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

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

local testify = testimony.new("== LITLS ECDSA P-256 ==")

testify:that("P-256 keygen produces correct key sizes", function()
	local priv, pub = litls.p256_keygen()
	testimony.assert_equal(32, #priv)
	testimony.assert_equal(65, #pub)
	-- Uncompressed point format: starts with 0x04
	testimony.assert_equal(4, string.byte(pub, 1))
end)

testify:that("P-256 sign/verify round-trip with SHA-256", function()
	local priv, pub = litls.p256_keygen()
	local hash = litls.sha256("test message for ECDSA")

	local sig = litls.p256_ecdsa_sign(hash, priv)
	testimony.assert_equal(64, #sig)

	local ok = litls.p256_ecdsa_verify(hash, pub, sig)
	testimony.assert_equal(true, ok)
end)

testify:that("P-256 verify rejects wrong hash", function()
	local priv, pub = litls.p256_keygen()
	local hash = litls.sha256("correct message")
	local sig = litls.p256_ecdsa_sign(hash, priv)

	local wrong_hash = litls.sha256("wrong message")
	local ok = litls.p256_ecdsa_verify(wrong_hash, pub, sig)
	testimony.assert_equal(false, ok)
end)

testify:that("P-256 verify rejects wrong public key", function()
	local priv1, pub1 = litls.p256_keygen()
	local _, pub2 = litls.p256_keygen()
	local hash = litls.sha256("message")
	local sig = litls.p256_ecdsa_sign(hash, priv1)

	local ok = litls.p256_ecdsa_verify(hash, pub2, sig)
	testimony.assert_equal(false, ok)
end)

-- RFC 6979 A.2.5 - ECDSA with P-256 and SHA-256 known-answer vector
testify:that("P-256 ECDSA deterministic signature (RFC 6979 A.2.5)", function()
	-- Private key from RFC 6979 A.2.5
	local x = unhex("C9AFA9D845BA75166B5C215767B1D6934E50C3DB36E89B127B8A622B120F6721")
	-- Message: "sample"
	local hash = litls.sha256("sample")

	local sig = litls.p256_ecdsa_sign(hash, x)
	-- Expected r and s from RFC 6979 A.2.5
	local r = string.sub(sig, 1, 32)
	local s = string.sub(sig, 33, 64)
	testimony.assert_equal("efd48b2aacb6a8fd1140dd9cd45e81d69d2c877b56aaf991c34d0ea84eaf3716", hex(r))
	testimony.assert_equal("f7cb1c942d657c41d436c7a1b6e29f65f3e900dbb9aff4064dc4ab2f843acda8", hex(s))
end)

testify:that("P-256 multiple keygens produce different keys", function()
	local priv1, pub1 = litls.p256_keygen()
	local priv2, pub2 = litls.p256_keygen()
	-- Extremely unlikely to be equal with random generation
	testimony.assert_equal(true, hex(priv1) ~= hex(priv2))
	testimony.assert_equal(true, hex(pub1) ~= hex(pub2))
end)

testify:conclude()