const fs = require('fs').promises;
const fsSync = require('fs');
const pth = require('path');
const { closeButton } = require('../utility/close');

const dataDir = pth.join(__dirname, '../../../data/');
const PAGE_SIZE = 5;

/**
 * Raccoglie ricorsivamente tutti i file nella cartella data/
 */
async function listDataFiles() {
    const results = [];

    async function scan(dir, prefix) {
        const entries = await fs.readdir(dir, { withFileTypes: true });
        for (const entry of entries) {
            const fullPath = pth.join(dir, entry.name);
            if (entry.isDirectory()) {
                await scan(fullPath, prefix ? `${prefix}/${entry.name}` : entry.name);
            } else {
                const stat = await fs.stat(fullPath);
                results.push({
                    name: prefix ? `${prefix}/${entry.name}` : entry.name,
                    path: fullPath,
                    size: stat.size,
                    modified: stat.mtime,
                    lines: null // calcolato on-demand
                });
            }
        }
    }

    try {
        await scan(dataDir, '');
    } catch (e) {
        console.error('[BACKUP] Errore scan:', e.message);
    }

    return results.sort((a, b) => b.modified - a.modified);
}

function formatSize(bytes) {
    if (bytes < 1024) return `${bytes} B`;
    if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
    return `${(bytes / (1024 * 1024)).toFixed(2)} MB`;
}

function buildPage(files, page, userMessageId) {
    const totalPages = Math.ceil(files.length / PAGE_SIZE);
    const start = page * PAGE_SIZE;
    const pageFiles = files.slice(start, start + PAGE_SIZE);

    const keyboard = pageFiles.map(f => {
        const date = new Date(f.modified).toLocaleDateString('it-IT', {
            day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit'
        });
        const label = `${f.name}  (${formatSize(f.size)}, ${date})`;
        // Encode file name as base64-safe identifier (index in full list)
        const fileIdx = files.indexOf(f);
        return [{ text: label, callback_data: `bkfile:${fileIdx}:${userMessageId}` }];
    });

    // Navigation row
    const navRow = [];
    if (page > 0) {
        navRow.push({ text: '<< Prec', callback_data: `bkpage:${page - 1}:${userMessageId}` });
    }
    navRow.push({ text: `${page + 1}/${totalPages}`, callback_data: `bknoop:0` });
    if (page < totalPages - 1) {
        navRow.push({ text: 'Succ >>', callback_data: `bkpage:${page + 1}:${userMessageId}` });
    }
    keyboard.push(navRow);

    // Close button
    keyboard.push([{ text: '<- Chiudi', callback_data: `close:${userMessageId}` }]);

    return keyboard;
}

module.exports = {
    command: 'backup',
    handler: async (bot, msg) => {
        const chatId = msg.chat.id;
        const files = await listDataFiles();

        if (files.length === 0) {
            bot.sendMessage(chatId, 'Nessun file nella cartella data.', {
                reply_to_message_id: msg.message_id,
                reply_markup: closeButton(msg.message_id)
            });
            return;
        }

        const text = `*Backup & Logs*\n\n${files.length} file disponibili nella cartella data.\n_Seleziona un file per info e download._`;
        const keyboard = buildPage(files, 0, msg.message_id);

        bot.sendMessage(chatId, text, {
            parse_mode: 'Markdown',
            reply_to_message_id: msg.message_id,
            reply_markup: { inline_keyboard: keyboard }
        });
    },

    // Export utilities for callbacks
    listDataFiles,
    formatSize,
    buildPage,
    PAGE_SIZE
};