// Copyright 2022 Christian Ulrich
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

use std::io;

#[derive(Debug)]
pub struct Stacks {
    inner: Vec<Vec<char>>,
}

pub struct Moves {}

#[derive(Debug)]
pub struct Move {
    count: usize,
    from: usize,
    to: usize,
}

impl Stacks {
    pub fn from_stdin() -> Result<Self, &'static str> {
        let mut stacks = vec![];
        for line in io::stdin().lines() {
            match Self::parse_line(&line.unwrap())? {
                None => break,
                Some(items) => {
                    if items.len() != stacks.len() {
                        if !stacks.is_empty() {
                            return Err("input file contains invalid line");
                        }
                        stacks = vec![vec![]; items.len()];
                    }
                    for i in 0..items.len() {
                        if let Some(item) = items[i] {
                            stacks[i].push(item);
                        }
                    }
                }
            }
        }
        for stack in stacks.iter_mut() {
            stack.reverse();
        }
        Ok(Self { inner: stacks })
    }

    fn parse_line(input: &str) -> Result<Option<Vec<Option<char>>>, &'static str> {
        if input.starts_with(" 1 ") {
            return Ok(None);
        }
        let mut result = vec![];
        for chunk in input.chars().collect::<Vec<_>>().chunks(4) {
            match chunk.iter().collect::<String>().as_str() {
                "" => break,
                item => result.push(Self::parse_item(item)?),
            }
        }
        Ok(Some(result))
    }

    fn parse_item(input: &str) -> Result<Option<char>, &'static str> {
        match input.trim() {
            "" => return Ok(None),
            item => {
                if item.len() == 3
                    && item.chars().nth(0).unwrap() == '['
                    && item.chars().nth(2).unwrap() == ']'
                {
                    return Ok(item.chars().nth(1));
                }
            }
        }
        Err("cannot parse item")
    }

    pub fn move_items(&mut self, spec: Move) -> Result<(), &'static str> {
        if spec.from >= self.inner.len()
            || spec.to >= self.inner.len()
            || spec.count > self.inner[spec.from].len()
        {
            return Err("invalid move");
        }
        for _ in 0..spec.count {
            let item = self.inner[spec.from].pop().unwrap();
            self.inner[spec.to].push(item);
        }
        Ok(())
    }

    pub fn move_items_retain_order(&mut self, spec: Move) -> Result<(), &'static str> {
        if spec.from >= self.inner.len()
            || spec.to >= self.inner.len()
            || spec.count > self.inner[spec.from].len()
        {
            return Err("invalid move");
        }
        let split_index = self.inner[spec.from].len() - spec.count;
        let mut items = self.inner[spec.from].split_off(split_index);
        self.inner[spec.to].append(&mut items);
        Ok(())
    }
}

impl Iterator for Stacks {
    type Item = Vec<char>;

    fn next(&mut self) -> Option<Self::Item> {
        match self.inner.len() {
            0 => None,
            _ => Some(self.inner.remove(0)),
        }
    }
}

impl Move {
    pub fn from_str(input: &str) -> Result<Self, &'static str> {
        let parts = input.split(' ').collect::<Vec<_>>();
        if parts.len() != 6 || parts[0] != "move" || parts[2] != "from" || parts[4] != "to" {
            return Err("cannot parse move");
        }
        let from = match parts[3].parse::<usize>().map_err(|_| "cannot parse move")? {
            value if { value > 0 } => Ok(value - 1),
            _ => Err("integer out of range"),
        };
        let to = match parts[5].parse::<usize>().map_err(|_| "cannot parse move")? {
            value if { value > 0 } => Ok(value - 1),
            _ => Err("integer out of range"),
        };
        Ok(Self {
            count: parts[1].parse().map_err(|_| "cannot parse integer")?,
            from: from?,
            to: to?,
        })
    }
}

impl Moves {
    pub fn from_stdin() -> Self {
        Self {}
    }
}

impl Iterator for Moves {
    type Item = Result<Move, &'static str>;

    fn next(&mut self) -> Option<Self::Item> {
        for line in io::stdin().lines() {
            let line = line.unwrap();
            if line.len() > 0 {
                return Some(Move::from_str(&line));
            }
        }
        None
    }
}