#!/usr/bin/env node

// Manual update script for semester timetable data
// Run this script manually each semester to update timetable IDs and dates
// Usage: node src/scripts/update-semester-data.js

import https from 'https';
import fs from 'fs';

// Get current academic year
function getCurrentAcademicYear() {
    const now = new Date();
    const currentYear = now.getFullYear();
    const currentMonth = now.getMonth(); // 0-based
    
    // Academic year starts in September, but August belongs to the new year
    const startYear = currentMonth >= 7 ? currentYear : currentYear - 1;
    const endYear = startYear + 1;
    
    return { startYear, endYear };
}

// Fetch webpage content
function fetchPage(url) {
    return new Promise((resolve, reject) => {
        https.get(url, (res) => {
            let data = '';
            
            res.on('data', (chunk) => {
                data += chunk;
            });
            
            res.on('end', () => {
                resolve(data);
            });
        }).on('error', (err) => {
            reject(err);
        });
    });
}

// Parse timetable IDs from the schedule page
async function parseTimetableIds() {
    try {
        const html = await fetchPage('https://www.dm.unipi.it/didattica/lezioni-esami/orario-delle-lezioni/');
        const ids = {};
        
        // Extract links with their text to match correctly
        const linkPattern = /<a[^>]*href="[^"]*linkCalendarioId=([a-f0-9]{24})"[^>]*>([^<]+)<\/a>/g;
        const links = [...html.matchAll(linkPattern)];
        
        for (const [fullMatch, id, text] of links) {
            const cleanText = text.trim();
            
            if (cleanText === 'Triennale I anno') {
                ids['anno-1'] = id;
            } else if (cleanText === 'Triennale II anno') {
                ids['anno-2'] = id;
            } else if (cleanText === 'Triennale III anno') {
                ids['anno-3'] = id;
            } else if (cleanText === 'Magistrale') {
                ids['magistrale'] = id;
            }
        }
        
        return Object.keys(ids).length > 0 ? ids : null;
    } catch (error) {
        console.error('Error parsing timetable IDs:', error.message);
        return null;
    }
}

// Parse semester start date from calendar page
async function parseSemesterStartDate() {
    try {
        const { startYear, endYear } = getCurrentAcademicYear();
        const currentMonth = new Date().getMonth();
        const currentSemester = currentMonth >= 1 && currentMonth <= 6 ? 2 : 1;
        
        const url = `https://www.dm.unipi.it/didattica/lezioni-esami/calendario-delle-attivita-didattiche/calendario-delle-attivita-didattiche-a-a-${startYear}-${endYear.toString().slice(-2)}/`;
        
        const html = await fetchPage(url);
        
        // Look for the appropriate semester start date
        const semesterText = currentSemester === 1 ? 'I semestre' : 'II semestre';
        const semesterRegex = new RegExp(`Lezioni\\s+${semesterText}.*?(\\d{1,2}\\s+\\w+\\s+\\d{4})`, 'si');
        const match = html.match(semesterRegex);
        
        if (match) {
            return match[1];
        } else {
            console.error(`Could not find ${semesterText} start date in calendar`);
            return null;
        }
    } catch (error) {
        console.error('Error parsing semester start date:', error.message);
        return null;
    }
}

// Find the first Monday after a given date string
function getFirstMondayAfter(dateStr) {
    // Parse Italian date format (e.g., "24 settembre 2025")
    const [day, monthName, year] = dateStr.split(' ');
    
    const monthMap = {
        'gennaio': 0, 'febbraio': 1, 'marzo': 2, 'aprile': 3,
        'maggio': 4, 'giugno': 5, 'luglio': 6, 'agosto': 7,
        'settembre': 8, 'ottobre': 9, 'novembre': 10, 'dicembre': 11
    };
    
    const month = monthMap[monthName.toLowerCase()];
    if (month === undefined) {
        throw new Error(`Unknown month: ${monthName}`);
    }
    
    const startDate = new Date(parseInt(year), month, parseInt(day));
    const dayOfWeek = startDate.getDay(); // 0=Sunday, 1=Monday, etc.
    
    // Calculate days to add to get to the next Monday
    let daysToAdd;
    if (dayOfWeek === 0) { // Sunday
        daysToAdd = 1; // Next day is Monday
    } else if (dayOfWeek === 1) { // Monday
        daysToAdd = 7; // Next Monday
    } else { // Tuesday-Saturday (2-6)
        daysToAdd = 8 - dayOfWeek; // Days until next Monday
    }
    
    const result = new Date(startDate);
    result.setDate(startDate.getDate() + daysToAdd);
    
    // Create a new date in UTC to avoid timezone issues with the calendar
    return new Date(Date.UTC(result.getFullYear(), result.getMonth(), result.getDate()));
}

// Format date for button text (Italian format)
function formatDateForButton(date) {
    const day = date.getUTCDate();
    const monthNames = [
        'gennaio', 'febbraio', 'marzo', 'aprile', 'maggio', 'giugno',
        'luglio', 'agosto', 'settembre', 'ottobre', 'novembre', 'dicembre'
    ];
    const month = monthNames[date.getUTCMonth()];
    
    return `${day} ${month}`;
}

// Main function
async function updateAcademicData() {
    const [timetableIds, semesterStartDateStr] = await Promise.all([
        parseTimetableIds(),
        parseSemesterStartDate()
    ]);
    
    // Fail fast if parsing failed
    if (!timetableIds) {
        throw new Error('Failed to parse timetable IDs from the website');
    }
    
    if (!semesterStartDateStr) {
        throw new Error('Failed to parse semester start date from the calendar');
    }
    
    const firstMonday = getFirstMondayAfter(semesterStartDateStr);
    
    const semesterData = {
        timetableIds,
        semesterStartDateStr,
        firstMondayDate: firstMonday.toISOString(),
        buttonText: `Vai al ${formatDateForButton(firstMonday)}! 🚀`,
        lastUpdated: new Date().toISOString(),
        academicYear: getCurrentAcademicYear()
    };

    // Save to src/semester-data.json
    fs.writeFileSync('src/semester-data.json', JSON.stringify(semesterData, null, 2));

    console.log('✅ Semester data updated successfully');
}

// Run the script
updateAcademicData().catch(error => {
    console.error('💥 Script failed:', error);
    process.exit(1);
});