use std::fs::File;
use std::io::{self, prelude::*, BufReader};
use std::collections::HashMap;
use regex::Regex;

fn find_S(line: &str) -> Vec<(i32, i32)> {
    let re = Regex::new(r"\d+").unwrap();
    let matches: Vec<_> = re.find_iter(line).map(|m| m.range()).collect();
    let mut return_vec: Vec<(i32, i32)> = vec![];
    for i in matches {
        return_vec.push((i.start as i32, i.end as i32));
        // println!("first {}, Last {}", i.start, i.end); 
        // println!("number {}", line.get(i.start..i.end).unwrap().parse::<u32>().unwrap()); 
    }
    return return_vec;
}

fn find_next_location(wall_of_text: &Vec<String>, current_location: (i32, i32), previous_location: (i32, i32)) -> (i32, i32)
{
    let current_char = wall_of_text[current_location.0 as usize].get(current_location.1 as usize..current_location.1 as usize+1).unwrap();
    println!("current_char {}", current_char);
    match current_char{
        "|" => (current_location.0 + (current_location.0 - previous_location.0) , current_location.1),
        "-" => (current_location.0, current_location.1 + (current_location.1 - previous_location.1)),
        "L" => {
            if current_location.0 == previous_location.0 {
                (current_location.0-1 , current_location.1)
            }
            else
            {
                (current_location.0 , current_location.1+1)
            }
        },
        "J" => {
            if current_location.0 == previous_location.0 {
                (current_location.0-1 , current_location.1)
            }
            else
            {
                (current_location.0 , current_location.1-1)
            }
        }
        "7" => {
            if current_location.0 == previous_location.0 {
                (current_location.0+1 , current_location.1)
            }
            else
            {
                (current_location.0 , current_location.1-1)
            }
        }
        "F" => {
            if current_location.0 == previous_location.0 {
                (current_location.0+1 , current_location.1)
            }
            else
            {
                (current_location.0 , current_location.1+1)
            }
        }
        "." => (current_location.0 , current_location.1),
        &_ => (current_location.0 , current_location.1),
    }

}

fn process_text(wall_of_text: Vec<String>) -> u32 {
    let mut starting_location = (0,0);
    for (line_count, line) in wall_of_text.clone().into_iter().enumerate() {
        let x = line.find("S");
        
        if x.is_some(){
            println!("S is located at {} {}", line_count, x.unwrap());
            starting_location = (line_count as i32, x.unwrap() as i32);
            let _ignore = find_next_location(&wall_of_text, starting_location, starting_location);
            break;
        }
    }
    let mut cardinal_directions: Vec<_> = vec![];
    let mut heads: Vec<(i32, i32)> = vec![];
    let mut prev_locs: Vec<(i32, i32)> = vec![];
    prev_locs.push(starting_location);
    prev_locs.push(starting_location);
    cardinal_directions.push(wall_of_text[(starting_location.0 - 1)  as usize].get(starting_location.1 as usize..starting_location.1 as usize+1).unwrap());
    cardinal_directions.push(wall_of_text[(starting_location.0 + 1) as usize].get(starting_location.1 as usize..starting_location.1 as usize+1).unwrap());
    cardinal_directions.push(wall_of_text[starting_location.0 as usize].get((starting_location.1 + 1) as usize..(starting_location.1 + 1) as usize+1).unwrap());
    cardinal_directions.push(wall_of_text[starting_location.0 as usize].get((starting_location.1 - 1) as usize..(starting_location.1 - 1) as usize+1).unwrap());

    if match cardinal_directions[0]{
        "|" => true,
        "-" => false,
        "L" => false,
        "J" => false,
        "7" => true,
        "F" => true,
        "." => false,
        &_ => false,
    } {heads.push(((starting_location.0 - 1), (starting_location.1)))};

    if match cardinal_directions[1]{
        "|" => true,
        "-" => false,
        "L" => true,
        "J" => true,
        "7" => false,
        "F" => false,
        "." => false,
        &_ => false,
    } {heads.push(((starting_location.0 + 1), (starting_location.1)))};

    if match cardinal_directions[2]{
        "|" => false,
        "-" => true,
        "L" => false,
        "J" => true,
        "7" => true,
        "F" => false,
        "." => false,
        &_ => false,
    } {heads.push(((starting_location.0), (starting_location.1+1)))};

    if match cardinal_directions[3]{
        "|" => false,
        "-" => true,
        "L" => true,
        "J" => false,
        "7" => false,
        "F" => true,
        "." => false,
        &_ => false,
    } {heads.push(((starting_location.0), (starting_location.1-1)))};

    let mut count = 1;
    while heads[0] != heads[1]
    {
        let temp0 = heads[0];
        let temp1 = heads[1];
        heads[0] = find_next_location(&wall_of_text, heads[0], prev_locs[0]);
        heads[1] = find_next_location(&wall_of_text, heads[1], prev_locs[1]);
        prev_locs[0] = temp0;
        prev_locs[1] = temp1;
        count += 1;
    }
    
    return count;
}

fn main() -> io::Result<()>  {
    // let file = File::open("../test.txt")?;
    let file = File::open("../input.txt")?;
    let reader = BufReader::new(file);
    let answer: u32 = process_text(
        reader.lines().collect::<io::Result<Vec<String>>>().expect("failed")
    );
    println!("{}", answer);

    Ok(())
}