/*
 * asklyphe-frontend unit_converter.rs
 * - wrapper for the unit converter library
 *
 * Copyright (C) 2025 Real Microsoft, LLC
 *
 * This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
*/

use std::str::FromStr;
use unit_converter::length_units::{LengthUnit, LENGTH_NAMES};
use unit_converter::unit_defs::{BestUnit, ConvertTo, FromUnitName, UnitName};
use unit_converter::{parse_number, remove_leading_conversion_word};

#[derive(Clone, Debug)]
pub struct UnitConversion {
    pub value: String,
    pub unit_a: String,
    pub equals: String,
    pub unit_b: String,
}

pub fn convert_unit(query_text: &str) -> Option<UnitConversion> {
    let (number, remainder) = parse_number(query_text);
    if number.is_nan() {
        return None;
    }
    let og_number = number.clone();
    let unit = LengthUnit::parse(remainder);
    unit.as_ref()?;
    let (unit_a, remainder) = unit.unwrap();
    let remainder = remove_leading_conversion_word(&remainder);
    if let Some((unit_b, _)) = LengthUnit::parse(remainder) {
        let conversion = unit_a.convert_to(number, unit_b);
        let approx = f64::from_str(&format!("{}", conversion)).unwrap();
        let approx_og = f64::from_str(&format!("{}", og_number)).unwrap();
        Some(UnitConversion {
            value: format!("{}", approx_og),
            unit_a: unit_a.unit_name(og_number),
            equals: format!("{}", approx),
            unit_b: unit_b.unit_name(conversion),
        })
    } else {
        let best_unit = LengthUnit::best_unit(unit_a, number.clone());
        let conversion = unit_a.convert_to(number, best_unit);
        let approx = f64::from_str(&format!("{}", conversion)).unwrap();
        let approx_og = f64::from_str(&format!("{}", og_number)).unwrap();
        Some(UnitConversion {
            value: format!("{}", approx_og),
            unit_a: unit_a.unit_name(og_number),
            equals: format!("{}", approx),
            unit_b: best_unit.unit_name(conversion),
        })
    }
}