feat(cli): add an "agama config edit" command

rust/agama-cli/src/config.rs

@@ -1,9 +1,19 @@
-use std::io::{self, Read};
+use std::{
+    io::{self, Read},
+    path::PathBuf,
+    process::Command,
+};
 
+use crate::show_progress;
 use agama_lib::{
     auth::AuthToken, connection, install_settings::InstallSettings, Store as SettingsStore,
 };
+use anyhow::anyhow;
 use clap::Subcommand;
+use std::io::Write;
+use tempfile::Builder;
+
+const DEFAULT_EDITOR: &str = "/usr/bin/vim";
 
 #[derive(Subcommand, Debug)]
 pub enum ConfigCommands {
@@ -17,6 +27,13 @@ pub enum ConfigCommands {
 
     /// Reads and loads a profile from the standard input.
     Load,
+
+    /// Edits and updates Agama's configuration on an external editor.
+    Edit {
+        /// Editor command (including additional arguments if needed)
+        #[arg(short, long)]
+        editor: Option<String>,
+    },
 }
 
 pub async fn run(subcommand: ConfigCommands) -> anyhow::Result<()> {
@@ -42,5 +59,49 @@ pub async fn run(subcommand: ConfigCommands) -> anyhow::Result<()> {
             let result: InstallSettings = serde_json::from_str(&contents)?;
             Ok(store.store(&result).await?)
         }
+        ConfigCommands::Edit { editor } => {
+            let model = store.load().await?;
+            let editor = editor
+                .or_else(|| std::env::var("EDITOR").ok())
+                .unwrap_or(DEFAULT_EDITOR.to_string());
+            let result = edit(&model, &editor)?;
+            tokio::spawn(async move {
+                show_progress().await.unwrap();
+            });
+            store.store(&result).await?;
+            Ok(())
+        }
+    }
+}
+
+/// Edit command.
+///
+/// Loads the configuration on an editor. If the editor returns a successful error code, it updates
+/// the configuration.
+///
+/// * `model`: current installation settings.
+fn edit(model: &InstallSettings, editor: &str) -> anyhow::Result<InstallSettings> {
+    let content = serde_json::to_string_pretty(model)?;
+    let mut file = Builder::new().suffix(".json").tempfile()?;
+    let path = PathBuf::from(file.path());
+    write!(file, "{}", content)?;
+
+    let mut command = editor_command(&editor);
+    let status = command.arg(path.as_os_str()).status()?;
+    if status.success() {
+        return Ok(InstallSettings::from_file(path)?);
     }
+
+    Err(anyhow!(
+        "Ignoring the changes becase the editor was closed with an error code."
+    ))
+}
+
+fn editor_command(command: &str) -> Command {
+    let mut parts = command.split_whitespace();
+    let program = parts.next().unwrap_or(DEFAULT_EDITOR);
+
+    let mut command = Command::new(program);
+    command.args(parts.collect::<Vec<&str>>());
+    command
 }