package vaultik_test

import (
	"context"
	"io"
	"testing"

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

// TestFetchAndDecryptBlobBoundsPlaintext feeds a small, highly
// compressible blob (256 KiB of zeros) whose decompressed size far exceeds
// the plaintext bound passed to FetchAndDecryptBlob. Decompression must
// stop with blobgen.ErrOutputTooLarge within the bound rather than
// expanding the whole blob into the restore cache.
func TestFetchAndDecryptBlobBoundsPlaintext(t *testing.T) {
	t.Parallel()

	identity, err := age.GenerateX25519Identity()
	require.NoError(t, err)

	plaintext := make([]byte, 256*1024)
	encryptedData, correctHash := buildHashTestBlob(t, identity, plaintext)

	mockStorage := NewMockStorer()
	blobPath := "blobs/" + correctHash[:2] + "/" +
		correctHash[2:4] + "/" + correctHash

	mockStorage.mu.Lock()
	mockStorage.data[blobPath] = encryptedData
	mockStorage.mu.Unlock()

	tv := vaultik.NewForTesting(mockStorage)

	const maxPlaintext = 1024

	rc, err := tv.FetchAndDecryptBlob(
		context.Background(), correctHash, maxPlaintext, identity)
	require.NoError(t, err)

	n, copyErr := io.Copy(io.Discard, rc)
	_ = rc.Close()

	require.ErrorIs(t, copyErr, blobgen.ErrOutputTooLarge)
	require.LessOrEqual(t, n, int64(maxPlaintext)+1,
		"decompression must stop within the recorded plaintext bound")
}