package bip39

import (
	"bytes"
	"testing"
)

// hexNibble returns the value of a single hex digit, or -1 if invalid.
func hexNibble(c byte) int {
	if c >= '0' && c <= '9' {
		return int(c - '0')
	}
	if c >= 'a' && c <= 'f' {
		return int(c-'a') + 10
	}
	if c >= 'A' && c <= 'F' {
		return int(c-'A') + 10
	}
	return -1
}

func hexDecode(s string) []byte {
	if len(s)%2 != 0 {
		return nil
	}
	out := []byte{:len(s)/2}
	for i := 0; i < len(s); i += 2 {
		hi := hexNibble(s[i])
		lo := hexNibble(s[i+1])
		if hi < 0 || lo < 0 {
			return nil
		}
		out[i/2] = byte(hi<<4 | lo)
	}
	return out
}

// TestBIP39EnglishVectors runs a subset of Trezor English vectors covering
// entropy → mnemonic and mnemonic → seed. Source:
// https://github.com/trezor/python-mnemonic/blob/master/vectors.json
// Subset is the 16-byte (128-bit / 12-word) entries.
func TestBIP39EnglishVectors(t *testing.T) {
	type vec struct {
		entropy  string
		mnemonic string
		seed     string // PBKDF2-SHA512(phrase, "mnemonic"+"TREZOR", 2048, 64)
	}
	vectors := []vec{
		{
			entropy:  "00000000000000000000000000000000",
			mnemonic: "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about",
			seed:     "c55257c360c07c72029aebc1b53c05ed0362ada38ead3e3e9efa3708e53495531f09a6987599d18264c1e1c92f2cf141630c7a3c4ab7c81b2f001698e7463b04",
		},
		{
			entropy:  "7f7f7f7f7f7f7f7f7f7f7f7f7f7f7f7f",
			mnemonic: "legal winner thank year wave sausage worth useful legal winner thank yellow",
			seed:     "2e8905819b8723fe2c1d161860e5ee1830318dbf49a83bd451cfb8440c28bd6fa457fe1296106559a3c80937a1c1069be3a3a5bd381ee6260e8d9739fce1f607",
		},
		{
			entropy:  "80808080808080808080808080808080",
			mnemonic: "letter advice cage absurd amount doctor acoustic avoid letter advice cage above",
			seed:     "d71de856f81a8acc65e6fc851a38d4d7ec216fd0796d0a6827a3ad6ed5511a30fa280f12eb2e47ed2ac03b5c462a0358d18d69fe4f985ec81778c1b370b652a8",
		},
		{
			entropy:  "ffffffffffffffffffffffffffffffff",
			mnemonic: "zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo wrong",
			seed:     "ac27495480225222079d7be181583751e86f571027b0497b5b5d11218e0a8a13332572917f0f8e5a589620c6f15b11c61dee327651a14c34e18231052e48c069",
		},
	}
	const passphrase = "TREZOR"
	for i, v := range vectors {
		gotMnemonic := EntropyToMnemonic(hexDecode(v.entropy))
		if gotMnemonic != v.mnemonic {
			t.Errorf("vec %d: mnemonic mismatch\n want %s\n got  %s", i, v.mnemonic, gotMnemonic)
		}
		if !ValidateMnemonic(v.mnemonic) {
			t.Errorf("vec %d: ValidateMnemonic returned false on known-good mnemonic", i)
		}
		gotSeed := MnemonicToSeed(v.mnemonic, passphrase)
		wantSeed := hexDecode(v.seed)
		if !bytes.Equal(gotSeed, wantSeed) {
			t.Errorf("vec %d: seed mismatch\n want %x\n got  %x", i, wantSeed, gotSeed)
		}
	}
}

func TestValidateMnemonicRejection(t *testing.T) {
	cases := []struct {
		name  string
		input string
	}{
		{"empty", ""},
		{"11 words", "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon"},
		{"unknown word", "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon xyzzy"},
		{"bad checksum (zoo at end of all-zero entropy)", "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon zoo"},
	}
	for _, c := range cases {
		if ValidateMnemonic(c.input) {
			t.Errorf("ValidateMnemonic should have rejected %q (%s)", c.input, c.name)
		}
	}
}