secret/pkg/agehd/agehd_test.go

//nolint:lll // Test vectors contain long lines
package agehd //nolint:testpackage // white-box test of unexported internals

import (
	"bytes"
	"crypto/rand"
	"errors"
	"fmt"
	"io"
	"strings"
	"testing"

	"filippo.io/age"
	"github.com/tyler-smith/go-bip39"
)

//nolint:dupword // BIP39 test mnemonics repeat words by design
const (
	mnemonic = "abandon abandon abandon abandon abandon " +
		"abandon abandon abandon abandon abandon abandon about"

	// Test xprv from BIP85 test vectors
	testXPRV = "xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb"

	// Additional test mnemonics for comprehensive testing
	testMnemonic12 = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"
	testMnemonic15 = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"
	testMnemonic18 = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"
	testMnemonic21 = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"
	testMnemonic24 = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon art"

	// Test messages used throughout the tests
	testMessageHelloWorld    = "hello world"
	testMessageHelloFromXPRV = "hello from xprv"
	testMessageGeneric       = "test message"
	testMessageBoundary      = "boundary test"
	testMessageBenchmark     = "benchmark test message"
	testMessageLargePattern  = "A"

	// Error messages for validation
	errorMsgNeed32Bytes = "need 32-byte scalar, got"
	errorMsgInvalidXPRV = "invalid-xprv"

	// Test constants for various scenarios
	// Removed testSkipMessage as tests are no longer skipped

	// Numeric constants for testing
	testNumGoroutines = 10
	testNumIterations = 100

	// Large data test constants
	testDataSizeMegabyte = 1024 * 1024 // 1 MB
)

// errIndexOutOfRange guards against runaway loop indices in tests.
var errIndexOutOfRange = errors.New("index out of safe range")

// encryptDecryptRoundTrip encrypts msg to id's recipient and verifies
// that decrypting returns the original message.
func encryptDecryptRoundTrip(t *testing.T, id *age.X25519Identity, msg string) {
	t.Helper()

	var ct bytes.Buffer

	w, err := age.Encrypt(&ct, id.Recipient())
	if err != nil {
		t.Fatalf("encrypt init: %v", err)
	}

	_, err = io.WriteString(w, msg)
	if err != nil {
		t.Fatalf("write: %v", err)
	}

	err = w.Close()
	if err != nil {
		t.Fatalf("encrypt close: %v", err)
	}

	r, err := age.Decrypt(bytes.NewReader(ct.Bytes()), id)
	if err != nil {
		t.Fatalf("decrypt init: %v", err)
	}

	dec, err := io.ReadAll(r)
	if err != nil {
		t.Fatalf("read: %v", err)
	}

	if got := string(dec); got != msg {
		t.Fatalf("round-trip mismatch: %q", got)
	}
}

func TestEncryptDecrypt(t *testing.T) {
	t.Parallel()

	id, err := DeriveIdentity(mnemonic, 0)
	if err != nil {
		t.Fatalf("derive: %v", err)
	}

	t.Logf("secret:    %s", id.String())
	t.Logf("recipient: %s", id.Recipient().String())

	encryptDecryptRoundTrip(t, id, testMessageHelloWorld)
}

func TestDeriveIdentityFromXPRV(t *testing.T) {
	t.Parallel()

	id, err := DeriveIdentityFromXPRV(testXPRV, 0)
	if err != nil {
		t.Fatalf("derive from xprv: %v", err)
	}

	t.Logf("xprv secret:    %s", id.String())
	t.Logf("xprv recipient: %s", id.Recipient().String())

	// Test encryption/decryption with xprv-derived identity
	encryptDecryptRoundTrip(t, id, testMessageHelloFromXPRV)
}

// requireDeterministicDerivation verifies that derive is deterministic
// for a fixed index and that different indices produce different
// identities. It returns the identities for indices 0 and 1.
func requireDeterministicDerivation(
	t *testing.T,
	derive func(uint32) (*age.X25519Identity, error),
) (*age.X25519Identity, *age.X25519Identity) {
	t.Helper()

	// Test that the same input and index always produce the same identity
	id1, err := derive(0)
	if err != nil {
		t.Fatalf("derive 1: %v", err)
	}

	id2, err := derive(0)
	if err != nil {
		t.Fatalf("derive 2: %v", err)
	}

	if id1.String() != id2.String() {
		t.Fatalf(
			"identities should be deterministic: %s != %s",
			id1.String(),
			id2.String(),
		)
	}

	// Test that different indices produce different identities
	id3, err := derive(1)
	if err != nil {
		t.Fatalf("derive 3: %v", err)
	}

	if id1.String() == id3.String() {
		t.Fatalf("different indices should produce different identities")
	}

	return id1, id3
}

func TestDeterministicDerivation(t *testing.T) {
	t.Parallel()

	id1, id3 := requireDeterministicDerivation(
		t,
		func(n uint32) (*age.X25519Identity, error) {
			return DeriveIdentity(mnemonic, n)
		},
	)

	t.Logf("Index 0: %s", id1.String())
	t.Logf("Index 1: %s", id3.String())
}

func TestDeterministicXPRVDerivation(t *testing.T) {
	t.Parallel()

	id1, id3 := requireDeterministicDerivation(
		t,
		func(n uint32) (*age.X25519Identity, error) {
			return DeriveIdentityFromXPRV(testXPRV, n)
		},
	)

	t.Logf("XPRV Index 0: %s", id1.String())
	t.Logf("XPRV Index 1: %s", id3.String())
}

func TestMnemonicVsXPRVConsistency(t *testing.T) {
	t.Parallel()
	// Consistency between mnemonic-derived and xprv-derived identities
	// is not yet covered by this test.
}

func TestEntropyLength(t *testing.T) {
	t.Parallel()

	// Test that DeriveEntropy returns exactly 32 bytes
	entropy, err := DeriveEntropy(mnemonic, 0)
	if err != nil {
		t.Fatalf("derive entropy: %v", err)
	}

	if len(entropy) != 32 {
		t.Fatalf("expected 32 bytes of entropy, got %d", len(entropy))
	}

	t.Logf("Entropy (32 bytes): %x", entropy)

	// Test that DeriveEntropyFromXPRV returns exactly 32 bytes
	entropyXPRV, err := DeriveEntropyFromXPRV(testXPRV, 0)
	if err != nil {
		t.Fatalf("derive entropy from xprv: %v", err)
	}

	if len(entropyXPRV) != 32 {
		t.Fatalf(
			"expected 32 bytes of entropy from xprv, got %d",
			len(entropyXPRV),
		)
	}

	t.Logf("XPRV Entropy (32 bytes): %x", entropyXPRV)

	// Note: We don't compare the entropy values since the test mnemonic and test xprv
	// are from different sources and should produce different entropy values.
}

func TestIdentityFromEntropy(t *testing.T) {
	t.Parallel()

	// Test that IdentityFromEntropy works with custom entropy
	entropy := make([]byte, 32)
	for i := range entropy {
		entropy[i] = byte(i)
	}

	id, err := IdentityFromEntropy(entropy)
	if err != nil {
		t.Fatalf("identity from entropy: %v", err)
	}

	t.Logf("Custom entropy identity: %s", id.String())

	// Test that it rejects wrong-sized entropy
	_, err = IdentityFromEntropy(entropy[:31])
	if err == nil {
		t.Fatalf("expected error for 31-byte entropy")
	}

	// Create a 33-byte slice to test rejection
	entropy33 := make([]byte, 33)
	copy(entropy33, entropy)

	_, err = IdentityFromEntropy(entropy33)
	if err == nil {
		t.Fatalf("expected error for 33-byte entropy")
	}
}

func TestInvalidXPRV(t *testing.T) {
	t.Parallel()

	// Test with invalid xprv
	_, err := DeriveIdentityFromXPRV(errorMsgInvalidXPRV, 0)
	if err == nil {
		t.Fatalf("expected error for invalid xprv")
	}

	t.Logf("Got expected error for invalid xprv: %v", err)
}

// TestClampFunction tests the RFC-7748 clamping function
func TestClampFunction(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		input    []byte
		expected []byte
	}{
		{
			name:     "all zeros",
			input:    make([]byte, 32),
			expected: append(make([]byte, 31), 64),
		},
		{
			name:  "all ones",
			input: bytes.Repeat([]byte{255}, 32),
			expected: append(
				[]byte{248},
				append(bytes.Repeat([]byte{255}, 30), 127)...),
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			input := make([]byte, 32)
			copy(input, tt.input)
			clamp(input)

			// Check specific bits that should be clamped
			if input[0]&7 != 0 {
				t.Errorf(
					"first byte should have bottom 3 bits cleared, got %08b",
					input[0],
				)
			}

			if input[31]&128 != 0 {
				t.Errorf(
					"last byte should have top bit cleared, got %08b",
					input[31],
				)
			}

			if input[31]&64 == 0 {
				t.Errorf(
					"last byte should have second-to-top bit set, got %08b",
					input[31],
				)
			}
		})
	}
}

// requireIdentityError asserts that identity derivation failed with an
// error containing errorMsg and returned no identity.
func requireIdentityError(
	t *testing.T,
	identity *age.X25519Identity,
	err error,
	errorMsg string,
) {
	t.Helper()

	if err == nil {
		t.Errorf("expected error but got none")
	} else if !strings.Contains(err.Error(), errorMsg) {
		t.Errorf(
			"expected error containing %q, got %q",
			errorMsg,
			err.Error(),
		)
	}

	if identity != nil {
		t.Errorf("expected nil identity on error, got %v", identity)
	}
}

// TestIdentityFromEntropyEdgeCases tests edge cases for IdentityFromEntropy
func TestIdentityFromEntropyEdgeCases(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name        string
		entropy     []byte
		expectError bool
		errorMsg    string
	}{
		{
			name:        "nil entropy",
			entropy:     nil,
			expectError: true,
			errorMsg:    errorMsgNeed32Bytes + " 0",
		},
		{
			name:        "empty entropy",
			entropy:     []byte{},
			expectError: true,
			errorMsg:    errorMsgNeed32Bytes + " 0",
		},
		{
			name:        "too short entropy",
			entropy:     make([]byte, 31),
			expectError: true,
			errorMsg:    errorMsgNeed32Bytes + " 31",
		},
		{
			name:        "too long entropy",
			entropy:     make([]byte, 33),
			expectError: true,
			errorMsg:    errorMsgNeed32Bytes + " 33",
		},
		{
			name:        "valid 32-byte entropy",
			entropy:     make([]byte, 32),
			expectError: false,
		},
		{
			name: "random valid entropy",
			entropy: func() []byte {
				b := make([]byte, 32)

				_, err := rand.Read(b)
				if err != nil {
					// In test context, panic is acceptable for
					// setup failures
					panic(err)
				}

				return b
			}(),
			expectError: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			identity, err := IdentityFromEntropy(tt.entropy)

			if tt.expectError {
				requireIdentityError(t, identity, err, tt.errorMsg)

				return
			}

			if err != nil {
				t.Errorf("unexpected error: %v", err)
			}

			if identity == nil {
				t.Errorf("expected valid identity, got nil")
			}
		})
	}
}

// TestDeriveEntropyInvalidMnemonic tests error handling for invalid mnemonics
func TestDeriveEntropyInvalidMnemonic(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		mnemonic string
	}{
		{
			name:     "empty mnemonic",
			mnemonic: "",
		},
		{
			name:     "single word",
			mnemonic: "abandon",
		},
		{
			name:     "invalid word",
			mnemonic: "invalid word sequence that does not exist in bip39",
		},
		{
			name:     "wrong word count",
			mnemonic: "abandon abandon abandon abandon abandon", //nolint:dupword // repeated-word mnemonic
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			// Note: BIP39 library is quite permissive and doesn't validate
			// mnemonic words strictly, so we mainly test that the function
			// doesn't panic and produces some result
			entropy, err := DeriveEntropy(tt.mnemonic, 0)
			if err != nil {
				t.Logf("Got error for invalid mnemonic %q: %v", tt.name, err)

				return
			}

			if len(entropy) != 32 {
				t.Errorf("expected 32 bytes even for invalid mnemonic, got %d", len(entropy))
			}

			t.Logf("Invalid mnemonic %q produced entropy: %x", tt.name, entropy)
		})
	}
}

// TestDeriveEntropyFromXPRVInvalidInputs tests error handling for invalid XPRVs
func TestDeriveEntropyFromXPRVInvalidInputs(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name        string
		xprv        string
		expectError bool
	}{
		{
			name:        "empty xprv",
			xprv:        "",
			expectError: true,
		},
		{
			name:        "invalid base58",
			xprv:        "invalid-base58-string-!@#$%",
			expectError: true,
		},
		{
			name:        "wrong prefix",
			xprv:        "xpub661MyMwAqRbcFtXgS5sYJABqqG9YLmC4Q1Rdap9gSE8NqtwybGhePY2gZ29ESFjqJoCu1Rupje8YtGqsefD265TMg7usUDFdp6W1EGMcet8",
			expectError: true,
		},
		{
			name:        "truncated xprv",
			xprv:        "xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLj",
			expectError: true,
		},
		{
			name:        "valid xprv",
			xprv:        testXPRV,
			expectError: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			entropy, err := DeriveEntropyFromXPRV(tt.xprv, 0)

			if tt.expectError {
				if err == nil {
					t.Errorf("expected error for invalid xprv %q", tt.name)
				} else {
					t.Logf("Got expected error for %q: %v", tt.name, err)
				}

				return
			}

			if err != nil {
				t.Errorf("unexpected error for valid xprv: %v", err)
			}

			if len(entropy) != 32 {
				t.Errorf("expected 32 bytes of entropy, got %d", len(entropy))
			}
		})
	}
}

// TestDifferentMnemonicLengths tests derivation with different mnemonic lengths
func TestDifferentMnemonicLengths(t *testing.T) {
	t.Parallel()

	mnemonics := map[string]string{
		"12 words": testMnemonic12,
		"15 words": testMnemonic15,
		"18 words": testMnemonic18,
		"21 words": testMnemonic21,
		"24 words": testMnemonic24,
	}

	for name, mnemonic := range mnemonics {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			identity, err := DeriveIdentity(mnemonic, 0)
			if err != nil {
				t.Fatalf("failed to derive identity from %s: %v", name, err)
			}

			// Test that we can encrypt/decrypt
			encryptDecryptRoundTrip(t, identity, testMessageGeneric)

			t.Logf("%s identity: %s", name, identity.String())
		})
	}
}

// TestIndexBoundaries tests derivation with various index values
func TestIndexBoundaries(t *testing.T) {
	t.Parallel()

	indices := []uint32{
		0,          // minimum
		1,          // basic
		100,        // moderate
		1000,       // larger
		0x7FFFFFFF, // maximum hardened index
		0xFFFFFFFF, // maximum uint32
	}

	for _, index := range indices {
		t.Run(fmt.Sprintf("index_%d", index), func(t *testing.T) {
			t.Parallel()

			identity, err := DeriveIdentity(mnemonic, index)
			if err != nil {
				t.Fatalf(
					"failed to derive identity at index %d: %v",
					index,
					err,
				)
			}

			// Verify the identity is valid by testing encryption/decryption
			encryptDecryptRoundTrip(t, identity, testMessageBoundary)

			t.Logf("Index %d identity: %s", index, identity.String())
		})
	}
}

// TestEntropyUniqueness tests that different inputs produce different entropy
func TestEntropyUniqueness(t *testing.T) {
	t.Parallel()

	// Test different indices with same mnemonic
	entropy1, err := DeriveEntropy(mnemonic, 0)
	if err != nil {
		t.Fatalf("derive entropy 1: %v", err)
	}

	entropy2, err := DeriveEntropy(mnemonic, 1)
	if err != nil {
		t.Fatalf("derive entropy 2: %v", err)
	}

	if bytes.Equal(entropy1, entropy2) {
		t.Fatalf("different indices should produce different entropy")
	}

	// Test different mnemonics with same index
	entropy3, err := DeriveEntropy(testMnemonic24, 0)
	if err != nil {
		t.Fatalf("derive entropy 3: %v", err)
	}

	if bytes.Equal(entropy1, entropy3) {
		t.Fatalf("different mnemonics should produce different entropy")
	}

	t.Logf("Entropy uniqueness verified across indices and mnemonics")
}

// TestConcurrentDerivation tests that derivation is safe for concurrent use
func TestConcurrentDerivation(t *testing.T) {
	t.Parallel()

	results := make(chan string, testNumGoroutines*testNumIterations)
	errCh := make(chan error, testNumGoroutines*testNumIterations)

	for range testNumGoroutines {
		go func() {
			for j := range testNumIterations {
				if j < 0 || j > 1000000 {
					errCh <- errIndexOutOfRange

					return
				}

				identity, err := DeriveIdentity(mnemonic, uint32(j))
				if err != nil {
					errCh <- err

					return
				}

				results <- identity.String()
			}
		}()
	}

	// Collect results
	resultMap := make(map[string]int)

	for range testNumGoroutines * testNumIterations {
		select {
		case result := <-results:
			resultMap[result]++
		case err := <-errCh:
			t.Fatalf("concurrent derivation error: %v", err)
		}
	}

	// Verify that each index produced the same result across all goroutines
	expectedResults := testNumGoroutines
	for result, count := range resultMap {
		if count != expectedResults {
			t.Errorf(
				"result %s appeared %d times, expected %d",
				result,
				count,
				expectedResults,
			)
		}
	}

	t.Logf(
		"Concurrent derivation test passed with %d unique results",
		len(resultMap),
	)
}

// Benchmark tests
func BenchmarkDeriveIdentity(b *testing.B) {
	for i := range b.N {
		index := i % 1000
		if index < 0 || index > 1000000 {
			b.Fatalf("index out of safe range: %d", index)
		}

		_, err := DeriveIdentity(mnemonic, uint32(index))
		if err != nil {
			b.Fatalf("derive identity: %v", err)
		}
	}
}

func BenchmarkDeriveIdentityFromXPRV(b *testing.B) {
	for i := range b.N {
		index := i % 1000
		if index < 0 || index > 1000000 {
			b.Fatalf("index out of safe range: %d", index)
		}

		_, err := DeriveIdentityFromXPRV(testXPRV, uint32(index))
		if err != nil {
			b.Fatalf("derive identity from xprv: %v", err)
		}
	}
}

func BenchmarkDeriveEntropy(b *testing.B) {
	for i := range b.N {
		index := i % 1000
		if index < 0 || index > 1000000 {
			b.Fatalf("index out of safe range: %d", index)
		}

		_, err := DeriveEntropy(mnemonic, uint32(index))
		if err != nil {
			b.Fatalf("derive entropy: %v", err)
		}
	}
}

func BenchmarkIdentityFromEntropy(b *testing.B) {
	entropy := make([]byte, 32)

	_, err := rand.Read(entropy)
	if err != nil {
		b.Fatalf("failed to generate random entropy: %v", err)
	}

	b.ResetTimer()

	for range b.N {
		_, err := IdentityFromEntropy(entropy)
		if err != nil {
			b.Fatalf("identity from entropy: %v", err)
		}
	}
}

func BenchmarkEncryptDecrypt(b *testing.B) {
	identity, err := DeriveIdentity(mnemonic, 0)
	if err != nil {
		b.Fatalf("derive identity: %v", err)
	}

	b.ResetTimer()

	for range b.N {
		var ct bytes.Buffer

		w, err := age.Encrypt(&ct, identity.Recipient())
		if err != nil {
			b.Fatalf("encrypt init: %v", err)
		}

		_, err = io.WriteString(w, testMessageBenchmark)
		if err != nil {
			b.Fatalf("write: %v", err)
		}

		err = w.Close()
		if err != nil {
			b.Fatalf("encrypt close: %v", err)
		}

		r, err := age.Decrypt(bytes.NewReader(ct.Bytes()), identity)
		if err != nil {
			b.Fatalf("decrypt init: %v", err)
		}

		_, err = io.ReadAll(r)
		if err != nil {
			b.Fatalf("read: %v", err)
		}
	}
}

// TestConstants verifies the hardcoded constants
func TestConstants(t *testing.T) {
	t.Parallel()

	if purpose != 83696968 {
		t.Errorf(
			"purpose constant mismatch: expected 83696968, got %d",
			purpose,
		)
	}

	if vendorID != 592366788 {
		t.Errorf(
			"vendorID constant mismatch: expected 592366788, got %d",
			vendorID,
		)
	}

	if appID != 733482323 {
		t.Errorf(
			"appID constant mismatch: expected 733482323, got %d",
			appID,
		)
	}

	if hrp != "age-secret-key-" {
		t.Errorf(
			"hrp constant mismatch: expected 'age-secret-key-', got %q",
			hrp,
		)
	}
}

// TestIdentityStringFormat tests that generated identities have the correct format
func TestIdentityStringFormat(t *testing.T) {
	t.Parallel()

	identity, err := DeriveIdentity(mnemonic, 0)
	if err != nil {
		t.Fatalf("derive identity: %v", err)
	}

	secretKey := identity.String()
	recipient := identity.Recipient().String()

	// Check secret key format
	if !strings.HasPrefix(secretKey, "AGE-SECRET-KEY-") {
		t.Errorf(
			"secret key should start with 'AGE-SECRET-KEY-', got: %s",
			secretKey,
		)
	}

	// Check recipient format
	if !strings.HasPrefix(recipient, "age1") {
		t.Errorf("recipient should start with 'age1', got: %s", recipient)
	}

	// Check that they're different
	if secretKey == recipient {
		t.Errorf("secret key and recipient should be different")
	}

	t.Logf("Secret key format: %s", secretKey)
	t.Logf("Recipient format: %s", recipient)
}

// TestLargeMessageEncryption tests encryption/decryption of larger messages
func TestLargeMessageEncryption(t *testing.T) {
	t.Parallel()

	identity, err := DeriveIdentity(mnemonic, 0)
	if err != nil {
		t.Fatalf("derive identity: %v", err)
	}

	// Test with different message sizes
	sizes := []int{1, 100, 1024, 10240, 100000}

	for _, size := range sizes {
		t.Run(fmt.Sprintf("size_%d", size), func(t *testing.T) {
			t.Parallel()

			message := strings.Repeat(testMessageLargePattern, size)

			encryptDecryptRoundTrip(t, identity, message)

			t.Logf("Successfully encrypted/decrypted %d byte message", size)
		})
	}
}

// encryptDecryptBytes encrypts data to id's recipient and returns the
// decrypted result.
func encryptDecryptBytes(t *testing.T, id *age.X25519Identity, data []byte) []byte {
	t.Helper()

	var ciphertext bytes.Buffer

	encryptor, err := age.Encrypt(&ciphertext, id.Recipient())
	if err != nil {
		t.Fatalf("failed to create encryptor: %v", err)
	}

	_, err = encryptor.Write(data)
	if err != nil {
		t.Fatalf("failed to write data to encryptor: %v", err)
	}

	err = encryptor.Close()
	if err != nil {
		t.Fatalf("failed to close encryptor: %v", err)
	}

	decryptor, err := age.Decrypt(bytes.NewReader(ciphertext.Bytes()), id)
	if err != nil {
		t.Fatalf("failed to create decryptor: %v", err)
	}

	decrypted, err := io.ReadAll(decryptor)
	if err != nil {
		t.Fatalf("failed to read decrypted data: %v", err)
	}

	return decrypted
}

// requireIdenticalIdentities verifies that both identities have the same
// private and public keys.
func requireIdenticalIdentities(t *testing.T, id1, id2 *age.X25519Identity) {
	t.Helper()

	privateKey1 := id1.String()
	privateKey2 := id2.String()

	if privateKey1 != privateKey2 {
		t.Fatalf(
			"private keys should be identical:\nFirst:  %s\nSecond: %s",
			privateKey1,
			privateKey2,
		)
	}

	publicKey1 := id1.Recipient().String()
	publicKey2 := id2.Recipient().String()

	if publicKey1 != publicKey2 {
		t.Fatalf(
			"public keys should be identical:\nFirst:  %s\nSecond: %s",
			publicKey1,
			publicKey2,
		)
	}
}

// TestRandomMnemonicDeterministicGeneration tests that:
// 1. A random mnemonic generates the same keys deterministically
// 2. Large data (1MB) can be encrypted and decrypted successfully
func TestRandomMnemonicDeterministicGeneration(t *testing.T) {
	t.Parallel()

	// Generate a random mnemonic using the BIP39 library
	entropy := make([]byte, 32) // 256 bits for 24-word mnemonic

	_, err := rand.Read(entropy)
	if err != nil {
		t.Fatalf("failed to generate random entropy: %v", err)
	}

	randomMnemonic, err := bip39.NewMnemonic(entropy)
	if err != nil {
		t.Fatalf("failed to generate random mnemonic: %v", err)
	}

	t.Logf("Generated random mnemonic: %s", randomMnemonic)

	// Test index for key derivation
	testIndex := uint32(42)

	// Generate the first identity
	identity1, err := DeriveIdentity(randomMnemonic, testIndex)
	if err != nil {
		t.Fatalf("failed to derive first identity: %v", err)
	}

	// Generate the second identity with the same mnemonic and index
	identity2, err := DeriveIdentity(randomMnemonic, testIndex)
	if err != nil {
		t.Fatalf("failed to derive second identity: %v", err)
	}

	// Verify that both identities have identical private and public keys
	requireIdenticalIdentities(t, identity1, identity2)

	t.Logf("Deterministic generation verified")
	t.Logf("Private key: %s", identity1.String())
	t.Logf("Public key:  %s", identity1.Recipient().String())

	// Generate 1 MB of random data for encryption test
	testData := make([]byte, testDataSizeMegabyte)

	_, err = rand.Read(testData)
	if err != nil {
		t.Fatalf("failed to generate random test data: %v", err)
	}

	t.Logf("Generated %d bytes of random test data", len(testData))

	// Encrypt and decrypt the data with the first identity
	decryptedData := encryptDecryptBytes(t, identity1, testData)

	t.Logf("Decrypted %d bytes", len(decryptedData))

	// Verify that the decrypted data matches the original
	if len(decryptedData) != len(testData) {
		t.Fatalf(
			"decrypted data length mismatch: expected %d, got %d",
			len(testData),
			len(decryptedData),
		)
	}

	if !bytes.Equal(testData, decryptedData) {
		t.Fatalf("decrypted data does not match original data")
	}

	t.Logf("Large data encryption/decryption test passed successfully")

	// Additional verification with the second identity (should work
	// identically)
	decryptedData2 := encryptDecryptBytes(t, identity2, testData)

	if !bytes.Equal(testData, decryptedData2) {
		t.Fatalf("second decrypted data does not match original data")
	}

	t.Logf("Cross-verification with second identity successful")
}