// Copyright 2022 Christian Ulrich
//
// 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/>.
//
// usage: ./part2 < input

pub mod common;

use common::{FileSystem, Node};

const DISK_SIZE: usize = 70000000;
const SPACE_REQUIRED: usize = 30000000;

fn main() -> Result<(), &'static str> {
    let fs = FileSystem::from_stdin()?;
    let total_size = fs.root().size();
    let free_space = DISK_SIZE - total_size;
    if free_space >= SPACE_REQUIRED {
        return Err("Sufficient free space, nothing to be done!");
    }
    // we need to find a directory of at least this size
    let min_directory_size = SPACE_REQUIRED - free_space;
    let mut result = total_size;
    for node in fs.root().walk() {
        if let Node::Directory {
            name: _,
            children: _,
        } = node
        {
            let size = node.size();
            if size >= min_directory_size && size < result {
                result = size;
            }
        }
    }
    println!("{result}");
    Ok(())
}