"""Read a split JS subpackage the way the module graph does.

``static/js/emailLibrary.js`` is a re-export wrapper; the implementation lives
in ``static/js/emailLibrary/``. A test that asserts on email-library behaviour
has to look at every module in that package, because reading one file ties the
test to whichever module a function happens to sit in today — it goes red the
next time something moves without any behaviour changing.

That is the mistake the stylesheet split made, which is why
``tests/helpers/stylesheets.py`` exists. This is the same helper for JS.

Order is deterministic: the entry module first, then the rest alphabetically.
Tests that assert "A appears before B" are asserting about one module's source,
not about the package, so the concatenation order only has to be stable.
"""

from __future__ import annotations

from pathlib import Path

_STATIC_JS = Path(__file__).resolve().parents[2] / "static" / "js"

EMAIL_LIBRARY_WRAPPER = _STATIC_JS / "emailLibrary.js"
EMAIL_LIBRARY_PACKAGE = _STATIC_JS / "emailLibrary"
EMAIL_LIBRARY_ENTRY = EMAIL_LIBRARY_PACKAGE / "index.js"


def _package_paths(package: Path, entry: Path) -> list[Path]:
    if not entry.is_file():
        raise AssertionError(f"missing package entry module: {entry}")
    rest = sorted(p for p in package.glob("*.js") if p != entry)
    return [entry, *rest]


def email_library_paths(include_wrapper: bool = False) -> list[Path]:
    """Every module of the email-library package, entry module first.

    ``include_wrapper`` adds the compatibility file at the old top-level path.
    Leave it off for assertions about implementation code: the wrapper holds
    only an ``export … from`` list.
    """
    paths = _package_paths(EMAIL_LIBRARY_PACKAGE, EMAIL_LIBRARY_ENTRY)
    return [EMAIL_LIBRARY_WRAPPER, *paths] if include_wrapper else paths


def email_library_source(include_wrapper: bool = False) -> str:
    """The whole email-library package as one string."""
    return "\n".join(
        p.read_text(encoding="utf-8") for p in email_library_paths(include_wrapper)
    )