git-closure 0.1.0

use std::fs;
use std::io::Read as _;
use std::path::{Component, Path, PathBuf};
use std::process::Command;

use flate2::read::GzDecoder;
use tempfile::TempDir;

use crate::error::GitClosureError;
use crate::utils::{
    ensure_no_symlink_ancestors, lexical_normalize, reject_if_symlink, truncate_stderr,
};

type Result<T> = std::result::Result<T, GitClosureError>;

const GITHUB_API_BASE: &str = "https://api.github.com/repos";
const GITHUB_TOKEN_ENV: &str = "GCL_GITHUB_TOKEN";

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProviderKind {
    Auto,
    Local,
    GitClone,
    Nix,
    GithubApi,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum SourceSpec {
    LocalPath(PathBuf),
    GitHubRepo {
        owner: String,
        repo: String,
        reference: Option<String>,
    },
    GitLabRepo {
        group: String,
        repo: String,
        reference: Option<String>,
    },
    NixFlakeRef(String),
    GitRemoteUrl(String),
    Unknown(String),
}

impl SourceSpec {
    pub fn parse(source: &str) -> Result<Self> {
        if source.trim().is_empty() {
            return Err(GitClosureError::Parse(
                "source must not be empty".to_string(),
            ));
        }

        if Path::new(source).exists() {
            return Ok(Self::LocalPath(PathBuf::from(source)));
        }

        if looks_like_nix_flake_ref(source) {
            return Ok(Self::NixFlakeRef(source.to_string()));
        }

        if let Some(rest) = source.strip_prefix("gh:") {
            return parse_hosted_repo(rest, "github", false).map(|(owner, repo, reference)| {
                Self::GitHubRepo {
                    owner,
                    repo,
                    reference,
                }
            });
        }

        if let Some(rest) = source.strip_prefix("gl:") {
            return parse_hosted_repo(rest, "gitlab", true).map(|(group, repo, reference)| {
                Self::GitLabRepo {
                    group,
                    repo,
                    reference,
                }
            });
        }

        if let Some(rest) = source.strip_prefix("https://github.com/") {
            if let Ok((owner, repo, reference)) = parse_hosted_repo(rest, "github", false) {
                return Ok(Self::GitHubRepo {
                    owner,
                    repo,
                    reference,
                });
            }
            return Ok(Self::Unknown(source.to_string()));
        }

        if let Some(rest) = source.strip_prefix("https://gitlab.com/") {
            if let Ok((group, repo, reference)) = parse_hosted_repo(rest, "gitlab", true) {
                return Ok(Self::GitLabRepo {
                    group,
                    repo,
                    reference,
                });
            }
            return Ok(Self::Unknown(source.to_string()));
        }

        if source.starts_with("http://")
            || source.starts_with("https://")
            || source.starts_with("git@")
            || source.ends_with(".git")
        {
            return Ok(Self::GitRemoteUrl(source.to_string()));
        }

        Ok(Self::Unknown(source.to_string()))
    }
}

pub struct FetchedSource {
    pub root: PathBuf,
    // TempDir does not implement Debug; keep field private and suppress the
    // derive — Debug is only needed for test assertions on the Err branch.
    _tempdir: Option<TempDir>,
}

impl FetchedSource {
    pub fn local(root: PathBuf) -> Self {
        Self {
            root,
            _tempdir: None,
        }
    }

    pub fn temporary(root: PathBuf, tempdir: TempDir) -> Self {
        Self {
            root,
            _tempdir: Some(tempdir),
        }
    }
}

pub trait Provider {
    fn fetch(&self, source: &str) -> Result<FetchedSource>;
}

pub fn fetch_source(source: &str, provider_kind: ProviderKind) -> Result<FetchedSource> {
    let spec = SourceSpec::parse(source)?;
    let local = LocalProvider;
    let git = GitCloneProvider;
    let nix = NixProvider;
    let github_api = GithubApiProvider;

    let selected = choose_provider(&spec, provider_kind)?;

    match selected {
        ProviderKind::Local => local.fetch(source),
        ProviderKind::GitClone => git.fetch(source),
        ProviderKind::Nix => nix.fetch(source),
        ProviderKind::GithubApi => github_api.fetch(source),
        ProviderKind::Auto => unreachable!("auto is resolved by choose_provider"),
    }
}

fn choose_provider(spec: &SourceSpec, requested: ProviderKind) -> Result<ProviderKind> {
    if requested != ProviderKind::Auto {
        return Ok(requested);
    }

    let selected = match spec {
        SourceSpec::LocalPath(_) => ProviderKind::Local,
        SourceSpec::NixFlakeRef(_) => ProviderKind::Nix,
        SourceSpec::GitHubRepo { .. } => ProviderKind::GithubApi,
        SourceSpec::GitLabRepo { .. } | SourceSpec::GitRemoteUrl(_) => ProviderKind::GitClone,
        SourceSpec::Unknown(value) => {
            return Err(GitClosureError::Parse(format!(
                "unsupported source syntax for auto provider: {value}"
            )));
        }
    };
    Ok(selected)
}

pub struct LocalProvider;

impl Provider for LocalProvider {
    fn fetch(&self, source: &str) -> Result<FetchedSource> {
        let path = Path::new(source);
        if !path.exists() {
            return Err(GitClosureError::Parse(format!(
                "local source path does not exist: {source}"
            )));
        }
        let absolute = fs::canonicalize(path)?;
        Ok(FetchedSource::local(absolute))
    }
}

pub struct GitCloneProvider;

impl Provider for GitCloneProvider {
    fn fetch(&self, source: &str) -> Result<FetchedSource> {
        let parsed = parse_git_source(source)?;
        let tempdir = TempDir::new()?;
        let checkout = tempdir.path().join("repo");
        let checkout_str = checkout
            .to_str()
            .ok_or_else(|| GitClosureError::Parse("invalid checkout path".to_string()))?;

        let clone_output = run_command_output(
            "git",
            &[
                "clone",
                "--depth",
                "1",
                "--no-tags",
                &parsed.url,
                checkout_str,
            ],
            None,
        )?;

        if !clone_output.status.success() {
            return Err(GitClosureError::CommandExitFailure {
                command: "git",
                status: clone_output.status.to_string(),
                stderr: truncate_stderr(&clone_output.stderr),
            });
        }

        if let Some(reference) = parsed.reference {
            let fetch_output = run_command_output(
                "git",
                &[
                    "-C",
                    checkout_str,
                    "fetch",
                    "--depth",
                    "1",
                    "origin",
                    &reference,
                ],
                None,
            )?;

            if !fetch_output.status.success() {
                return Err(GitClosureError::CommandExitFailure {
                    command: "git",
                    status: fetch_output.status.to_string(),
                    stderr: truncate_stderr(&fetch_output.stderr),
                });
            }

            let checkout_output = run_command_output(
                "git",
                &["-C", checkout_str, "checkout", "--detach", "FETCH_HEAD"],
                None,
            )?;

            if !checkout_output.status.success() {
                return Err(GitClosureError::CommandExitFailure {
                    command: "git",
                    status: checkout_output.status.to_string(),
                    stderr: truncate_stderr(&checkout_output.stderr),
                });
            }
        }

        Ok(FetchedSource::temporary(checkout, tempdir))
    }
}

pub struct NixProvider;

impl Provider for NixProvider {
    fn fetch(&self, source: &str) -> Result<FetchedSource> {
        let normalized = source.strip_prefix("nix:").unwrap_or(source);
        let output = run_command_output("nix", &["flake", "metadata", normalized, "--json"], None)?;

        if !output.status.success() {
            return Err(GitClosureError::CommandExitFailure {
                command: "nix",
                status: output.status.to_string(),
                stderr: truncate_stderr(&output.stderr),
            });
        }

        let path = parse_nix_metadata_path(&output.stdout)?;
        if !path.is_dir() {
            return Err(GitClosureError::Parse(format!(
                "nix flake metadata path is not a directory: {}",
                path.display()
            )));
        }

        Ok(FetchedSource::local(path))
    }
}

pub struct GithubApiProvider;

impl Provider for GithubApiProvider {
    fn fetch(&self, source: &str) -> Result<FetchedSource> {
        let parsed = parse_github_api_source(source)?;
        let tarball = download_github_tarball(&parsed)?;

        let tempdir = TempDir::new()?;
        let checkout = tempdir.path().join("repo");
        fs::create_dir_all(&checkout)?;

        extract_github_tarball(&tarball, &checkout)?;
        Ok(FetchedSource::temporary(checkout, tempdir))
    }
}

#[derive(Debug, serde::Deserialize)]
struct NixFlakeMetadata {
    path: String,
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct ParsedGitSource {
    url: String,
    reference: Option<String>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct ParsedGithubApiSource {
    owner: String,
    repo: String,
    reference: Option<String>,
}

impl ParsedGithubApiSource {
    fn archive_url(&self) -> String {
        let reference = self.reference.as_deref().unwrap_or("HEAD");
        format!(
            "{GITHUB_API_BASE}/{}/{}/tarball/{reference}",
            self.owner, self.repo
        )
    }

    fn display_name(&self) -> String {
        let reference = self.reference.as_deref().unwrap_or("HEAD");
        format!("{}/{}@{reference}", self.owner, self.repo)
    }
}

fn parse_github_api_source(source: &str) -> Result<ParsedGithubApiSource> {
    match SourceSpec::parse(source)? {
        SourceSpec::GitHubRepo {
            owner,
            repo,
            reference,
        } => Ok(ParsedGithubApiSource {
            owner,
            repo,
            reference,
        }),
        _ => Err(GitClosureError::Parse(format!(
            "github-api provider requires a GitHub source (gh:owner/repo[@ref] or https://github.com/owner/repo[@ref]); got: {source}"
        ))),
    }
}

fn download_github_tarball(source: &ParsedGithubApiSource) -> Result<Vec<u8>> {
    let url = source.archive_url();
    let token = std::env::var(GITHUB_TOKEN_ENV)
        .ok()
        .filter(|v| !v.is_empty());
    download_tarball_url(&url, &source.display_name(), token.as_deref())
}

fn download_tarball_url(url: &str, source_name: &str, token: Option<&str>) -> Result<Vec<u8>> {
    let agent = ureq::builder().build();
    let mut request = agent
        .get(url)
        .set("Accept", "application/vnd.github+json")
        .set("User-Agent", "git-closure");
    if let Some(token) = token {
        request = request.set("Authorization", &format!("Bearer {token}"));
    }

    match request.call() {
        Ok(response) => {
            let mut body = Vec::new();
            response
                .into_reader()
                .read_to_end(&mut body)
                .map_err(|err| {
                    GitClosureError::Parse(format!(
                        "github-api: failed to read tarball response for {source_name}: {err}",
                    ))
                })?;
            Ok(body)
        }
        Err(ureq::Error::Status(status, response)) => {
            let rate_remaining = response.header("X-RateLimit-Remaining").map(str::to_string);
            let body = response.into_string().unwrap_or_default();
            Err(github_api_status_error(
                status,
                rate_remaining.as_deref(),
                source_name,
                &body,
            ))
        }
        Err(ureq::Error::Transport(err)) => Err(GitClosureError::Parse(format!(
            "github-api: request failed for {source_name}: {err}",
        ))),
    }
}

fn github_api_status_error(
    status: u16,
    rate_remaining: Option<&str>,
    source_name: &str,
    body: &str,
) -> GitClosureError {
    let body_summary = body.trim();
    let suffix = if body_summary.is_empty() {
        String::new()
    } else {
        format!(": {body_summary}")
    };

    match status {
        401 => GitClosureError::Parse(format!(
            "github-api: authentication failed for {source_name} (HTTP 401). Set {GITHUB_TOKEN_ENV}."
        )),
        403 if rate_remaining == Some("0") => GitClosureError::Parse(format!(
            "github-api: rate limit exceeded while downloading {source_name}. Set {GITHUB_TOKEN_ENV} for higher limits."
        )),
        404 => GitClosureError::Parse(format!(
            "github-api: repository or reference not found: {source_name}"
        )),
        _ => GitClosureError::Parse(format!(
            "github-api: request failed for {source_name} with HTTP {status}{suffix}"
        )),
    }
}

fn extract_github_tarball(bytes: &[u8], destination: &Path) -> Result<()> {
    let decoder = GzDecoder::new(bytes);
    let mut archive = tar::Archive::new(decoder);
    let mut top_level: Option<std::ffi::OsString> = None;

    for entry_result in archive.entries().map_err(|err| {
        GitClosureError::Parse(format!("github-api: failed to read tar entries: {err}"))
    })? {
        let mut entry = entry_result.map_err(|err| {
            GitClosureError::Parse(format!("github-api: invalid tar entry: {err}"))
        })?;
        let entry_path = entry.path().map_err(|err| {
            GitClosureError::Parse(format!("github-api: invalid tar path entry: {err}"))
        })?;
        let relative = strip_github_archive_prefix(entry_path.as_ref(), &mut top_level)?;
        let Some(relative) = relative else {
            continue;
        };

        let output_path = destination.join(&relative);
        if let Some(parent) = output_path.parent() {
            ensure_no_symlink_ancestors(destination, parent)?;
            fs::create_dir_all(parent)?;
        }

        let entry_type = entry.header().entry_type();
        if entry_type.is_dir() {
            reject_if_symlink(&output_path)?;
            fs::create_dir_all(&output_path)?;
            continue;
        }

        if entry_type.is_file() {
            reject_if_symlink(&output_path)?;
            if output_path.exists() {
                return Err(GitClosureError::Parse(format!(
                    "github-api: duplicate file entry path in archive: {}",
                    relative.display()
                )));
            }
            entry.unpack(&output_path).map_err(|err| {
                GitClosureError::Parse(format!(
                    "github-api: failed to unpack file {}: {err}",
                    output_path.display()
                ))
            })?;
            continue;
        }

        if entry_type.is_symlink() {
            reject_if_symlink(&output_path)?;
            if output_path.exists() {
                return Err(GitClosureError::Parse(format!(
                    "github-api: duplicate symlink entry path in archive: {}",
                    relative.display()
                )));
            }
            let target = entry.link_name().map_err(|err| {
                GitClosureError::Parse(format!("github-api: invalid symlink entry target: {err}"))
            })?;
            let target = target.ok_or_else(|| {
                GitClosureError::Parse("github-api: symlink entry missing target".to_string())
            })?;
            let target_path = target.as_ref();
            let effective_target = if target_path.is_absolute() {
                target_path.to_path_buf()
            } else {
                output_path
                    .parent()
                    .unwrap_or(destination)
                    .join(target_path)
            };
            let normalized = lexical_normalize(&effective_target)?;
            if !normalized.starts_with(destination) {
                return Err(GitClosureError::UnsafePath(format!(
                    "github-api: symlink target escapes destination: {}",
                    relative.display()
                )));
            }
            #[cfg(unix)]
            {
                std::os::unix::fs::symlink(target_path, &output_path)?;
            }
            #[cfg(not(unix))]
            {
                let _ = target_path;
                return Err(GitClosureError::Parse(
                    "github-api: symlink extraction is unsupported on this platform".to_string(),
                ));
            }
            continue;
        }

        return Err(GitClosureError::Parse(format!(
            "github-api: unsupported tar entry type for {}",
            relative.display()
        )));
    }

    if top_level.is_none() {
        return Err(GitClosureError::Parse(
            "github-api: archive contained no entries".to_string(),
        ));
    }

    Ok(())
}

fn strip_github_archive_prefix(
    path: &Path,
    top_level: &mut Option<std::ffi::OsString>,
) -> Result<Option<PathBuf>> {
    let mut components = path.components();
    let first = match components.next() {
        Some(Component::Normal(name)) => name.to_os_string(),
        _ => {
            return Err(GitClosureError::UnsafePath(path.display().to_string()));
        }
    };

    match top_level {
        Some(existing) if existing != &first => {
            return Err(GitClosureError::Parse(format!(
                "github-api: archive has multiple top-level directories: {} and {}",
                existing.to_string_lossy(),
                first.to_string_lossy(),
            )));
        }
        Some(_) => {}
        None => {
            *top_level = Some(first);
        }
    }

    let mut relative = PathBuf::new();
    for component in components {
        match component {
            Component::Normal(part) => relative.push(part),
            _ => {
                return Err(GitClosureError::UnsafePath(path.display().to_string()));
            }
        }
    }

    if relative.as_os_str().is_empty() {
        return Ok(None);
    }

    Ok(Some(relative))
}

fn parse_git_source(source: &str) -> Result<ParsedGitSource> {
    if let Some(rest) = source.strip_prefix("gh:") {
        let (repo, reference) = split_repo_ref(rest);
        return Ok(ParsedGitSource {
            url: format!("https://github.com/{repo}.git"),
            reference,
        });
    }

    if let Some(rest) = source.strip_prefix("gl:") {
        let (repo, reference) = split_repo_ref(rest);
        return Ok(ParsedGitSource {
            url: format!("https://gitlab.com/{repo}.git"),
            reference,
        });
    }

    Ok(ParsedGitSource {
        url: source.to_string(),
        reference: None,
    })
}

fn split_repo_ref(input: &str) -> (&str, Option<String>) {
    if let Some((repo, reference)) = input.rsplit_once('@') {
        if !repo.is_empty() && !reference.is_empty() {
            return (repo, Some(reference.to_string()));
        }
    }
    (input, None)
}

fn looks_like_nix_flake_ref(source: &str) -> bool {
    source.starts_with("nix:")
        || source.starts_with("github:")
        || source.starts_with("gitlab:")
        || source.starts_with("sourcehut:")
        || source.starts_with("git+")
        || source.starts_with("path:")
        || source.starts_with("tarball+")
        || source.starts_with("file+")
}

fn parse_hosted_repo(
    source: &str,
    host: &str,
    allow_nested_group: bool,
) -> Result<(String, String, Option<String>)> {
    let (repo_part, reference) = split_repo_ref(source);
    let repo_part = repo_part.trim_end_matches(".git");
    let mut segments = repo_part.split('/').collect::<Vec<_>>();
    if segments.len() < 2 {
        return Err(GitClosureError::Parse(format!(
            "invalid {host} source, expected <owner>/<repo>: {source}"
        )));
    }
    if !allow_nested_group && segments.len() != 2 {
        return Err(GitClosureError::Parse(format!(
            "invalid {host} source, expected <owner>/<repo>: {source}"
        )));
    }

    let repo = segments.pop().unwrap().to_string();
    let owner_or_group = segments.join("/");
    if owner_or_group.is_empty() || repo.is_empty() {
        return Err(GitClosureError::Parse(format!(
            "invalid {host} source, expected <owner>/<repo>: {source}"
        )));
    }

    Ok((owner_or_group, repo, reference))
}

fn parse_nix_metadata_path(output: &[u8]) -> Result<PathBuf> {
    let metadata: NixFlakeMetadata = serde_json::from_slice(output).map_err(|err| {
        GitClosureError::Parse(format!("failed to parse nix flake metadata JSON: {err}"))
    })?;
    Ok(PathBuf::from(metadata.path))
}

pub(crate) fn run_command_output(
    command: &'static str,
    args: &[&str],
    current_dir: Option<&Path>,
) -> Result<std::process::Output> {
    let mut cmd = Command::new(command);
    cmd.args(args);
    if let Some(dir) = current_dir {
        cmd.current_dir(dir);
    }
    cmd.output()
        .map_err(|source| GitClosureError::CommandSpawnFailed { command, source })
}

/// `run_command_status` is only used in tests (spawn/exit-code assertions).
/// Keeping it test-only avoids a `#[allow(dead_code)]` annotation on a
/// `pub(crate)` function that has no production call site.
#[cfg(test)]
pub(crate) fn run_command_status(
    command: &'static str,
    args: &[&str],
    current_dir: Option<&Path>,
) -> Result<std::process::ExitStatus> {
    let mut cmd = Command::new(command);
    cmd.args(args);
    if let Some(dir) = current_dir {
        cmd.current_dir(dir);
    }
    cmd.status()
        .map_err(|source| GitClosureError::CommandSpawnFailed { command, source })
}

#[cfg(test)]
mod tests {
    use super::{
        choose_provider, fetch_source, github_api_status_error, parse_git_source,
        parse_github_api_source, parse_nix_metadata_path, run_command_output, run_command_status,
        split_repo_ref, strip_github_archive_prefix, GitCloneProvider, NixProvider,
        ParsedGithubApiSource, Provider, ProviderKind, SourceSpec,
    };
    use crate::error::GitClosureError;
    use crate::utils::truncate_stderr;
    use flate2::write::GzEncoder;
    use flate2::Compression;
    use std::io::ErrorKind;
    use std::io::{Read, Write};
    use std::net::TcpListener;
    use std::path::Path;
    use std::time::Duration;

    fn make_gzipped_tar(entries: &[(&str, &[u8])]) -> Vec<u8> {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);
            for (path, bytes) in entries {
                let mut header = tar::Header::new_gnu();
                header.set_size(bytes.len() as u64);
                header.set_mode(0o644);
                header.set_cksum();
                builder
                    .append_data(&mut header, *path, *bytes)
                    .expect("append tar file entry");
            }
            builder.finish().expect("finish tar builder");
        }
        gz.finish().expect("finish gzip stream")
    }

    #[test]
    fn split_repo_ref_parses_optional_reference() {
        assert_eq!(split_repo_ref("owner/repo"), ("owner/repo", None));
        assert_eq!(
            split_repo_ref("owner/repo@main"),
            ("owner/repo", Some("main".to_string()))
        );
    }

    #[test]
    fn source_spec_parse_documented_examples() {
        let gh = SourceSpec::parse("gh:owner/repo@main").expect("parse gh");
        assert!(matches!(
            gh,
            SourceSpec::GitHubRepo {
                owner,
                repo,
                reference: Some(reference)
            } if owner == "owner" && repo == "repo" && reference == "main"
        ));

        let gl = SourceSpec::parse("gl:group/project").expect("parse gl");
        assert!(matches!(
            gl,
            SourceSpec::GitLabRepo {
                group,
                repo,
                reference: None
            } if group == "group" && repo == "project"
        ));

        let nix = SourceSpec::parse("nix:github:NixOS/nixpkgs/nixos-unstable").expect("parse nix");
        assert!(matches!(nix, SourceSpec::NixFlakeRef(_)));

        let github_flake = SourceSpec::parse("github:owner/repo").expect("parse github flake ref");
        assert!(matches!(github_flake, SourceSpec::NixFlakeRef(_)));

        let https = SourceSpec::parse("https://github.com/owner/repo").expect("parse github https");
        assert!(matches!(https, SourceSpec::GitHubRepo { .. }));

        let archive = SourceSpec::parse("https://github.com/owner/repo/archive/main.tar.gz")
            .expect("parse github archive URL as unsupported");
        assert!(matches!(archive, SourceSpec::Unknown(_)));
    }

    #[test]
    fn choose_provider_auto_from_source_spec() {
        let local = SourceSpec::LocalPath(std::path::PathBuf::from("."));
        assert_eq!(
            choose_provider(&local, ProviderKind::Auto).expect("choose local"),
            ProviderKind::Local
        );

        let gh = SourceSpec::GitHubRepo {
            owner: "owner".to_string(),
            repo: "repo".to_string(),
            reference: None,
        };
        assert_eq!(
            choose_provider(&gh, ProviderKind::Auto).expect("choose git clone for github"),
            ProviderKind::GithubApi
        );

        let nix = SourceSpec::NixFlakeRef("github:owner/repo".to_string());
        assert_eq!(
            choose_provider(&nix, ProviderKind::Auto).expect("choose nix for flake refs"),
            ProviderKind::Nix
        );

        let unknown = SourceSpec::Unknown("wat://unknown".to_string());
        let err = choose_provider(&unknown, ProviderKind::Auto)
            .expect_err("unknown auto source should fail before subprocess");
        assert!(matches!(err, GitClosureError::Parse(_)));
    }

    #[test]
    fn parse_git_source_supports_gh_and_gl_shortcuts() {
        let gh = parse_git_source("gh:foo/bar@main").expect("parse gh source");
        assert_eq!(gh.url, "https://github.com/foo/bar.git");
        assert_eq!(gh.reference.as_deref(), Some("main"));

        let gl = parse_git_source("gl:foo/bar").expect("parse gl source");
        assert_eq!(gl.url, "https://gitlab.com/foo/bar.git");
        assert!(gl.reference.is_none());
    }

    #[test]
    fn parse_nix_metadata_extracts_store_path() {
        let json = br#"{ "path": "/nix/store/abc123-source", "locked": { "rev": "deadbeef" } }"#;
        let path = parse_nix_metadata_path(json).expect("parse nix metadata JSON");
        assert_eq!(path, std::path::PathBuf::from("/nix/store/abc123-source"));
    }

    #[test]
    fn missing_binary_maps_to_command_spawn_failed() {
        let err = run_command_status("__nonexistent_binary_for_testing__", &[], None)
            .expect_err("missing binary should produce spawn error");

        match err {
            GitClosureError::CommandSpawnFailed { command, source } => {
                assert_eq!(command, "__nonexistent_binary_for_testing__");
                assert_eq!(source.kind(), ErrorKind::NotFound);
            }
            other => panic!("expected CommandSpawnFailed, got {other:?}"),
        }
    }

    #[test]
    fn missing_binary_with_current_dir_maps_to_command_spawn_failed() {
        let dir = std::env::temp_dir();
        let err = run_command_status("__nonexistent_binary_for_testing__", &[], Some(&dir))
            .expect_err("missing binary should fail");
        assert!(
            matches!(
                err,
                GitClosureError::CommandSpawnFailed {
                    command: "__nonexistent_binary_for_testing__",
                    ..
                }
            ),
            "expected CommandSpawnFailed, got {err:?}"
        );
    }

    #[test]
    fn git_clone_failure_maps_to_command_exit_failure() {
        let provider = GitCloneProvider;
        let err = match provider.fetch("::::") {
            Ok(_) => panic!("invalid git source should fail clone"),
            Err(err) => err,
        };

        match err {
            GitClosureError::CommandExitFailure {
                command, stderr, ..
            } => {
                assert_eq!(command, "git");
                assert!(!stderr.is_empty(), "stderr payload should be captured");
            }
            other => panic!("expected CommandExitFailure, got {other:?}"),
        }
    }

    #[test]
    fn command_exit_failure_display_includes_stderr() {
        let output = run_command_output(
            "git",
            &["rev-parse", "--verify", "nonexistent-ref-xyz-abc"],
            None,
        )
        .expect("git command should execute");
        assert!(
            !output.status.success(),
            "rev-parse on nonexistent ref should fail"
        );

        let err = GitClosureError::CommandExitFailure {
            command: "git",
            status: output.status.to_string(),
            stderr: truncate_stderr(&output.stderr),
        };

        let display = err.to_string();
        assert!(
            display.contains("nonexistent-ref")
                || display.contains("fatal")
                || display.contains("unknown"),
            "error display must include stderr context, got: {display:?}"
        );
    }

    #[test]
    fn nix_provider_exit_failure_maps_to_command_exit_failure() {
        let provider = NixProvider;
        let err = match provider.fetch("path:/definitely/not/here") {
            Ok(_) => panic!("invalid local flake path should fail"),
            Err(err) => err,
        };

        // On systems without the `nix` binary the error is CommandSpawnFailed
        // (ENOENT).  On systems with `nix`, the path does not exist so it
        // exits non-zero → CommandExitFailure.  Both are acceptable outcomes
        // for this test; what we assert is that the error correctly identifies
        // the `nix` command and does not silently succeed.
        match err {
            GitClosureError::CommandExitFailure {
                command, stderr, ..
            } => {
                assert_eq!(command, "nix");
                assert!(
                    !stderr.is_empty(),
                    "stderr should be captured for nix exit failure"
                );
                let lowered = stderr.to_lowercase();
                assert!(
                    lowered.contains("does not exist")
                        || lowered.contains("while fetching the input")
                        || lowered.contains("nix"),
                    "stderr should include actionable nix context, got: {stderr:?}"
                );
            }
            GitClosureError::CommandSpawnFailed { command, .. } => {
                // nix binary is not installed; spawn failure is the expected path.
                assert_eq!(command, "nix");
            }
            other => panic!("expected CommandExitFailure or CommandSpawnFailed, got {other:?}"),
        }
    }

    #[test]
    fn parse_github_api_source_accepts_gh_and_https_syntax() {
        let gh = parse_github_api_source("gh:owner/repo@main").expect("parse gh syntax");
        assert_eq!(
            gh,
            ParsedGithubApiSource {
                owner: "owner".to_string(),
                repo: "repo".to_string(),
                reference: Some("main".to_string())
            }
        );

        let https =
            parse_github_api_source("https://github.com/owner/repo").expect("parse https syntax");
        assert_eq!(
            https,
            ParsedGithubApiSource {
                owner: "owner".to_string(),
                repo: "repo".to_string(),
                reference: None
            }
        );
    }

    #[test]
    fn parse_github_api_source_rejects_non_github_inputs() {
        let err = parse_github_api_source("gl:group/repo").expect_err("gl source must fail");
        assert!(
            matches!(err, GitClosureError::Parse(_)),
            "expected parse error for non-github source"
        );
    }

    #[test]
    fn github_api_download_follows_redirects() {
        let listener = TcpListener::bind("127.0.0.1:0").expect("bind test listener");
        let addr = listener.local_addr().expect("listener addr");
        let payload = b"redirect-ok".to_vec();
        let payload_for_server = payload.clone();

        let server = std::thread::spawn(move || {
            let mut seen_redirect = false;
            for _ in 0..2 {
                let (mut stream, _) = listener.accept().expect("accept connection");
                stream
                    .set_read_timeout(Some(Duration::from_secs(2)))
                    .expect("set read timeout");
                let mut req_buf = [0u8; 2048];
                let n = stream.read(&mut req_buf).expect("read request");
                let request = String::from_utf8_lossy(&req_buf[..n]);

                if request.starts_with("GET /redirect ") {
                    let response = format!(
                        "HTTP/1.1 302 Found\r\nLocation: http://{addr}/tarball\r\nContent-Length: 0\r\nConnection: close\r\n\r\n"
                    );
                    stream
                        .write_all(response.as_bytes())
                        .expect("write redirect response");
                    seen_redirect = true;
                } else if request.starts_with("GET /tarball ") {
                    let headers = format!(
                        "HTTP/1.1 200 OK\r\nContent-Length: {}\r\nConnection: close\r\n\r\n",
                        payload_for_server.len()
                    );
                    stream
                        .write_all(headers.as_bytes())
                        .expect("write ok headers");
                    stream
                        .write_all(&payload_for_server)
                        .expect("write payload");
                    return seen_redirect;
                }
            }
            false
        });

        let bytes = super::download_tarball_url(
            &format!("http://{addr}/redirect"),
            "owner/repo@HEAD",
            None,
        )
        .expect("redirected download should succeed");

        assert_eq!(bytes, payload);
        assert!(
            server.join().expect("join test server"),
            "server should observe redirect then tarball request"
        );
    }

    #[test]
    fn github_api_status_error_maps_auth_and_rate_limit_cases() {
        let auth = github_api_status_error(401, None, "owner/repo@HEAD", "");
        assert!(
            auth.to_string().contains("authentication failed")
                && auth.to_string().contains("GCL_GITHUB_TOKEN"),
            "401 must mention authentication and token env var"
        );

        let rate = github_api_status_error(403, Some("0"), "owner/repo@HEAD", "rate limited");
        assert!(
            rate.to_string().contains("rate limit")
                && rate.to_string().contains("GCL_GITHUB_TOKEN"),
            "rate-limit errors must be actionable"
        );

        let missing = github_api_status_error(404, None, "owner/repo@badref", "");
        assert!(
            missing.to_string().contains("not found")
                && missing.to_string().contains("owner/repo@badref"),
            "404 must mention missing repo/ref"
        );
    }

    #[test]
    fn strip_github_archive_prefix_rejects_parent_traversal() {
        let mut top = None;
        let err = strip_github_archive_prefix(Path::new("repo-abc/../../evil.txt"), &mut top)
            .expect_err("path traversal in archive must be rejected");
        assert!(matches!(err, GitClosureError::UnsafePath(_)));
    }

    #[test]
    fn split_github_archive_prefix_strips_top_level_directory() {
        let mut top = None;
        let rel = strip_github_archive_prefix(Path::new("repo-abc/src/lib.rs"), &mut top)
            .expect("valid github archive entry path")
            .expect("non-root entry must remain after stripping");
        assert_eq!(rel, std::path::PathBuf::from("src/lib.rs"));
    }

    #[test]
    fn github_archive_extraction_strips_prefix_and_writes_files() {
        let tarball = make_gzipped_tar(&[
            ("repo-abc/README.md", b"hello\n"),
            ("repo-abc/src/lib.rs", b"pub fn x() {}\n"),
        ]);
        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        super::extract_github_tarball(&tarball, &dest).expect("extract archive");
        let readme = std::fs::read_to_string(dest.join("README.md")).expect("read README");
        let lib = std::fs::read_to_string(dest.join("src/lib.rs")).expect("read src/lib.rs");
        assert_eq!(readme, "hello\n");
        assert_eq!(lib, "pub fn x() {}\n");
    }

    #[cfg(unix)]
    #[test]
    fn github_archive_extraction_preserves_symlink_entries() {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);

            let mut file_header = tar::Header::new_gnu();
            let file_bytes = b"target\n";
            file_header.set_size(file_bytes.len() as u64);
            file_header.set_mode(0o644);
            file_header.set_cksum();
            builder
                .append_data(&mut file_header, "repo-abc/target.txt", &file_bytes[..])
                .expect("append regular file");

            let mut link_header = tar::Header::new_gnu();
            link_header.set_entry_type(tar::EntryType::Symlink);
            link_header.set_size(0);
            link_header.set_mode(0o777);
            link_header
                .set_link_name("target.txt")
                .expect("set symlink target");
            link_header.set_cksum();
            builder
                .append_data(&mut link_header, "repo-abc/link", std::io::empty())
                .expect("append symlink entry");

            builder.finish().expect("finish tar builder");
        }
        let tarball = gz.finish().expect("finish gzip stream");

        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        super::extract_github_tarball(&tarball, &dest).expect("extract archive");
        let target = std::fs::read_link(dest.join("link")).expect("read extracted symlink");
        assert_eq!(target, std::path::PathBuf::from("target.txt"));
    }

    #[cfg(unix)]
    #[test]
    fn github_archive_extraction_rejects_absolute_symlink_target_escape() {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);

            let mut link_header = tar::Header::new_gnu();
            link_header.set_entry_type(tar::EntryType::Symlink);
            link_header.set_size(0);
            link_header.set_mode(0o777);
            link_header
                .set_link_name("/etc")
                .expect("set absolute target");
            link_header.set_cksum();
            builder
                .append_data(&mut link_header, "repo-abc/link", std::io::empty())
                .expect("append symlink entry");

            builder.finish().expect("finish tar builder");
        }
        let tarball = gz.finish().expect("finish gzip stream");

        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        let err = super::extract_github_tarball(&tarball, &dest)
            .expect_err("absolute symlink target must be rejected");
        assert!(matches!(err, GitClosureError::UnsafePath(_)));
    }

    #[cfg(unix)]
    #[test]
    fn github_archive_extraction_rejects_relative_symlink_target_escape() {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);

            let mut link_header = tar::Header::new_gnu();
            link_header.set_entry_type(tar::EntryType::Symlink);
            link_header.set_size(0);
            link_header.set_mode(0o777);
            link_header
                .set_link_name("../../escape")
                .expect("set traversal target");
            link_header.set_cksum();
            builder
                .append_data(&mut link_header, "repo-abc/sub/link", std::io::empty())
                .expect("append symlink entry");

            builder.finish().expect("finish tar builder");
        }
        let tarball = gz.finish().expect("finish gzip stream");

        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        let err = super::extract_github_tarball(&tarball, &dest)
            .expect_err("relative symlink escape target must be rejected");
        assert!(matches!(err, GitClosureError::UnsafePath(_)));
    }

    #[cfg(unix)]
    #[test]
    fn github_archive_extraction_allows_safe_relative_symlink_target() {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);

            let mut file_header = tar::Header::new_gnu();
            let file_bytes = b"ok\n";
            file_header.set_size(file_bytes.len() as u64);
            file_header.set_mode(0o644);
            file_header.set_cksum();
            builder
                .append_data(&mut file_header, "repo-abc/sub/sibling", &file_bytes[..])
                .expect("append sibling file");

            let mut link_header = tar::Header::new_gnu();
            link_header.set_entry_type(tar::EntryType::Symlink);
            link_header.set_size(0);
            link_header.set_mode(0o777);
            link_header
                .set_link_name("./sibling")
                .expect("set safe target");
            link_header.set_cksum();
            builder
                .append_data(&mut link_header, "repo-abc/sub/link", std::io::empty())
                .expect("append symlink entry");

            builder.finish().expect("finish tar builder");
        }
        let tarball = gz.finish().expect("finish gzip stream");

        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        super::extract_github_tarball(&tarball, &dest).expect("safe symlink should extract");
        let target = std::fs::read_link(dest.join("sub/link")).expect("read extracted symlink");
        assert_eq!(target, std::path::PathBuf::from("./sibling"));
    }

    #[cfg(unix)]
    #[test]
    fn github_archive_extraction_rejects_symlink_parent_escape() {
        let mut gz = GzEncoder::new(Vec::new(), Compression::default());
        {
            let mut builder = tar::Builder::new(&mut gz);

            let mut dir_link_header = tar::Header::new_gnu();
            dir_link_header.set_entry_type(tar::EntryType::Symlink);
            dir_link_header.set_size(0);
            dir_link_header.set_mode(0o777);
            dir_link_header
                .set_link_name("../escape")
                .expect("set symlink target");
            dir_link_header.set_cksum();
            builder
                .append_data(&mut dir_link_header, "repo-abc/dir", std::io::empty())
                .expect("append symlinked directory entry");

            let mut file_header = tar::Header::new_gnu();
            let payload = b"owned\n";
            file_header.set_size(payload.len() as u64);
            file_header.set_mode(0o644);
            file_header.set_cksum();
            builder
                .append_data(&mut file_header, "repo-abc/dir/payload.txt", &payload[..])
                .expect("append nested file");

            builder.finish().expect("finish tar builder");
        }
        let tarball = gz.finish().expect("finish gzip stream");

        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");
        let escape = tmp.path().join("escape");
        std::fs::create_dir_all(&escape).expect("create would-be escape dir");

        let err = super::extract_github_tarball(&tarball, &dest)
            .expect_err("archive writing through symlink parent must be rejected");
        assert!(
            matches!(err, GitClosureError::UnsafePath(_)),
            "expected UnsafePath, got {err:?}"
        );
        assert!(
            !escape.join("payload.txt").exists(),
            "extraction must not write outside destination root"
        );
    }

    #[test]
    fn github_archive_extraction_rejects_duplicate_file_entries() {
        let tarball = make_gzipped_tar(&[
            ("repo-abc/dup.txt", b"first\n"),
            ("repo-abc/dup.txt", b"second\n"),
        ]);
        let tmp = tempfile::TempDir::new().expect("create tempdir");
        let dest = tmp.path().join("out");
        std::fs::create_dir_all(&dest).expect("create destination dir");

        let err = super::extract_github_tarball(&tarball, &dest)
            .expect_err("duplicate file entries must be rejected");
        assert!(
            matches!(err, GitClosureError::Parse(_)),
            "expected Parse error, got {err:?}"
        );
        assert!(
            err.to_string().contains("duplicate file entry path"),
            "error must mention duplicate file entry path: {err}"
        );
    }

    #[test]
    fn github_api_provider_rejects_non_github_source() {
        use super::GithubApiProvider;
        let provider = GithubApiProvider;
        let err = match provider.fetch("gl:group/repo") {
            Ok(_) => panic!("github-api provider must reject non-github source syntax"),
            Err(e) => e,
        };
        assert!(
            matches!(err, GitClosureError::Parse(_)),
            "expected Parse error, got {err:?}"
        );
        let msg = err.to_string();
        assert!(
            msg.contains("github-api") || msg.contains("GitHub"),
            "error message must mention github-api source requirement, got: {msg:?}"
        );
    }

    #[test]
    fn auto_provider_github_repo_routes_to_github_api() {
        let gh = SourceSpec::parse("gh:owner/repo").expect("parse gh source");
        assert_eq!(
            choose_provider(&gh, ProviderKind::Auto).expect("choose provider"),
            ProviderKind::GithubApi
        );
    }

    #[test]
    fn auto_provider_github_https_routes_to_github_api() {
        let gh = SourceSpec::parse("https://github.com/owner/repo").expect("parse github https");
        assert_eq!(
            choose_provider(&gh, ProviderKind::Auto).expect("choose provider"),
            ProviderKind::GithubApi
        );
    }

    #[test]
    fn auto_provider_github_prefix_is_still_treated_as_nix_flake_ref() {
        let err = match fetch_source("github:owner/repo", ProviderKind::Auto) {
            Ok(_) => return,
            Err(err) => err,
        };
        match err {
            GitClosureError::CommandExitFailure { command, .. }
            | GitClosureError::CommandSpawnFailed { command, .. } => {
                assert_eq!(command, "nix");
            }
            other => panic!("expected nix-command failure path for github: refs, got {other:?}"),
        }
    }
}