added filesystem abstraction layer and implemented basic filesystem - testing not complete yet, still features missing

src/filesystem/native.rs

@@ -0,0 +1,105 @@
+// ────────────────────────────────────────────────────────────────
+// Imports
+// ────────────────────────────────────────────────────────────────
+use std::fs;
+use std::io::{ErrorKind, Read};
+use std::path::{Path, PathBuf};
+
+use serde::Serialize;
+use serde::de::DeserializeOwned;
+
+use crate::filesystem::{FsError, LegacyFileSystem};
+
+// ────────────────────────────────────────────────────────────────
+// Concrete implementation
+// ────────────────────────────────────────────────────────────────
+/// The concrete file‑system.  All paths are interpreted relative to
+/// `project_root`.
+pub struct NativeFileSystem {
+    project_root: PathBuf,
+}
+
+impl NativeFileSystem {
+    /// Create a new instance.
+    pub fn new(root: impl Into<PathBuf>) -> Self {
+        Self {
+            project_root: root.into(),
+        }
+    }
+
+    /// Resolve the user supplied *relative* path against the project root.
+    #[inline]
+    fn full_path(&self, path: &Path) -> PathBuf {
+        self.project_root.join(path)
+    }
+}
+
+// ────────────────────────────────────────────────────────────────
+// Implementation of the trait
+// ────────────────────────────────────────────────────────────────
+impl LegacyFileSystem for NativeFileSystem {
+    fn read<T: DeserializeOwned>(&self, path: &Path) -> Result<T, FsError> {
+        let full_path = self.full_path(path);
+        let file = fs::File::open(full_path).map_err(FsError::Io)?;
+        serde_json::from_reader(file).map_err(FsError::Serde)
+    }
+
+    fn read_bytes(&self, path: &Path) -> Result<Vec<u8>, FsError> {
+        let full_path = self.full_path(path);
+        let mut contents = Vec::new();
+        fs::File::open(full_path)?.read_to_end(&mut contents)?;
+        Ok(contents)
+    }
+
+    fn write<T: Serialize>(&self, path: &Path, data: T) -> Result<(), FsError> {
+        let full_path = self.full_path(path);
+
+        // Ensure the parent directory exists.
+        if let Some(parent) = full_path.parent() {
+            fs::create_dir_all(parent)?;
+        }
+
+        let file = fs::File::create(full_path)?;
+        serde_json::to_writer(file, &data).map_err(FsError::Serde)
+    }
+
+    fn delete(&self, path: &Path) -> Result<(), FsError> {
+        let full_path = self.full_path(path);
+        match fs::remove_file(&full_path) {
+            Ok(()) => Ok(()),
+            Err(e) if e.kind() == ErrorKind::IsADirectory => {
+                // Remove a directory tree.
+                fs::remove_dir_all(full_path).map_err(FsError::Io)
+            }
+            Err(e) => Err(FsError::Io(e)),
+        }
+    }
+
+    fn mkdir(&self, path: &Path) -> Result<(), FsError> {
+        let full_path = self.full_path(path);
+        fs::create_dir_all(full_path).map_err(FsError::Io)
+    }
+
+    fn exists(&self, path: &Path) -> bool {
+        let full_path = self.full_path(path);
+        full_path.exists()
+    }
+
+    fn rename(&self, path: &Path, other: &Path) -> Result<(), FsError> {
+        let full_path = self.full_path(path);
+        let full_other = self.full_path(other);
+        fs::rename(full_path, full_other).map_err(FsError::Io)
+    }
+
+    fn config_path(&self) -> PathBuf {
+        match std::env::var("HOME") {
+            Ok(path) => PathBuf::from(path + "/.config/worldcoder/settings.json"),
+            Err(_) => {
+                eprintln!(
+                    "XDG_CONFIG_HOME not set, using default path of ~/.config/worldcoder/settings.json"
+                );
+                "~/.config/worldcoder/settings.json".into()
+            }
+        }
+    }
+}