const fs = require('fs');
const readline = require('readline');

class CsvToHtmlConverter {
    /**
     * Erstellt eine HTML-Tabelle aus einer CSV-Datei
     * @param {string} csvFilePath Pfad zur CSV-Datei
     * @returns {Promise<string>} HTML-Tabelle als String
     */
    async convertToHtml(csvFilePath) {
        if (!fs.existsSync(csvFilePath)) {
            throw new Error(`CSV file not found: ${csvFilePath}`);
        }

        const fileStream = fs.createReadStream(csvFilePath);
        const rl = readline.createInterface({
            input: fileStream,
            crlfDelay: Infinity,
        });

        let html = this.getHtmlHeader();
        let isFirstLine = true;

        for await (const line of rl) {
            const cells = this.parseCsvLine(line);

            if (isFirstLine) {
                html += '<thead><tr>';
                cells.forEach(cell => {
                    html += `<th>${this.escapeHtml(cell)}</th>`;
                });
                html += '</tr></thead><tbody>';
                isFirstLine = false;
            } else {
                html += '<tr>';
                cells.forEach(cell => {
                    html += `<td>${this.escapeHtml(cell)}</td>`;
                });
                html += '</tr>';
            }
        }

        html += '</tbody></table>';
        return html;
    }

    /**
     * Gibt das HTML- und CSS-Headergerüst für die Tabelle zurück
     */
    getHtmlHeader() {
        return `
        <style>
            table {
                border-collapse: collapse;
                width: 100%;
                font-family: Arial, sans-serif;
            }
            th, td {
                border: 1px solid #ccc;
                padding: 6px 12px;
                text-align: left;
            }
            thead {
                background-color: #f2f2f2;
            }
            tbody tr:nth-child(odd) {
                background-color: #ffffff;
            }
            tbody tr:nth-child(even) {
                background-color: #f9f9f9;
            }
        </style>
        <table>
        `;
    }

    /**
     * Wandelt eine CSV-Zeile in Felder um
     * @param {string} line
     * @returns {string[]}
     */
    parseCsvLine(line) {
        // Für einfache Fälle (Kommas, kein Quote-Parsing)
        return line.split(',').map(field => field.trim());
    }

    /**
     * Wandelt Sonderzeichen in HTML-Entities um
     * @param {string} text
     * @returns {string}
     */
    escapeHtml(text) {
        return String(text)
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;')
            .replace(/"/g, '&quot;');
    }
}

module.exports = CsvToHtmlConverter;