import pytest
from openpyxl import Workbook
from openpyxl.styles import Font
import io
from core.renderer import ExcelRenderer
from PIL import Image

@pytest.fixture
def font_size_excel_bytes():
    wb = Workbook()
    ws = wb.active
    ws.title = "FontTest"
    
    # Standard size
    ws['A1'] = "Standard 12"
    ws['A1'].font = Font(size=12)
    
    # Large size
    ws['A2'] = "Large 20"
    ws['A2'].font = Font(size=20)
    
    # Small size
    ws['A3'] = "Small 8"
    ws['A3'].font = Font(size=8)
    
    out = io.BytesIO()
    wb.save(out)
    out.seek(0)
    return out.getvalue()

def test_font_size_rendering(font_size_excel_bytes):
    """
    Test that rendering handles different font sizes without crashing.
    Note: Visual verification is hard in unit tests, but we can ensure
    the code paths for dynamic font loading are executed.
    """
    renderer = ExcelRenderer(font_size_excel_bytes)
    
    try:
        img_bytes = renderer.render_to_bytes(sheet_name="FontTest")
    except Exception as e:
        pytest.fail(f"Rendering failed with error: {e}")

    assert isinstance(img_bytes, bytes)
    img = Image.open(io.BytesIO(img_bytes))
    assert img.format == "PNG"
    
    # We can also inspect the internal cache to see if different fonts were loaded
    # (Accessing private attribute for testing purpose)
    assert len(renderer.font_cache) >= 3, "Should have cached at least 3 different font configurations"