use std::{fs, str};
use std::error::Error;
use std::fs::File;
use std::io::{self, BufRead, Write};
use std::path::Path;

pub type AOCResult = Result<[Option<String>; 2], Box<dyn Error>>;

pub trait AOCProgram {
    fn run(&self, input: &Vec<String>) -> AOCResult;
}

impl<F: Fn(&Vec<String>) -> AOCResult> AOCProgram for F {
    fn run(&self, input: &Vec<String>) -> AOCResult {
        self(input)
    }
}

fn read_lines<P>(filename: P) -> io::Result<Vec<String>>
    where P: AsRef<Path> {
    let file = File::open(filename)?;
    let lines = io::BufReader::new(file).lines();
    return lines.collect();
}

fn pretty_print_iter(vec: &[String]) -> String {
    vec.iter().fold(String::new(), |acc, s| acc + &s + "\n")
}

pub fn run<F: AOCProgram>(day: &str, prog: &F) -> Result<(), Box<dyn Error>> {
    let arguments = std::env::args();
    let arguments = arguments::parse(arguments)?;
    let part: Option<usize> = arguments.get("part");
    let output_file: Option<String> = arguments.get("output-file");
    // let skip_test = arguments.get::<bool>("skip-test").unwrap_or(false);

    let input = read_lines(format!("./inputs/{}.txt", day))?;

    let result = prog.run(&input);

    let output: Result<String, Box<dyn Error>> = match result {
        Err(e) => {
            let res = format!("Failed on input\"\n{}\" with error\n{}", pretty_print_iter(&input), e).into();
            return Err(res);
        }
        Ok(result) =>
            if part.is_none() {
                match &result {
                    [Some(o1), Some(o2)] => Ok(format!("1:{}\n2:{}", o1, o2)),
                    [Some(o1), None] => Ok(format!("1:{}", o1)),
                    [None, Some(o2)] => Ok(format!("2:{}", o2)),
                    [None, None] => Ok(format!("No output"))
                }
            } else {
                let part = part.unwrap();
                let result = &result[part - 1];
                match result {
                    None => {
                        let res = format!("Part {} not implemented", part).into();
                        return Err(res);
                    }
                    Some(s) => Ok(s.to_owned())
                }
            }
    };

    let output = output?;

    return match output_file {
        Some(output_file) => {
            let output = output.as_bytes();
            let mut file = File::create(output_file)?;
            file.write(output).map(|_| ())
        }
        None => Ok(println!("{}", output))
    }.map_err(|e| e.into());
}

pub fn run_prog<F: AOCProgram>(day: &str, prog: &F) {
    let inputs = files_to_vec(day, "./inputs");

    if let Err(e) = inputs {
        eprintln!("Error occurred while reading input files {}", e);
        return;
    }
    let inputs = inputs.unwrap();
    
    for (path, input) in inputs {
        let result = prog.run(&input);
        match result {
            Err(e) => println!("{}: Failed on input\"\n{}\" with error\n{}", path, pretty_print_iter(&input), e),
            Ok(result) => match &result {
                [Some(o1), Some(o2)] => println!("{}:\n\t1:{}\n\t2:{}", path, o1, o2),
                [Some(o1), None] => println!("{}:\n\t1:{}", path, o1),
                [None, Some(o2)] => println!("{}:\n\t2:{}", path, o2),
                [None, None] => println!("{}: No output", path)
            }
        }
    }
}


pub fn run_test<F: AOCProgram>(day: &str, prog: &F) -> bool {
    let expected_re: regex::Regex = regex::Regex::new(r"^([^\$]+)?(?:\$([^\$]+))?$").unwrap();

    let inputs = files_to_vec(day, "./test_inputs");

    if let Err(e) = inputs {
        eprintln!("Error occurred while reading test input files {}", e);
        return false;
    }
    let inputs = inputs.unwrap();

    if inputs.len() == 0 {
        println!("Tests failed: No valid input files given");
        return false;
    }

    let mut succeed = true;

    for (path, mut input) in inputs.clone() {
        let expected = input.pop();
        if expected.is_none() {
            println!("{}: empty", path);
            continue;
        }
        let expected = expected.unwrap();

        let exp_caps = expected_re.captures(&expected);
        let exp1 = exp_caps.as_ref().and_then(|cap| cap.get(1)).map(|m| m.as_str());
        let exp2 = exp_caps.as_ref().and_then(|cap| cap.get(2)).map(|m| m.as_str());

        let result = test::<F>(prog, &input, [exp1, exp2], &path);
        succeed = succeed && result[0].unwrap_or(true) && result[1].unwrap_or(true);
    }

    return succeed;
}

fn test<F: AOCProgram>(prog: &F, input: &Vec<String>, expected: [Option<&str>; 2], path: &str) -> [Option<bool>; 2] {
    let result = prog.run(input);
    if result.is_err() {
        println!("{}: Program failed on input\"\n{}\" with error\n{}",
                 path, pretty_print_iter(&input[..10.min(input.len())]), result.unwrap_err());
        return [Some(false), Some(false)];
    }
    let result = &result.unwrap();

    let succeeded = [
        result[0]
            .as_ref()
            .ok_or("Program did not produce output")
            .and_then(|r| expected[0]
                .ok_or("No expected output")
                .map(|e| e == r.as_str())
            ),
        result[1]
            .as_ref()
            .ok_or("Program did not produce output")
            .and_then(|r| expected[1]
                .ok_or("No expected output")
                .map(|e| e == r.as_str())
            ),
    ];

    if succeeded[0].is_err() {
        println!("{}: Skipped testing result 1: {}", path, succeeded[0].unwrap_err())
    } else {
        if succeeded[0].unwrap() {
            println!("{}: Result 1 succeeded", path)
        } else {
            eprintln!("{}: Result 1 failed: Wrong output for input \"\n{}\".\n\tExpected \"{}\"\n\tReceived \"{}\"",
                      path, pretty_print_iter(&input[..10.min(input.len())]), expected[0].as_ref().unwrap(), result[0].as_ref().unwrap());
        }
    }

    if succeeded[1].is_err() {
        println!("{}: Skipped testing result 2: {}", path, succeeded[1].unwrap_err())
    } else {
        if succeeded[1].unwrap() {
            println!("{}: Result 2 succeeded", path)
        } else {
            eprintln!("{}: Result 2 failed: Wrong output for input \"\n{}\".\n\tExpected {}\n\tReceived {}",
                      path, pretty_print_iter(&input[..10.min(input.len())]), expected[1].as_ref().unwrap(), result[1].as_ref().unwrap());
        }
    }

    return [succeeded[0].ok(), succeeded[1].ok()];
}

fn files_to_vec<'a>(day: &str, input_path: &str) -> Result<Vec<(String, Vec<String>)>, Box<dyn Error>> {
    let dir = fs::read_dir(input_path)?;

    let file_name_re = regex::Regex::new(&format!(r"{}(?:-.*)?(?:\..*)", day))?;

    let results = dir.map::<io::Result<_>, _>(|f| {
        let f = f?;

        if !f.metadata()?.is_file() {
            return Ok(None);
        }

        let path = f.path();

        let file_name = path.file_name().and_then(|s| s.to_str());

        if !file_name.map(|s| file_name_re.is_match(s)).unwrap_or(false) {
            return Ok(None);
        }
        let file_name = String::from(file_name.unwrap());

        return Ok(Some((file_name, read_lines(f.path())?)));
    }).fold(vec![], |mut acc, r| {
        match r {
            Ok(None) => (),
            Ok(Some(v)) => acc.push(v),
            Err(e) => eprintln!("Error while processing file: {}", e),
        }
        return acc;
    });

    return Ok(results);
}