use arrow::{
    array::{Int64Array, TimestampNanosecondArray},
    datatypes::{DataType, TimeUnit}
};

let data = vec![1701325744956, 1701325744956];
let array = Int64Array::from(data);
let array = arrow_cast_guess_precision::cast(
    &array,
    &DataType::Timestamp(TimeUnit::Nanosecond, None),
)
.unwrap();
let nanos = array
    .as_any()
    .downcast_ref::<TimestampNanosecondArray>()
    .unwrap();
assert_eq!(nanos.value(0), 1701325744956 * 1000 * 1000);

use arrow::datatypes::TimeUnit;

const GUESSING_BOUND_YEARS: i64 = 10000;
const LOWER_BOUND_MILLIS: i64 = 86400 * 365 * GUESSING_BOUND_YEARS;
const LOWER_BOUND_MICROS: i64 = 1000 * 86400 * 365 * GUESSING_BOUND_YEARS;
const LOWER_BOUND_NANOS: i64 = 1000 * 1000 * 86400 * 365 * GUESSING_BOUND_YEARS;

#[inline]
const fn guess_precision(timestamp: i64) -> TimeUnit {
    let timestamp = timestamp.abs();
    if timestamp > LOWER_BOUND_NANOS {
        return TimeUnit::Nanosecond;
    }
    if timestamp > LOWER_BOUND_MICROS {
        return TimeUnit::Microsecond;
    }
    if timestamp > LOWER_BOUND_MILLIS {
        return TimeUnit::Millisecond;
    }
    TimeUnit::Second
}