1 files changed, 75 insertions, 0 deletions
diff --git a/src/repo/profile/packages/mod.rs b/src/repo/profile/packages/mod.rs
new file mode 100644
index 0000000..4fd6559
--- /dev/null
+++ b/src/repo/profile/packages/mod.rs
@@ -0,0 +1,75 @@
+use std::{
+    fs, io,
+    path::{Path, PathBuf},
+};
+
+use mon::{Parser, ParserIter, ascii_whitespace1, input::InputIter};
+
+use crate::{
+    Parseable,
+    atom::Atom,
+    repo::profile::{LineBasedFileExpr, Profile},
+};
+
+mod parsers;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("{0}: io error: {1}")]
+    Io(PathBuf, io::Error),
+    #[error("parser error: {0}")]
+    Parser(String),
+}
+
+#[derive(Debug, Clone)]
+enum Package {
+    Add(Atom),
+    Remove(Atom),
+}
+
+pub(super) fn evaluate<P: AsRef<Path>>(parents: &[Profile], path: P) -> Result<Vec<Atom>, Error> {
+    let parsed = match fs::read_to_string(path.as_ref().join("packages")) {
+        Ok(contents) => parse(&contents)?,
+        Err(e) if matches!(e.kind(), io::ErrorKind::NotFound) => Vec::new(),
+        Err(e) => return Err(Error::Io(path.as_ref().to_path_buf(), e)),
+    };
+
+    Ok(inherit(parents, parsed))
+}
+
+fn inherit(parents: &[Profile], packages: Vec<Package>) -> Vec<Atom> {
+    let mut accumulated = Vec::new();
+
+    for parent in parents {
+        for package in parent.packages() {
+            accumulated.push(package.clone());
+        }
+    }
+
+    for package in packages {
+        match package {
+            Package::Add(package) => {
+                accumulated.push(package);
+            }
+            Package::Remove(package) => {
+                accumulated.retain(|p| *p != package);
+            }
+        }
+    }
+
+    accumulated
+}
+
+fn parse(contents: &str) -> Result<Vec<Package>, Error> {
+    Ok(LineBasedFileExpr::<Package>::parser()
+        .separated_by_with_opt_trailing(ascii_whitespace1())
+        .many()
+        .parse_finished(InputIter::new(contents))
+        .map_err(|e| Error::Parser(e.rest().to_string()))?
+        .into_iter()
+        .filter_map(|expr| match expr {
+            LineBasedFileExpr::Comment => None,
+            LineBasedFileExpr::Expr(package) => Some(package),
+        })
+        .collect())
+}