// 标准库入口来自实际 Dever 源码；参照只使用 dec，不调用 Dever 运行库。
use dec::{Context, Decimal128};
use std::sync::LazyLock;

static NATIVE_CONTEXT: LazyLock<Context<Decimal128>> = LazyLock::new(Context::default);

struct DecimalInput {
    text: String,
    value: Decimal,
    native: Decimal128,
    places: i64,
}

fn native_parse(text: &str) -> Option<Decimal128> {
    let mut context = NATIVE_CONTEXT.clone();
    let value = context.parse(text).ok()?;
    (value.is_finite() && !context.status().inexact()).then_some(value)
}

fn parsed<const NATIVE: bool>(values: &[String]) -> Result<Vec<Option<[u8; 16]>>, Fault> {
    values
        .iter()
        .map(|text| {
            Ok(if NATIVE {
                native_parse(text).map(|value| value.to_be_bytes())
            } else {
                DECIMAL_PARSE(text)?.map(Decimal::to_be_bytes)
            })
        })
        .collect()
}

struct NativeDisplay(Decimal128);
impl std::fmt::Display for NativeDisplay {
    fn fmt(&self, output: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let value = Context::<Decimal128>::default().reduce(self.0);
        if value.is_zero() {
            output.write_str("0")
        } else {
            write!(output, "{value}")
        }
    }
}

fn formatted<const NATIVE: bool>(values: &[DecimalInput]) -> Result<Vec<String>, Fault> {
    values
        .iter()
        .map(|input| {
            if NATIVE {
                Ok(NativeDisplay(input.native).to_string())
            } else {
                DECIMAL_TEXT(input.value)
            }
        })
        .collect()
}

fn native_round(value: Decimal128, places: i64) -> Option<Decimal128> {
    let exponent = i32::try_from(places.checked_neg()?).ok()?;
    if !(-6176..=6111).contains(&exponent) {
        return None;
    }
    let mut context = NATIVE_CONTEXT.clone();
    let mut quantum = Decimal128::ONE;
    context.set_exponent(&mut quantum, exponent);
    let value = context.quantize(value, quantum);
    (value.is_finite() && !context.status().underflow() && !context.status().invalid_context())
        .then_some(value)
}

fn rounded<const NATIVE: bool>(values: &[DecimalInput]) -> Result<Vec<Option<[u8; 16]>>, Fault> {
    Ok(values
        .iter()
        .map(|input| {
            if NATIVE {
                native_round(input.native, input.places).map(|value| value.to_be_bytes())
            } else {
                DECIMAL_ROUND(input.value, input.places)
                    .ok()
                    .map(Decimal::to_be_bytes)
            }
        })
        .collect())
}

fn negated<const NATIVE: bool>(values: &[DecimalInput]) -> Result<Vec<[u8; 16]>, Fault> {
    Ok(values
        .iter()
        .map(|input| {
            if NATIVE {
                (-input.native).to_be_bytes()
            } else {
                (-input.value).to_be_bytes()
            }
        })
        .collect())
}

fn compared<const NATIVE: bool>(
    values: &[DecimalInput],
) -> Result<Vec<(bool, Option<std::cmp::Ordering>)>, Fault> {
    Ok(values
        .windows(2)
        .map(|pair| {
            if NATIVE {
                (
                    pair[0].native == pair[1].native,
                    pair[0].native.partial_cmp(&pair[1].native),
                )
            } else {
                (
                    pair[0].value == pair[1].value,
                    pair[0].value.partial_cmp(&pair[1].value),
                )
            }
        })
        .collect())
}

fn byte_score(values: &[Option<[u8; 16]>]) -> u64 {
    values
        .iter()
        .flatten()
        .flat_map(|value| value.iter())
        .map(|value| u64::from(*value))
        .sum()
}

fn text_score(values: &[String]) -> u64 {
    values
        .iter()
        .flat_map(|value| value.bytes())
        .map(u64::from)
        .sum()
}

fn main() {
    println!("case,sample,implementation,nanoseconds,checksum");
    let spellings = [
        "0",
        "-0",
        "1.2300",
        "-12.345",
        "1E-6176",
        "1E6111",
        "9.999999999999999999999999999999999E6144",
        "1234567890123456789012345678901234",
        "1.25",
        "1.35",
        "-250",
        "+.125",
        "1e-34",
        "1.000000000000000000000000000000000",
    ];
    let texts = spellings
        .iter()
        .cycle()
        .take(112)
        .map(|text| (*text).to_owned())
        .collect::<Vec<_>>();
    let inputs = texts
        .iter()
        .enumerate()
        .map(|(index, text)| DecimalInput {
            text: text.clone(),
            value: Decimal::parse(text).unwrap(),
            native: native_parse(text).unwrap(),
            places: [0, 1, 2, -2, 6176, -6111][index % 6],
        })
        .collect::<Vec<_>>();
    compare(
        "decimal_parse_valid",
        &texts,
        1000,
        parsed::<false>,
        parsed::<true>,
        |value| byte_score(value),
    );
    let invalid = [
        "",
        "+",
        "NaN",
        "-sNaN",
        "Infinity",
        "nan123",
        " 1",
        "1 ",
        "1_000",
        "1e",
        "1\0",
        "雪",
        "1e9999",
        "1e-9999",
        "12345678901234567890123456789012345",
    ]
    .iter()
    .cycle()
    .take(120)
    .map(|value| (*value).to_owned())
    .collect::<Vec<_>>();
    assert!(
        parsed::<false>(&invalid)
            .unwrap()
            .iter()
            .all(Option::is_none)
    );
    compare(
        "decimal_parse_invalid",
        &invalid,
        1000,
        parsed::<false>,
        parsed::<true>,
        |value| byte_score(value),
    );
    compare(
        "decimal_format",
        &inputs,
        1000,
        formatted::<false>,
        formatted::<true>,
        |value| text_score(value),
    );
    compare(
        "decimal_round",
        &inputs,
        1000,
        rounded::<false>,
        rounded::<true>,
        |value| byte_score(value),
    );
    compare(
        "decimal_negate",
        &inputs,
        1000,
        negated::<false>,
        negated::<true>,
        |value| value.iter().flatten().map(|value| u64::from(*value)).sum(),
    );
    compare(
        "decimal_compare",
        &inputs,
        1000,
        compared::<false>,
        compared::<true>,
        |value| {
            value
                .iter()
                .map(|(equal, order)| {
                    u64::from(*equal) + u64::from(order == &Some(std::cmp::Ordering::Less))
                })
                .sum()
        },
    );
    wire_cases(&inputs);
    storage_cases();
}