alef 0.62.6

//! Build provenance rendered into `alef --version`.
//!
//! `build.rs` stamps the commit sha, working-tree state, and build time into `rustc-env` vars at
//! compile time; this module turns them into the long version string clap prints for `--version`.
//!
//! The bare semver stays alone on the first line. Existing consumers — release gates, the
//! `alef_version` pin in `alef.toml`, `expect_contains` checks in generated Homebrew test apps —
//! read that line, and provenance must not cost them anything. ~keep

use std::sync::LazyLock;

/// Full commit sha, or `"unknown"` when git could not answer at build time.
pub(crate) const COMMIT: &str = env!("ALEF_BUILD_COMMIT");

/// First 12 characters of [`COMMIT`], or `"unknown"`.
pub(crate) const COMMIT_SHORT: &str = env!("ALEF_BUILD_COMMIT_SHORT");

/// `"clean"`, `"dirty"`, or `"unknown"`. See `build.rs` for why `clean` is the weakest of the
/// three claims: it can be stale, while `dirty` and the sha cannot. ~keep
pub(crate) const TREE_STATE: &str = env!("ALEF_BUILD_TREE_STATE");

/// Build time as seconds since the Unix epoch, or `"unknown"`.
pub(crate) const TIMESTAMP: &str = env!("ALEF_BUILD_TIMESTAMP");

/// The value `build.rs` emits when git cannot answer.
const UNKNOWN: &str = "unknown";

const TREE_CLEAN: &str = "clean";
const TREE_DIRTY: &str = "dirty";

/// The token an operator or a script greps for to reject a non-reproducible binary. Uppercase and
/// unhyphenated so it cannot be confused with the lowercase `tree:` state token. ~keep
const DIRTY_MARKER: &str = "DIRTY";

static LONG_VERSION: LazyLock<String> =
    LazyLock::new(|| render_long_version(env!("CARGO_PKG_VERSION"), COMMIT_SHORT, COMMIT, TREE_STATE, TIMESTAMP));

/// The multi-line body clap prints after the binary name for `--version`.
///
/// `-V` keeps printing the short, single-line `alef <semver>`. ~keep
pub(crate) fn long_version() -> &'static str {
    LONG_VERSION.as_str()
}

fn render_long_version(
    semver: &str,
    commit_short: &str,
    commit_full: &str,
    tree_state: &str,
    timestamp: &str,
) -> String {
    let mut out = String::with_capacity(320);
    out.push_str(semver);

    out.push_str("\ncommit:  ");
    if commit_short == UNKNOWN || commit_full == UNKNOWN {
        out.push_str(UNKNOWN);
    } else {
        out.push_str(commit_short);
        out.push_str(" (");
        out.push_str(commit_full);
        out.push(')');
    }

    out.push_str("\nbuilt:   ");
    out.push_str(&render_timestamp(timestamp));

    out.push_str("\ntree:    ");
    match tree_state {
        TREE_CLEAN => out.push_str(TREE_CLEAN),
        TREE_DIRTY => {
            out.push_str(DIRTY_MARKER);
            out.push_str("\nWARNING: built from a ");
            out.push_str(DIRTY_MARKER);
            out.push_str(" working tree — this binary is not reproducible from ");
            if commit_short == UNKNOWN {
                out.push_str("any commit.\n         ");
            } else {
                out.push_str("commit\n         ");
                out.push_str(commit_short);
                out.push_str(". ");
            }
            out.push_str("Do not attribute a measurement made with it to a source revision.");
        }
        _ => {
            out.push_str(UNKNOWN);
            out.push_str("\nWARNING: build provenance is UNKNOWN — no git metadata was available at build time.");
            out.push_str("\n         This binary is not attributable to any commit.");
        }
    }

    // No trailing newline: clap appends one when it renders `{name} {long_version}`. ~keep
    out
}

/// Render epoch seconds as an RFC 3339 UTC instant, degrading to `"unknown"` rather than to an
/// empty field: the point of the timestamp is telling apart same-version binaries built hours
/// apart, and a blank one tells you nothing while looking like it did. ~keep
fn render_timestamp(epoch_seconds: &str) -> String {
    epoch_seconds
        .parse::<i64>()
        .ok()
        .and_then(|seconds| chrono::DateTime::from_timestamp(seconds, 0))
        .map_or_else(
            || UNKNOWN.to_string(),
            |instant| instant.format("%Y-%m-%dT%H:%M:%SZ").to_string(),
        )
}

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

    const FULL_SHA: &str = "964c552a267ccfb50a0e6f1d3b2c4a8e7f019d24";
    const SHORT_SHA: &str = "964c552a267c";
    /// 2001-09-09T01:46:40Z — a well-known instant, so the exact rendering below is checkable by
    /// inspection rather than by trusting a date library to agree with itself.
    const EPOCH: &str = "1000000000";

    fn render(tree_state: &str) -> String {
        render_long_version("0.61.0", SHORT_SHA, FULL_SHA, tree_state, EPOCH)
    }

    /// The whole point of the first line staying bare: `hooks/alef_hook.py`, release gates, and
    /// generated Homebrew `--version` checks all read the semver out of it.
    #[test]
    fn first_line_is_the_bare_semver_for_every_tree_state() {
        for state in [TREE_CLEAN, TREE_DIRTY, UNKNOWN] {
            let rendered = render(state);
            let first_line = rendered.lines().next().expect("rendered version has a first line");
            assert_eq!(first_line, "0.61.0", "first line changed for tree state {state}");
        }
    }

    /// The load-bearing assertion: the marker appears when and only when the build was stamped
    /// dirty. A clean or unattributable build must never print it, and a dirty one must never
    /// omit it.
    #[test]
    fn dirty_marker_appears_if_and_only_if_the_tree_state_is_dirty() {
        for (state, expected) in [(TREE_CLEAN, false), (TREE_DIRTY, true), (UNKNOWN, false)] {
            let rendered = render(state);
            assert_eq!(
                rendered.contains(DIRTY_MARKER),
                expected,
                "tree state {state} rendered the wrong dirty marker presence:\n{rendered}"
            );
        }
    }

    #[test]
    fn dirty_build_names_the_commit_it_cannot_be_reproduced_from() {
        let rendered = render(TREE_DIRTY);
        assert!(rendered.contains("not reproducible from commit"), "{rendered}");
        assert!(rendered.contains(SHORT_SHA), "{rendered}");
    }

    #[test]
    fn clean_build_reports_both_short_and_full_sha() {
        let rendered = render(TREE_CLEAN);
        assert!(
            rendered.contains(&format!("commit:  {SHORT_SHA} ({FULL_SHA})")),
            "{rendered}"
        );
        assert!(rendered.contains("tree:    clean"), "{rendered}");
        assert!(!rendered.contains("WARNING"), "{rendered}");
        assert!(!rendered.ends_with('\n'), "clap appends the trailing newline itself");
    }

    /// A tarball build with no `.git` must say so out loud. An empty or absent field would read as
    /// a clean, attributable build, which is the failure this stamp exists to prevent.
    #[test]
    fn missing_git_metadata_renders_explicit_unknown_never_an_empty_field() {
        let rendered = render_long_version("0.61.0", UNKNOWN, UNKNOWN, UNKNOWN, UNKNOWN);
        assert!(rendered.contains("commit:  unknown"), "{rendered}");
        assert!(rendered.contains("built:   unknown"), "{rendered}");
        assert!(rendered.contains("tree:    unknown"), "{rendered}");
        assert!(rendered.contains("not attributable to any commit"), "{rendered}");
        assert!(!rendered.contains(DIRTY_MARKER), "{rendered}");
    }

    #[test]
    fn timestamp_renders_as_utc_rfc3339() {
        assert_eq!(render_timestamp("0"), "1970-01-01T00:00:00Z");
        assert_eq!(render_timestamp(EPOCH), "2001-09-09T01:46:40Z");
        assert_eq!(render_timestamp(UNKNOWN), UNKNOWN);
        assert_eq!(render_timestamp(""), UNKNOWN);
    }

    /// Guards the vars `build.rs` actually stamped into this build: whatever the environment was,
    /// none of them may be empty, because an empty field is the shape of a clean build.
    #[test]
    fn stamped_constants_are_never_empty() {
        for (name, value) in [
            ("ALEF_BUILD_COMMIT", COMMIT),
            ("ALEF_BUILD_COMMIT_SHORT", COMMIT_SHORT),
            ("ALEF_BUILD_TREE_STATE", TREE_STATE),
            ("ALEF_BUILD_TIMESTAMP", TIMESTAMP),
        ] {
            assert!(!value.trim().is_empty(), "{name} was stamped empty");
        }
        assert!(
            matches!(TREE_STATE, TREE_CLEAN | TREE_DIRTY | UNKNOWN),
            "unexpected tree state {TREE_STATE}"
        );
    }

    #[test]
    fn long_version_is_stable_across_calls_and_contains_the_package_version() {
        let first = long_version();
        assert_eq!(first, long_version());
        assert!(first.starts_with(env!("CARGO_PKG_VERSION")), "{first}");
    }
}