formal-ai 0.254.0

//! Translation source/target language detection.
//!
//! Neither routine matches a hardcoded natural-language phrase. Each asks the
//! language-independent meaning lexicon (`data/seed/meanings-translation.lino`)
//! "which surface forms evidence a translation *source* / *target* marker?" and
//! resolves the marker's language by walking its `defined_by` edges down to one
//! of the four `language_*` meanings. Adding a spelling variant, a synonym, or a
//! whole new supported language is therefore a pure data edit: drop a
//! `word`/`description` into the relevant marker meaning and this code reasons
//! about it automatically.
//!
//! Surfaces are matched as raw substrings ([`str::contains`]), exactly as the
//! previous hardcoded disjunction did, so detection stays byte-faithful — a
//! Chinese marker like `从中文` has no inter-word spaces, and a Cyrillic marker
//! like `с английского` must match inside a longer sentence. Marker meanings are
//! walked in declaration order (English → Russian → Hindi → Chinese), which
//! preserves the original first-match priority.

use crate::seed::{
    self, Meaning, ROLE_COMPREHENSION_FAILURE_MARKER, ROLE_RESPONSE_LANGUAGE_MARKER,
    ROLE_TRANSLATION_SOURCE_MARKER, ROLE_TRANSLATION_TARGET_MARKER,
};

/// Detect the language a translation reads *from*, or `None`.
///
/// Walks every meaning carrying [`ROLE_TRANSLATION_SOURCE_MARKER`] and returns
/// the language of the first whose surface appears in `normalized`.
pub fn detect_source_language(normalized: &str) -> Option<&'static str> {
    detect_marker_language(ROLE_TRANSLATION_SOURCE_MARKER, normalized)
}

/// Detect the language a translation renders *into*, or `None`.
///
/// Walks every meaning carrying [`ROLE_TRANSLATION_TARGET_MARKER`] and returns
/// the language of the first whose surface appears in `normalized`.
pub fn detect_target_language(normalized: &str) -> Option<&'static str> {
    detect_marker_language(ROLE_TRANSLATION_TARGET_MARKER, normalized)
}

/// Detect the language a non-translation answer should be rendered in, or
/// `None`.
///
/// This reads the same seed-backed marker role concept lookup uses for prompts
/// such as "tell me about X in Russian", but leaves response-language
/// application to callers that have enough context to rerender the answer.
pub fn detect_response_language(normalized: &str) -> Option<&'static str> {
    detect_marker_language(ROLE_RESPONSE_LANGUAGE_MARKER, normalized)
}

/// Detect whether the user reports they cannot understand the prior answer's
/// language (issue #556).
///
/// Walks every meaning carrying [`ROLE_COMPREHENSION_FAILURE_MARKER`] and
/// reports `true` when any of its seeded surfaces — "do not understand",
/// "не понимаю", "समझ नहीं", "不懂", … — appears in `normalized`. The phrase
/// table lives entirely in `data/seed/meanings-translation.lino`; this routine
/// only names the language-independent role, so widening the vocabulary is a
/// pure data edit.
pub fn detect_comprehension_failure(normalized: &str) -> bool {
    seed::lexicon()
        .meanings_with_role(ROLE_COMPREHENSION_FAILURE_MARKER)
        .any(|meaning| meaning.words().any(|word| normalized.contains(word)))
}

/// The shared recogniser: the first marker meaning of `role` (in declaration
/// order) whose any surface word is a substring of `normalized` reports its
/// language, read off the `language_*` meaning it is `defined_by`.
fn detect_marker_language(role: &str, normalized: &str) -> Option<&'static str> {
    seed::lexicon()
        .meanings_with_role(role)
        .filter(|meaning| meaning.words().any(|word| normalized.contains(word)))
        .find_map(language_code_of)
}

/// The ISO 639-1 code of the `language_*` meaning a marker is `defined_by`.
fn language_code_of(meaning: &Meaning) -> Option<&'static str> {
    meaning
        .defined_by
        .iter()
        .find_map(|slug| language_code(slug))
}

/// Map a `language_*` meaning slug to its fixed ISO 639-1 code.
///
/// The code is the one identifier that stays in the handler: it is the key the
/// [`crate::translation::TranslationPipeline`] and the Wiktionary client are
/// addressed by, not a surface word. The surface *names* of each language live
/// in the seed; only this slug → code bridge is code.
fn language_code(slug: &str) -> Option<&'static str> {
    match slug {
        "language_english" => Some("en"),
        "language_russian" => Some("ru"),
        "language_hindi" => Some("hi"),
        "language_chinese" => Some("zh"),
        _ => None,
    }
}