refactor(core,player): move the language table into pstr-core

The crawl needs it to read a subtitle file's language from its name
(en, eng, English), and pstr-player re-exports it unchanged.

crates/pstr-core/src/language.rs

@@ -0,0 +1,126 @@
+//! Language tags: what a container or a file name calls a language, and what a
+//! viewer calls it.
+
+/// The languages offered by name where a preference is chosen ahead of any
+/// file, as the three-letter tag a Matroska file carries. The same list
+/// [`language_name`] knows, and the phones' `LANGUAGES`; mpv treats the two-
+/// and three-letter forms as one.
+pub const LANGUAGES: [&str; 29] = [
+    "jpn", "eng", "ger", "fre", "spa", "ita", "por", "dut", "rus", "pol", "swe", "dan", "nor",
+    "fin", "cze", "hun", "tur", "ara", "heb", "hin", "kor", "chi", "tha", "vie", "ukr", "rum",
+    "gre", "ind", "may",
+];
+
+/// Each language's name and the tags it goes by, the [`LANGUAGES`] form first.
+///
+/// Deliberately a short list rather than a full ISO 639 table: it covers what
+/// the shares this app is pointed at actually contain, and an unrecognised tag
+/// still shows as something a viewer can pick between — `"por-BR"` reads fine
+/// on its own.
+const TABLE: [(&str, &[&str]); 29] = [
+    ("English", &["eng", "en"]),
+    ("Japanese", &["jpn", "ja"]),
+    ("German", &["ger", "de", "deu"]),
+    ("French", &["fre", "fr", "fra"]),
+    ("Spanish", &["spa", "es"]),
+    ("Italian", &["ita", "it"]),
+    ("Portuguese", &["por", "pt"]),
+    ("Dutch", &["dut", "nl", "nld"]),
+    ("Russian", &["rus", "ru"]),
+    ("Polish", &["pol", "pl"]),
+    ("Swedish", &["swe", "sv"]),
+    ("Danish", &["dan", "da"]),
+    ("Norwegian", &["nor", "no"]),
+    ("Finnish", &["fin", "fi"]),
+    ("Czech", &["cze", "cs", "ces"]),
+    ("Hungarian", &["hun", "hu"]),
+    ("Turkish", &["tur", "tr"]),
+    ("Arabic", &["ara", "ar"]),
+    ("Hebrew", &["heb", "he"]),
+    ("Hindi", &["hin", "hi"]),
+    ("Korean", &["kor", "ko"]),
+    ("Chinese", &["chi", "zh", "zho"]),
+    ("Thai", &["tha", "th"]),
+    ("Vietnamese", &["vie", "vi"]),
+    ("Ukrainian", &["ukr", "uk"]),
+    ("Romanian", &["rum", "ro", "ron"]),
+    ("Greek", &["gre", "el", "ell"]),
+    ("Indonesian", &["ind", "id"]),
+    ("Malay", &["may", "ms", "msa"]),
+];
+
+/// A readable name for a language tag, falling back to the tag itself.
+pub fn language_name(tag: &str) -> String {
+    // Container tags come in both the two- and three-letter forms, and often
+    // with a region suffix: "en", "eng", "en-US", "pt-BR".
+    let base = tag.split(['-', '_']).next().unwrap_or(tag);
+    let Some((name, _)) = TABLE
+        .iter()
+        .find(|(_, tags)| tags.iter().any(|known| known.eq_ignore_ascii_case(base)))
+    else {
+        return tag.to_string();
+    };
+
+    // The region matters when there is one — Brazilian Portuguese is not
+    // Portuguese to anyone choosing between the two.
+    match tag.split_once(['-', '_']) {
+        Some((_, region)) if !region.is_empty() => {
+            format!("{name} ({})", region.to_ascii_uppercase())
+        }
+        _ => (*name).to_string(),
+    }
+}
+
+/// Whether two container tags name the same language: "en" and "eng" do.
+pub fn same_language(a: &str, b: &str) -> bool {
+    a.eq_ignore_ascii_case(b) || language_name(a) == language_name(b)
+}
+
+/// The [`LANGUAGES`] tag for one word of a file name, if it names a language:
+/// "en", "eng" and "English" are all `"eng"`.
+///
+/// For the words around a subtitle file's name — `Episode 01.en.srt`,
+/// `2_English.srt` — where a two-letter word is far more often a language than
+/// anything else.
+pub fn language_tag(word: &str) -> Option<&'static str> {
+    TABLE
+        .iter()
+        .find(|(name, tags)| {
+            name.eq_ignore_ascii_case(word) || tags.iter().any(|tag| tag.eq_ignore_ascii_case(word))
+        })
+        .map(|(_, tags)| tags[0])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn language_tags_resolve_in_both_iso_forms_and_keep_their_region() {
+        assert_eq!(language_name("jpn"), "Japanese");
+        assert_eq!(language_name("ja"), "Japanese");
+        assert_eq!(language_name("pt-BR"), "Portuguese (BR)");
+        // An unknown tag is shown as it stands rather than as "Unknown", which
+        // would make two of them indistinguishable.
+        assert_eq!(language_name("mis"), "mis");
+    }
+
+    #[test]
+    fn a_language_named_by_either_tag_or_by_its_name_has_the_tag_a_preference_uses() {
+        assert_eq!(language_tag("en"), Some("eng"));
+        assert_eq!(language_tag("ENG"), Some("eng"));
+        assert_eq!(language_tag("German"), Some("ger"));
+        assert_eq!(language_tag("deu"), Some("ger"));
+        assert_eq!(language_tag("forced"), None);
+    }
+
+    #[test]
+    fn every_language_offered_by_name_is_one_the_table_knows() {
+        let firsts: Vec<&str> = TABLE.iter().map(|(_, tags)| tags[0]).collect();
+        let mut offered = LANGUAGES.to_vec();
+        let mut known = firsts.clone();
+        offered.sort_unstable();
+        known.sort_unstable();
+        assert_eq!(offered, known);
+    }
+}

crates/pstr-core/src/lib.rs

@@ -13,6 +13,7 @@ pub mod chapters;
 pub mod config;
 pub mod error;
 pub mod franchise;
+pub mod language;
 pub mod library;
 pub mod metadata;
 pub mod naming;