import forge from 'node-forge'

export class CPCard {

	private static readonly _pubKey = '-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEArBZ1NNjvszen6BNWsgyDUJvDUZDtvR4jKNQtEwW1iW7hqJr0TdD8hgTxw3DfH+Hi/7ZjSNdH5EfChvgVW9wtTxrvUXCOyJndReq7qNMo94lHpoSIVW82dp4rcDB4kU+q+ekh5rj9Oj6EReCTuXr3foLLBVpH0/z1vtgcCfQzsLlGkSTwgLqASTUsuzfI8viVUbxE1a+600hN0uBh/CYKoMnCp/EhxV8g7eUmNsWjZyiUrV8AA/5DgZUCB+jqGQT/Dhc8e21tAkQ3qan/jQ5i/QYocA/4jW3WQAldMLj0PA36kINEbuDKq8qRh25v+k4qyjb7Xp4W2DywmNtG3Q20MQIDAQAB\n-----END PUBLIC KEY-----'

	private static readonly _keyVersion = '04'

	private constructor(
		private _number: string,
		private _expirationDate: string,
		private _cvv: string
	) {
	}

	private static getPublicKey = () => forge.pki.publicKeyFromPem(CPCard._pubKey) as forge.pki.rsa.PublicKey

	static create = (number: string, expirationDate: string, cvv: string) => new Promise<CPCard>((resolve, reject) => {
		if (!CPCard.isValidNumber(number)) {
			return reject('Wrong card number')
		}

		if (!CPCard.isValidExpDate(expirationDate)) {
			return reject('Wrong expiration date')
		}

		return resolve(new CPCard(number, expirationDate, cvv))
	})

	cardCryptogram = (publicId: string) => new Promise<string> ((resolve, _) => {
		const cardNumber = CPCard.prepareCardNumber(this._number)
		const shortNumber = cardNumber.substring(0, 6) + cardNumber.substring(cardNumber.length - 4)
		const exp = this._expirationDate.substring(2, 4) + this._expirationDate.substring(0, 2)
		const s = `${cardNumber}@${exp}@${this._cvv}@${publicId}`
		const forgeBytes = CPCard.getPublicKey().encrypt(s, 'RSA-OAEP')
		const forge64 = '02' +
			shortNumber +
			exp + CPCard._keyVersion +
			forge.util.encode64(forgeBytes)

		return resolve(forge64)
	})

	static isValidNumber = (inputNum: string): boolean => {
		let sum = 0
		let i: number
		const number = CPCard.prepareCardNumber(inputNum)

		if (number.trim().length === 0) {
			return false
		}

		if (number.length % 2 == 0) {
			for (i = 0; i < number.length; i += 2) {
				let c = parseInt(number.substring(i, i + 1))
				c *= 2
				if (c > 9) {
					c -= 9
				}
				sum += c
				sum += parseInt(number.substring(i + 1, i + 2))
			}
		}
		else {
			for (i = 1; i < number.length; i += 2) {
				let c = parseInt(number.substring(i, i + 1))
				c *= 2
				if (c > 9) {
					c -= 9
				}
				sum += c
				sum += parseInt(number.substring(i - 1, i))
			}

			sum += parseInt(number.substring(i - 1, i))
		}

		return sum % 10 === 0
	}

	static isValidExpDate = (inputDate: string) => {
		if (inputDate.length !== 4) {
			return false
		}

		// todo check between 1 and 12
		const month = parseInt(inputDate.substr(0, 2))
		const year = parseInt(inputDate.substr(2, 2)) + 2000

		const dateToCompare = new Date(year, month).getTime() - 1
		return dateToCompare > new Date().getTime()
	}

	private static prepareCardNumber = (cardNumber: string) => cardNumber.split(/\s/).join('')
}