Create impl_tag attribute proc macro

.gitignore

@@ -1,6 +1,6 @@
 # Generated by Cargo
 # will have compiled files and executables
-/target/
+**/target/
 
 # These are backup files generated by rustfmt
 **/*.rs.bk

Cargo.toml

@@ -33,6 +33,10 @@ thiserror = "1.0.24"
 base64 = "0.13.0"
 byteorder = "1.4.3"
 
+[dependencies.lofty_attr]
+path = "./lofty-attr"
+version = "0.1.0"
+
 [features]
 default = ["full"]
 full = ["all_tags", "duration"]

lofty-attr/Cargo.lock

@@ -0,0 +1,46 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "lofty_attr"
+version = "0.1.0"
+dependencies = [
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a152013215dca273577e18d2bf00fa862b89b24169fb78c4c95aeb07992c9cec"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3d0b9745dc2debf507c8422de05d7226cc1f0644216dfdfead988f9b1ab32a7"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.72"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1e8cdbefb79a9a5a65e0db8b47b723ee907b7c7f8496c76a1770b5c310bab82"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"

lofty-attr/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "lofty_attr"
+version = "0.1.0"
+authors = ["Serial <69764315+Serial-ATA@users.noreply.github.com>"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/Serial-ATA/lofty-rs"
+edition = "2018"
+
+[dependencies]
+quote = "1.0.9"
+
+[dependencies.syn]
+version = "1.0.72"
+features = ["full"]
+
+[lib]
+proc-macro = true

lofty-attr/src/lib.rs

@@ -0,0 +1,177 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, AttributeArgs, Error, ItemStruct, Meta, NestedMeta};
+
+#[proc_macro_attribute]
+#[allow(clippy::too_many_lines)]
+pub fn impl_tag(args: TokenStream, input: TokenStream) -> TokenStream {
+	let input = parse_macro_input!(input as ItemStruct);
+	let args = parse_macro_input!(args as AttributeArgs);
+
+	if args.len() != 2 {
+		return Error::new(
+			input.ident.span(),
+			"impl_tag requires an inner tag and TagType",
+		)
+		.to_compile_error()
+		.into();
+	}
+
+	if let (NestedMeta::Meta(Meta::Path(inner)), NestedMeta::Meta(tag_type)) =
+		(args[0].clone(), args[1].clone())
+	{
+		if let Some(inner) = inner.get_ident() {
+			let input_ident = input.ident;
+
+			let expanded = quote! {
+				#[doc(hidden)]
+				pub struct #input_ident {
+					inner: #inner,
+					#[cfg(feature = "duration")]
+					duration: Option<std::time::Duration>
+				}
+
+				impl Default for #input_ident {
+					fn default() -> Self {
+						Self {
+							inner: #inner::default(),
+							#[cfg(feature = "duration")]
+							duration: None,
+						}
+					}
+				}
+
+				impl #input_ident {
+					/// Creates a new default tag
+					pub fn new() -> Self {
+						Self::default()
+					}
+				}
+
+				use std::any::Any;
+
+				impl ToAnyTag for #input_ident {
+					fn to_anytag(&self) -> AnyTag<'_> {
+						self.into()
+					}
+				}
+
+				impl ToAny for #input_ident {
+					fn to_any(&self) -> &dyn Any {
+						self
+					}
+					fn to_any_mut(&mut self) -> &mut dyn Any {
+						self
+					}
+				}
+
+				impl AudioTag for #input_ident {}
+
+				// From wrapper to inner (same type)
+				impl From<#input_ident> for #inner {
+					fn from(inp: #input_ident) -> Self {
+						inp.inner
+					}
+				}
+
+				// From inner to wrapper (same type)
+				impl From<#inner> for #input_ident {
+					fn from(inp: #inner) -> Self {
+						Self {
+							inner: inp,
+							#[cfg(feature = "duration")]
+							duration: None,
+						}
+					}
+				}
+
+				impl<'a> From<&'a #input_ident> for AnyTag<'a> {
+					fn from(inp: &'a #input_ident) -> Self {
+						Self {
+							title: inp.title(),
+							artists: inp.artists_vec(),
+							year: inp.year().map(|y| y as i32),
+							album: Album::new(
+								inp.album_title(),
+								inp.album_artists_vec(),
+								inp.album_covers(),
+							),
+							track_number: inp.track_number(),
+							total_tracks: inp.total_tracks(),
+							disc_number: inp.disc_number(),
+							total_discs: inp.total_discs(),
+							comments: None, // TODO
+							date: inp.date(),
+						}
+					}
+				}
+
+				impl<'a> From<AnyTag<'a>> for #input_ident {
+					fn from(inp: AnyTag<'a>) -> Self {
+						let mut tag = #input_ident::default();
+
+						if let Some(v) = inp.title() {
+							tag.set_title(v)
+						}
+						if let Some(v) = inp.artists_as_string() {
+							tag.set_artist(&v)
+						}
+						if let Some(v) = inp.year {
+							tag.set_year(v)
+						}
+						if let Some(v) = inp.album().title {
+							tag.set_album_title(v)
+						}
+						if let Some(v) = inp.album().artists {
+							tag.set_album_artist(&v.join("/"))
+						}
+						if let Some(v) = inp.track_number() {
+							tag.set_track_number(v)
+						}
+						if let Some(v) = inp.total_tracks() {
+							tag.set_total_tracks(v)
+						}
+						if let Some(v) = inp.disc_number() {
+							tag.set_disc_number(v)
+						}
+						if let Some(v) = inp.total_discs() {
+							tag.set_total_discs(v)
+						}
+
+						tag
+					}
+				}
+
+				// From dyn AudioTag to wrapper (any type)
+				impl From<Box<dyn AudioTag>> for #input_ident {
+					fn from(inp: Box<dyn AudioTag>) -> Self {
+						let mut inp = inp;
+						if let Some(t_refmut) = inp.to_any_mut().downcast_mut::<#input_ident>() {
+							let t = std::mem::replace(t_refmut, #input_ident::new()); // TODO: can we avoid creating the dummy tag?
+							t
+						} else {
+							let mut t = inp.to_dyn_tag(#tag_type);
+							let t_refmut = t.to_any_mut().downcast_mut::<#input_ident>().unwrap();
+							let t = std::mem::replace(t_refmut, #input_ident::new());
+							t
+						}
+					}
+				}
+
+				// From dyn AudioTag to inner (any type)
+				impl From<Box<dyn AudioTag>> for #inner {
+					fn from(inp: Box<dyn AudioTag>) -> Self {
+						let t: #input_ident = inp.into();
+						t.into()
+					}
+				}
+			};
+
+			return TokenStream::from(expanded);
+		}
+	}
+
+	Error::new(input.ident.span(), "impl_tag provided invalid arguments")
+		.to_compile_error()
+		.into()
+}