import DiffieHellman from './diffie-hellman'

describe('diffie-hellman', () => {
    const p = 23
    const g = 5
    const diffieHellman = new DiffieHellman(p, g)

    const alicePrivateKey = 6
    const alicePublicKey = 8

    const bobPrivateKey = 15
    const bobPublicKey = 19

    it('throws an error if the constructor arguments are out of range', () => {
        expect(() => {
            new DiffieHellman(0, 9999)
        }).toThrow()
    })

    it('throws an error if the constructor arguments are not prime', () => {
        expect(() => {
            new DiffieHellman(10, 13)
        }).toThrow()
    })

    it('throws an error if private key is negative', () => {
        expect(() => {
            diffieHellman.getPublicKeyFromPrivateKey(-1)
        }).toThrow()
    })

    it('throws an error if private key is zero', () => {
        expect(() => {
            diffieHellman.getPublicKeyFromPrivateKey(0)
        }).toThrow()
    })

    it('throws an error if private key is one', () => {
        expect(() => {
            diffieHellman.getPublicKeyFromPrivateKey(1)
        }).toThrow()
    })

    it('throws an error if private key equals the modulus parameter p', () => {
        expect(() => {
            diffieHellman.getPublicKeyFromPrivateKey(p)
        }).toThrow()
    })

    it('throws an error if private key is greater than the modulus parameter p', () => {
        expect(() => {
            diffieHellman.getPublicKeyFromPrivateKey(p + 1)
        }).toThrow()
    })

    it('when given a private key, returns the correct public one', () => {
        expect(diffieHellman.getPublicKeyFromPrivateKey(alicePrivateKey)).toEqual(alicePublicKey)
    })

    it('when given a different private key, returns the correct public one', () => {
        expect(diffieHellman.getPublicKeyFromPrivateKey(bobPrivateKey)).toEqual(bobPublicKey)
    })

    it('can generate a shared secret from our private key and their public key', () => {
        const sharedSecret = 2

        expect(diffieHellman.getSharedSecret(alicePrivateKey, bobPublicKey))
            .toEqual(sharedSecret)

        expect(diffieHellman.getSharedSecret(bobPrivateKey, alicePublicKey))
            .toEqual(sharedSecret)
    })
})