package vaultik //nolint:testpackage // drives unexported restore and verify steps

import (
	"context"
	"math"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/spf13/afero"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/vaultik/internal/database"
	"sneak.berlin/go/vaultik/internal/types"
)

// These tests feed restore and --verify a snapshot database written by
// hand, as a damaged or hostile store could serve one. Each malformed row
// must end in an error, not a panic.

// shortChunkHash is shorter than the hash prefix that error messages print.
const shortChunkHash = "abc"

// restoredFileContent is the content of the restored file under verify.
const restoredFileContent = "xyz"

// craftedSnapshotDB opens an empty snapshot database in a temp directory.
func craftedSnapshotDB(t *testing.T) (*database.DB, *database.Repositories) {
	t.Helper()

	db, err := database.New(context.Background(),
		filepath.Join(t.TempDir(), "snapshot.db"))
	require.NoError(t, err)

	t.Cleanup(func() { _ = db.Close() })

	return db, database.NewRepositories(db)
}

// craftedFile adds a regular file whose only chunk has the given hash.
// Adding the chunks row, if any, is left to the caller.
func craftedFile(
	t *testing.T, repos *database.Repositories, chunkHash string,
) *database.File {
	t.Helper()

	ctx := context.Background()
	file := &database.File{
		Path:  "/src/f",
		MTime: time.Now().UTC(),
		Size:  int64(len(restoredFileContent)),
		Mode:  0o644,
	}
	require.NoError(t, repos.Files.Create(ctx, nil, file))
	require.NoError(t, repos.FileChunks.Create(ctx, nil, &database.FileChunk{
		FileID:    file.ID,
		ChunkHash: types.ChunkHash(chunkHash),
	}))

	return file
}

// TestRestoreShortChunkHashInNoBlob proves a file whose short chunk hash
// has no blob_chunks row fails restore planning and the chunk write with
// an error.
func TestRestoreShortChunkHashInNoBlob(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	_, repos := craftedSnapshotDB(t)
	require.NoError(t, repos.Chunks.Create(ctx, nil,
		&database.Chunk{ChunkHash: shortChunkHash, Size: 3}))
	file := craftedFile(t, repos, shortChunkHash)

	v := NewForTesting(nil)

	chunkToBlobMap, err := v.buildChunkToBlobMap(ctx, repos)
	require.NoError(t, err)

	_, err = newRestorePlan(ctx, repos, []*database.File{file},
		chunkToBlobMap, map[string]string{})
	require.ErrorIs(t, err, errPlanChunkMissing)

	fileChunks, err := repos.FileChunks.GetByFileID(ctx, file.ID)
	require.NoError(t, err)

	out, err := afero.NewMemMapFs().Create("out")
	require.NoError(t, err)

	session := &restoreSession{
		v: v.Vaultik, ctx: ctx, chunkToBlobMap: chunkToBlobMap,
	}

	_, _, err = session.writeFileChunks(out, fileChunks)
	require.ErrorIs(t, err, errChunkNotInAnyBlob)
}

// TestRestoreShortChunkHashReadPastBlobEnd proves a short chunk hash
// whose blob_chunks row reads past the end of its blob fails the chunk
// write with an error.
func TestRestoreShortChunkHashReadPastBlobEnd(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	_, repos := craftedSnapshotDB(t)

	blobHash := strings.Repeat("b", blobHashHexLen)
	blob := &database.Blob{
		ID:        types.NewBlobID(),
		Hash:      types.BlobHash(blobHash),
		CreatedTS: time.Now().UTC(),
	}
	require.NoError(t, repos.Blobs.Create(ctx, nil, blob))
	require.NoError(t, repos.Chunks.Create(ctx, nil,
		&database.Chunk{ChunkHash: shortChunkHash, Size: 3}))
	require.NoError(t, repos.BlobChunks.Create(ctx, nil, &database.BlobChunk{
		BlobID:    blob.ID,
		ChunkHash: shortChunkHash,
		Length:    100,
	}))
	file := craftedFile(t, repos, shortChunkHash)

	cache, err := newBlobDiskCache(1 << 20)
	require.NoError(t, err)

	t.Cleanup(func() { _ = cache.Close() })

	require.NoError(t, cache.Put(blobHash, []byte("abc")))

	v := NewForTesting(nil)

	chunkToBlobMap, err := v.buildChunkToBlobMap(ctx, repos)
	require.NoError(t, err)

	_, blobIDToHash, err := v.buildBlobIndexes(repos)
	require.NoError(t, err)

	fileChunks, err := repos.FileChunks.GetByFileID(ctx, file.ID)
	require.NoError(t, err)

	out, err := afero.NewMemMapFs().Create("out")
	require.NoError(t, err)

	session := &restoreSession{
		v:              v.Vaultik,
		ctx:            ctx,
		chunkToBlobMap: chunkToBlobMap,
		blobIDToHash:   blobIDToHash,
		blobCache:      cache,
	}

	_, _, err = session.writeFileChunks(out, fileChunks)
	require.ErrorIs(t, err, errCacheReadBeyondBlob)
}

// TestVerifyFileMalformedChunkRow proves --verify returns an error for a
// chunk with no chunks row, a short chunk hash, and a chunk size from the
// database that is negative or larger than the restored file.
func TestVerifyFileMalformedChunkRow(t *testing.T) {
	t.Parallel()

	fullHash := types.ChunkHash(strings.Repeat("c", blobHashHexLen))

	tests := []struct {
		name  string
		hash  types.ChunkHash
		chunk *database.Chunk // nil adds no chunks row
		want  error
	}{
		{
			name: "missing chunk row",
			hash: fullHash,
			want: errChunkRowMissing,
		},
		{
			name:  "short hash",
			hash:  shortChunkHash,
			chunk: &database.Chunk{ChunkHash: shortChunkHash, Size: 3},
			want:  errChunkHashMismatch,
		},
		{
			name:  "size larger than the file",
			hash:  fullHash,
			chunk: &database.Chunk{ChunkHash: fullHash, Size: math.MaxInt64},
			want:  errShortChunkRead,
		},
		{
			name:  "negative size",
			hash:  fullHash,
			chunk: &database.Chunk{ChunkHash: fullHash, Size: -1},
			want:  errNegativeChunkLength,
		},
	}

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

			ctx := context.Background()
			db, repos := craftedSnapshotDB(t)

			if tt.chunk == nil {
				// A crafted database need not satisfy its foreign keys.
				_, err := db.Conn().ExecContext(ctx, "PRAGMA foreign_keys = OFF")
				require.NoError(t, err)
			} else {
				require.NoError(t, repos.Chunks.Create(ctx, nil, tt.chunk))
			}

			file := craftedFile(t, repos, tt.hash.String())

			v := NewForTesting(nil)
			v.Fs = afero.NewMemMapFs()
			require.NoError(t, afero.WriteFile(v.Fs, "/restore/f",
				[]byte(restoredFileContent), 0o600))

			_, err := v.verifyFile(ctx, repos, file, "/restore/f")
			require.ErrorIs(t, err, tt.want)
		})
	}
}