import fetch from 'node-fetch';
import cron from 'node-cron';
import fs from 'fs';
import path from 'path';

// Configuration
const CONFIG = {
    API_URL: 'https://gateway.bibliocommons.com/v2/libraries/sandiego/bibs/S161C1805116/availability',
    BRANCH_NAME: 'Rancho Penasquitos',
    NTFY_TOPIC: 'sdparkpass', // Change this to your preferred topic
    NTFY_SERVER: 'https://ntfy.sh', // Change this if using your own ntfy server
    STATE_FILE: path.join(process.cwd(), 'last_availability.json'),
    POLL_INTERVAL: '0 * * * *', // Every hour at minute 0
    USER_AGENT: 'SD Park Pass Monitor/1.0'
};

// Merge in any overrides from config.js
import { CONFIG_OVERRIDE } from './config.js';
Object.assign(CONFIG, CONFIG_OVERRIDE);

/**
 * Loads the last known availability count from the state file
 * @returns {number} The last availability count, or 0 if file doesn't exist
 */
function loadLastAvailabilityCount() {
    try {
        if (fs.existsSync(CONFIG.STATE_FILE)) {
            const data = JSON.parse(fs.readFileSync(CONFIG.STATE_FILE, 'utf8'));
            return data.availabilityCount || 0;
        }
    } catch (error) {
        console.error('Error reading state file:', error.message);
    }
    return 0;
}

/**
 * Saves the current availability count to the state file
 * @param {number} count - The current availability count
 * @param {Object} metadata - Additional metadata to save
 */
function saveAvailabilityCount(count, metadata = {}) {
    try {
        const data = {
            availabilityCount: count,
            lastUpdated: new Date().toISOString(),
            ...metadata
        };
        fs.writeFileSync(CONFIG.STATE_FILE, JSON.stringify(data, null, 2));
        console.log(`Saved availability count: ${count}`);
    } catch (error) {
        console.error('Error saving state file:', error.message);
    }
}

/**
 * Sends a notification via ntfy
 * @param {string} title - Notification title
 * @param {string} message - Notification message
 * @param {string} priority - Priority level (low, default, high)
 */
async function sendNotification(title, message, priority = 'default') {
    try {
        const response = await fetch(`${CONFIG.NTFY_SERVER}/${CONFIG.NTFY_TOPIC}`, {
            method: 'POST',
            headers: {
                'Title': title,
                'Priority': priority,
                'Tags': 'park,pass,library',
                'User-Agent': CONFIG.USER_AGENT
            },
            body: message
        });

        if (response.ok) {
            console.log('Notification sent successfully');
        } else {
            console.error('Failed to send notification:', response.status, response.statusText);
        }
    } catch (error) {
        console.error('Error sending notification:', error.message);
    }
}

/**
 * Counts available or recently returned items for the specified branch
 * @param {Object} apiResponse - The API response object
 * @returns {number} Count of available/recently returned items
 */
function countAvailableItems(apiResponse) {
    try {
        if (!apiResponse?.entities?.bibItems) {
            console.log('No bibItems found in API response');
            return 0;
        }

        let availableCount = 0;
        
        // Loop through all bibItems in the response
        const bibItems = apiResponse.entities.bibItems;
        for (const itemId in bibItems) {
            const item = bibItems[itemId];
            
            // Check if this is the Rancho Penasquitos branch
            if (item.branchName?.includes(CONFIG.BRANCH_NAME)) {
                // Check if item is available (statusType is not "UNAVAILABLE")
                if (item.availability?.statusType && 
                    item.availability.statusType !== 'UNAVAILABLE') {
                    
                    availableCount++;
                    console.log(`Found available item at ${CONFIG.BRANCH_NAME}: ${item.availability.statusType} (${item.availability.libraryStatus || 'No status'})`);
                }
                // Also check for items with no dueDate (not checked out)
                else if (item.availability && 
                         !item.dueDate && 
                         item.branchName.includes(CONFIG.BRANCH_NAME)) {
                    
                    availableCount++;
                    console.log(`Found available item at ${CONFIG.BRANCH_NAME}: Available (no due date)`);
                }
            }
        }

        return availableCount;
    } catch (error) {
        console.error('Error counting available items:', error.message);
        return 0;
    }
}

/**
 * Fetches availability data from the library API
 * @returns {Object|null} The API response or null if failed
 */
async function fetchAvailabilityData() {
    try {
        console.log(`Fetching availability data from: ${CONFIG.API_URL}`);
        
        const response = await fetch(CONFIG.API_URL, {
            headers: {
                'User-Agent': CONFIG.USER_AGENT,
                'Accept': 'application/json'
            }
        });

        if (!response.ok) {
            throw new Error(`HTTP ${response.status}: ${response.statusText}`);
        }

        const data = await response.json();
        console.log('Successfully fetched availability data');
        return data;
    } catch (error) {
        console.error('Error fetching availability data:', error.message);
        return null;
    }
}

/**
 * Main monitoring function that checks availability and sends notifications
 */
async function checkAvailability() {
    console.log('\n--- Starting availability check ---');
    console.log(`Time: ${new Date().toISOString()}`);
    
    try {
        // Fetch current availability data
        const apiResponse = await fetchAvailabilityData();
        if (!apiResponse) {
            console.log('Failed to fetch data, skipping this check');
            return;
        }

        // Count currently available items
        const currentCount = countAvailableItems(apiResponse);
        console.log(`Current available items at ${CONFIG.BRANCH_NAME}: ${currentCount}`);

        // Load previous count
        const previousCount = loadLastAvailabilityCount();
        console.log(`Previous available items: ${previousCount}`);

        // Check if availability increased (new items became available)
        if (currentCount > previousCount) {
            const newItems = currentCount - previousCount;
            const title = 'Parking Pass Available!';
            const message = `${newItems} new parking pass(es) became available at ${CONFIG.BRANCH_NAME} branch. Total available: ${currentCount}`;

            console.log(`📢 Sending notification: ${message}`);
            await sendNotification(title, message, 'high');
        } else if (currentCount < previousCount) {
            console.log(`Availability decreased by ${previousCount - currentCount} parking pass(es)`);
        } else {
            console.log('No change in availability');
        }

        // Save current state
        saveAvailabilityCount(currentCount, {
            previousCount,
            branch: CONFIG.BRANCH_NAME,
            apiUrl: CONFIG.API_URL
        });

    } catch (error) {
        console.error('Error in checkAvailability:', error.message);
        
        // Send error notification
        await sendNotification(
            'SD Park Pass Monitor Error',
            `Error checking availability: ${error.message}`,
            'low'
        );
    }
    
    console.log('--- Availability check completed ---\n');
}

/**
 * Initializes the monitoring service
 */
async function initialize() {
    console.log('🚀 SD Park Pass Monitor Starting...');
    console.log(`Monitoring: ${CONFIG.API_URL}`);
    console.log(`Branch: ${CONFIG.BRANCH_NAME}`);
    console.log(`Ntfy Topic: ${CONFIG.NTFY_TOPIC}`);
    console.log(`Poll Interval: ${CONFIG.POLL_INTERVAL}`);
    
    // Send startup notification
    await sendNotification(
        'SD Park Pass Monitor Started',
        `Now monitoring ${CONFIG.BRANCH_NAME} branch for park pass availability`,
        'low'
    );
    
    // Run initial check
    console.log('Running initial availability check...');
    await checkAvailability();
    
    // Schedule hourly checks
    console.log('Setting up hourly monitoring schedule...');
    cron.schedule(CONFIG.POLL_INTERVAL, checkAvailability, {
        scheduled: true,
        timezone: "America/Los_Angeles" // San Diego timezone
    });
    
    console.log('✅ SD Park Pass Monitor is now running!');
    console.log('Press Ctrl+C to stop the monitor');
}

/**
 * Graceful shutdown handler
 */
process.on('SIGINT', async () => {
    console.log('\n🛑 Shutting down SD Park Pass Monitor...');
    
    await sendNotification(
        'SD Park Pass Monitor Stopped',
        'SD Park Pass monitoring has been stopped',
        'low'
    );
    
    console.log('Goodbye! 👋');
    process.exit(0);
});

// Handle uncaught errors
process.on('uncaughtException', async (error) => {
    console.error('Uncaught Exception:', error);
    await sendNotification(
        'SD Park Pass Monitor Crashed',
        `Critical error: ${error.message}`,
        'high'
    );
    process.exit(1);
});

// Start the application
if (import.meta.url === `file://${process.argv[1]}`) {
    initialize().catch(console.error);
}

export { checkAvailability, sendNotification, CONFIG, countAvailableItems, loadLastAvailabilityCount, saveAvailabilityCount };