/**
 * Player Identifier Management
 * 
 * Generates and manages a unique player identifier (UUID) that is stored
 * in localStorage. This identifier is used to sync game states across
 * different domains (hoerdle.de and hördle.de).
 */

const STORAGE_KEY = 'hoerdle_player_id';

/**
 * Generate a UUID v4
 */
function generatePlayerId(): string {
    // UUID v4 format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
        const r = Math.random() * 16 | 0;
        const v = c === 'x' ? r : (r & 0x3 | 0x8);
        return v.toString(16);
    });
}

/**
 * Try to find an existing player ID from the backend
 * 
 * @param genreKey - Genre key to search for
 * @returns Player ID if found, null otherwise
 */
async function findExistingPlayerId(genreKey: string): Promise<string | null> {
    try {
        const response = await fetch('/api/player-id/suggest', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({ genreKey }),
        });

        if (response.ok) {
            const data = await response.json();
            if (data.playerId) {
                return data.playerId;
            }
        }
    } catch (error) {
        console.warn('[playerId] Failed to find existing player ID:', error);
    }
    return null;
}

/**
 * Get or create a player identifier
 * 
 * If no identifier exists in localStorage, tries to find an existing one from the backend
 * (based on recently updated states). If none found, generates a new UUID.
 * This enables cross-domain synchronization between hoerdle.de and hördle.de.
 * 
 * @param genreKey - Optional genre key to search for existing player ID
 * @returns Player identifier (UUID v4)
 */
export async function getOrCreatePlayerIdAsync(genreKey?: string): Promise<string> {
    if (typeof window === 'undefined') {
        // Server-side: return empty string (not used on server)
        return '';
    }
    
    let playerId = localStorage.getItem(STORAGE_KEY);
    
    if (!playerId) {
        // Try to find an existing player ID from backend if genreKey is provided
        if (genreKey) {
            const existingId = await findExistingPlayerId(genreKey);
            if (existingId) {
                playerId = existingId;
                localStorage.setItem(STORAGE_KEY, playerId);
                return playerId;
            }
        }
        
        // Generate new UUID if no existing ID found
        playerId = generatePlayerId();
        localStorage.setItem(STORAGE_KEY, playerId);
    }
    
    return playerId;
}

/**
 * Get or create a player identifier (synchronous version)
 * 
 * This is the legacy synchronous version. For cross-domain sync, use getOrCreatePlayerIdAsync instead.
 * 
 * @returns Player identifier (UUID v4)
 */
export function getOrCreatePlayerId(): string {
    if (typeof window === 'undefined') {
        // Server-side: return empty string (not used on server)
        return '';
    }
    
    let playerId = localStorage.getItem(STORAGE_KEY);
    if (!playerId) {
        playerId = generatePlayerId();
        localStorage.setItem(STORAGE_KEY, playerId);
    }
    return playerId;
}

/**
 * Get the current player identifier without creating a new one
 * 
 * @returns Player identifier or null if not set
 */
export function getPlayerId(): string | null {
    if (typeof window === 'undefined') {
        return null;
    }
    return localStorage.getItem(STORAGE_KEY);
}