Set up initial structure for the nix builder.

src/config/target.rs

@@ -0,0 +1,45 @@
+use std::borrow::Cow;
+use std::path::Path;
+
+use serde::Deserialize;
+use serde::Serialize;
+
+use crate::error::CustomError;
+
+use super::Config;
+
+#[derive(Debug, Deserialize, Serialize, Default)]
+pub(crate) struct TargetConfig {
+    pub(super) name: String,
+
+    #[serde(default)]
+    pub(super) repo: Option<String>,
+    #[serde(default)]
+    pub(super) branch: Option<String>,
+    #[serde(default)]
+    pub(super) path: Option<String>,
+    #[serde(default)]
+    pub(super) attr: Option<String>,
+    #[serde(default)]
+    pub(super) update: Option<bool>,
+    #[serde(default)]
+    pub(super) update_branch: Option<String>,
+}
+
+impl TargetConfig {
+    pub(crate) fn get_target_directory<'target, 'root>(
+        &'target self,
+        config_root: &'root Config,
+    ) -> Result<Cow<'target, Path>, CustomError> {
+        let work_directory = config_root.get_work_directory()?;
+        Ok(Cow::Owned(work_directory.join(&self.name)))
+    }
+
+    pub(crate) fn get_flake_directory<'target, 'root>(
+        &'target self,
+        config_root: &'root Config,
+    ) -> Result<Cow<'target, Path>, CustomError> {
+        let target_directory = self.get_target_directory(config_root)?;
+        Ok(Cow::Owned(target_directory.join("flake")))
+    }
+}