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

@pytest.fixture
def merged_cell_excel_bytes():
    wb = Workbook()
    ws = wb.active
    ws.title = "MergedTest"
    
    # Merge A1:B2
    ws.merge_cells('A1:B2')
    cell = ws['A1']
    cell.value = "Merged Content"
    cell.alignment = Alignment(horizontal='center', vertical='center')
    
    # Add some other content
    ws['C1'] = "C1"
    ws['C2'] = "C2"
    ws['A3'] = "A3"
    
    out = io.BytesIO()
    wb.save(out)
    out.seek(0)
    return out.getvalue()

def test_merged_cell_rendering(merged_cell_excel_bytes):
    """
    Test that rendering an Excel file with merged cells does not raise an AttributeError.
    Specifically checking for 'MergedCell' object has no attribute 'column_letter'.
    """
    renderer = ExcelRenderer(merged_cell_excel_bytes)
    
    try:
        img_bytes = renderer.render_to_bytes(sheet_name="MergedTest")
    except AttributeError as e:
        pytest.fail(f"Rendering failed with AttributeError: {e}")
    except Exception as e:
        pytest.fail(f"Rendering failed with unexpected error: {e}")

    assert isinstance(img_bytes, bytes)
    img = Image.open(io.BytesIO(img_bytes))
    assert img.format == "PNG"