from django.contrib.staticfiles import finders
import os

def available_themes(request):
    """
    Return clean theme names by scanning /static/themes/*.css.
    Works whether finder paths are 'themes/xxx.css' or '.../themes/xxx.css'
    and collapses fingerprinted files (e.g., midnight.400a2f.css -> midnight).
    """
    bases = set()

    for finder in finders.get_finders():
        # 1) Try listing the 'themes' directory directly (some storages support this)
        try:
            for path, storage in finder.list(['themes']):
                if path.endswith('.css'):
                    filename = os.path.basename(path)[:-4]          # drop .css
                    base = filename.split('.', 1)[0]                # drop fingerprint
                    if base:
                        bases.add(base)
        except Exception:
            pass

        # 2) Fallback: list everything and filter anything under /themes/
        try:
            for path, storage in finder.list([]):
                if path.endswith('.css') and ('/themes/' in path or path.startswith('themes/')):
                    filename = os.path.basename(path)[:-4]
                    base = filename.split('.', 1)[0]
                    if base:
                        bases.add(base)
        except Exception:
            pass

    # If scan found nothing (e.g., dev env quirk), propose common themes
    if not bases:
        candidates = ["classic", "dawn", "forest", "midnight", "mint", "sandstone"]
        for name in candidates:
            if finders.find(f"themes/{name}.css"):
                bases.add(name)

    # Order: preferred list first, then alphabetical for anything else
    preferred = ["classic", "dawn", "forest", "midnight", "mint", "sandstone", "original"]
    names = sorted(bases, key=lambda n: (preferred.index(n) if n in preferred else len(preferred)+1, n))

    return {"available_themes": names}