impl profile evaluationprofiles

11 files changed, 867 insertions, 0 deletions

diff --git a/src/repo/profile/make_defaults/mod.rs b/src/repo/profile/make_defaults/mod.rs
new file mode 100644
index 0000000..334f165
--- /dev/null
+++ b/src/repo/profile/make_defaults/mod.rs
@@ -0,0 +1,135 @@
+use std::{
+    collections::{HashMap, HashSet},
+    fs, io,
+    path::{Path, PathBuf},
+};
+
+use mon::{Parser, ParserIter, ascii_whitespace1, input::InputIter};
+
+use crate::{
+    Parseable,
+    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, PartialEq, Eq, Hash)]
+struct Key(String);
+
+#[derive(Debug, Clone)]
+struct Literal(String);
+
+#[derive(Debug, Clone)]
+struct Interpolation(String);
+
+#[derive(Debug, Clone)]
+enum Segment {
+    Literal(Literal),
+    Interpolation(Interpolation),
+}
+
+#[derive(Debug, Clone)]
+struct Assignment(Key, Vec<Segment>);
+
+pub(super) fn evaluate<P: AsRef<Path>>(
+    parents: &[Profile],
+    path: P,
+) -> Result<HashMap<String, String>, Error> {
+    let parsed = match fs::read_to_string(path.as_ref().join("make.defaults")) {
+        Ok(contents) => parse(&contents)?,
+        Err(e) if matches!(e.kind(), io::ErrorKind::NotFound) => HashMap::new(),
+        Err(e) => return Err(Error::Io(path.as_ref().to_path_buf(), e)),
+    };
+
+    let mut vars = interpolate(parents, parsed);
+
+    incremental(parents, &mut vars);
+
+    Ok(vars)
+}
+
+fn incremental(parents: &[Profile], vars: &mut HashMap<String, String>) {
+    for key in [
+        "USE",
+        "USE_EXPAND",
+        "USE_EXPAND_HIDDEN",
+        "CONFIG_PROTECT",
+        "CONFIG_PROTECT_MASK",
+    ] {
+        let mut accumulated = Vec::new();
+
+        for parent in parents {
+            if let Some(values) = parent.make_defaults().get(key) {
+                accumulated.extend(values.split_ascii_whitespace());
+            }
+        }
+
+        if let Some(values) = vars.get(key) {
+            accumulated.extend(values.split_ascii_whitespace());
+        }
+
+        let mut final_values = Vec::new();
+
+        for var in accumulated {
+            if var == "-*" {
+                final_values.clear();
+            } else if let Some(stripped) = var.strip_prefix("-") {
+                final_values.retain(|v| *v != stripped);
+            } else {
+                final_values.push(var);
+            }
+        }
+
+        let mut seen = HashSet::new();
+        final_values.retain(|v| seen.insert(*v));
+
+        if !final_values.is_empty() {
+            vars.insert(key.to_string(), final_values.join(" "));
+        }
+    }
+}
+
+fn interpolate(parents: &[Profile], vars: HashMap<Key, Vec<Segment>>) -> HashMap<String, String> {
+    let parent_vars = parents
+        .iter()
+        .flat_map(|parent| parent.make_defaults().clone().into_iter())
+        .collect::<HashMap<_, _>>();
+
+    vars.into_iter()
+        .map(|(key, segments)| {
+            let interpolated = segments
+                .into_iter()
+                .map(|segment| match segment {
+                    Segment::Interpolation(i) => parent_vars.get(&i.0).cloned().unwrap_or_default(),
+                    Segment::Literal(literal) => literal.0.trim().to_string(),
+                })
+                .collect::<Vec<_>>();
+
+            let joined = interpolated.join("");
+
+            (key.0, joined)
+        })
+        .collect::<HashMap<String, String>>()
+}
+
+fn parse(contents: &str) -> Result<HashMap<Key, Vec<Segment>>, Error> {
+    Ok(LineBasedFileExpr::<Assignment>::parser()
+        .separated_by_with_opt_trailing(ascii_whitespace1())
+        .many()
+        .parse_finished(InputIter::new(contents))
+        .map_err(|e| Error::Parser(dbg!(e).rest().to_string()))?
+        .into_iter()
+        .filter_map(|expr| match expr {
+            LineBasedFileExpr::Comment => None,
+            LineBasedFileExpr::Expr(Assignment(key, value)) => Some((key, value)),
+        })
+        .collect())
+}
diff --git a/src/repo/profile/make_defaults/parsers.rs b/src/repo/profile/make_defaults/parsers.rs
new file mode 100644
index 0000000..4d27791
--- /dev/null
+++ b/src/repo/profile/make_defaults/parsers.rs
@@ -0,0 +1,88 @@
+use mon::{Parser, ParserIter, ascii_alpha, ascii_alphanumeric, r#if, one_of, tag};
+
+use crate::{
+    Parseable,
+    repo::profile::make_defaults::{Assignment, Interpolation, Key, Literal, Segment},
+};
+
+impl<'a> Parseable<'a, &'a str> for Key {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        let start = ascii_alpha();
+        let rest = ascii_alphanumeric()
+            .or(one_of("_".chars()))
+            .repeated()
+            .many();
+
+        start
+            .followed_by(rest)
+            .recognize()
+            .map(|output: &str| Key(output.to_string()))
+    }
+}
+
+impl<'a> Parseable<'a, &'a str> for Literal {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        r#if(|c: &char| *c != '"')
+            .and_not(Interpolation::parser())
+            .repeated()
+            .at_least(1)
+            .recognize()
+            .map(|output: &str| Literal(output.to_string()))
+    }
+}
+
+impl<'a> Parseable<'a, &'a str> for Interpolation {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Key::parser()
+            .recognize()
+            .delimited_by(tag("{"), tag("}"))
+            .preceded_by(tag("$"))
+            .map(|output: &str| Interpolation(output.to_string()))
+    }
+}
+
+impl<'a> Parseable<'a, &'a str> for Segment {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Literal::parser()
+            .map(Segment::Literal)
+            .or(Interpolation::parser().map(Segment::Interpolation))
+    }
+}
+
+impl<'a> Parseable<'a, &'a str> for Assignment {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Key::parser()
+            .followed_by(tag("="))
+            .and(
+                Segment::parser()
+                    .repeated()
+                    .many()
+                    .delimited_by(tag("\""), tag("\"")),
+            )
+            .map(|(key, value)| Assignment(key, value))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use mon::input::InputIter;
+
+    use super::*;
+
+    #[test]
+    fn test_parse_value() {
+        let it = InputIter::new(r#"KEY="foo ${bar}""#);
+
+        Assignment::parser().check_finished(it).unwrap();
+    }
+}
diff --git a/src/repo/profile/mod.rs b/src/repo/profile/mod.rs
new file mode 100644
index 0000000..3edd170
--- /dev/null
+++ b/src/repo/profile/mod.rs
@@ -0,0 +1,157 @@
+use std::{
+    collections::HashMap,
+    fs::{self, File},
+    io::{self, Read},
+    path::{Path, PathBuf},
+};
+
+use get::Get;
+use itertools::Itertools;
+
+use crate::{atom::Atom, useflag::UseFlag};
+
+mod make_defaults;
+mod package;
+mod package_use;
+mod packages;
+mod parsers;
+mod useflags;
+
+#[derive(Debug, Clone)]
+enum LineBasedFileExpr<T> {
+    Comment,
+    Expr(T),
+}
+
+#[derive(Debug, Clone)]
+enum FlagOperation {
+    Add(UseFlag),
+    Remove(UseFlag),
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("{0}: io error: {1}")]
+    Io(PathBuf, io::Error),
+    #[error("error evaluating make.defaults settings: {0}")]
+    MakeDefaults(#[from] make_defaults::Error),
+    #[error("error evaluating packages settings: {0}")]
+    Packages(#[from] packages::Error),
+    #[error("error evaluating package settings: {0}")]
+    Package(#[from] package::Error),
+    #[error("error evaluating package.use settings: {0}")]
+    PackageUse(#[from] package_use::Error),
+    #[error("error evaluating use settings: {0}")]
+    Use(#[from] useflags::Error),
+}
+
+#[derive(Debug, Clone, Get)]
+pub struct Profile {
+    #[get(kind = "deref")]
+    path: PathBuf,
+    #[get(kind = "deref")]
+    parents: Vec<Profile>,
+    make_defaults: HashMap<String, String>,
+    #[get(kind = "deref")]
+    packages: Vec<Atom>,
+    #[get(kind = "deref")]
+    package_mask: Vec<Atom>,
+    #[get(kind = "deref")]
+    package_provided: Vec<Atom>,
+    package_use: HashMap<Atom, Vec<UseFlag>>,
+    package_use_force: HashMap<Atom, Vec<UseFlag>>,
+    package_use_mask: HashMap<Atom, Vec<UseFlag>>,
+    package_use_stable_force: HashMap<Atom, Vec<UseFlag>>,
+    package_use_stable_mask: HashMap<Atom, Vec<UseFlag>>,
+    #[get(kind = "deref")]
+    use_force: Vec<UseFlag>,
+    #[get(kind = "deref")]
+    use_mask: Vec<UseFlag>,
+    #[get(kind = "deref")]
+    use_stable_force: Vec<UseFlag>,
+    #[get(kind = "deref")]
+    use_stable_mask: Vec<UseFlag>,
+}
+
+impl Profile {
+    pub(super) fn evaluate<P: AsRef<Path>>(path: P) -> Result<Self, Error> {
+        let parents_path = path.as_ref().join("parent");
+
+        let parents = match fs::read_to_string(&parents_path) {
+            Ok(parents) => parents
+                .lines()
+                .map(|line| path.as_ref().join(line))
+                .map(Profile::evaluate)
+                .collect::<Result<_, _>>()?,
+            Err(e) if matches!(e.kind(), io::ErrorKind::NotFound) => Vec::new(),
+            Err(e) => return Err(Error::Io(parents_path, e)),
+        };
+
+        let make_defaults = make_defaults::evaluate(&parents, &path)?;
+
+        let packages = packages::evaluate(&parents, &path)?;
+
+        let package_mask = package::evaluate(&parents, package::Kind::Mask, &path)?;
+        let package_provided = package::evaluate(&parents, package::Kind::Provided, &path)?;
+
+        let package_use = package_use::evaluate(&parents, package_use::Kind::Use, &path)?;
+        let package_use_force = package_use::evaluate(&parents, package_use::Kind::Force, &path)?;
+        let package_use_mask = package_use::evaluate(&parents, package_use::Kind::Mask, &path)?;
+        let package_use_stable_force =
+            package_use::evaluate(&parents, package_use::Kind::StableForce, &path)?;
+        let package_use_stable_mask =
+            package_use::evaluate(&parents, package_use::Kind::StableMask, &path)?;
+
+        let use_force = useflags::evaluate(&parents, useflags::Kind::Force, &path)?;
+        let use_mask = useflags::evaluate(&parents, useflags::Kind::Mask, &path)?;
+        let use_stable_force = useflags::evaluate(&parents, useflags::Kind::StableForce, &path)?;
+        let use_stable_mask = useflags::evaluate(&parents, useflags::Kind::StableMask, &path)?;
+
+        Ok(Self {
+            path: path.as_ref().to_path_buf(),
+            parents,
+            make_defaults,
+            packages,
+            package_mask,
+            package_provided,
+            package_use,
+            package_use_force,
+            package_use_mask,
+            package_use_stable_force,
+            package_use_stable_mask,
+            use_force,
+            use_mask,
+            use_stable_force,
+            use_stable_mask,
+        })
+    }
+}
+
+fn read_config_files<P: AsRef<Path>>(path: P) -> Result<String, io::Error> {
+    let metadata = fs::metadata(&path)?;
+
+    if metadata.is_file() {
+        fs::read_to_string(&path)
+    } else if metadata.is_dir() {
+        let mut buffer = String::new();
+        let paths = fs::read_dir(&path)?
+            .collect::<Result<Vec<_>, _>>()?
+            .into_iter()
+            .map(|entry| entry.path())
+            .filter(|path| path.starts_with("."))
+            .sorted()
+            .collect::<Vec<_>>();
+
+        for path in &paths {
+            let mut file = File::open(path)?;
+
+            file.read_to_string(&mut buffer)?;
+        }
+
+        Ok(buffer)
+    } else {
+        let path = fs::canonicalize(&path)?;
+
+        read_config_files(path)
+    }
+}
diff --git a/src/repo/profile/package/mod.rs b/src/repo/profile/package/mod.rs
new file mode 100644
index 0000000..facf9ea
--- /dev/null
+++ b/src/repo/profile/package/mod.rs
@@ -0,0 +1,95 @@
+use std::{
+    io,
+    path::{Path, PathBuf},
+};
+
+use mon::{Parser, ParserIter, ascii_whitespace1, input::InputIter};
+
+use crate::{
+    Parseable,
+    atom::Atom,
+    repo::profile::{LineBasedFileExpr, Profile, read_config_files},
+};
+
+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, Copy)]
+pub(super) enum Kind {
+    Mask,
+    Provided,
+}
+
+#[derive(Debug, Clone)]
+enum Package {
+    Add(Atom),
+    Remove(Atom),
+}
+
+pub(super) fn evaluate<P: AsRef<Path>>(
+    parents: &[Profile],
+    kind: Kind,
+    path: P,
+) -> Result<Vec<Atom>, Error> {
+    let file_path = match kind {
+        Kind::Mask => "package.mask",
+        Kind::Provided => "package.provided",
+    };
+
+    let parsed = match read_config_files(path.as_ref().join(file_path)) {
+        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, kind, parsed))
+}
+
+fn inherit(parents: &[Profile], kind: Kind, packages: Vec<Package>) -> Vec<Atom> {
+    let mut accumulated = Vec::new();
+
+    for parent in parents {
+        let source = match kind {
+            Kind::Mask => parent.package_mask(),
+            Kind::Provided => parent.package_provided(),
+        };
+
+        for package in source {
+            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())
+}
diff --git a/src/repo/profile/package/parsers.rs b/src/repo/profile/package/parsers.rs
new file mode 100644
index 0000000..74d9acc
--- /dev/null
+++ b/src/repo/profile/package/parsers.rs
@@ -0,0 +1,13 @@
+use mon::{Parser, tag};
+
+use crate::{Parseable, atom::Atom, repo::profile::package::Package};
+
+impl<'a> Parseable<'a, &'a str> for Package {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Atom::parser()
+            .map(Package::Add)
+            .or(Atom::parser().preceded_by(tag("-")).map(Package::Remove))
+    }
+}
diff --git a/src/repo/profile/package_use/mod.rs b/src/repo/profile/package_use/mod.rs
new file mode 100644
index 0000000..ddad8b3
--- /dev/null
+++ b/src/repo/profile/package_use/mod.rs
@@ -0,0 +1,125 @@
+use std::{
+    collections::HashMap,
+    io,
+    path::{Path, PathBuf},
+};
+
+use mon::{Parser, ParserIter, ascii_whitespace1, input::InputIter};
+
+use crate::{
+    Parseable,
+    atom::Atom,
+    repo::profile::{FlagOperation, LineBasedFileExpr, Profile, read_config_files},
+    useflag::UseFlag,
+};
+
+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)]
+struct Expr(Atom, Vec<FlagOperation>);
+
+#[derive(Debug, Clone, Copy)]
+pub(super) enum Kind {
+    Use,
+    Force,
+    Mask,
+    StableForce,
+    StableMask,
+}
+
+pub(super) fn evaluate<P: AsRef<Path>>(
+    parents: &[Profile],
+    kind: Kind,
+    path: P,
+) -> Result<HashMap<Atom, Vec<UseFlag>>, Error> {
+    let file_path = match kind {
+        Kind::Use => "package.use",
+        Kind::Force => "package.use.force",
+        Kind::Mask => "package.use.mask",
+        Kind::StableForce => "package.use.stable.force",
+        Kind::StableMask => "package.use.stable.mask",
+    };
+
+    let parsed = match read_config_files(path.as_ref().join(file_path)) {
+        Ok(contents) => parse(&contents)?,
+        Err(e) if matches!(e.kind(), io::ErrorKind::NotFound) => HashMap::new(),
+        Err(e) => return Err(Error::Io(path.as_ref().to_path_buf(), e)),
+    };
+
+    Ok(inherit(parents, kind, parsed))
+}
+
+fn inherit(
+    parents: &[Profile],
+    kind: Kind,
+    vars: HashMap<Atom, Vec<FlagOperation>>,
+) -> HashMap<Atom, Vec<UseFlag>> {
+    let mut accumulated: HashMap<Atom, Vec<UseFlag>> = HashMap::new();
+
+    for parent in parents {
+        let source = match kind {
+            Kind::Use => parent.package_use(),
+            Kind::Force => parent.package_use_force(),
+            Kind::Mask => parent.package_use_mask(),
+            Kind::StableForce => parent.package_use_stable_force(),
+            Kind::StableMask => parent.package_use_stable_mask(),
+        };
+
+        for (atom, flags) in source {
+            accumulated
+                .entry(atom.clone())
+                .and_modify(|f| f.extend(flags.iter().cloned()))
+                .or_insert(flags.clone());
+        }
+    }
+
+    for (atom, flags) in vars {
+        match accumulated.get_mut(&atom) {
+            Some(accumulated) => {
+                for flag in flags {
+                    match flag {
+                        FlagOperation::Add(flag) => accumulated.push(flag),
+                        FlagOperation::Remove(flag) => accumulated.retain(|v| *v != flag),
+                    }
+                }
+            }
+            None => {
+                accumulated.insert(
+                    atom.clone(),
+                    flags
+                        .iter()
+                        .filter_map(|flag| match flag {
+                            FlagOperation::Add(flag) => Some(flag),
+                            FlagOperation::Remove(_) => None,
+                        })
+                        .cloned()
+                        .collect(),
+                );
+            }
+        }
+    }
+
+    accumulated
+}
+
+fn parse(contents: &str) -> Result<HashMap<Atom, Vec<FlagOperation>>, Error> {
+    Ok(LineBasedFileExpr::<Expr>::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(Expr(atom, operations)) => Some((atom, operations)),
+        })
+        .collect())
+}
diff --git a/src/repo/profile/package_use/parsers.rs b/src/repo/profile/package_use/parsers.rs
new file mode 100644
index 0000000..f7bc801
--- /dev/null
+++ b/src/repo/profile/package_use/parsers.rs
@@ -0,0 +1,36 @@
+use mon::{Parser, ParserIter, ascii_whitespace, ascii_whitespace1, tag};
+
+use crate::{
+    Parseable,
+    atom::Atom,
+    repo::profile::{FlagOperation, package_use::Expr},
+};
+
+impl<'a> Parseable<'a, &'a str> for Expr {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Atom::parser()
+            .followed_by(ascii_whitespace1())
+            .and(
+                FlagOperation::parser()
+                    .separated_by(ascii_whitespace().and_not(tag("\n")).repeated().at_least(1))
+                    .at_least(1),
+            )
+            .map(|(atom, operations)| Expr(atom, operations))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use mon::input::InputIter;
+
+    use super::*;
+
+    #[test]
+    fn test_parse_expr() {
+        let it = InputIter::new("foo/bar a -b");
+
+        Expr::parser().check_finished(it).unwrap();
+    }
+}
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())
+}
diff --git a/src/repo/profile/packages/parsers.rs b/src/repo/profile/packages/parsers.rs
new file mode 100644
index 0000000..e5dc727
--- /dev/null
+++ b/src/repo/profile/packages/parsers.rs
@@ -0,0 +1,14 @@
+use mon::{Parser, tag};
+
+use crate::{Parseable, atom::Atom, repo::profile::packages::Package};
+
+impl<'a> Parseable<'a, &'a str> for Package {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        Atom::parser()
+            .preceded_by(tag("*"))
+            .map(Package::Add)
+            .or(Atom::parser().preceded_by(tag("-*")).map(Package::Remove))
+    }
+}
diff --git a/src/repo/profile/parsers.rs b/src/repo/profile/parsers.rs
new file mode 100644
index 0000000..44e767e
--- /dev/null
+++ b/src/repo/profile/parsers.rs
@@ -0,0 +1,35 @@
+use mon::{Parser, ParserIter, any, ascii_whitespace1, tag};
+
+use crate::{
+    Parseable,
+    repo::profile::{FlagOperation, LineBasedFileExpr},
+    useflag::UseFlag,
+};
+
+impl<'a, T> Parseable<'a, &'a str> for LineBasedFileExpr<T>
+where
+    T: Parseable<'a, &'a str>,
+{
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        let comment = tag("#")
+            .preceded_by(ascii_whitespace1().opt())
+            .followed_by(any().and_not(tag("\n")).repeated().many())
+            .map(|_| LineBasedFileExpr::Comment);
+        let expr = T::parser().map(|expr| LineBasedFileExpr::Expr(expr));
+
+        comment.or(expr)
+    }
+}
+
+impl<'a> Parseable<'a, &'a str> for FlagOperation {
+    type Parser = impl Parser<&'a str, Output = Self>;
+
+    fn parser() -> Self::Parser {
+        UseFlag::parser()
+            .preceded_by(tag("-"))
+            .map(FlagOperation::Remove)
+            .or(UseFlag::parser().map(FlagOperation::Add))
+    }
+}
diff --git a/src/repo/profile/useflags/mod.rs b/src/repo/profile/useflags/mod.rs
new file mode 100644
index 0000000..d7fb96c
--- /dev/null
+++ b/src/repo/profile/useflags/mod.rs
@@ -0,0 +1,94 @@
+use std::{
+    io,
+    path::{Path, PathBuf},
+};
+
+use mon::{Parser, ParserIter, ascii_whitespace1, input::InputIter};
+
+use crate::{
+    Parseable,
+    repo::profile::{FlagOperation, LineBasedFileExpr, Profile, read_config_files},
+    useflag::UseFlag,
+};
+
+#[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, Copy)]
+pub(super) enum Kind {
+    Force,
+    Mask,
+    StableForce,
+    StableMask,
+}
+
+#[allow(clippy::unnecessary_wraps)]
+pub(super) fn evaluate<P: AsRef<Path>>(
+    parents: &[Profile],
+    kind: Kind,
+    path: P,
+) -> Result<Vec<UseFlag>, Error> {
+    let file_path = match kind {
+        Kind::Force => "use.force",
+        Kind::Mask => "use.mask",
+        Kind::StableForce => "use.stable.force",
+        Kind::StableMask => "use.stable.mask",
+    };
+
+    let parsed = match read_config_files(path.as_ref().join(file_path)) {
+        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, kind, parsed))
+}
+
+fn inherit(parents: &[Profile], kind: Kind, operations: Vec<FlagOperation>) -> Vec<UseFlag> {
+    let mut accumulated = Vec::new();
+
+    for parent in parents {
+        let source = match kind {
+            Kind::Force => parent.use_force(),
+            Kind::Mask => parent.use_mask(),
+            Kind::StableForce => parent.use_stable_force(),
+            Kind::StableMask => parent.use_stable_mask(),
+        };
+
+        for flag in source {
+            accumulated.push(flag.clone());
+        }
+    }
+
+    for operation in operations {
+        match operation {
+            FlagOperation::Add(flag) => {
+                accumulated.push(flag);
+            }
+            FlagOperation::Remove(flag) => {
+                accumulated.retain(|v| *v != flag);
+            }
+        }
+    }
+
+    accumulated
+}
+
+fn parse(contents: &str) -> Result<Vec<FlagOperation>, Error> {
+    Ok(LineBasedFileExpr::<FlagOperation>::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(flag_operation) => Some(flag_operation),
+        })
+        .collect())
+}