use aoc2019::*;
use std::io;
use std::io::prelude::*;
use std::process;
use structopt::StructOpt;

#[derive(Debug, StructOpt)]
#[structopt(name = "Day 2: 1202 Program Alarm")]
/// Executes an Intcode program
///
/// The program is read from stdin as a series of comma-separated
/// values. Newlines are ignored. When the program halts, the value at
/// position 0 is returned.
///
/// If an output is provided, all possible inputs are tried to find
/// the input that results in the desired output. In this case, the
/// inputs are returned in the format (noun, verb).
///
///See https://adventofcode.com/2019/day/2 for details.
struct Opt {
    #[structopt(short = "n", long = "noun")]
    noun: Option<Intcode>,
    #[structopt(short = "v", long = "verb")]
    verb: Option<Intcode>,
    #[structopt(short = "o", long = "output")]
    output: Option<Intcode>,
}

fn main() {
    let stdin = io::stdin();
    let opt = Opt::from_args();

    let program: IntcodeProgram = stdin
        .lock()
        .split(b',')
        .map(|x| exit_on_failed_assertion(x, "Error reading input"))
        .map(|x| exit_on_failed_assertion(String::from_utf8(x), "Input was not valid UTF-8"))
        .map(|x| exit_on_failed_assertion(x.trim().parse::<Intcode>(), "Invalid number"))
        .collect();

    match (opt.noun, opt.verb, opt.output) {
        (Some(noun), Some(verb), _) => {
            let result = exit_on_failed_assertion(
                program
                    .with_noun_verb_input(noun, verb)
                    .execute_returning_memory_0(),
                "Program errored",
            );
            println!("{}", result);
        }
        (_, _, Some(output)) => {
            let (noun, verb) =
                exit_on_failed_assertion(find_input(&program, output), "Program errored");
            println!("({}, {})", noun, verb);
        }
        (None, None, None) => {
            let result =
                exit_on_failed_assertion(program.execute_returning_memory_0(), "Program errored");
            println!("{}", result);
        }
        _ => {
            eprintln!("Either a noun and verb or an expected output must be provided");
            process::exit(1);
        }
    }
}

fn exit_on_failed_assertion<A, E: std::error::Error>(data: Result<A, E>, message: &str) -> A {
    match data {
        Ok(data) => data,
        Err(e) => {
            eprintln!("{}: {}", message, e);
            process::exit(1);
        }
    }
}

fn find_input(
    program: &IntcodeProgram,
    output: Intcode,
) -> Result<(Intcode, Intcode), IntcodeProgramError> {
    (0..99)
        .flat_map(|noun| (0..99).map(move |verb| (Intcode::from(noun), Intcode::from(verb))))
        .map(|(noun, verb)| {
            (
                noun.clone(),
                verb.clone(),
                program
                    .with_noun_verb_input(noun, verb)
                    .execute_returning_memory_0(),
            )
        })
        .find(|(_noun, _verb, out)| *out == Ok(output.clone()))
        .map(|(noun, verb, _out)| Ok((noun, verb)))
        .unwrap_or(Err(IntcodeProgramError::Unknown))
}