EBML: add generic conversion to MatroskaTagRef

lofty/src/ebml/tag/generic.rs

@@ -6,6 +6,7 @@ use super::{Language, MatroskaTag, SimpleTag, TargetType, TOMBSTONE_SIMPLE_TAG};
 use crate::tag::items::Lang;
 use crate::tag::{ItemKey, ItemValue, Tag, TagItem, TagType};
 
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::sync::LazyLock;
 
@@ -203,7 +204,7 @@ fn split_simple_tags(
 
 pub(super) fn merge_tag(tag: Tag, mut matroska_tag: MatroskaTag) -> MatroskaTag {
 	for item in tag.items {
-		let Some((simple_tag, target_type)) = simple_tag_for_item(item) else {
+		let Some((simple_tag, target_type)) = simple_tag_for_item(Cow::Owned(item)) else {
 			continue;
 		};
 
@@ -215,21 +216,24 @@ pub(super) fn merge_tag(tag: Tag, mut matroska_tag: MatroskaTag) -> MatroskaTag
 	matroska_tag
 }
 
-fn simple_tag_for_item(item: TagItem) -> Option<(SimpleTag<'static>, TargetType)> {
+pub(super) fn simple_tag_for_item(
+	item: Cow<'_, TagItem>,
+) -> Option<(SimpleTag<'static>, TargetType)> {
+	if !matches!(item.item_value, ItemValue::Text(_) | ItemValue::Locator(_)) {
+		return None;
+	}
+
+	let (target_type, simple_tag_name) = REVERSE_MAPPINGS.get(&item.item_key).copied()?;
+
 	let TagItem {
 		mut lang,
-		item_key,
 		item_value: ItemValue::Text(text) | ItemValue::Locator(text),
 		..
-	} = item
+	} = item.into_owned()
 	else {
 		return None;
 	};
 
-	let Some((target_type, simple_tag_name)) = REVERSE_MAPPINGS.get(&item_key) else {
-		return None;
-	};
-
 	// Matroska uses "und" for unknown languages
 	if lang == *b"XXX" {
 		lang = *b"und";
@@ -237,8 +241,8 @@ fn simple_tag_for_item(item: TagItem) -> Option<(SimpleTag<'static>, TargetType)
 
 	let lang_str = std::str::from_utf8(lang.as_slice()).unwrap_or("und");
 
-	let mut simple_tag = SimpleTag::new(simple_tag_name.to_string(), text);
+	let mut simple_tag = SimpleTag::new((*simple_tag_name).to_string(), text);
 	simple_tag.language = Language::Iso639_2(lang_str.to_string());
 
-	Some((simple_tag, *target_type))
+	Some((simple_tag, target_type))
 }

lofty/src/ebml/tag/mod.rs

@@ -23,6 +23,7 @@ use crate::tag::companion_tag::CompanionTag;
 use crate::tag::{Accessor, MergeTag, SplitTag, TagExt, TagType};
 
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::io::Write;
 use std::ops::Deref;
 
@@ -405,28 +406,36 @@ impl From<crate::tag::Tag> for MatroskaTag {
 	}
 }
 
-pub(crate) struct MatroskaTagRef<'a, I, S>
+pub(crate) struct MatroskaTagRef<'a, I>
 where
-	I: Iterator<Item = TagRef<'a, S>>,
-	S: Iterator<Item = Cow<'a, SimpleTag<'a>>> + 'a,
+	I: Iterator<Item = TagRef<'a>>,
 {
-	tags: I,
+	pub(crate) tags: I,
 }
 
-impl<'a, I, S> From<&'a crate::tag::Tag> for MatroskaTagRef<'a, I, S>
-where
-	I: Iterator<Item = TagRef<'a, S>>,
-	S: Iterator<Item = Cow<'a, SimpleTag<'a>>>,
-{
-	fn from(_tag: &'a crate::tag::Tag) -> Self {
-		todo!()
+pub(crate) fn simple_tags_for_tag(tag: &crate::tag::Tag) -> impl Iterator<Item = TagRef<'static>> {
+	let mut mapped_tags: HashMap<TargetType, Vec<Cow<'static, SimpleTag<'static>>>> =
+		HashMap::new();
+	for item in &tag.items {
+		if let Some((simple_tag, target_type)) = generic::simple_tag_for_item(Cow::Borrowed(item)) {
+			mapped_tags
+				.entry(target_type)
+				.or_default()
+				.push(Cow::Owned(simple_tag))
+		}
 	}
+
+	mapped_tags
+		.into_iter()
+		.map(|(target_type, simple_tags)| TagRef {
+			targets: TargetDescriptor::Basic(target_type),
+			simple_tags: Box::new(simple_tags.into_iter()),
+		})
 }
 
-impl<'a, I, S> MatroskaTagRef<'a, I, S>
+impl<'a, I> MatroskaTagRef<'a, I>
 where
-	I: Iterator<Item = TagRef<'a, S>>,
-	S: Iterator<Item = Cow<'a, SimpleTag<'a>>>,
+	I: Iterator<Item = TagRef<'a>>,
 {
 	pub(crate) fn write_to<F>(&mut self, _file: &mut F, _write_options: WriteOptions) -> Result<()>
 	where
@@ -434,10 +443,14 @@ where
 		LoftyError: From<<F as Truncate>::Error>,
 		LoftyError: From<<F as Length>::Error>,
 	{
-		todo!()
+		todo!("Writing matroska tags")
 	}
 
-	fn dump_to<W: Write>(&self, _writer: &mut W, _write_options: WriteOptions) -> Result<()> {
-		todo!()
+	pub(crate) fn dump_to<W: Write>(
+		&self,
+		_writer: &mut W,
+		_write_options: WriteOptions,
+	) -> Result<()> {
+		todo!("Dumping matroska tags")
 	}
 }

lofty/src/ebml/tag/tag.rs

@@ -122,10 +122,7 @@ impl Tag<'static> {
 	}
 }
 
-pub(crate) struct TagRef<'a, I>
-where
-	I: Iterator<Item = Cow<'a, SimpleTag<'a>>>,
-{
+pub(crate) struct TagRef<'a> {
 	pub(crate) targets: TargetDescriptor<'a>,
-	pub(crate) simple_tags: &'a mut I,
+	pub(crate) simple_tags: Box<dyn Iterator<Item = Cow<'a, SimpleTag<'a>>>>,
 }

lofty/src/ebml/tag/write/elements/tags.rs

@@ -1,14 +1,10 @@
 use crate::ebml::tag::write::{write_element, ElementWriterCtx, WriteableElement};
-use crate::ebml::{ElementId, SimpleTag, TagRef};
+use crate::ebml::{ElementId, TagRef};
 use crate::io::FileLike;
 
-use std::borrow::Cow;
 use std::io::Cursor;
 
-impl<'a, I> WriteableElement for TagRef<'a, I>
-where
-	I: Iterator<Item = Cow<'a, SimpleTag<'a>>>,
-{
+impl WriteableElement for TagRef<'_> {
 	const ID: ElementId = ElementId(0x7373);
 
 	fn write_element<F: FileLike>(

lofty/src/tag/utils.rs

@@ -99,9 +99,10 @@ pub(crate) fn dump_tag<W: Write>(
 			}
 		}
 		.dump_to(writer, write_options),
-		TagType::Matroska => {
-			todo!("Dump EBML tags")
-		},
+		TagType::Matroska => ebml::tag::MatroskaTagRef {
+			tags: ebml::tag::simple_tags_for_tag(tag),
+		}
+		.dump_to(writer, write_options),
 		_ => Ok(()),
 	}
 }

lofty_attr/src/internal.rs

@@ -51,7 +51,12 @@ pub(crate) fn init_write_lookup(
 		.write_to(file, write_options)
 	});
 
-	insert!(map, Matroska, { todo!("Generated Matroska tag writer") });
+	insert!(map, Matroska, {
+		lofty::ebml::tag::MatroskaTagRef {
+			tags: lofty::ebml::tag::simple_tags_for_tag(tag),
+		}
+		.write_to(file, write_options)
+	});
 
 	insert!(map, Id3v1, {
 		Into::<lofty::id3::v1::tag::Id3v1TagRef<'_>>::into(tag).write_to(file, write_options)