import pandas as pd
from dagster import op


@op
def fetch_data() -> list:
    """Fetches raw data from a source."""
    return [{"id": 1, "value": "A"}, {"id": 2, "value": "B"}]


@op
def process_data(data: list) -> dict:
    """Processes raw data and returns a summary."""
    return {"count": len(data), "status": "success"}


@op
def generate_example_dataset() -> pd.DataFrame:
    """Generates a small example dataset as a pandas DataFrame."""
    return pd.DataFrame(
        [
            {"order_id": 1001, "customer": "Alice", "quantity": 2, "unit_price": 9.50},
            {"order_id": 1002, "customer": "Bob", "quantity": 1, "unit_price": 15.00},
            {"order_id": 1003, "customer": "Charlie", "quantity": 4, "unit_price": 7.25},
            {"order_id": 1004, "customer": "Dora", "quantity": 3, "unit_price": 11.00},
        ]
    )


@op
def transform_example_dataset(df: pd.DataFrame) -> pd.DataFrame:
    """Applies a simple transformation to the example dataset."""
    
    df["price_band"] = df["total_price"].apply(
        lambda value: "high" if value >= 25 else "standard"
    )
    
    df["total_price"] = df["quantity"] * df["unit_price"]
    
    return df