package blobgen_test

import (
	"bytes"
	"fmt"
	"testing"

	"filippo.io/age"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/vaultik/internal/blobgen"
)

// TestNewReaderWrongIdentity covers issue case 4: opening a blob with an
// identity other than the recipient reports no matching identity.
func TestNewReaderWrongIdentity(t *testing.T) {
	t.Parallel()

	_, recipient := makeIdentity(t)
	other, _ := makeIdentity(t)

	blob := encryptBlob(t, []byte("secret payload"), recipient)

	_, err := blobgen.NewReader(bytes.NewReader(blob), other)
	require.Error(t, err)

	var noMatch *age.NoIdentityMatchError
	assert.ErrorAs(t, err, &noMatch)
}

// TestNewReaderTruncated covers issue case 6: a multi-segment blob cut at
// several points must never read back as valid data. The point immediately
// after the header and nonce is intentionally excluded: it reads as a valid
// empty blob today and is the regression case for
// https://git.eeqj.de/sneak/vaultik/issues/152.
func TestNewReaderTruncated(t *testing.T) {
	t.Parallel()

	id, recipient := makeIdentity(t)
	blob := encryptBlob(t, randomBytes(t, 4*65536+123), recipient)
	h := ageHeaderLen(t, blob)

	require.Greater(t, len(blob), h+ageNonceSize+ageSegmentSize,
		"test needs a blob of at least two age segments")

	cases := []struct {
		name string
		size int
	}{
		{"inside header", h / 2},
		{"inside nonce", h + 8},
		{"inside first segment", h + ageNonceSize + 100},
		{"end of first full segment", h + ageNonceSize + ageSegmentSize},
		{"last byte removed", len(blob) - 1},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			requireBlobUnreadable(t, blob[:tc.size], id)
		})
	}
}

// TestNewReaderCorrupted covers issue case 7: one flipped byte in each region
// of a multi-segment blob makes it unreadable.
func TestNewReaderCorrupted(t *testing.T) {
	t.Parallel()

	id, recipient := makeIdentity(t)
	blob := encryptBlob(t, randomBytes(t, 4*65536+123), recipient)
	h := ageHeaderLen(t, blob)

	firstNL := bytes.IndexByte(blob, '\n')
	require.Positive(t, firstNL, "header must have a version line")

	cases := []struct {
		name string
		pos  int
	}{
		{"header stanza", firstNL + 5},
		{"header MAC line", h - 2},
		{"nonce", h + 4},
		{"body segment", h + ageNonceSize + 50},
		{"final tag", len(blob) - 1},
	}

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

			corrupt := append([]byte(nil), blob...)
			corrupt[tc.pos] ^= 0xff
			requireBlobUnreadable(t, corrupt, id)
		})
	}
}

// TestNewReaderTrailingAndGarbage covers issue case 8: bytes appended after a
// valid blob, empty input, and random garbage each fail to read.
func TestNewReaderTrailingAndGarbage(t *testing.T) {
	t.Parallel()

	id, recipient := makeIdentity(t)

	valid := encryptBlob(t, []byte("small payload"), recipient)
	appended := append(append([]byte(nil), valid...), []byte("trailing junk")...)

	t.Run("appended bytes", func(t *testing.T) {
		t.Parallel()
		requireBlobUnreadable(t, appended, id)
	})
	t.Run("empty input", func(t *testing.T) {
		t.Parallel()
		requireBlobUnreadable(t, []byte{}, id)
	})
	t.Run("random garbage", func(t *testing.T) {
		t.Parallel()
		requireBlobUnreadable(t, randomBytes(t, 512), id)
	})
}

// TestNewWriterInvalidLevel covers the rejected end of issue case 9: an
// out-of-range compression level errors and writes nothing to the destination.
func TestNewWriterInvalidLevel(t *testing.T) {
	t.Parallel()

	_, recipient := makeIdentity(t)

	for _, level := range []int{0, -1, 20} {
		t.Run(fmt.Sprintf("level%d", level), func(t *testing.T) {
			t.Parallel()

			var buf bytes.Buffer

			w, err := blobgen.NewWriter(&buf, level, []string{recipient})
			require.ErrorIs(t, err, blobgen.ErrInvalidCompressionLevel)
			assert.Nil(t, w)
			assert.Zero(t, buf.Len(), "nothing written on an invalid level")
		})
	}
}

// TestNewWriterInvalidRecipients covers issue case 10: nil and empty recipient
// lists and an unparsable recipient string each error.
func TestNewWriterInvalidRecipients(t *testing.T) {
	t.Parallel()

	cases := []struct {
		name       string
		recipients []string
	}{
		{"nil list", nil},
		{"empty list", []string{}},
		{"invalid recipient string", []string{"not-a-recipient"}},
	}

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

			var buf bytes.Buffer

			w, err := blobgen.NewWriter(&buf, 1, tc.recipients)
			require.Error(t, err)
			assert.Nil(t, w)
		})
	}
}

// TestNewWriterFailingDestination covers issue case 11: a destination that
// fails mid-blob surfaces its error from Write or Close.
func TestNewWriterFailingDestination(t *testing.T) {
	t.Parallel()

	_, recipient := makeIdentity(t)

	// The limit clears the age header and nonce so NewWriter succeeds, then
	// trips once the compressed body starts flowing.
	dst := &failAfterWriter{limit: 512}

	w, err := blobgen.NewWriter(dst, 1, []string{recipient})
	require.NoError(t, err)

	_, writeErr := w.Write(randomBytes(t, 256*1024))
	closeErr := w.Close()

	assert.True(t, writeErr != nil || closeErr != nil,
		"destination failure must surface from Write or Close")
}