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2026-07-25 21:28:35 +02:00
parent ae1db15bd2
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+//! Language-code normalization — ISO 639 alias folding, **not** filename
+//! parsing.
+//!
+//! This lives apart from [`crate::filename_meta`] on purpose: it doesn't read a
+//! release title, it canonicalizes a *language code* (an indexer's declared
+//! language, a query's `languages:` filter, a title-derived stamp) onto the
+//! single ISO 639-2/B alpha-3 vocabulary the rest of the stack compares against.
+//! It is the one piece of the old `filename_meta` module that has no equivalent
+//! in the `metamesh-plugin-filename-parser` plugin — because it isn't filename
+//! parsing — so it stays in Rust while the title-parsing algorithm itself is
+//! owned by the plugin. Callers in the **request hot path** (e.g. the torznab
+//! indexer-language fan-out skip) need it synchronously, with no network hop.
+
+/// Normalize a language code to the ISO 639-2/B alpha-3 vocabulary the stack
+/// emits (`fre`/`ger`/`chi`, **not** the 639-2/T `fra`/`deu`/`zho` nor the
+/// 639-1 two-letter forms), lowercased. This is the space meta-share's
+/// "languages I read" preference uses and that the title-derived language stamps
+/// write, so an operator who declares an indexer's language as `fra`/`de`/`zh`
+/// still lines up with a `fre`/`ger`/`chi` query filter. Unknown /
+/// already-canonical codes pass through lowercased+trimmed unchanged.
+pub fn normalize_lang_code(code: &str) -> String {
+    let c = code.trim().to_ascii_lowercase();
+    let mapped = match c.as_str() {
+        // 639-2/T and 639-1 → 639-2/B for the codes that actually differ.
+        "fra" | "fr" => "fre",
+        "deu" | "de" => "ger",
+        "zho" | "zh" => "chi",
+        "nld" | "nl" => "dut",
+        "ell" | "el" => "gre",
+        "ron" | "ro" => "rum",
+        "slk" | "sk" => "slo",
+        "ces" | "cs" => "cze",
+        // 639-1 → 639-2 for the rest of the language-tag output space (these
+        // share the same /B and /T alpha-3, so only the two-letter form maps).
+        "en" => "eng",
+        "ja" => "jpn",
+        "it" => "ita",
+        "es" => "spa",
+        "pt" => "por",
+        "ko" => "kor",
+        "ru" => "rus",
+        "pl" => "pol",
+        "hu" => "hun",
+        "uk" => "ukr",
+        "bg" => "bul",
+        "sv" => "swe",
+        "no" => "nor",
+        "da" => "dan",
+        "fi" => "fin",
+        "tr" => "tur",
+        "ar" => "ara",
+        "hi" => "hin",
+        "ta" => "tam",
+        "te" => "tel",
+        "ml" => "mal",
+        "vi" => "vie",
+        "th" => "tha",
+        _ => return c,
+    };
+    mapped.to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn normalize_lang_maps_to_639_2b_vocabulary() {
+        // 639-2/T and 639-1 spellings collapse onto the /B forms the stack uses.
+        assert_eq!(normalize_lang_code("fra"), "fre");
+        assert_eq!(normalize_lang_code("FR"), "fre");
+        assert_eq!(normalize_lang_code("deu"), "ger");
+        assert_eq!(normalize_lang_code("zh"), "chi");
+        assert_eq!(normalize_lang_code("nld"), "dut");
+        // Already-canonical / unknown codes pass through trimmed + lowercased.
+        assert_eq!(normalize_lang_code("  ENG "), "eng");
+        assert_eq!(normalize_lang_code("fre"), "fre");
+        assert_eq!(normalize_lang_code("mul"), "mul");
+        assert_eq!(normalize_lang_code("xyz"), "xyz");
+    }
+}