pkgwatch/src/builder.rs

//! Turns an already-downloaded, already-verified artifact into a built
//! pacman package: generates a PKGBUILD, then runs `makepkg`. Hides all
//! PKGBUILD templating and upstream-string validation behind `build()`.

use crate::config::Package;
use crate::hash;
use anyhow::{Context, Result, bail};
use std::path::{Path, PathBuf};
use std::process::Command;

/// Archive extensions `makepkg` auto-extracts before `package()` runs.
/// Longest-first so `.tar.gz` isn't shadowed by a hypothetical `.gz` entry.
const ARCHIVE_EXTENSIONS: &[&str] = &[".tar.gz", ".tar.xz", ".tar.zst", ".tar.bz2", ".tgz", ".zip"];

/// Everything needed to generate and build a PKGBUILD for one release.
pub struct BuildRequest<'a> {
    pub pkg_name: &'a str,
    pub pkg: &'a Package,
    pub version: &'a str,
    pub repo: &'a str,
    pub asset_name: &'a str,
    pub download_url: &'a str,
    pub artifact_path: &'a Path,
}

pub struct BuildResult {
    /// The built `.pkg.tar.zst`, ready for `publisher::publish`.
    pub package_path: PathBuf,
    /// `makepkg`'s package staging directory (`$pkgdir`), still present
    /// after a successful build — lets `sanity` exercise the freshly built
    /// binary without installing it system-wide first.
    pub pkgdir: PathBuf,
}

/// Generates a PKGBUILD around an already-downloaded, already-verified
/// artifact, then runs `makepkg` in `build_dir`.
///
/// Deliberately one fixed "prebuilt binary" shape, not a templating engine
/// — see docs/SPEC.md > Scaling > Template reuse. Covers the two shapes the two
/// currently-tracked packages actually need: a bare-binary download
/// (scaleway-cli) and a tarball containing a same-named directory (uv).
/// Extend when a third real shape shows up rather than guessing at
/// generality now.
pub fn build(req: &BuildRequest, build_dir: &Path) -> Result<BuildResult> {
    let pkgbuild = generate_pkgbuild(req)?;

    std::fs::create_dir_all(build_dir)
        .with_context(|| format!("creating build dir {}", build_dir.display()))?;
    std::fs::write(build_dir.join("PKGBUILD"), pkgbuild)?;
    // makepkg looks for the source file by its declared name next to
    // PKGBUILD; pre-seed it with the copy pkgwatch already downloaded and
    // verified so makepkg's own sha256 check passes without re-fetching
    // from the network (and without trusting the network a second time).
    std::fs::copy(req.artifact_path, build_dir.join(req.asset_name))?;

    let status = Command::new("makepkg")
        .args(["--noconfirm", "--force"])
        .current_dir(build_dir)
        .status()
        .context("running makepkg (is base-devel installed?)")?;
    if !status.success() {
        bail!("makepkg failed for {} {}", req.pkg_name, req.version);
    }

    let package_path = find_built_package(build_dir, req.pkg_name, req.version)?;
    let pkgdir = build_dir.join("pkg").join(req.pkg_name);
    Ok(BuildResult {
        package_path,
        pkgdir,
    })
}

/// Builds the PKGBUILD text for `req`, validating every upstream-controlled
/// string first (see docs/SPEC.md > Architecture > Builder: "strict validation
/// on any upstream-controlled string ... never unescaped interpolation").
/// Pure and side-effect-free so it's testable without invoking `makepkg`.
fn generate_pkgbuild(req: &BuildRequest) -> Result<String> {
    validate_pkgname(req.pkg_name)?;
    validate_pkgver(req.version)?;
    validate_shell_safe("asset name", req.asset_name)?;
    validate_shell_safe("download url", req.download_url)?;
    validate_shell_safe("repo", req.repo)?;

    let binary_name = req.pkg.binary_name(req.pkg_name);
    validate_pkgname(binary_name)?;

    let sha256 = hash::sha256_hex_file(req.artifact_path)?;

    let install_source = match archive_stem(req.asset_name) {
        Some(stem) => format!("{stem}/{binary_name}"),
        None => req.asset_name.to_string(),
    };

    Ok(format!(
        "# Maintainer: pkgwatch (auto-generated — do not edit by hand,\n\
         # edits are overwritten on the next update)\n\
         pkgname='{name}'\n\
         pkgver='{version}'\n\
         pkgrel=1\n\
         pkgdesc='{repo} release {version}, packaged by pkgwatch'\n\
         arch=('x86_64')\n\
         url='https://github.com/{repo}'\n\
         license=('unknown')\n\
         options=('!strip')\n\
         source=('{asset}::{url}')\n\
         sha256sums=('{sha256}')\n\
         \n\
         package() {{\n\
         \x20   install -Dm755 \"${{srcdir}}/{install_source}\" \"${{pkgdir}}/usr/bin/{binary_name}\"\n\
         }}\n",
        name = req.pkg_name,
        version = req.version,
        repo = req.repo,
        asset = req.asset_name,
        url = req.download_url,
    ))
}

/// Matches `<prefix><anything>.pkg.tar.<compression>` — not hardcoded to
/// `.zst` specifically, since `PKGEXT` in makepkg.conf can be set to any
/// of pacman's supported compressions (`.xz`, `.gz`, `.bz2`, ...). This
/// box's default happens to be `.zst`, but guessing wrong would otherwise
/// report a false "makepkg failed" for a build that actually succeeded.
fn find_built_package(build_dir: &Path, pkg_name: &str, version: &str) -> Result<PathBuf> {
    let prefix = format!("{pkg_name}-{version}-");
    for entry in std::fs::read_dir(build_dir)? {
        let path = entry?.path();
        let Some(file_name) = path.file_name().and_then(|n| n.to_str()) else {
            continue;
        };
        if file_name.starts_with(&prefix) && file_name.contains(".pkg.tar.") {
            return Ok(path);
        }
    }
    bail!(
        "makepkg reported success but no {prefix}*.pkg.tar.* found in {}",
        build_dir.display()
    )
}

/// Strips a recognized archive extension, returning the resulting stem —
/// the directory name `makepkg` extracts a same-named tarball into, by
/// the convention every currently-tracked tarball-shaped package follows.
/// `None` means the asset is a bare binary download (no extraction).
fn archive_stem(asset_name: &str) -> Option<&str> {
    ARCHIVE_EXTENSIONS
        .iter()
        .find_map(|ext| asset_name.strip_suffix(ext))
}

/// Rejects characters that are dangerous in *either* quoting style the
/// PKGBUILD template uses: a single quote breaks out of the single-quoted
/// fields (`pkgname`, `sha256sums`, ...); `$`, a backtick, or a backslash
/// are still live inside the double-quoted `install()` line, where
/// `asset_name` (via `install_source`) and `binary_name` end up embedded
/// so `${srcdir}`/`${pkgdir}` can expand. A single check covering both
/// contexts is safer than trying to remember which fields land in which
/// quoting style. See docs/SPEC.md > Architecture > Builder ("never unescaped
/// interpolation").
fn validate_shell_safe(field: &str, value: &str) -> Result<()> {
    if value.contains(['\'', '\n', '$', '`', '\\']) {
        bail!("{field} '{value}' contains an unsafe character for a generated PKGBUILD");
    }
    Ok(())
}

/// A pacman `pkgver` may only contain alphanumerics, `.`, `_`, `+` — no
/// hyphens (pacman reserves `-` as the pkgver/pkgrel separator in the
/// final package filename) and no shell metacharacters.
fn validate_pkgver(version: &str) -> Result<()> {
    let valid = !version.is_empty()
        && version
            .chars()
            .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '+'));
    if !valid {
        bail!("'{version}' is not a valid pacman pkgver (only [A-Za-z0-9._+] allowed)");
    }
    Ok(())
}

/// A pacman package/binary name may only contain lowercase alphanumerics
/// plus `@ . _ + -`.
fn validate_pkgname(name: &str) -> Result<()> {
    let valid = !name.is_empty()
        && name.chars().all(|c| {
            c.is_ascii_lowercase() || c.is_ascii_digit() || matches!(c, '@' | '.' | '_' | '+' | '-')
        });
    if !valid {
        bail!("'{name}' is not a valid pacman package name");
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn archive_stem_strips_known_extensions() {
        assert_eq!(
            archive_stem("uv-x86_64-unknown-linux-gnu.tar.gz"),
            Some("uv-x86_64-unknown-linux-gnu")
        );
        assert_eq!(archive_stem("thing.zip"), Some("thing"));
    }

    #[test]
    fn archive_stem_none_for_bare_binary() {
        assert_eq!(archive_stem("scaleway-cli_2.62.0_linux_amd64"), None);
    }

    #[test]
    fn find_built_package_matches_default_zst_extension() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("uv-0.12.15-1-x86_64.pkg.tar.zst"), b"").unwrap();
        let found = find_built_package(dir.path(), "uv", "0.12.15").unwrap();
        assert_eq!(found, dir.path().join("uv-0.12.15-1-x86_64.pkg.tar.zst"));
    }

    #[test]
    fn find_built_package_matches_non_default_pkgext() {
        // A box with PKGEXT='.pkg.tar.xz' in makepkg.conf shouldn't report
        // a false failure just because this crate's default assumption
        // (.zst) doesn't match.
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("uv-0.12.15-1-x86_64.pkg.tar.xz"), b"").unwrap();
        let found = find_built_package(dir.path(), "uv", "0.12.15").unwrap();
        assert_eq!(found, dir.path().join("uv-0.12.15-1-x86_64.pkg.tar.xz"));
    }

    #[test]
    fn find_built_package_ignores_non_matching_prefix() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("other-0.12.15-1-x86_64.pkg.tar.zst"), b"").unwrap();
        assert!(find_built_package(dir.path(), "uv", "0.12.15").is_err());
    }

    #[test]
    fn find_built_package_errors_with_clear_message_when_nothing_matches() {
        let dir = tempfile::tempdir().unwrap();
        let err = find_built_package(dir.path(), "uv", "0.12.15").unwrap_err();
        assert!(err.to_string().contains("uv-0.12.15-"));
        assert!(err.to_string().contains(".pkg.tar.*"));
    }

    #[test]
    fn validate_pkgver_accepts_dotted_version() {
        assert!(validate_pkgver("2.62.0").is_ok());
    }

    #[test]
    fn validate_pkgver_rejects_hyphen() {
        assert!(validate_pkgver("2.62.0-dbg1").is_err());
    }

    #[test]
    fn validate_pkgver_rejects_shell_metacharacters() {
        assert!(validate_pkgver("2.62.0; rm -rf /").is_err());
    }

    #[test]
    fn validate_pkgver_rejects_empty() {
        assert!(validate_pkgver("").is_err());
    }

    #[test]
    fn validate_pkgname_accepts_hyphenated_name() {
        assert!(validate_pkgname("scaleway-cli").is_ok());
    }

    #[test]
    fn validate_pkgname_rejects_uppercase() {
        assert!(validate_pkgname("Scaleway-CLI").is_err());
    }

    #[test]
    fn validate_shell_safe_rejects_single_quote() {
        assert!(validate_shell_safe("asset name", "thing'; touch pwned #.tar.gz").is_err());
    }

    #[test]
    fn validate_shell_safe_rejects_newline() {
        assert!(validate_shell_safe("download url", "https://example.com/a\nb").is_err());
    }

    #[test]
    fn validate_shell_safe_rejects_dollar_sign() {
        // asset_name lands inside a double-quoted string via
        // install_source — $() command substitution is still live there
        // even though single-quote breakout isn't.
        assert!(validate_shell_safe("asset name", "thing$(touch pwned).tar.gz").is_err());
    }

    #[test]
    fn validate_shell_safe_rejects_backtick() {
        assert!(validate_shell_safe("asset name", "thing`touch pwned`.tar.gz").is_err());
    }

    #[test]
    fn validate_shell_safe_rejects_backslash() {
        assert!(validate_shell_safe("asset name", "thing\\$(touch pwned).tar.gz").is_err());
    }

    #[test]
    fn validate_shell_safe_accepts_normal_url() {
        assert!(validate_shell_safe("download url", "https://example.com/a/b.tar.gz").is_ok());
    }

    fn make_package(binary_name: Option<&str>) -> Package {
        let toml_text = match binary_name {
            Some(bin) => format!(
                r#"
                repo = "o/r"
                asset_pattern = "x"
                binary_name = "{bin}"
                [verification]
                method = "github-attestation"
                "#
            ),
            None => r#"
                repo = "o/r"
                asset_pattern = "x"
                [verification]
                method = "github-attestation"
                "#
            .to_string(),
        };
        toml::from_str(&toml_text).unwrap()
    }

    #[test]
    fn build_rejects_unsafe_version() {
        let pkg = make_package(None);
        let dir = tempfile::tempdir().unwrap();
        let artifact_path = dir.path().join("thing.tar.gz");
        std::fs::write(&artifact_path, b"data").unwrap();

        let req = BuildRequest {
            pkg_name: "thing",
            pkg: &pkg,
            version: "1.0.0-dbg1",
            repo: "o/r",
            asset_name: "thing.tar.gz",
            download_url: "https://example.com/thing.tar.gz",
            artifact_path: &artifact_path,
        };
        let build_dir = dir.path().join("build");
        assert!(build(&req, &build_dir).is_err());
    }

    #[test]
    fn generate_pkgbuild_bare_binary_installs_under_binary_name_override() {
        let pkg = make_package(Some("scw"));
        let dir = tempfile::tempdir().unwrap();
        let artifact_path = dir.path().join("scaleway-cli_2.62.0_linux_amd64");
        std::fs::write(&artifact_path, b"binary-bytes").unwrap();
        let expected_sha = hash::sha256_hex(b"binary-bytes");

        let req = BuildRequest {
            pkg_name: "scaleway-cli",
            pkg: &pkg,
            version: "2.62.0",
            repo: "scaleway/scaleway-cli",
            asset_name: "scaleway-cli_2.62.0_linux_amd64",
            download_url: "https://github.com/scaleway/scaleway-cli/releases/download/v2.62.0/scaleway-cli_2.62.0_linux_amd64",
            artifact_path: &artifact_path,
        };
        let pkgbuild = generate_pkgbuild(&req).unwrap();

        assert!(pkgbuild.contains("pkgname='scaleway-cli'"));
        assert!(pkgbuild.contains("pkgver='2.62.0'"));
        assert!(pkgbuild.contains(&format!("sha256sums=('{expected_sha}')")));
        // Bare binary (no archive extension) — installed straight from
        // srcdir under the overridden binary name, not the pkgname.
        assert!(pkgbuild.contains(
            "install -Dm755 \"${srcdir}/scaleway-cli_2.62.0_linux_amd64\" \"${pkgdir}/usr/bin/scw\""
        ));
    }

    #[test]
    fn generate_pkgbuild_tarball_installs_from_extracted_stem_dir() {
        let pkg = make_package(None);
        let dir = tempfile::tempdir().unwrap();
        let artifact_path = dir.path().join("uv-x86_64-unknown-linux-gnu.tar.gz");
        std::fs::write(&artifact_path, b"tarball-bytes").unwrap();

        let req = BuildRequest {
            pkg_name: "uv",
            pkg: &pkg,
            version: "0.12.15",
            repo: "astral-sh/uv",
            asset_name: "uv-x86_64-unknown-linux-gnu.tar.gz",
            download_url: "https://github.com/astral-sh/uv/releases/download/0.12.15/uv-x86_64-unknown-linux-gnu.tar.gz",
            artifact_path: &artifact_path,
        };
        let pkgbuild = generate_pkgbuild(&req).unwrap();

        // No binary_name override — pkgname doubles as the binary name,
        // and makepkg extracts the tarball into a same-named directory.
        assert!(pkgbuild.contains(
            "install -Dm755 \"${srcdir}/uv-x86_64-unknown-linux-gnu/uv\" \"${pkgdir}/usr/bin/uv\""
        ));
    }

    #[test]
    fn generate_pkgbuild_rejects_download_url_with_single_quote() {
        let pkg = make_package(None);
        let dir = tempfile::tempdir().unwrap();
        let artifact_path = dir.path().join("thing.tar.gz");
        std::fs::write(&artifact_path, b"data").unwrap();

        let req = BuildRequest {
            pkg_name: "thing",
            pkg: &pkg,
            version: "1.0.0",
            repo: "o/r",
            asset_name: "thing.tar.gz",
            download_url: "https://example.com/x'; touch pwned #.tar.gz",
            artifact_path: &artifact_path,
        };
        assert!(generate_pkgbuild(&req).is_err());
    }

    #[test]
    fn generate_pkgbuild_rejects_asset_name_with_command_substitution() {
        // Regression test: asset_name feeds install_source, which is
        // embedded in the double-quoted install() line, not a
        // single-quoted field — a single-quote-only check would miss this.
        let pkg = make_package(None);
        let dir = tempfile::tempdir().unwrap();
        let artifact_path = dir.path().join("thing.tar.gz");
        std::fs::write(&artifact_path, b"data").unwrap();

        let req = BuildRequest {
            pkg_name: "thing",
            pkg: &pkg,
            version: "1.0.0",
            repo: "o/r",
            asset_name: "thing$(touch pwned).tar.gz",
            download_url: "https://example.com/thing.tar.gz",
            artifact_path: &artifact_path,
        };
        assert!(generate_pkgbuild(&req).is_err());
    }
}