import { parse } from 'csv-parse';
import fs from 'node:fs';
import zlib from 'node:zlib';
import { pipeline } from 'node:stream/promises';
import { Writable } from 'node:stream';
import mysql from 'mysql2/promise';
import './lib/dotenv.js';

const BASE_URL = 'https://files.data.gouv.fr/geo-dvf/latest/csv';
const GEODVF_DIR = 'geodvf';

const connectionString = process.env.MYSQL;
if (!connectionString) {
    throw new Error('MYSQL environment variable not set');
}

// parse mysql connection string
const url = new URL(connectionString);
const dbConfig = {
    host: url.hostname,
    port: url.port || 3306,
    user: url.username,
    password: decodeURIComponent(url.password),
    database: url.pathname.slice(1),
    charset: 'utf8mb4',
};

async function getYearsOnServer() {
    const res = await fetch(`${BASE_URL}/`);
    const html = await res.text();
    const years = [];
    for (const match of html.matchAll(/href="(\d{4})\/"/g)) {
        years.push(Number(match[1]));
    }
    return years.toSorted();
}

async function getYearsInDb(connection) {
    const [rows] = await connection.query('SELECT DISTINCT YEAR(date_mutation) as annee FROM dvf ORDER BY annee');
    return rows.map(r => r.annee);
}

async function downloadYear(year) {
    const file = `${GEODVF_DIR}/${year}.csv.gz`;
    if (fs.existsSync(file)) {
        console.log(`  ${file} déjà présent, skip download`);
        return file;
    }
    const url = `${BASE_URL}/${year}/full.csv.gz`;
    console.log(`  Téléchargement ${url} ...`);
    const res = await fetch(url);
    if (!res.ok) throw new Error(`HTTP ${res.status} pour ${url}`);
    fs.mkdirSync(GEODVF_DIR, { recursive: true });
    const dest = fs.createWriteStream(file);
    await pipeline(res.body, dest);
    const size = fs.statSync(file).size;
    console.log(`  Téléchargé ${file} (${(size / 1024 / 1024).toFixed(1)} Mo)`);
    return file;
}

async function importYear(connection, year, file) {
    console.log(`  Parsing et insertion de ${file} ...`);

    let columns = null;
    let inserted = 0;
    const BATCH_SIZE = 5000;
    let batch = [];

    const flush = async () => {
        if (batch.length === 0) return;
        const placeholders = batch.map(row => `(${row.map(() => '?').join(', ')})`).join(', ');
        const sql = `INSERT INTO dvf (${columns.join(', ')}) VALUES ${placeholders}`;
        const flat = batch.flat();
        await connection.query(sql, flat);
        inserted += batch.length;
        if (inserted % 100_000 < BATCH_SIZE) {
            process.stdout.write(`  ... ${inserted.toLocaleString()} lignes insérées\r`);
        }
        batch = [];
    };

    const parser = parse({ delimiter: ',', columns: true });

    const writer = new Writable({
        objectMode: true,
        async write(record, _encoding, callback) {
            try {
                if (!columns) {
                    columns = Object.keys(record).map(col => `\`${col}\``);
                }
                const values = Object.values(record).map(v => (v === '' ? null : v));
                batch.push(values);
                if (batch.length >= BATCH_SIZE) {
                    await flush();
                }
                callback();
            } catch (err) {
                callback(err);
            }
        },
        async final(callback) {
            try {
                await flush();
                callback();
            } catch (err) {
                callback(err);
            }
        },
    });

    const input = fs.createReadStream(file).pipe(zlib.createGunzip());
    await pipeline(input, parser, writer);

    console.log(`  ${inserted.toLocaleString()} lignes insérées pour ${year}`);
    return inserted;
}

async function main() {
    const forceYear = process.argv[2] ? Number(process.argv[2]) : null;

    console.log('Connexion à la base...');
    const connection = await mysql.createConnection(dbConfig);

    console.log('Vérification des années sur le serveur...');
    const serverYears = await getYearsOnServer();
    console.log(`Années disponibles : ${serverYears.join(', ')}`);

    const dbYears = await getYearsInDb(connection);
    console.log(`Années en base : ${dbYears.join(', ')}`);

    let missing = serverYears.filter(y => !dbYears.includes(y));
    if (forceYear) {
        missing = [forceYear];
        console.log(`Mode forcé : import de ${forceYear}`);
    }

    if (missing.length === 0) {
        console.log('Tout est à jour !');
        await connection.end();
        return;
    }

    console.log(`Années manquantes : ${missing.join(', ')}`);

    for (const year of missing) {
        console.log(`\n=== ${year} ===`);
        const file = await downloadYear(year);
        await importYear(connection, year, file);
    }

    console.log('\nTerminé !');
    await connection.end();
}

await main();