local testimony = require("testimony")
local litls = require("litls.core")

local hex = litls.hex_encode
local unhex = litls.hex_decode

local testify = testimony.new("== LITLS X25519 ==")

-- RFC 7748 Section 6.1 - X25519 test vector
testify:that("X25519 ECDH (RFC 7748 6.1)", function()
	local alice_priv = unhex("77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a")
	local alice_pub = unhex("8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a")
	local bob_priv = unhex("5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb")
	local bob_pub = unhex("de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f")
	local expected = "4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742"

	-- Alice computes shared secret
	local shared_a = litls.x25519(alice_priv, bob_pub)
	testimony.assert_equal(expected, hex(shared_a))

	-- Bob computes same shared secret
	local shared_b = litls.x25519(bob_priv, alice_pub)
	testimony.assert_equal(expected, hex(shared_b))
end)

-- Base point multiplication: private key -> public key
testify:that("X25519 base point multiplication (RFC 7748 6.1)", function()
	local alice_priv = unhex("77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a")
	local expected = "8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a"

	local pub = litls.x25519_base(alice_priv)
	testimony.assert_equal(expected, hex(pub))
end)

-- Key generation round-trip
testify:that("X25519 keygen round-trip", function()
	local priv_a = litls.random_bytes(32)
	local priv_b = litls.random_bytes(32)
	local pub_a = litls.x25519_base(priv_a)
	local pub_b = litls.x25519_base(priv_b)

	local shared_a = litls.x25519(priv_a, pub_b)
	local shared_b = litls.x25519(priv_b, pub_a)
	testimony.assert_equal(hex(shared_a), hex(shared_b))
end)

testify:conclude()