use dec::{Context, Decimal128, Rounding};
use dever_runtime::number::DecimalValue;
use std::hint::black_box;
use std::time::Instant;

fn finite(context: &Context<Decimal128>, value: Decimal128) -> Decimal128 {
    let status = context.status();
    assert!(!status.division_by_zero() && !status.division_undefined());
    assert!(!status.overflow() && !status.underflow());
    assert!(!status.invalid_operation() && !status.invalid_context() && value.is_finite());
    value
}

fn measure(mode: &str, ticks: &str, initial: &str, factor: &str) -> serde_json::Value {
    let bytes = black_box(ticks.as_bytes());
    let (checksum, elapsed) = if mode == "runtime" {
        let mut total = DecimalValue::parse(initial).expect("initial");
        let factor = DecimalValue::parse(factor).expect("factor");
        let begin = Instant::now();
        for value in bytes {
            let product = DecimalValue::from_int(i64::from(*value))
                .checked_mul(factor)
                .expect("multiply");
            total = total.checked_add(product).expect("add");
        }
        black_box(total);
        let elapsed = begin.elapsed();
        (total.to_string(), elapsed)
    } else {
        assert_eq!(mode, "decimal128");
        let mut context = Context::<Decimal128>::default();
        let mut total = context.parse(initial).expect("initial");
        assert!(!context.status().inexact() && total.is_finite());
        context.clear_status();
        let factor = context.parse(factor).expect("factor");
        assert!(!context.status().inexact() && factor.is_finite());
        context.set_rounding(Rounding::HalfEven);
        let begin = Instant::now();
        for value in bytes {
            let item = Decimal128::from(i64::from(*value));
            context.clear_status();
            let product = context.mul(item, factor);
            let product = finite(&context, product);
            context.clear_status();
            let sum = context.add(total, product);
            total = finite(&context, sum);
        }
        black_box(total);
        let elapsed = begin.elapsed();
        (context.reduce(total).to_string(), elapsed)
    };
    serde_json::json!({"checksum": checksum, "elapsed_ns": elapsed.as_nanos()})
}

fn main() {
    let arguments = std::env::args().collect::<Vec<_>>();
    let input: serde_json::Value = serde_json::from_str(&arguments[3]).expect("input object");
    let ticks = input["ticks"].as_str().expect("ticks");
    let initial = input["initial"].as_str().expect("initial");
    let factor = input["factor"].as_str().expect("factor");
    let output = match arguments[2].as_str() {
        "run" => measure(&arguments[1], ticks, initial, factor),
        "continuous" => serde_json::Value::Array(
            (0..10)
                .map(|_| measure(&arguments[1], ticks, initial, factor))
                .collect(),
        ),
        _ => panic!("unknown measurement"),
    };
    println!("{output}");
}