refactor(nix): tidy things into separate functions (this should be typestate but I'm eepy)

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

crates/nix-weather/src/nix.rs

@@ -10,6 +10,7 @@ use std::{
 };
 
 /// Get nixosConfiguration derivation path
+#[inline]
 fn get_config_drv_path(host: &str, config_dir: &str) -> std::io::Result<std::process::Output> {
   Command::new("nix")
     .current_dir(Path::new(config_dir))
@@ -27,6 +28,7 @@ fn get_config_drv_path(host: &str, config_dir: &str) -> std::io::Result<std::pro
 }
 
 /// Get installable derivation path
+#[inline]
 fn get_installable_drv_path(
   host: &str,
   config_dir: &str,
@@ -37,7 +39,36 @@ fn get_installable_drv_path(
     .output()
 }
 
+/// Takes a drv_path and gets all it's requisites from the nix store.
+#[inline]
+fn get_requisites_from_drv_path(drv_path: &str) -> std::io::Result<std::process::Child> {
+  Command::new("nix-store")
+    .args(["--query", "--requisites", drv_path])
+    .stdout(Stdio::piped())
+    .spawn()
+}
+
+/// Turns requisites into hashes
+#[inline]
+fn requisites_to_hashes(
+  drv_requisites: std::process::Child,
+) -> std::io::Result<std::process::Child> {
+  let drv_requisites_remove_base = Command::new("cut")
+    .args(["-d", "/", "-f4"])
+    .stdin(Stdio::from(drv_requisites.stdout.unwrap()))
+    .stdout(Stdio::piped())
+    .spawn()
+    .unwrap();
+  Command::new("cut")
+    .args(["-d", "-", "-f1"])
+    .stdin(Stdio::from(drv_requisites_remove_base.stdout.unwrap()))
+    .stdout(Stdio::piped())
+    .spawn()
+}
+
 pub fn get_requisites(host: &str, config_dir: &str, installable: Option<String>) -> String {
+  // If the users specified an installable, we interpret that, instead of trying
+  // to guess their config location.
   let mut drv_path;
   if let Some(installable) = installable {
     drv_path = get_installable_drv_path(host, config_dir, &installable).unwrap();
@@ -51,23 +82,16 @@ pub fn get_requisites(host: &str, config_dir: &str, installable: Option<String>)
 
   log::debug!("drv_path: {}", &drv_path);
 
-  let get_drv_requisites = Command::new("nix-store")
-    .args(["--query", "--requisites", drv_path.as_str().unwrap()])
-    .stdout(Stdio::piped())
-    .spawn()
-    .unwrap();
-  let drv_requisites_remove_base = Command::new("cut")
-    .args(["-d", "/", "-f4"])
-    .stdin(Stdio::from(get_drv_requisites.stdout.unwrap()))
-    .stdout(Stdio::piped())
-    .spawn()
-    .unwrap();
-  let drv_requisites_to_hash = Command::new("cut")
-    .args(["-d", "-", "-f1"])
-    .stdin(Stdio::from(drv_requisites_remove_base.stdout.unwrap()))
-    .stdout(Stdio::piped())
-    .spawn()
-    .unwrap();
+  let drv_requisites = get_requisites_from_drv_path(drv_path.as_str().unwrap()).unwrap();
 
-  String::from_utf8(drv_requisites_to_hash.wait_with_output().unwrap().stdout).unwrap()
+  let drv_requisite_hashes = requisites_to_hashes(drv_requisites);
+
+  String::from_utf8(
+    drv_requisite_hashes
+      .unwrap()
+      .wait_with_output()
+      .unwrap()
+      .stdout,
+  )
+  .unwrap()
 }