import {NachklangFeedbackDB} from '../Feedback.db.js';
import {formatDatetime} from '../feedback.dates.js';

const CSV_SEPARATOR = ';';
const UTF8_BOM = '';

/**
 * RFC 4180 field escaping for a `;`-separated CSV, plus a formula-injection
 * guard: a field starting with = + - @ gets a leading apostrophe so
 * German-locale Excel never evaluates it as a formula.
 */
export const escapeCsvField = (value: string | number | null | undefined): string => {
	let str = value === null || value === undefined ? '' : String(value);
	str = str.replace(/\r\n|\r|\n/g, ' ');

	if (/^[=+\-@]/.test(str)) {
		str = `'${str}`;
	}

	if (str.includes(CSV_SEPARATOR) || str.includes('"')) {
		str = `"${str.replace(/"/g, '""')}"`;
	}

	return str;
};

const buildCsv = (headers: string[], rows: (string | number | null | undefined)[][]): string => {
	const lines = [headers.map(escapeCsvField).join(CSV_SEPARATOR)];
	for (const row of rows) {
		lines.push(row.map(escapeCsvField).join(CSV_SEPARATOR));
	}
	return UTF8_BOM + lines.join('\r\n');
};

export const buildResponsesCsv = async (eventId: number): Promise<string> => {
	let conn = await NachklangFeedbackDB.getConnection();
	try {
		const rows = await conn.query(
			`SELECT sa.submission_id, s.submitted_at, sa.question_label_snapshot, sa.question_type,
				sa.song_title_snapshot, sa.rating, sa.text_answer
			FROM submission_answers sa
			INNER JOIN submissions s ON s.submission_id = sa.submission_id
			WHERE sa.event_id = ?
			ORDER BY sa.submission_id ASC`,
			[eventId]
		);
		return buildCsv(
			['submission_id', 'submitted_at', 'question_label', 'question_type', 'song_title', 'rating', 'text_answer'],
			rows.map((r: any) => [r.submission_id, formatDatetime(r.submitted_at), r.question_label_snapshot, r.question_type, r.song_title_snapshot, r.rating, r.text_answer])
		);
	} finally {
		await conn.end();
	}
};

export const buildGuestBookCsv = async (eventId: number): Promise<string> => {
	let conn = await NachklangFeedbackDB.getConnection();
	try {
		const rows = await conn.query(
			'SELECT entry_id, created_at, display_name, message FROM guest_book_entries WHERE event_id = ? ORDER BY created_at ASC',
			[eventId]
		);
		return buildCsv(
			['entry_id', 'submitted_at', 'display_name', 'message'],
			rows.map((r: any) => [r.entry_id, formatDatetime(r.created_at), r.display_name, r.message])
		);
	} finally {
		await conn.end();
	}
};