podbox/

build.rs

use std::ffi::OsString;
use std::os::unix::fs::PermissionsExt;
use std::path::PathBuf;

use anyhow::{Context, Result};
use nix::fcntl::{Flock, FlockArg};
use sha2::{Digest, Sha256};

use crate::codegen::containerfile;
use crate::codegen::distros::DistroFamily;
use crate::config::Config;
use crate::env::HostEnv;
use crate::error::PodboxError;
use crate::xdg::ResolvedXdgDirs;

/// SHA-256 hex digest of a string, used for lock-file invalidation.
pub fn checksum(content: &str) -> String {
    let mut hasher = Sha256::new();
    hasher.update(content.as_bytes());
    hex::encode(hasher.finalize())
}

/// Build context directory: ~/.local/share/podbox/<name>/
pub fn build_context_dir(name: &str) -> PathBuf {
    dirs::data_dir()
        .unwrap_or_else(|| PathBuf::from("~/.local/share"))
        .join("podbox")
        .join(name)
}

/// Run the full build orchestration.
pub fn run(
    config: &Config,
    env: &HostEnv,
    xdg: &ResolvedXdgDirs,
    dry_run: bool,
    rebuild: bool,
) -> Result<()> {
    if config.image.source().is_prebuilt() {
        run_prebuilt(config, dry_run, rebuild)
    } else {
        // Custom builds bake the embedded guest into the image. Builds from
        // the published crate have no guest (PODBOX_GUEST is None); reject
        // up front so the user never gets partway through codegen first.
        if crate::guest::PODBOX_GUEST.is_none() {
            return Err(PodboxError::GuestBinaryUnavailable.into());
        }
        run_build(config, env, xdg, dry_run, rebuild)
    }
}

// --- Prebuilt image path ----------------------------------------------------

fn run_prebuilt(config: &Config, dry_run: bool, rebuild: bool) -> Result<()> {
    let image_ref = match config.image.source() {
        crate::config::ImageSource::Prebuilt { ref_str } => ref_str,
        _ => config.image.base.clone(),
    };
    let local_tag = format!("localhost/podbox-{}:latest", config.image.name);
    let context_dir = build_context_dir(&config.container.name);
    let lock_path = context_dir.join(".podbox.lock");
    let has_packages = !config.image.packages.install.is_empty();

    // Acquire exclusive build lock (auto-releases on panic/crash via kernel flock)
    let _build_lock = if !dry_run {
        std::fs::create_dir_all(&context_dir)?;
        let file = std::fs::File::create(context_dir.join(".build.lock"))?;
        Some(Flock::lock(file, FlockArg::LockExclusive).map_err(|(_, e)| e)?)
    } else {
        None
    };

    // Checksum covers both the image ref and the install list so that
    // changing either triggers a rebuild.
    let definition_toml = toml::to_string(config)
        .with_context(|| "failed to serialize definition config".to_string())?;
    let config_checksum = checksum(&definition_toml);

    if !rebuild {
        if let Some(lock) = crate::lock::read(&lock_path)? {
            if lock.config_checksum == config_checksum && crate::podman::image_exists(&local_tag)? {
                println!("Prebuilt image already present as {local_tag}. Skipping pull.");
                println!("Use --rebuild to re-pull.");
                return Ok(());
            }
        }
    }

    if dry_run {
        println!("Would pull: {image_ref}");
        if has_packages {
            println!(
                "Would install packages on top: {}",
                config.image.packages.install.join(", ")
            );
        }
        println!("Would tag as: {local_tag}");
        println!("Would write lock file at: {}", lock_path.display());
        return Ok(());
    }

    // Warn on version mismatch from labels (best-effort, image may not exist yet)
    if let Ok(labels) = crate::podman::image_labels(&image_ref) {
        if let Some(guest_ver) = labels
            .get("podbox.guest_version")
            .or_else(|| labels.get("podmgr.guest_version"))
        {
            let guest_clean = guest_ver.trim_start_matches('v');
            let host_clean = crate::VERSION.trim_start_matches('v');
            if guest_clean != host_clean {
                eprintln!(
                    "Warning: image guest version (v{guest_clean}) differs from host (v{host_clean}). \
                     Protocol compatibility will be validated at runtime."
                );
            }
        }
    }

    println!("Pulling {image_ref}...");
    let status = std::process::Command::new("podman")
        .args(["pull", &image_ref])
        .status()?;
    if !status.success() {
        return Err(PodboxError::PullFailed {
            image: image_ref.clone(),
        }
        .into());
    }

    if has_packages {
        // Layer the config's packages on top of the prebuilt image.
        let distro = resolve_prebuilt_distro(config);
        let install_cmd = distro.install_cmd();
        let clean_cmd = distro.clean_cmd();

        let packages = config.image.packages.install.join(" ");
        let run_line = if clean_cmd.is_empty() {
            format!("RUN {install_cmd} {packages}")
        } else {
            format!("RUN {install_cmd} {packages} && {clean_cmd}")
        };

        let containerfile = format!("FROM {image_ref}\n{run_line}\n");

        std::fs::create_dir_all(&context_dir)
            .with_context(|| format!("failed to create context dir '{}'", context_dir.display()))?;

        let containerfile_path = context_dir.join("Containerfile");
        std::fs::write(&containerfile_path, &containerfile).with_context(|| {
            format!(
                "failed to write Containerfile to '{}'",
                containerfile_path.display()
            )
        })?;

        println!("Installing packages on top of prebuilt image...");
        let args: Vec<std::ffi::OsString> = vec![
            "build".into(),
            "-t".into(),
            local_tag.clone().into(),
            "-f".into(),
            containerfile_path.clone().into(),
            context_dir.clone().into(),
        ];
        let status = crate::process::spawn_interactive("podman", &args)
            .with_context(|| format!("failed to build prebuilt overlay for '{image_ref}'"))?;
        if !status.success() {
            return Err(PodboxError::BuildFailed("overlay build failed".into()).into());
        }
        println!("Image {local_tag} ready with packages installed.");
    } else {
        println!("Tagging as {local_tag}...");
        let status = std::process::Command::new("podman")
            .args(["tag", &image_ref, &local_tag])
            .status()?;
        if !status.success() {
            return Err(PodboxError::TagFailed {
                image: local_tag.clone(),
            }
            .into());
        }
        println!("Image {local_tag} ready.");
    }

    std::fs::create_dir_all(&config.container.home).with_context(|| {
        format!(
            "failed to create home dir '{}'",
            config.container.home.display()
        )
    })?;
    let digest = crate::podman::image_digest(&local_tag)?;
    let lock = crate::lock::LockFile {
        config_checksum,
        image_digest: digest,
    };
    crate::lock::write(&lock_path, &lock)?;

    Ok(())
}

/// Resolve the distro family for package installation on a prebuilt image.
/// Respects the explicit `manager` field in the config, falling back to
/// name-based detection via `DistroFamily`.
fn resolve_prebuilt_distro(config: &Config) -> DistroFamily {
    match config.image.packages.manager {
        crate::config::PackageManager::Apt => DistroFamily::DebianLike,
        crate::config::PackageManager::Dnf => DistroFamily::FedoraLike,
        crate::config::PackageManager::Pacman => DistroFamily::ArchLike,
        crate::config::PackageManager::Apk => DistroFamily::AlpineLike,
        crate::config::PackageManager::Zypper => DistroFamily::SuseLike,
    }
}

// --- Custom build path ------------------------------------------------------

fn run_build(
    config: &Config,
    _env: &HostEnv,
    _xdg: &ResolvedXdgDirs,
    dry_run: bool,
    rebuild: bool,
) -> Result<()> {
    let name = &config.container.name;
    let context_dir = build_context_dir(name);
    let containerfile_path = context_dir.join("Containerfile");
    let lock_path = context_dir.join(".podbox.lock");

    // Acquire exclusive build lock (auto-releases on panic/crash via kernel flock)
    let _build_lock = if !dry_run {
        std::fs::create_dir_all(&context_dir)?;
        let file = std::fs::File::create(context_dir.join(".build.lock"))?;
        Some(Flock::lock(file, FlockArg::LockExclusive).map_err(|(_, e)| e)?)
    } else {
        None
    };

    // Guarded by `run()` for custom builds; prebuilt builds never reach here.
    let guest_bin = crate::guest::PODBOX_GUEST.expect("custom build without embedded guest");

    let definition_toml = toml::to_string(config)
        .with_context(|| "failed to serialize definition config".to_string())?;
    let config_checksum = checksum(&definition_toml);

    if !rebuild {
        if let Some(lock) = crate::lock::read(&lock_path)? {
            if lock.config_checksum == config_checksum {
                println!("Definition unchanged and image already built. Skipping.");
                println!("Use --rebuild to force.");
                return Ok(());
            }
        }
    }

    let containerfile = containerfile::generate(config, "podbox-guest")?;

    if dry_run {
        println!("=== Build context: {} ===", context_dir.display());
        println!("=== Containerfile ===");
        println!("{containerfile}");
        println!();
        println!("=== Embedded podbox-guest ===");
        println!("{} bytes (embedded in podbox binary)", guest_bin.len());
        println!(
            "podman build -t localhost/podbox-{}:latest {}",
            config.image.name,
            context_dir.display()
        );
        return Ok(());
    }

    std::fs::create_dir_all(&context_dir).map_err(|e| PodboxError::HomeCreateFailed {
        path: context_dir.clone(),
        source: e,
    })?;
    let _ = std::fs::set_permissions(&context_dir, std::fs::Permissions::from_mode(0o700));

    std::fs::write(&containerfile_path, containerfile).with_context(|| {
        format!(
            "failed to write Containerfile to '{}'",
            containerfile_path.display()
        )
    })?;

    let guest_dest = context_dir.join("podbox-guest");
    std::fs::write(&guest_dest, guest_bin)
        .with_context(|| format!("failed to write guest binary to '{}'", guest_dest.display()))?;

    std::fs::create_dir_all(&config.container.home).with_context(|| {
        format!(
            "failed to create home dir '{}'",
            config.container.home.display()
        )
    })?;

    let tag = format!("localhost/podbox-{}:latest", config.image.name);
    let args: Vec<OsString> = vec![
        "build".into(),
        "-t".into(),
        tag.clone().into(),
        context_dir.clone().into(),
    ];

    println!("Building image {tag}...");
    let status = crate::process::spawn_interactive("podman", &args)
        .with_context(|| format!("failed to execute podman build for image '{tag}'"))?;
    if !status.success() {
        return Err(PodboxError::BuildFailed("build failed".into()).into());
    }
    println!("Image {tag} built successfully.");

    let digest = crate::podman::image_digest(&tag)?;
    let lock = crate::lock::LockFile {
        config_checksum,
        image_digest: digest,
    };
    crate::lock::write(&lock_path, &lock)?;

    Ok(())
}