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use std::collections::{BTreeMap, HashMap};

use structopt::StructOpt;

mod day_01;
mod day_02;
mod day_03;
mod day_04;
mod day_05;
mod day_06;
mod day_07;
pub mod day_08;
pub mod day_20;
pub mod day_21;
pub mod day_22;
pub mod day_23;
pub mod day_24;
pub mod day_25;

#[derive(StructOpt)]
pub struct Cli {
    #[structopt(long)]
    day: Option<u32>,
    #[structopt(long)]
    part: Option<u32>,
}

const NUM_DAY: u32 = 7;

type AnyError = Box<dyn std::error::Error>;
type Solver = dyn Fn(&str) -> Result<String, AnyError>;

fn _candidates(args: &Cli) -> Result<BTreeMap<(u32, u32), &Solver>, AnyError> {
    let mut functions: HashMap<(u32, u32), &Solver> = HashMap::new();
    functions.insert((1, 1), &day_01::part_1);
    functions.insert((1, 2), &day_01::part_2);
    functions.insert((2, 1), &day_02::part_1);
    functions.insert((2, 2), &day_02::part_2);
    functions.insert((3, 1), &day_03::part_1);
    functions.insert((3, 2), &day_03::part_2);
    functions.insert((4, 1), &day_04::part_1);
    functions.insert((4, 2), &day_04::part_2);
    functions.insert((5, 1), &day_05::part_1);
    functions.insert((5, 2), &day_05::part_2);
    functions.insert((6, 1), &day_06::part_1);
    functions.insert((6, 2), &day_06::part_2);
    functions.insert((7, 1), &day_07::part_1);
    functions.insert((7, 2), &day_07::part_2);
    let functions = functions;

    let mut result = BTreeMap::new();
    let parts: Vec<u32> = match args.part {
        None => 1..=2,
        Some(1) => 1..=1,
        Some(2) => 2..=2,
        _ => return Err("Invalid part".into()),
    }
    .collect();

    let days = match args.day {
        None => 1..=NUM_DAY,
        Some(day) if (1..=NUM_DAY).contains(&day) => day..=day,
        _ => return Err("Invalid day".into()),
    };

    for day in days {
        for part in &parts {
            result.insert((day, *part), functions[&(day, *part)]);
        }
    }

    Ok(result)
}

pub fn helper(args: &Cli, text: &str) -> Result<Vec<String>, AnyError> {
    let candidates: BTreeMap<(u32, u32), &Solver> = _candidates(args)?;
    if candidates.is_empty() {
        return Err("Invalid day and part".into());
    }

    let mut result = Vec::new();
    for ((day, part), func) in candidates.iter() {
        eprintln!("Trying day {} part {}", day, part);
        match func(text) {
            Ok(output) => result.push(output),
            Err(error) => match args.day {
                None => eprintln!("{}", error),
                Some(_) => return Err(error),
            },
        }
    }
    Ok(result)
}

#[cfg(test)]
mod tests {
    use std::fs;

    use super::*;

    const STEMS: [&str; 2] = ["example", "input"];

    #[test]
    fn specific_day_returns_2_solutions_on_right_input() {
        for day in 1..=NUM_DAY {
            let args = Cli {
                day: Some(day),
                part: None,
            };
            let input_day = day;
            for stem in STEMS {
                let stdin =
                    fs::read_to_string(format!("inputs/{:02}/{}.txt", input_day, stem)).unwrap();
                println!("day:{} input_day:{} stem:{}", day, input_day, stem);
                assert_eq!(helper(&args, &stdin).unwrap().len(), 2);
            }
        }
    }

    // It is possible to construct input for day 3 that would trigger day 1, would be
    // nice to eliminate this if it is even possible.
    #[test]
    fn specific_part_returns_1_solution_on_right_input() {
        for part in 1..=2 {
            let args = Cli {
                day: None,
                part: Some(part),
            };
            for input_day in 1..=NUM_DAY {
                for stem in STEMS {
                    let stdin = fs::read_to_string(format!("inputs/{:02}/{}.txt", input_day, stem))
                        .unwrap();
                    println!("day:* input_day:{} stem:{}", input_day, stem);
                    assert_eq!(helper(&args, &stdin).unwrap().len(), 1);
                }
            }
        }
    }

    #[test]
    #[ignore]
    fn specific_day_returns_error_on_wrong_input() {
        for day in 1..=NUM_DAY {
            let args = Cli {
                day: Some(day),
                part: None,
            };
            for input_day in (1..=NUM_DAY).filter(|d| *d != day) {
                for stem in STEMS {
                    let stdin = fs::read_to_string(format!("inputs/{:02}/{}.txt", input_day, stem))
                        .unwrap();
                    println!("day:{} input_day:{} stem:{}", day, input_day, stem);
                    helper(&args, &stdin).unwrap().len();
                }
            }
        }
    }
}