use rpn_calculator::*;

fn calculator_input(s: &str) -> Vec<CalculatorInput> {
    s.split_whitespace()
        .map(|s| match s {
            "+" => CalculatorInput::Add,
            "-" => CalculatorInput::Subtract,
            "*" => CalculatorInput::Multiply,
            "/" => CalculatorInput::Divide,
            n => CalculatorInput::Value(n.parse().unwrap()),
        })
        .collect()
}

#[test]
fn test_empty_input_returns_none() {
    let input = calculator_input("");
    assert_eq!(evaluate(&input), None);
}

#[test]
fn test_simple_value() {
    let input = calculator_input("10");
    assert_eq!(evaluate(&input), Some(10));
}

#[test]
fn test_simple_addition() {
    let input = calculator_input("2 2 +");
    assert_eq!(evaluate(&input), Some(4));
}

#[test]
fn test_simple_subtraction() {
    let input = calculator_input("7 11 -");
    assert_eq!(evaluate(&input), Some(-4));
}

#[test]
fn test_simple_multiplication() {
    let input = calculator_input("6 9 *");
    assert_eq!(evaluate(&input), Some(54));
}

#[test]
fn test_simple_division() {
    let input = calculator_input("57 19 /");
    assert_eq!(evaluate(&input), Some(3));
}

#[test]
fn test_complex_operation() {
    let input = calculator_input("4 8 + 7 5 - /");
    assert_eq!(evaluate(&input), Some(6));
}

#[test]
fn test_too_few_operands_returns_none() {
    let input = calculator_input("2 +");
    assert_eq!(evaluate(&input), None);
}

#[test]
fn test_too_many_operands_returns_none() {
    let input = calculator_input("2 2");
    assert_eq!(evaluate(&input), None);
}