use crate::board;
use crate::board::GridAxis;
use crate::engine;
use std::io::BufRead;

impl std::fmt::Display for board::Color {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            board::Color::White => write!(f, "W"),
            board::Color::Black => write!(f, "B"),
        }
    }
}

impl std::fmt::Display for board::PieceType {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            board::PieceType::Pawn => write!(f, "P"),
            board::PieceType::Knight => write!(f, "N"),
        }
    }
}

impl std::fmt::Display for board::Piece {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}{}", self.piece_type, self.color)
    }
}

trait GridAxisIO: std::fmt::Display
where
    Self: GridAxis,
{
    fn parse(c: char) -> Result<Self, ()>;
}

impl GridAxisIO for board::Rank {
    fn parse(c: char) -> Result<Self, ()> {
        match c {
            '1' => Ok(board::Rank::_1),
            '2' => Ok(board::Rank::_2),
            '3' => Ok(board::Rank::_3),
            '4' => Ok(board::Rank::_4),
            '5' => Ok(board::Rank::_5),
            '6' => Ok(board::Rank::_6),
            '7' => Ok(board::Rank::_7),
            '8' => Ok(board::Rank::_8),
            _ => Err(()),
        }
    }
}

impl std::fmt::Display for board::Rank {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let c = match self {
            board::Rank::_1 => '1',
            board::Rank::_2 => '2',
            board::Rank::_3 => '3',
            board::Rank::_4 => '4',
            board::Rank::_5 => '5',
            board::Rank::_6 => '6',
            board::Rank::_7 => '7',
            board::Rank::_8 => '8',
        };
        write!(f, "{}", c)
    }
}

impl GridAxisIO for board::File {
    fn parse(c: char) -> Result<Self, ()> {
        match c {
            'a' => Ok(board::File::A),
            'b' => Ok(board::File::B),
            'c' => Ok(board::File::C),
            'd' => Ok(board::File::D),
            'e' => Ok(board::File::E),
            'f' => Ok(board::File::F),
            'g' => Ok(board::File::G),
            'h' => Ok(board::File::H),
            _ => Err(()),
        }
    }
}

impl std::fmt::Display for board::File {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let c = match self {
            board::File::A => 'a',
            board::File::B => 'b',
            board::File::C => 'c',
            board::File::D => 'd',
            board::File::E => 'e',
            board::File::F => 'f',
            board::File::G => 'g',
            board::File::H => 'h',
        };
        write!(f, "{}", c)
    }
}

impl board::Position {
    fn parse(s: &str) -> Result<Self, ()> {
        let mut chars = s.chars();
        let file = board::File::parse(chars.next().ok_or(())?)?;
        let rank = board::Rank::parse(chars.next().ok_or(())?)?;
        if chars.next().is_none() {
            Ok(board::Position::new(file, rank))
        } else {
            Err(())
        }
    }
}

impl board::PieceType {
    fn parse(c: char) -> Result<Self, ()> {
        match c {
            'P' => Ok(board::PieceType::Pawn),
            _ => Err(()),
        }
    }
}

impl board::Color {
    fn parse(c: char) -> Result<Self, ()> {
        match c {
            'B' => Ok(board::Color::Black),
            'W' => Ok(board::Color::White),
            _ => Err(()),
        }
    }
}

impl board::Piece {
    fn parse(s: &str) -> Result<Self, ()> {
        let mut chars = s.chars();
        let piece_type = board::PieceType::parse(chars.next().ok_or(())?)?;
        let color = board::Color::parse(chars.next().ok_or(())?)?;
        if chars.next().is_none() {
            Ok(board::Piece {
                piece_type,
                color,
            })
        } else {
            Err(())
        }
    }
}

impl std::fmt::Display for board::Position {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}{}", self.file, self.rank)
    }
}

impl std::fmt::Display for board::Board {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        for (position, piece) in self.iter() {
            write!(f, "{}{}", piece, position)?;
        }
        Ok(())
    }
}

impl board::Board {
    fn parse(s: &str) -> Result<Self, ()> {
        if s.chars().all(|c| char::is_ascii_alphanumeric(&c)) {
            let mut board = board::Board::new();
            for piece_pos in s.as_bytes().chunks(4) {
                let position = board::Position::parse(
                    std::str::from_utf8(&piece_pos[2..]).unwrap(),
                )?;
                let piece = board::Piece::parse(
                    std::str::from_utf8(&piece_pos[..2]).unwrap(),
                )?;
                board.set_at(position, Some(piece));
            }
            Ok(board)
        } else {
            Err(())
        }
    }
}

pub struct Ui {
    engine: engine::Engine,
}

impl Ui {
    pub fn new() -> Self {
        Ui {
            engine: engine::Engine::new(),
        }
    }
    fn get_state(&self, args: &[&str]) -> Result<String, String> {
        if let [] = args {
            let result = format!("{}", self.engine.get_state());
            Ok(result)
        } else {
            Err("get_state takes no args".to_owned())
        }
    }
    fn set_state(&mut self, args: &[&str]) -> Result<String, String> {
        if let [state_str] = args {
            self.engine.set_state(
                board::Board::parse(state_str).map_err(|_| {
                    format!("Error parsing state {}", state_str)
                })?,
            );
            let result = format!("{}", self.engine.get_state());
            Ok(result)
        } else {
            Err("set_state takes 1 arg".to_owned())
        }
    }
    fn get_moves(&self, args: &[&str]) -> Result<String, String> {
        if let [position_str] = args {
            let position =
                board::Position::parse(position_str).map_err(|_| {
                    format!("Error parsing position {}", position_str)
                })?;
            match self.engine.get_legal_moves(&position) {
                Err(_) => {
                    let error = format!("No moves possible from {}", position);
                    Err(error)
                }
                Ok(positions) => {
                    Ok(positions.map(|pos| format!("{}", pos)).collect())
                }
            }
        } else {
            Err("get_moves takes 1 arg".to_owned())
        }
    }
    fn make_move(&mut self, args: &[&str]) -> Result<String, String> {
        if let [source_str, target_str] = args {
            let source = board::Position::parse(source_str)
                .map_err(|_| format!("Error parsing source {}", source_str))?;
            let target = board::Position::parse(target_str)
                .map_err(|_| format!("Error parsing target {}", target_str))?;
            match self.engine.make_move(&source, target) {
                Err(()) => Err(format!(
                    "Move not possible {}-{}",
                    source_str, target_str
                )),
                Ok(()) => Ok(format!("{}", self.engine.get_state())),
            }
        } else {
            Err("make_move takes 2 args".to_owned())
        }
    }
    fn choose_move(&self, args: &[&str]) -> Result<String, String> {
        if let [color_str] = args {
            if let [color_char] = color_str.chars().collect::<Vec<char>>()[..]
            {
                match self.engine.choose_move(
                    &board::Color::parse(color_char).map_err(|_| {
                        format!("Couldn't parse color code {}", color_char)
                    })?,
                ) {
                    Some((source, target)) => {
                        Ok(format!("{},{}", source, target))
                    }
                    None => {
                        Err(format!("No move possible for {}", color_char))
                    }
                }
            } else {
                Err(format!("Invalid color string {}", color_str))
            }
        } else {
            Err("choose_move takes 1 arg".to_owned())
        }
    }
    fn reset(&mut self, args: &[&str]) -> Result<String, String> {
        if let [] = args {
            self.engine.reset();
            Ok(format!("{}", self.engine.get_state()))
        } else {
            Err("reset doesn't take args".to_owned())
        }
    }
    fn handle_command(&mut self, s: &str) -> Result<String, String> {
        let mut cmd = s.split(',');
        // There will be at least an empty string => otherwise panic
        let cmd_type = cmd.next().unwrap();
        let args: Vec<&str> = cmd.collect();
        match cmd_type {
            "get_state" => self.get_state(&args),
            "get_moves" => self.get_moves(&args),
            "make_move" => self.make_move(&args),
            "set_state" => self.set_state(&args),
            "choose_move" => self.choose_move(&args),
            "reset" => self.reset(&args),
            "" => Err("No command given".to_owned()),
            _ => Err("Invalid command".to_owned()),
        }
    }
    pub fn run(&mut self) -> Result<(), ()> {
        let stdin = std::io::stdin();
        let mut input_lines = stdin.lock().lines();
        loop {
            match input_lines.next() {
                None => break Ok(()),
                Some(line) => match line {
                    Err(_) => break Err(()),
                    Ok(line) => match self.handle_command(&line) {
                        Ok(result) => println!("ok,{}", result),
                        Err(reason) => println!("err,{}", reason),
                    },
                },
            }
        }
    }
}