const crypto = require('crypto');

// Characters used when generating a random API key: letters, digits and a handful of symbols.
const API_KEY_CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()-_=+';
const API_KEY_LENGTH = 64;

// Characters used when generating a random reader id: letters and digits only.
const READER_ID_CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
const READER_ID_LENGTH = 16;

// Generates a new place id as a random UUID (v4).
function generatePlaceId() {
	return crypto.randomUUID();
}

// Generates a random 16-character alphanumeric reader (access point) id.
// Uses crypto.randomInt for unbiased selection of each character.
function generateReaderId(length = READER_ID_LENGTH) {
	let id = '';
	for (let i = 0; i < length; i++) {
		id += READER_ID_CHARS[crypto.randomInt(READER_ID_CHARS.length)];
	}
	return id;
}

// Generates a random alphanumeric+symbol API key of the given length (default 64 characters).
// Uses crypto.randomInt for unbiased selection of each character (rather than bytes % length,
// which would skew towards characters at the start of the alphabet).
function generateApiKey(length = API_KEY_LENGTH) {
	let key = '';
	for (let i = 0; i < length; i++) {
		key += API_KEY_CHARS[crypto.randomInt(API_KEY_CHARS.length)];
	}
	return key;
}

module.exports = { generatePlaceId, generateApiKey, generateReaderId };