import pytest
from fastapi.testclient import TestClient
from app import app
from openpyxl import Workbook
import io

client = TestClient(app)

@pytest.fixture
def sample_excel_file():
    wb = Workbook()
    ws = wb.active
    ws.title = "APITest"
    ws['A1'] = "API"
    
    out = io.BytesIO()
    wb.save(out)
    out.seek(0)
    return out

def test_health_check():
    response = client.get("/health")
    assert response.status_code == 200
    assert response.json() == {"status": "ok"}

def test_convert_endpoint(sample_excel_file):
    files = {'file': ('test.xlsx', sample_excel_file, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet')}
    response = client.post("/api/v1/convert", files=files)
    
    assert response.status_code == 200
    assert response.headers["content-type"] == "image/png"
    assert len(response.content) > 0

def test_convert_invalid_file_type():
    files = {'file': ('test.txt', io.BytesIO(b"dummy"), 'text/plain')}
    response = client.post("/api/v1/convert", files=files)
    
    assert response.status_code == 400
    assert "Invalid file format" in response.json()["detail"]

def test_convert_specific_sheet(sample_excel_file):
    # Re-create file because previous read might have consumed it if not handled carefully (TestClient usually handles this)
    # But let's be safe and use the fixture which returns a new BytesIO if we construct it that way. 
    # Actually the fixture returns the same object, let's seek 0 just in case.
    sample_excel_file.seek(0)
    
    files = {'file': ('test.xlsx', sample_excel_file, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet')}
    data = {'sheet_name': 'APITest'}
    response = client.post("/api/v1/convert", files=files, data=data)
    
    assert response.status_code == 200

def test_convert_missing_sheet(sample_excel_file):
    sample_excel_file.seek(0)
    files = {'file': ('test.xlsx', sample_excel_file, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet')}
    data = {'sheet_name': 'MissingSheet'}
    response = client.post("/api/v1/convert", files=files, data=data)
    
    assert response.status_code == 400
    assert "Sheet 'MissingSheet' not found" in response.json()["detail"]