/**
 * Offline Manager
 * Handles offline detection and feedback queueing for the mobile app
 */

(function() {
    'use strict';
    
    const OFFLINE_QUEUE_KEY = 'bbplease_offline_feedback_queue';
    const SYNC_INTERVAL = 30000; // Sync every 30 seconds when online
    let syncIntervalId = null;
    
    /**
     * Initialize offline manager
     */
    function init() {
        // Listen for online/offline events
        window.addEventListener('online', handleOnline);
        window.addEventListener('offline', handleOffline);
        
        // Check initial state
        if (navigator.onLine) {
            syncPendingFeedback();
            startSyncInterval();
        } else {
            handleOffline();
        }
        
        // Try to sync on page load
        syncPendingFeedback();
    }
    
    /**
     * Handle going online
     */
    function handleOnline() {
        console.log('📶 Online - syncing pending feedback...');
        syncPendingFeedback();
        startSyncInterval();
        
        // Show notification if there was pending feedback
        const queue = getQueue();
        if (queue.length > 0) {
            showToast(`Syncing ${queue.length} pending feedback...`);
        }
    }
    
    /**
     * Handle going offline
     */
    function handleOffline() {
        console.log('📴 Offline - feedback will be queued');
        stopSyncInterval();
        showToast('You are offline. Feedback will be saved and synced when online.');
    }
    
    /**
     * Start periodic sync interval
     */
    function startSyncInterval() {
        if (syncIntervalId) {
            clearInterval(syncIntervalId);
        }
        syncIntervalId = setInterval(() => {
            if (navigator.onLine) {
                syncPendingFeedback();
            }
        }, SYNC_INTERVAL);
    }
    
    /**
     * Stop sync interval
     */
    function stopSyncInterval() {
        if (syncIntervalId) {
            clearInterval(syncIntervalId);
            syncIntervalId = null;
        }
    }
    
    /**
     * Get offline queue from localStorage
     */
    function getQueue() {
        try {
            const queueJson = localStorage.getItem(OFFLINE_QUEUE_KEY);
            return queueJson ? JSON.parse(queueJson) : [];
        } catch (e) {
            console.error('Error reading offline queue:', e);
            return [];
        }
    }
    
    /**
     * Save queue to localStorage
     */
    function saveQueue(queue) {
        try {
            localStorage.setItem(OFFLINE_QUEUE_KEY, JSON.stringify(queue));
        } catch (e) {
            console.error('Error saving offline queue:', e);
        }
    }
    
    /**
     * Add feedback to offline queue
     */
    function queueFeedback(feedbackData) {
        const queue = getQueue();
        const feedbackItem = {
            ...feedbackData,
            queued_at: new Date().toISOString(),
            id: feedbackData.audio_id || Date.now().toString()
        };
        queue.push(feedbackItem);
        saveQueue(queue);
        console.log('📦 Feedback queued offline:', feedbackItem.id);
        return feedbackItem.id;
    }
    
    /**
     * Remove feedback from queue
     */
    function removeFromQueue(feedbackId) {
        const queue = getQueue();
        const filtered = queue.filter(item => item.id !== feedbackId);
        saveQueue(filtered);
        return queue.length - filtered.length; // Return number removed
    }
    
    /**
     * Sync pending feedback when online
     */
    async function syncPendingFeedback() {
        if (!navigator.onLine) {
            return { synced: 0, failed: 0 };
        }
        
        const queue = getQueue();
        if (queue.length === 0) {
            return { synced: 0, failed: 0 };
        }
        
        console.log(`🔄 Syncing ${queue.length} queued feedback items...`);
        
        let synced = 0;
        let failed = 0;
        const failedItems = [];
        
        for (const item of queue) {
            try {
                const url = (window.APP_CONFIG && window.APP_CONFIG.getApiUrl) 
                    ? window.APP_CONFIG.getApiUrl('/feedback')
                    : '/feedback';
                
                const response = await fetch(url, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify({
                        audio_id: item.audio_id,
                        predicted_label: item.predicted_label,
                        correct_label: item.correct_label,
                        is_correct: item.is_correct
                    })
                });
                
                if (response.ok) {
                    removeFromQueue(item.id);
                    synced++;
                    console.log('✅ Synced feedback:', item.id);
                } else {
                    failed++;
                    failedItems.push(item);
                    console.warn('❌ Failed to sync feedback:', item.id, response.status);
                }
            } catch (error) {
                failed++;
                failedItems.push(item);
                console.error('❌ Error syncing feedback:', item.id, error);
            }
        }
        
        // If some failed, keep them in queue but update the queue
        if (failed > 0 && synced > 0) {
            // Remove only successfully synced items
            const remaining = queue.filter(item => 
                failedItems.some(failed => failed.id === item.id)
            );
            saveQueue(remaining);
        }
        
        if (synced > 0) {
            console.log(`✅ Synced ${synced} feedback items`);
            if (typeof showToast === 'function') {
                showToast(`Synced ${synced} feedback items`);
            }
        }
        
        return { synced, failed };
    }
    
    /**
     * Check if currently online
     */
    function isOnline() {
        return navigator.onLine !== false;
    }
    
    /**
     * Get queue status
     */
    function getQueueStatus() {
        const queue = getQueue();
        return {
            count: queue.length,
            items: queue,
            isOnline: isOnline()
        };
    }
    
    /**
     * Clear queue (use with caution)
     */
    function clearQueue() {
        saveQueue([]);
        console.log('🗑️ Offline queue cleared');
    }
    
    // Export to window
    window.OfflineManager = {
        init: init,
        queueFeedback: queueFeedback,
        syncPendingFeedback: syncPendingFeedback,
        getQueueStatus: getQueueStatus,
        clearQueue: clearQueue,
        isOnline: isOnline
    };
    
    // Auto-initialize when DOM is ready
    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', init);
    } else {
        init();
    }
})();