"""Five-language STRATA core contract.

The project deliberately keeps the primary multilingual build to five languages
so graph supervision, tokenizer pressure, and tool-surface coverage stay
balanced enough to interpret. Additions beyond this set should be treated as
diagnostic or tier-2 experiments, not silent changes to the core training mix.
"""

from __future__ import annotations

from dataclasses import dataclass


@dataclass(frozen=True, slots=True)
class LanguageSpec:
    code: str
    name: str
    primary_variety: str
    graph_source: tuple[str, str]


CORE_LANGUAGES: tuple[LanguageSpec, ...] = (
    LanguageSpec("en", "English", "English", ("up", "UP_English-EWT")),
    LanguageSpec("zh", "Mandarin Chinese", "Simplified Chinese primary", ("up", "UP_Chinese")),
    LanguageSpec("de", "German", "German", ("up", "UP_German")),
    LanguageSpec("es", "Spanish", "Spanish", ("up", "UP_Spanish")),
    LanguageSpec("ar", "Arabic", "MSA primary; dialectal optional", ("ud", "UD_Arabic-PADT")),
)

CORE_LANGUAGE_CODES: tuple[str, ...] = tuple(spec.code for spec in CORE_LANGUAGES)
CORE_LANGUAGE_NAMES: dict[str, str] = {spec.code: spec.name for spec in CORE_LANGUAGES}
CORE_GRAPH_SOURCES: dict[str, tuple[str, str]] = {
    spec.code: spec.graph_source for spec in CORE_LANGUAGES
}


def normalize_language_codes(value: str | list[str] | tuple[str, ...]) -> tuple[str, ...]:
    """Return normalized language codes from a comma-separated string or list."""

    if isinstance(value, str):
        codes = tuple(part.strip() for part in value.split(",") if part.strip())
    else:
        codes = tuple(str(part).strip() for part in value if str(part).strip())
    return codes


def require_core_languages(codes: str | list[str] | tuple[str, ...]) -> None:
    """Raise if ``codes`` is not exactly the STRATA five-language core."""

    got = normalize_language_codes(codes)
    if got != CORE_LANGUAGE_CODES:
        raise ValueError(
            f"expected STRATA core languages {','.join(CORE_LANGUAGE_CODES)}, "
            f"got {','.join(got) or '<empty>'}"
        )


__all__ = [
    "CORE_GRAPH_SOURCES",
    "CORE_LANGUAGES",
    "CORE_LANGUAGE_CODES",
    "CORE_LANGUAGE_NAMES",
    "LanguageSpec",
    "normalize_language_codes",
    "require_core_languages",
]