use super::funejson::Value;
use super::math_round_float::round_float;

/// The rectangle left for data once the margins are taken off the chart.
///
/// # Panics
/// Panics on a negative margin or margins that leave no room.
pub fn plot_area(width: f64, height: f64, margins: &Margins) -> PlotArea {
    let (top, right, bottom, left) = (margins.top, margins.right, margins.bottom, margins.left);
    if !(top >= 0.0 && right >= 0.0 && bottom >= 0.0 && left >= 0.0) {
        panic!("margins must not be negative");
    }
    let w = width - left - right;
    let h = height - top - bottom;
    // A zero or negative plot would draw nothing, or draw everything flipped.
    if !(w > 0.0 && h > 0.0) {
        panic!("margins leave no room to plot: {} x {} less margins is {} x {}", width, height, w, h);
    }
    PlotArea { x: round_float(left, 2), y: round_float(top, 2), width: round_float(w, 2), height: round_float(h, 2) }
}

pub fn plot_area_to_value(p: &PlotArea) -> Value {
    Value::obj(vec![
        ("x", Value::Float(p.x)),
        ("y", Value::Float(p.y)),
        ("width", Value::Float(p.width)),
        ("height", Value::Float(p.height)),
    ])
}

pub fn margins_from_value(v: &Value) -> Margins {
    Margins {
        top: v.get("top").as_f64(),
        right: v.get("right").as_f64(),
        bottom: v.get("bottom").as_f64(),
        left: v.get("left").as_f64(),
    }
}

pub fn fune_vector(args: &[Value]) -> Value {
    plot_area_to_value(&plot_area(args[0].as_f64(), args[1].as_f64(), &margins_from_value(&args[2])))
}