Implement better CLI API (closes #7).

src/generate.rs

@@ -14,16 +14,11 @@ struct NixBuildOutput {
     outputs: HashMap<String, String>,
 }
 
-pub fn generate(flake_uri: &str) -> Result<()> {
+pub fn generate(flake_uri: &str) -> Result<StorePath> {
-    // FIXME: we should not hard-code the system here
+    let store_path = build(flake_uri)?;
-    let flake_attr = format!("{FLAKE_ATTR}.x86_64-linux");
-
-    log::info!("Building new system-manager generation...");
-    log::info!("Running nix build...");
-    let store_path = run_nix_build(flake_uri, &flake_attr).and_then(get_store_path)?;
-
     let profile_dir = Path::new(PROFILE_DIR);
     let profile_name = Path::new(PROFILE_NAME);
+
     log::info!("Creating new generation from {}", store_path);
     install_nix_profile(&store_path, profile_dir, profile_name).map(print_out_and_err)?;
 
@@ -31,7 +26,16 @@ pub fn generate(flake_uri: &str) -> Result<()> {
     create_gcroot(GCROOT_PATH, &profile_dir.join(profile_name))?;
 
     log::info!("Done");
-    Ok(())
+    Ok(store_path)
+}
+
+pub fn build(flake_uri: &str) -> Result<StorePath> {
+    // FIXME: we should not hard-code the system here
+    let flake_attr = format!("{FLAKE_ATTR}.x86_64-linux");
+
+    log::info!("Building new system-manager generation...");
+    log::info!("Running nix build...");
+    run_nix_build(flake_uri, &flake_attr).and_then(get_store_path)
 }
 
 fn install_nix_profile(

src/main.rs

@@ -1,6 +1,6 @@
 use std::process::ExitCode;
 
-use anyhow::{anyhow, Result};
+use anyhow::Result;
 use clap::Parser;
 
 use system_manager::StorePath;
@@ -12,17 +12,39 @@ struct Args {
     action: Action,
 }
 
+#[derive(clap::Args, Debug)]
+struct BuildArgs {
+    #[arg(long)]
+    flake_uri: String,
+}
+
+#[derive(clap::Args, Debug)]
+struct ActivationArgs {
+    #[arg(long, action)]
+    ephemeral: bool,
+}
+
 #[derive(clap::Subcommand, Debug)]
 enum Action {
     Activate {
         #[arg(long)]
         store_path: StorePath,
-        #[arg(long, action)]
+        #[command(flatten)]
-        ephemeral: bool,
+        activation_args: ActivationArgs,
+    },
+    Build {
+        #[command(flatten)]
+        build_args: BuildArgs,
     },
     Generate {
-        #[arg(long)]
+        #[command(flatten)]
-        flake_uri: String,
+        build_args: BuildArgs,
+    },
+    Switch {
+        #[command(flatten)]
+        build_args: BuildArgs,
+        #[command(flatten)]
+        activation_args: ActivationArgs,
     },
 }
 
@@ -35,19 +57,55 @@ fn main() -> ExitCode {
 }
 
 fn go(action: Action) -> Result<()> {
-    check_root()?;
     match action {
         Action::Activate {
             store_path,
-            ephemeral,
+            activation_args: ActivationArgs { ephemeral },
-        } => system_manager::activate::activate(store_path, ephemeral),
+        } => {
-        Action::Generate { flake_uri } => system_manager::generate::generate(&flake_uri),
+            check_root()?;
+            activate(store_path, ephemeral)
+        }
+        Action::Build {
+            build_args: BuildArgs { flake_uri },
+        } => build(flake_uri),
+        Action::Generate {
+            build_args: BuildArgs { flake_uri },
+        } => {
+            check_root()?;
+            generate(flake_uri).map(|_| ())
+        }
+        Action::Switch {
+            build_args: BuildArgs { flake_uri },
+            activation_args: ActivationArgs { ephemeral },
+        } => {
+            check_root()?;
+            let store_path = generate(flake_uri)?;
+            activate(store_path, ephemeral)
+        }
     }
 }
 
+fn build(flake_uri: String) -> Result<()> {
+    let store_path = do_build(flake_uri)?;
+    log::info!("{store_path}");
+    Ok(())
+}
+
+fn do_build(flake_uri: String) -> Result<StorePath> {
+    system_manager::generate::build(&flake_uri)
+}
+
+fn generate(flake_uri: String) -> Result<StorePath> {
+    system_manager::generate::generate(&flake_uri)
+}
+
+fn activate(store_path: StorePath, ephemeral: bool) -> Result<()> {
+    system_manager::activate::activate(store_path, ephemeral)
+}
+
 fn check_root() -> Result<()> {
     if !nix::unistd::Uid::is_root(nix::unistd::getuid()) {
-        return Err(anyhow!("We need root permissions."));
+        anyhow::bail!("We need root permissions.")
     }
     Ok(())
 }