all(&target)?;

        } else if ft.is_symlink() {

            let to = std::fs::read_link(entry.path())?;

            std::os::unix::fs::symlink(&to, &target)?;

            files.push((rel_s, *blake3::hash(to.to_string_lossy().as_bytes()).as_bytes()));

        } else if ft.is_file() {

            std::fs::copy(entry.path(), &target)?;

            files.push((rel_s, *blake3::hash(&std::fs::read(entry.path())?).as_bytes()));

        }

    }

    Ok(files)

}

/// Pack `dir` into an ext4 image whose root belongs to this user, so the

/// job (which runs as the owner of `/src`) can write to it.

pub fn image(dir: &Path, out: &Path) -> Result<()> {

    let used: u64 = ignore::WalkBuilder::new(dir)

        .hidden(false)

        .ignore(false)

        .git_ignore(false)

        .build()

        .flatten()

        .filter_map(|e| e.metadata().ok())

        .map(|m| m.len().max(4096))

        .sum();

    let mib = used * 12 / 10 / (1 << 20) + 512;

    let (uid, gid) = unsafe { (libc::getuid(), libc::getgid()) };

    let status = std::process::Command::new("mkfs.ext4")

        .args(["-q", "-F", "-L", "workspace", "-E"])

        .arg(format!("root_owner={uid}:{gid}"))

        .arg("-d")

        .arg(dir)

        .arg(out)

        .arg(format!("{mib}M"))

        .status()

        .context("run mkfs.ext4 (e2fsprogs 1.43 or later)")?;

    if !status.success() {

        bail!("mkfs.ext4 failed for the workspace image");

    }

    Ok(())

}