Add stubbed command for notes

src/cli.rs

@@ -1,6 +1,9 @@
 use async_trait::async_trait;
 
-use crate::{commands::midi::MidiCommand, error::FNoteResult};
+use crate::{
+    commands::{midi::MidiCommand, note::NoteCommand},
+    error::FNoteResult,
+};
 
 /// Represents an `fnote` program command.
 #[async_trait]
@@ -16,15 +19,19 @@ pub trait Command {
     version = env!("CARGO_PKG_VERSION"),
 )]
 pub enum FNoteCommand {
-    /// Extracts the frequency and musical note from a MIDI note number (0-127).
+    /// Extracts the frequency and music note from a MIDI note number (0-127).
     Midi(MidiCommand),
+
+    /// Extracts the frequency and MIDI note number from a music note (e.g. C5).
+    Note(NoteCommand),
 }
 
 #[async_trait]
 impl Command for FNoteCommand {
     async fn run(&self) -> FNoteResult<()> {
         match self {
             Self::Midi(cmd) => cmd.run().await,
+            Self::Note(cmd) => cmd.run().await,
         }
     }
 }

src/commands/midi.rs

@@ -6,7 +6,7 @@ use crate::{
     error::{FNoteError, FNoteResult},
 };
 
-/// Extracts the frequency and musical note from a MIDI note number (0-127).
+/// Extracts the frequency and music note from a MIDI note number (0-127).
 #[derive(structopt::StructOpt)]
 pub struct MidiCommand {
     /// The MIDI note number to use.

src/commands/mod.rs

@@ -1 +1,2 @@
 pub(crate) mod midi;
+pub(crate) mod note;

src/commands/note.rs

@@ -0,0 +1,34 @@
+use async_trait::async_trait;
+use regex::Regex;
+
+use crate::{
+    cli::Command,
+    error::{FNoteError, FNoteResult},
+};
+
+/// Extracts the frequency and MIDI note number from a music note (e.g. C5).
+#[derive(structopt::StructOpt)]
+pub struct NoteCommand {
+    /// The music note to use.
+    #[structopt(parse(try_from_str = try_music_note_from_str))]
+    pub musical_note: String,
+}
+
+#[async_trait]
+impl Command for NoteCommand {
+    async fn run(&self) -> FNoteResult<()> {
+        println!("Converting music note: {:?}", self.musical_note);
+
+        Ok(())
+    }
+}
+
+/// Parses a music note from a string.
+fn try_music_note_from_str(arg: &str) -> FNoteResult<String> {
+    let regex = Regex::new(r"^[A-Ga-g][#b]?[0-9]$").unwrap();
+    if regex.is_match(arg) {
+        Ok(arg.to_string())
+    } else {
+        Err(FNoteError::InvalidMusicNote(arg.to_string()))
+    }
+}

src/error.rs

@@ -9,4 +9,7 @@ pub enum FNoteError {
 
     #[error("Invalid MIDI note number \"{0}\"")]
     InvalidMidiNoteNumber(String),
+
+    #[error("Invalid music note \"{0}\"")]
+    InvalidMusicNote(String),
 }