import io
import os
import pandas as pd
import importlib.util
import sys
import types


def load_scenar_module():
    repo_root = os.path.dirname(os.path.dirname(__file__))
    scenar_path = os.path.join(repo_root, 'cgi-bin', 'scenar.py')
    # Provide a minimal fake `cgi` module so top-level imports in the CGI script don't fail
    if 'cgi' not in sys.modules:
        fake_cgi = types.ModuleType('cgi')
        class FakeFieldStorage:
            def getvalue(self, key, default=None):
                return default
            def keys(self):
                return []
            def __contains__(self, item):
                return False
        fake_cgi.FieldStorage = FakeFieldStorage
        sys.modules['cgi'] = fake_cgi
    # minimal fake cgitb (some environments don't expose it)
    if 'cgitb' not in sys.modules:
        fake_cgitb = types.ModuleType('cgitb')
        def fake_enable():
            return None
        fake_cgitb.enable = fake_enable
        sys.modules['cgitb'] = fake_cgitb

    spec = importlib.util.spec_from_file_location('scenar', scenar_path)
    module = importlib.util.module_from_spec(spec)
    # executing the module will run top-level CGI code (prints etc.) but defines functions we need
    spec.loader.exec_module(module)
    return module


def make_excel_bytes(df: pd.DataFrame) -> bytes:
    bio = io.BytesIO()
    with pd.ExcelWriter(bio, engine='openpyxl') as writer:
        df.to_excel(writer, index=False)
    return bio.getvalue()


def test_read_excel_happy_path():
    scenar = load_scenar_module()

    df = pd.DataFrame({
        'Datum': [pd.Timestamp('2025-11-13').date()],
        'Zacatek': ['09:00'],
        'Konec': ['10:00'],
        'Program': ['Test program'],
        'Typ': ['WORKSHOP'],
        'Garant': ['Garant Name'],
        'Poznamka': ['Pozn']
    })

    content = make_excel_bytes(df)
    valid, errors = scenar.read_excel(content)

    assert isinstance(valid, pd.DataFrame)
    assert len(errors) == 0
    assert len(valid) == 1
    assert valid.iloc[0]['Program'] == 'Test program'


def test_read_excel_invalid_time():
    scenar = load_scenar_module()

    df = pd.DataFrame({
        'Datum': [pd.Timestamp('2025-11-13').date()],
        'Zacatek': ['not-a-time'],
        'Konec': ['10:00'],
        'Program': ['Bad Time'],
        'Typ': ['LECTURE'],
        'Garant': [None],
        'Poznamka': [None]
    })

    content = make_excel_bytes(df)
    valid, errors = scenar.read_excel(content)

    # invalid time should produce at least one error row and valid may be empty
    assert isinstance(errors, list)
    assert len(errors) >= 1