feat(xy): XDG path resolution

crates/xy/src/main.rs

@@ -1,3 +1,8 @@
+mod paths;
+#[allow(dead_code)]
+mod pidfile;
+
 fn main() {
-    println!("xy: not implemented yet");
+    let p = paths::Paths::resolve().unwrap();
+    eprintln!("xy: socket would be at {}", p.socket.display());
 }

crates/xy/src/paths.rs

@@ -0,0 +1,42 @@
+use etcetera::base_strategy::{BaseStrategy, Xdg};
+use std::path::PathBuf;
+
+#[derive(Debug, Clone)]
+pub struct Paths {
+    pub config_dir: PathBuf,
+    pub state_dir: PathBuf,
+    pub log_dir: PathBuf,
+    pub socket: PathBuf,
+    pub pidfile: PathBuf,
+}
+
+impl Paths {
+    pub fn resolve() -> std::io::Result<Self> {
+        let xdg = Xdg::new().map_err(std::io::Error::other)?;
+        let config_dir = xdg.config_dir().join("xy").join("servers");
+        let state_dir = xdg.state_dir().unwrap_or_else(|| xdg.data_dir()).join("xy");
+        let log_dir = state_dir.join("logs");
+        let socket = std::env::var_os("XDG_RUNTIME_DIR")
+            .map(|p| PathBuf::from(p).join("xy.sock"))
+            .unwrap_or_else(|| state_dir.join("xy.sock"));
+        let pidfile = state_dir.join("xy.pid");
+        Ok(Self { config_dir, state_dir, log_dir, socket, pidfile })
+    }
+
+    pub fn ensure_dirs(&self) -> std::io::Result<()> {
+        std::fs::create_dir_all(&self.state_dir)?;
+        std::fs::create_dir_all(&self.log_dir)?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn resolves_without_panicking() {
+        let p = Paths::resolve().unwrap();
+        assert!(p.pidfile.starts_with(&p.state_dir));
+    }
+}