Write generation state into a state file and restructure the services.json file produced by nix.

src/lib.rs

@@ -3,29 +3,34 @@ pub mod generate;
 mod systemd;
 
 use anyhow::Result;
+use serde::{Deserialize, Serialize};
 use std::os::unix;
 use std::path::Path;
 use std::{fs, str};
 
 const FLAKE_ATTR: &str = "serviceConfig";
-const PROFILE_NAME: &str = "service-manager";
+const PROFILE_PATH: &str = "/nix/var/nix/profiles/service-manager";
+const GCROOT_PATH: &str = "/nix/var/nix/gcroots/service-manager-current";
+const SYSTEMD_UNIT_DIR: &str = "/run/systemd/system";
+const SERVICE_MANAGER_STATE_DIR: &str = "/var/lib/service-manager/state";
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
 pub struct StorePath {
-    pub path: String,
+    pub store_path: String,
 }
 
 impl From<String> for StorePath {
     fn from(path: String) -> Self {
         StorePath {
-            path: path.trim().into(),
+            store_path: path.trim().into(),
         }
     }
 }
 
 impl std::fmt::Display for StorePath {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.path)
+        write!(f, "{}", self.store_path)
     }
 }
 
@@ -34,7 +39,7 @@ fn create_store_link(store_path: &StorePath, from: &Path) -> Result<()> {
     if from.is_symlink() {
         fs::remove_file(from)?;
     }
-    unix::fs::symlink(&store_path.path, from).map_err(anyhow::Error::from)
+    unix::fs::symlink(&store_path.store_path, from).map_err(anyhow::Error::from)
 }
 
 pub fn compose<A, B, C, G, F>(f: F, g: G) -> impl Fn(A) -> C