feat(multibinary): support running the binary without arguments (using a sensible user interface as the default), and improve error reporting by using snafu

multibinary/src/main.rs

@@ -1,6 +1,12 @@
-use std::{fs::create_dir_all, io::ErrorKind, path::PathBuf};
+use std::{
+    fs::create_dir_all,
+    io::ErrorKind,
+    path::{Path, PathBuf},
+};
 
+use cfg_if::cfg_if;
 use clap::{Parser, Subcommand};
+use snafu::{ResultExt, Snafu};
 
 #[derive(Debug, Parser)]
 struct Args {
@@ -11,24 +17,91 @@ struct Args {
     )]
     application_data_directory: PathBuf,
 
+    // If there is a GUI or TUI available from this binary,
+    // then calling this program without arguments
+    // is acceptable: it will launch a user interface
+    #[cfg(any(feature = "gui-eframe", feature = "tui-ratatui"))]
+    #[command(subcommand)]
+    command: Option<Command>,
+
+    #[cfg(not(any(feature = "gui-eframe", feature = "tui-ratatui")))]
     #[command(subcommand)]
     command: Command,
 }
 
 #[derive(Debug, Subcommand)]
 enum Command {
-    #[cfg(feature = "cli-clap")]
-    #[command(alias = "cli")]
-    CliClap(ac_qu_ai_nt_cli_clap::Args),
     #[cfg(feature = "gui-eframe")]
     #[command(alias = "gui")]
     GuiEframe,
+
     #[cfg(feature = "tui-ratatui")]
     #[command(alias = "tui")]
     TuiRatatui,
+
+    #[cfg(feature = "cli-clap")]
+    #[command(alias = "cli")]
+    CliClap(ac_qu_ai_nt_cli_clap::Args),
 }
 
-fn main() {
+// When this program is run without arguments,
+// it will launch a user interface
+cfg_if!(
+    // with the GUI (made with eframe)
+    // being considered more appealing (made the default)
+    if #[cfg(feature = "gui-eframe")] {
+        impl Default for Command {
+            fn default() -> Self {
+                Command::GuiEframe
+            }
+        }
+    }
+    // than the TUI (made with Ratatui)
+    else if #[cfg(feature = "tui-ratatui")] {
+        impl Default for Command {
+            fn default() -> Self {
+                Command::TuiRatatui
+            }
+        }
+    }
+    // with it not being logical to specify
+    // the CLI (made with clap)
+    // as an option,
+    // because if `ac-qu-ai-nt ask "why is the sky blue?"`
+    // were accepted and worked when `cli-clap` was the only
+    // interface enabled, then when another interface
+    // like `gui-eframe` were enabled, it would stop working
+    // (only able to work as `ac-qu-ai-nt cli-clap ask "why is the sky blue?"`)
+    // so it should be required to do it the way that would work
+    // in both cases from the beginning
+);
+
+#[derive(Debug, Snafu)]
+enum ApplicationError {
+    #[snafu(display("failed to create the {path:?} directory"))]
+    DirectoryCreationError {
+        path: PathBuf,
+        source: std::io::Error,
+    },
+}
+
+/// Create the directory and its parents,
+/// but don't return an error if it already exists and is a directory
+fn create_dir_all_exist_ok(path: impl AsRef<Path>) -> Result<(), std::io::Error> {
+    match create_dir_all(&path) {
+        Ok(()) => Ok(()),
+        Err(e) => {
+            if e.kind() == ErrorKind::AlreadyExists && path.as_ref().is_dir() {
+                Ok(())
+            } else {
+                Err(e)
+            }
+        }
+    }
+}
+
+#[snafu::report]
+fn main() -> Result<(), ApplicationError> {
     let Args {
         application_data_directory,
         command,
@@ -37,23 +110,19 @@ fn main() {
     #[cfg(feature = "tracing")]
     tracing_subscriber::fmt::init();
 
-    match create_dir_all(&application_data_directory) {
-        Ok(()) => {}
-        Err(e) if e.kind() == ErrorKind::AlreadyExists => {}
-        Err(e) => {
-            panic!("{}", e);
+    create_dir_all_exist_ok(&application_data_directory).with_context(|_| {
+        DirectoryCreationSnafu {
+            path: application_data_directory.clone(),
         }
-    }
+    })?;
 
     let tracing_directory = application_data_directory.join("logs");
+    create_dir_all_exist_ok(&tracing_directory).with_context(|_| DirectoryCreationSnafu {
+        path: tracing_directory.clone(),
+    })?;
 
-    match create_dir_all(&tracing_directory) {
-        Ok(()) => {}
-        Err(e) if e.kind() == ErrorKind::AlreadyExists => {}
-        Err(e) => {
-            panic!("{}", e);
-        }
-    }
+    #[cfg(any(feature = "gui-eframe", feature = "tui-ratatui"))]
+    let command = command.unwrap_or_default();
 
     match command {
         #[cfg(feature = "cli-clap")]
@@ -63,4 +132,6 @@ fn main() {
         #[cfg(feature = "tui-ratatui")]
         Command::TuiRatatui => ac_qu_ai_nt_tui_ratatui::main(),
     }
+
+    Ok(())
 }