use clap::{Arg, ArgMatches, Command, value_parser};
use crate::Cmd;
use std::{error::Error, io::{self, BufRead}};

#[derive(Debug)]
pub struct Factor {
    name: &'static str,
    path: Option<crate::Path>,
}

pub const FACTOR: Factor = Factor {
    name: "factor",
    path: Some(crate::Path::UsrBin),
};

impl Cmd for Factor {
    fn name(&self) -> &str {
        self.name
    }

    fn cli(&self) -> Command {
        Command::new("factor")
            .about("factor numbers")
            .after_help(
                "Print the prime factors of each specified integer NUMBER.  If none are\n\
                specified on the command line, read them from standard input."
            )
            .arg(
                Arg::new("number")
                    .help("the numbers to factor")
                    .num_args(0..)
                    .value_parser(value_parser!(u64))
            )
    }

    fn run(&self, matches: Option<&ArgMatches>) -> Result<(), Box<dyn Error>> {
        if let Some(matches) = matches {
            match matches.get_many::<u64>("number") {
                Some(numbers) => {
                    numbers.for_each(|n| print_factors(*n));
                },
                None => {
                    for line in io::stdin().lock().lines() {
                        for value in line.unwrap().split_whitespace() {
                            let num: u64 = value.parse()?;
                            print_factors(num);
                        }
                    }
                },
            }
        }
        Ok(())
    }

    fn path(&self) -> Option<crate::Path> {
        self.path
    }
}

fn is_prime(num: u64) -> bool {
    match num {
        0 | 1 => false,
        2 | 3 | 5 | 7 | 11 | 13 => true,
        x if x % 2 == 0 => false,
        _ => {
            let mut x: u64 = 2;
            while x < num / 2 {
                if num % x == 0 {
                    return false;
                }
                x += 1;
            }
            true
        }
    }
}

fn print_factors(num: u64) {
    print!("{num}:");
    for n in 2..=num / 2 {
        if num % n == 0 && is_prime(n) {
            print!(" {n}");
        }
    }
    println!();
}