package com.paymentlink.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.SecureRandom;

@Service
public class NodeIdService {

    private static final Logger logger = LoggerFactory.getLogger(NodeIdService.class);
    private static final SecureRandom RANDOM = new SecureRandom();
    private static final String CHARACTERS = "abcdefghijklmnopqrstuvwxyz0123456789";

    @Value("${app.server-id-file:incl/server-id.txt}")
    private String serverIdFile;

    @Value("${app.tld:ironpath.ai}")
    private String tld;

    private String nodeId;

    /**
     * Get or create node ID
     */
    public String getNodeId() {
        if (nodeId == null) {
            nodeId = loadOrCreateNodeId();
        }
        return nodeId;
    }

    /**
     * Get short ID (without TLD)
     */
    public String getShortId() {
        String fullId = getNodeId();
        return fullId.split("\\.")[0];
    }

    private String loadOrCreateNodeId() {
        try {
            Path filePath = Paths.get(serverIdFile);
            
            // Ensure parent directory exists
            if (filePath.getParent() != null) {
                Files.createDirectories(filePath.getParent());
            }

            // Try to read existing ID
            if (Files.exists(filePath)) {
                String id = Files.readString(filePath).trim();
                if (!id.isEmpty()) {
                    logger.info("Loaded existing server ID: {}", id);
                    return id;
                }
            }

            // Generate new ID
            String newId = generateNodeId();
            Files.writeString(filePath, newId);
            logger.info("Generated new server ID: {}", newId);
            return newId;

        } catch (IOException e) {
            logger.error("Failed to load/create server ID file", e);
            // Generate temporary ID
            String tempId = generateNodeId();
            logger.warn("Using temporary server ID: {}", tempId);
            return tempId;
        }
    }

    private String generateNodeId() {
        StringBuilder sb = new StringBuilder(6);
        for (int i = 0; i < 6; i++) {
            sb.append(CHARACTERS.charAt(RANDOM.nextInt(CHARACTERS.length())));
        }
        return sb.toString() + "." + tld;
    }
}