MP4: Move AdvisoryRating to a new module

Author: Serial-ATA

lofty/src/mp4/ilst/advisory_rating.rs

@@ -0,0 +1,52 @@
+/// The parental advisory rating
+///
+/// See also:
+/// * <https://docs.mp3tag.de/mapping/#itunesadvisory>
+/// * <https://exiftool.org/TagNames/QuickTime.html>
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum AdvisoryRating {
+	/// *Inoffensive*/*None* (0)
+	Inoffensive,
+	/// *Explicit* (1 or 4)
+	///
+	/// In the past Apple used the value `4` for explicit content
+	/// that has later been replaced by `1`. Both values are considered
+	/// as valid when reading but only the newer value `1` is written.
+	Explicit,
+	/// *Clean*/*Edited* (2)
+	Clean,
+}
+
+impl AdvisoryRating {
+	/// Returns the rating as it appears in the `rtng` atom
+	///
+	/// # Examples
+	///
+	/// ```rust
+	/// use lofty::mp4::AdvisoryRating;
+	///
+	/// assert_eq!(AdvisoryRating::Inoffensive.as_u8(), 0);
+	/// assert_eq!(AdvisoryRating::Explicit.as_u8(), 1);
+	/// assert_eq!(AdvisoryRating::Clean.as_u8(), 2);
+	/// ```
+	pub fn as_u8(&self) -> u8 {
+		match self {
+			AdvisoryRating::Inoffensive => 0,
+			AdvisoryRating::Explicit => 1,
+			AdvisoryRating::Clean => 2,
+		}
+	}
+}
+
+impl TryFrom<u8> for AdvisoryRating {
+	type Error = u8;
+
+	fn try_from(input: u8) -> Result<Self, Self::Error> {
+		match input {
+			0 => Ok(Self::Inoffensive),
+			1 | 4 => Ok(Self::Explicit),
+			2 => Ok(Self::Clean),
+			value => Err(value),
+		}
+	}
+}

lofty/src/mp4/ilst/mod.rs

@@ -1,3 +1,4 @@
+pub(super) mod advisory_rating;
 pub(super) mod atom;
 pub(super) mod constants;
 pub(super) mod read;
@@ -16,6 +17,7 @@ use crate::tag::{
 use crate::util::flag_item;
 use crate::util::io::{FileLike, Length, Truncate};
 use atom::{AdvisoryRating, Atom, AtomData};
+use advisory_rating::AdvisoryRating;
 
 use std::borrow::Cow;
 use std::io::Write;

lofty/src/mp4/mod.rs

@@ -24,6 +24,7 @@ pub mod constants {
 pub use crate::mp4::properties::{AudioObjectType, Mp4Codec, Mp4Properties};
 pub use atom_info::AtomIdent;
 pub use ilst::atom::{AdvisoryRating, Atom, AtomData};
+pub use ilst::advisory_rating::AdvisoryRating;
 pub use ilst::Ilst;
 
 pub(crate) use properties::SAMPLE_RATES;