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// Copyright 2017-2019 LEXUGE
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! The major part of APIs.
//! The API which balances the Chemical Equation by equation.
//!
//!  It provides a set of Basic Solutions. You can get infinite number of solutions by doing linear combination on the Basic Solution Set.
//!
//!  You can use any type which implemented the trait `api::traits::CheckedType`
//!

// inside use(s)
use super::{
    failures::ErrorCases,
    traits::{CheckedCalc, CheckedType},
    types::DataSet,
};
use crate::{balancer::handler::balancer, parser::handler::parser, public::cell::Cell};

/// A handler which store the equation and other information
pub struct Handler<'a, T> {
    equ: &'a str,
    ds: Option<DataSet<Cell<T>>>,
}

impl<'a, T: CheckedType + CheckedCalc> Handler<'a, T>
where
    std::num::ParseIntError: std::convert::From<<T as num::Num>::FromStrRadixErr>
        + std::convert::From<<T as std::str::FromStr>::Err>,
{
    /// Create a `Handler` by given equation
    pub fn new(equ: &'a str) -> Self {
        Handler { equ, ds: None }
    }
    /// Parse and balance the equation. If it has been parsed, then just balance it.
    ///
    /// If the equation can balance, function would return `Ok((ChemicalEquation, Vec<Vec<T>>))` which contains the answer.
    ///
    /// If not, it would return `Err(ErrorCases)` which contains the failure.
    ///
    /// # Panics
    ///
    /// -  A large number (bigger than [`usize::MAX`](https://doc.rust-lang.org/std/usize/constant.MAX.html)) of formula may cause **panic**. Because it is using `Vec`.
    ///
    /// And in the other failed situation, it'll return  `ErrorCases`.
    pub fn handle(mut self) -> Result<DataSet<T>, ErrorCases> {
        if self.ds.is_none() {
            self.parse()?;
        }
        Ok((self.ds.clone().unwrap().0, self.balance()?))
    }

    /// Parse the equation
    pub fn parse(&mut self) -> Result<DataSet<T>, ErrorCases> {
        self.ds = Some(parser::<Cell<T>>(self.equ)?);
        match self.ds.clone().unwrap() {
            (cd, data) => Ok((cd, fromcell(&data)?)),
        }
    }

    // AlphaForce Balancer
    fn balance(self) -> Result<Vec<Vec<T>>, ErrorCases> {
        match balancer::<Cell<T>>(&self.ds.unwrap()) {
            Ok(s) => Ok(fromcell(&s)?),
            Err(e) => Err(e),
        }
    }
}
// All `false` => `true` (It didn't overflow)
fn check_tag<T>(s: &[Vec<Cell<T>>]) -> bool {
    s.iter().all(|x| x.iter().all(|x| !x.get_tag()))
}

fn fromcell<T: Clone>(s: &[Vec<Cell<T>>]) -> Result<Vec<Vec<T>>, ErrorCases> {
    if !check_tag(s) {
        return Err(ErrorCases::Overflow);
    }
    Ok(s.iter()
        .map(|x| x.iter().map(|s| s.get_data()).collect::<Vec<_>>())
        .collect::<Vec<_>>())
}