feat(mingling): add directory environment resources and setup

Add four new resource types for common directory paths and a
convenience setup struct that registers all of them at once.

1 files changed, 82 insertions, 0 deletions

diff --git a/mingling/src/res/dirs/current_dir.rs b/mingling/src/res/dirs/current_dir.rs
new file mode 100644
index 0000000..1de84e0
--- /dev/null
+++ b/mingling/src/res/dirs/current_dir.rs
@@ -0,0 +1,82 @@
+use std::{
+    env::current_dir,
+    path::{Path, PathBuf},
+};
+
+/// A global resource for the Mingling library that provides the current working directory.
+///
+/// This struct wraps a `PathBuf` representing the current working directory at the time of
+/// creation. It is used as a shared resource in the Mingling framework so that multiple
+/// components can access the same base directory without repeatedly querying the OS.
+///
+/// # Default behavior
+///
+/// The `Default` implementation calls `std::env::current_dir().unwrap()` internally, which will
+/// **panic** if the current directory cannot be determined (e.g., if it has been deleted). If
+/// you want to handle this error gracefully, use [`ResCurrentDir::new`] instead, which returns
+/// a `Result`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ResCurrentDir {
+    cwd: PathBuf
+}
+
+impl ResCurrentDir {
+    /// Creates a new `ResCurrentDir` by querying the OS for the current working directory.
+    ///
+    /// Returns `Err` if the current directory cannot be determined (e.g., the directory has been
+    /// deleted or permissions are insufficient). Unlike the `Default` implementation, this
+    /// method does not panic on failure.
+    pub fn new() -> Result<Self, std::io::Error> {
+        Ok(Self { cwd: current_dir()? })
+    }
+}
+
+impl Default for ResCurrentDir {
+    fn default() -> Self {
+        Self { cwd: current_dir().unwrap() }
+    }
+}
+
+impl From<PathBuf> for ResCurrentDir {
+    fn from(path: PathBuf) -> Self {
+        Self { cwd: path }
+    }
+}
+
+impl From<&Path> for ResCurrentDir {
+    fn from(path: &Path) -> Self {
+        Self { cwd: path.to_path_buf() }
+    }
+}
+
+impl From<&PathBuf> for ResCurrentDir {
+    fn from(path: &PathBuf) -> Self {
+        Self { cwd: path.clone() }
+    }
+}
+
+impl From<ResCurrentDir> for PathBuf {
+    fn from(res: ResCurrentDir) -> Self {
+        res.cwd
+    }
+}
+
+impl AsRef<Path> for ResCurrentDir {
+    fn as_ref(&self) -> &Path {
+        self.cwd.as_path()
+    }
+}
+
+impl std::ops::Deref for ResCurrentDir {
+    type Target = PathBuf;
+
+    fn deref(&self) -> &Self::Target {
+        &self.cwd
+    }
+}
+
+impl std::ops::DerefMut for ResCurrentDir {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.cwd
+    }
+}