ChessBuilder/Assets/ChessEngines/fairy-chess-server/engine.js

// engine.js
import { spawn } from 'child_process';
import { EventEmitter } from 'events';

class ChessEngine extends EventEmitter {
    constructor(enginePath) {
        super();
        this.enginePath = enginePath;
        this.engine = null;
        this.isReady = false;
        this.currentFen = null;
    }

    start() {
        return new Promise((resolve, reject) => {
            try {
                this.engine = spawn(this.enginePath);
                
                this.engine.stdout.on('data', (data) => {
                    const messages = data.toString().trim().split('\n');
                    messages.forEach(msg => this.handleEngineMessage(msg));
                });

                this.engine.stderr.on('data', (data) => {
                    console.error('Engine Error:', data.toString());
                });

                this.engine.on('close', (code) => {
                    console.log('Engine process closed with code:', code);
                    this.isReady = false;
                });

                // Initialize engine
                this.sendCommand('uci');
                this.waitforReady(resolve);
                
            } catch (error) {
                reject(error);
            }
        });
    }

    waitforReady(resolve){
        this.sendCommand('isready');

        // Wait for readyok
        this.once('ready', () => {
            this.isReady = true;
            resolve();
        });
    }

    handleEngineMessage(message) {
        console.log('Engine:', message);
        
        if (message.includes('readyok')) {
            this.emit('ready');
        }
        else if (message.startsWith('bestmove')) {
            const [, move] = message.split(' ');
            this.emit('bestmove', move);
        }
        else if (message.startsWith('info')) {
            this.emit('info', this.parseInfo(message));
        }
    }

    parseInfo(info) {
        const parts = info.split(' ');
        const result = {};
        
        for (let i = 1; i < parts.length; i++) {
            switch (parts[i]) {
                case 'depth':
                    result.depth = parseInt(parts[++i]);
                    break;
                case 'seldepth':
                    result.seldepth = parseInt(parts[++i]);
                    break;
                case 'score':
                    result.score = {
                        type: parts[++i],
                        value: parseInt(parts[++i])
                    };
                    break;
                case 'nodes':
                    result.nodes = parseInt(parts[++i]);
                    break;
                case 'time':
                    result.time = parseInt(parts[++i]);
                    break;
                case 'pv':
                    result.pv = [];
                    while (++i < parts.length && !parts[i].includes('bmc')) {
                        result.pv.push(parts[i]);
                    }
                    break;
            }
        }
        
        return result;
    }

    sendCommand(cmd) {
        if (this.engine && this.engine.stdin.writable) {
            console.log('Sending:', cmd);
            this.engine.stdin.write(cmd + '\n');
        }
    }

    async setBoardPosition(fen) {
        if (!this.isReady) throw new Error('Engine not ready');
        
        this.currentFen = fen;
        this.sendCommand(`position fen ${fen}`);
        
        // Ensure engine is ready after position set
        this.sendCommand('isready');
        await new Promise(resolve => this.once('ready', resolve));
    }

    async getBestMove(options = {}) {
        if (!this.isReady) throw new Error('Engine not ready');
        if (!this.currentFen) throw new Error('Position not set');

        const {
            depth = 15,
            movetime = 1000,
            nodes = null,
        } = options;

        return new Promise((resolve) => {
            // Construct go command
            let goCmd = 'go';
            if (depth) goCmd += ` depth ${depth}`;
            if (movetime) goCmd += ` movetime ${movetime}`;
            if (nodes) goCmd += ` nodes ${nodes}`;

            this.sendCommand(goCmd);

            // Wait for bestmove response
            this.once('bestmove', (move) => {
                resolve(move);
            });
        });
    }

    async getAnalysis(fen, options = {}) {
        await this.setBoardPosition(fen);
        const bestMove = await this.getBestMove(options);
        return { bestMove };
    }

    quit() {
        if (this.engine) {
            this.sendCommand('quit');
            this.engine = null;
            this.isReady = false;
        }
    }
}

export default ChessEngine;