use vega_lite_4::*;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // The chart
    let chart = VegaliteBuilder::default()
        .title("Line Chart with Confidence Interval Band")
        .height(200.)
        .width(300.)
        .data(
            UrlDataBuilder::default()
                .url("https://raw.githubusercontent.com/vega/vega-datasets/master/data/cars.json")
                .build()?,
        )
        .mark(Mark::Line)
        .encoding(
            EdEncodingBuilder::default()
                .x(XClassBuilder::default()
                    .field("Year")
                    .position_def_type(Type::Temporal)
                    .time_unit(TimeUnit::Year)
                    .build()?)
                .build()?,
        )
        .layer(vec![
            LayerElementBuilder::default()
                .mark(Mark::Line)
                .encoding(
                    LayerEncodingBuilder::default()
                        .y(YClassBuilder::default()
                            .field("Miles_per_Gallon")
                            .position_def_type(Type::Quantitative)
                            .aggregate(NonArgAggregateOp::Mean)
                            .build()?)
                        .build()?,
                )
                .build()?,
            LayerElementBuilder::default()
                .mark(
                    DefBuilder::default()
                        .def_type(Mark::Errorband)
                        .extent(ExtentExtent::Ci)
                        .build()?,
                )
                .encoding(
                    LayerEncodingBuilder::default()
                        .y(YClassBuilder::default()
                            .title("Mean of Miles per Gallon (95% CIs)")
                            .field("Miles_per_Gallon")
                            .position_def_type(Type::Quantitative)
                            .build()?)
                        .build()?,
                )
                .build()?,
        ])
        .build()?;

    // display the chart using `showata`
    chart.show()?;

    // print the vega lite spec
    eprint!("{}", chart.to_string()?);

    Ok(())
}