grex_core/tree/
loader.rs

1//! Pluggable [`PackLoader`] for the tree walker.
2//!
3//! The walker never reads the filesystem directly: every manifest arrives via
4//! a [`PackLoader`] impl. This exists so:
5//!
6//! * Tests substitute an in-memory mock and avoid disk I/O entirely.
7//! * A future plugin backend (e.g. an HTTP-fetched manifest or a cached
8//!   manifest store) can slot in without touching walker logic.
9//! * Tree-walk tests stay hermetic on CI.
10
11use std::path::{Path, PathBuf};
12
13use crate::pack::{parse, PackManifest};
14
15use super::error::TreeError;
16
17/// Strategy object for turning a path into a parsed manifest.
18///
19/// Implementors must be `Send + Sync` so the walker can be used behind an
20/// `Arc` in a future parallel-walk slice.
21pub trait PackLoader: Send + Sync {
22    /// Resolve `path` and return the parsed manifest.
23    ///
24    /// # Path semantics
25    ///
26    /// * If `path` is a directory, the loader looks up
27    ///   `path.join(".grex/pack.yaml")`.
28    /// * If `path` ends in `.yaml` or `.yml`, it is read verbatim.
29    ///
30    /// The distinction is documented at the trait level so every backend
31    /// observes the same contract.
32    ///
33    /// # Errors
34    ///
35    /// Returns [`TreeError::ManifestNotFound`] when no manifest exists at the
36    /// resolved location, [`TreeError::ManifestRead`] for IO failures, and
37    /// [`TreeError::ManifestParse`] for structural failures.
38    fn load(&self, path: &Path) -> Result<PackManifest, TreeError>;
39}
40
41/// Filesystem-backed [`PackLoader`] used by the real walker.
42#[derive(Debug, Default)]
43pub struct FsPackLoader;
44
45impl FsPackLoader {
46    /// Construct a new loader. Equivalent to [`FsPackLoader::default`].
47    #[must_use]
48    pub const fn new() -> Self {
49        Self
50    }
51}
52
53impl PackLoader for FsPackLoader {
54    fn load(&self, path: &Path) -> Result<PackManifest, TreeError> {
55        let manifest_path = resolve_manifest_path(path);
56        if !manifest_path.is_file() {
57            return Err(TreeError::ManifestNotFound(manifest_path));
58        }
59        let raw = std::fs::read_to_string(&manifest_path)
60            .map_err(|e| TreeError::ManifestRead(format!("{}: {e}", manifest_path.display())))?;
61        parse(&raw)
62            .map_err(|e| TreeError::ManifestParse { path: manifest_path, detail: e.to_string() })
63    }
64}
65
66/// Resolve a user-supplied path to the concrete `pack.yaml` location.
67///
68/// Split out so cyclomatic budget on [`FsPackLoader::load`] stays tiny.
69fn resolve_manifest_path(path: &Path) -> PathBuf {
70    if has_yaml_extension(path) {
71        path.to_path_buf()
72    } else {
73        path.join(".grex").join("pack.yaml")
74    }
75}
76
77fn has_yaml_extension(path: &Path) -> bool {
78    matches!(path.extension().and_then(|e| e.to_str()), Some("yaml" | "yml"))
79}
grex_core/tree/loader.rs

grex_core/tree/
loader.rs
