chessfriend/explorer/src/main.rs

// Eryn Wells <eryn@erynwells.me>

use chessfriend_board::{fen::FromFenStr, Board};
use chessfriend_core::{Color, Piece, Shape, Square};
use chessfriend_moves::Builder as MoveBuilder;
use chessfriend_position::{fen::ToFenStr, PlacePieceStrategy, Position, ValidateMove};

use clap::{Arg, Command};
use rustyline::error::ReadlineError;
use rustyline::DefaultEditor;
use thiserror::Error;

struct CommandResult {
    should_continue: bool,
    should_print_position: bool,
}

impl Default for CommandResult {
    fn default() -> Self {
        CommandResult {
            should_continue: true,
            should_print_position: true,
        }
    }
}

struct State {
    position: Position,
}

fn command_line() -> Command {
    // strip out usage
    const PARSER_TEMPLATE: &str = "\
        {all-args}
    ";

    Command::new("explorer")
        .multicall(true)
        .arg_required_else_help(true)
        .subcommand_required(true)
        .subcommand_value_name("CMD")
        .subcommand_help_heading("COMMANDS")
        .help_template(PARSER_TEMPLATE)
        .subcommand(Command::new("fen").about("Print the current position as a FEN string"))
        .subcommand(
            Command::new("make")
                .arg(Arg::new("from").required(true))
                .arg(Arg::new("to").required(true))
                .alias("m")
                .about("Make a move"),
        )
        .subcommand(
            Command::new("place")
                .arg(Arg::new("color").required(true))
                .arg(Arg::new("piece").required(true))
                .arg(Arg::new("square").required(true))
                .alias("p")
                .about("Place a piece on the board"),
        )
        .subcommand(
            Command::new("sight")
                .arg(Arg::new("square").required(true))
                .about("Show sight of a piece on a square"),
        )
        .subcommand(
            Command::new("moves")
                .arg(Arg::new("square").required(true))
                .about("Show moves of a piece on a square"),
        )
        .subcommand(
            Command::new("reset")
                .subcommand(Command::new("clear").about("Reset to a cleared board"))
                .subcommand(Command::new("starting").about("Reset to the starting position"))
                .subcommand(
                    Command::new("fen")
                        .arg(Arg::new("fen").required(true))
                        .about("Reset to a position described by a FEN string"),
                )
                .about("Reset the board"),
        )
        .subcommand(Command::new("print").about("Print the board"))
        .subcommand(Command::new("quit").alias("exit").about("Quit the program"))
}

#[derive(Clone, Debug, Error, Eq, PartialEq)]
enum CommandHandlingError<'a> {
    #[error("lexer error")]
    LexerError,
    #[error("missing {0} argument")]
    MissingArgument(&'a str),
}

fn respond(line: &str, state: &mut State) -> anyhow::Result<CommandResult> {
    let args = shlex::split(line).ok_or(CommandHandlingError::LexerError)?;
    let matches = command_line().try_get_matches_from(args)?;

    let mut result = CommandResult::default();

    match matches.subcommand() {
        Some(("print", _matches)) => {}
        Some(("quit", _matches)) => {
            result.should_continue = false;
            result.should_print_position = false;
        }
        Some(("fen", _matches)) => {
            println!("{}", state.position.to_fen_str()?);
            result.should_print_position = false;
        }
        Some(("make", matches)) => {
            let from_square = Square::from_algebraic_str(
                matches
                    .get_one::<String>("from")
                    .ok_or(CommandHandlingError::MissingArgument("from"))?,
            )?;

            let to_square = Square::from_algebraic_str(
                matches
                    .get_one::<String>("to")
                    .ok_or(CommandHandlingError::MissingArgument("to"))?,
            )?;

            let ply = MoveBuilder::new().from(from_square).to(to_square).build()?;

            state.position.make_move(ply, ValidateMove::Yes)?;
        }
        Some(("place", matches)) => {
            let color = matches
                .get_one::<String>("color")
                .ok_or(CommandHandlingError::MissingArgument("color"))?;
            let color = color.parse::<Color>()?;

            let shape = matches
                .get_one::<String>("piece")
                .ok_or(CommandHandlingError::MissingArgument("piece"))?;
            let shape = shape.parse::<Shape>()?;

            let square = matches
                .get_one::<String>("square")
                .ok_or(CommandHandlingError::MissingArgument("square"))?;
            let square = Square::from_algebraic_str(square)?;

            let piece = Piece::new(color, shape);

            state
                .position
                .place_piece(piece, square, PlacePieceStrategy::default())?;
        }
        Some(("sight", matches)) => {
            let square = matches
                .get_one::<String>("square")
                .ok_or(CommandHandlingError::MissingArgument("square"))?;
            let square = square.parse::<Square>()?;

            let sight = state.position.sight(square);

            let display = state.position.display().highlight(sight);
            println!("\n{display}");

            result.should_print_position = false;
        }
        Some(("moves", matches)) => {
            let square = matches
                .get_one::<String>("square")
                .ok_or(CommandHandlingError::MissingArgument("square"))?;
            let square = square.parse::<Square>()?;

            let movement = state.position.movement(square);

            let display = state.position.display().highlight(movement);
            println!("\n{display}");

            result.should_print_position = false;
        }
        Some(("starting", _matches)) => {
            let starting_position = Position::starting();
            state.position = starting_position;
        }
        Some(("reset", matches)) => result = do_reset_command(state, matches)?,
        Some((name, _matches)) => unimplemented!("{name}"),
        None => unreachable!("Subcommand required"),
    }

    Ok(result)
}

fn do_reset_command(
    state: &mut State,
    matches: &clap::ArgMatches,
) -> anyhow::Result<CommandResult> {
    match matches.subcommand() {
        None | Some(("clear", _)) => state.position = Position::empty(),
        Some(("starting", _)) => state.position = Position::starting(),
        Some(("fen", matches)) => {
            let fen = matches
                .get_one::<String>("fen")
                .ok_or(CommandHandlingError::MissingArgument("fen"))?;
            let board = Board::from_fen_str(fen)?;
            state.position = Position::new(board);
        }
        Some((name, _matches)) => unimplemented!("{name}"),
    }

    Ok(CommandResult::default())
}

fn main() -> Result<(), String> {
    let mut editor = DefaultEditor::new().map_err(|err| format!("Error: {err}"))?;

    let starting_position = Position::starting();
    let mut state = State {
        position: starting_position,
    };

    let mut should_print_position = true;

    loop {
        if should_print_position {
            println!("{}", &state.position);
            println!("{} to move.", state.position.board.active_color);
        }

        let readline = editor.readline("\n? ");
        match readline {
            Ok(line) => {
                let line = line.trim();
                if line.is_empty() {
                    continue;
                }

                match respond(line, &mut state) {
                    Ok(result) => {
                        should_print_position = result.should_print_position;
                        if !result.should_continue {
                            break;
                        }
                    }
                    Err(message) => println!("{message}"),
                }
            }
            Err(ReadlineError::Interrupted) => {
                println!("CTRL-C");
                break;
            }
            Err(ReadlineError::Eof) => {
                println!("CTRL-D");
                break;
            }
            Err(err) => {
                println!("Error: {err}");
                break;
            }
        }
    }

    Ok(())
}