refactor(tvix/nar-bridge): rename writer package to exporter r/6696

Change-Id: I7cf6a3ed0dca4c450fadd9228dc0154ad6254f51
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9530
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>

1 files changed, 0 insertions, 279 deletions

diff --git a/tvix/nar-bridge/pkg/writer/writer.go b/tvix/nar-bridge/pkg/writer/writer.go
deleted file mode 100644
index fd154e061bf0..000000000000
--- a/tvix/nar-bridge/pkg/writer/writer.go
+++ /dev/null
@@ -1,279 +0,0 @@
-package writer
-
-import (
-	"fmt"
-	"io"
-	"path"
-
-	castorev1pb "code.tvl.fyi/tvix/castore/protos"
-	storev1pb "code.tvl.fyi/tvix/store/protos"
-	"github.com/nix-community/go-nix/pkg/nar"
-)
-
-type DirectoryLookupFn func([]byte) (*castorev1pb.Directory, error)
-type BlobLookupFn func([]byte) (io.ReadCloser, error)
-
-// Export will traverse a given pathInfo structure, and write the contents
-// in NAR format to the passed Writer.
-// It uses directoryLookupFn and blobLookupFn to resolve references.
-func Export(
-	w io.Writer,
-	pathInfo *storev1pb.PathInfo,
-	directoryLookupFn DirectoryLookupFn,
-	blobLookupFn BlobLookupFn,
-) error {
-	// initialize a NAR writer
-	narWriter, err := nar.NewWriter(w)
-	if err != nil {
-		return fmt.Errorf("unable to initialize nar writer: %w", err)
-	}
-	defer narWriter.Close()
-
-	// populate rootHeader
-	rootHeader := &nar.Header{
-		Path: "/",
-	}
-
-	// populate a stack
-	// we will push paths and directories to it when entering a directory,
-	// and emit individual elements to the NAR writer, draining the Directory object.
-	// once it's empty, we can pop it off the stack.
-	var stackPaths = []string{}
-	var stackDirectories = []*castorev1pb.Directory{}
-
-	// peek at the pathInfo root and assemble the root node and write to writer
-	// in the case of a regular file, we retrieve and write the contents, close and exit
-	// in the case of a symlink, we write the symlink, close and exit
-	switch v := (pathInfo.GetNode().GetNode()).(type) {
-	case *castorev1pb.Node_File:
-		rootHeader.Type = nar.TypeRegular
-		rootHeader.Size = int64(v.File.GetSize())
-		rootHeader.Executable = v.File.GetExecutable()
-		err := narWriter.WriteHeader(rootHeader)
-		if err != nil {
-			return fmt.Errorf("unable to write root header: %w", err)
-		}
-
-		// if it's a regular file, retrieve and write the contents
-		blobReader, err := blobLookupFn(v.File.GetDigest())
-		if err != nil {
-			return fmt.Errorf("unable to lookup blob: %w", err)
-		}
-		defer blobReader.Close()
-
-		_, err = io.Copy(narWriter, blobReader)
-		if err != nil {
-			return fmt.Errorf("unable to read from blobReader: %w", err)
-		}
-
-		err = blobReader.Close()
-		if err != nil {
-			return fmt.Errorf("unable to close content reader: %w", err)
-		}
-
-		err = narWriter.Close()
-		if err != nil {
-			return fmt.Errorf("unable to close nar reader: %w", err)
-		}
-
-		return nil
-
-	case *castorev1pb.Node_Symlink:
-		rootHeader.Type = nar.TypeSymlink
-		rootHeader.LinkTarget = string(v.Symlink.GetTarget())
-		err := narWriter.WriteHeader(rootHeader)
-		if err != nil {
-			return fmt.Errorf("unable to write root header: %w", err)
-		}
-
-		err = narWriter.Close()
-		if err != nil {
-			return fmt.Errorf("unable to close nar reader: %w", err)
-		}
-
-		return nil
-	case *castorev1pb.Node_Directory:
-		// We have a directory at the root, look it up and put in on the stack.
-		directory, err := directoryLookupFn(v.Directory.Digest)
-		if err != nil {
-			return fmt.Errorf("unable to lookup directory: %w", err)
-		}
-		stackDirectories = append(stackDirectories, directory)
-		stackPaths = append(stackPaths, "/")
-
-		err = narWriter.WriteHeader(&nar.Header{
-			Path: "/",
-			Type: nar.TypeDirectory,
-		})
-
-		if err != nil {
-			return fmt.Errorf("error writing header: %w", err)
-		}
-	}
-
-	// as long as the stack is not empty, we keep running.
-	for {
-		if len(stackDirectories) == 0 {
-			return nil
-		}
-
-		// Peek at the current top of the stack.
-		topOfStack := stackDirectories[len(stackDirectories)-1]
-		topOfStackPath := stackPaths[len(stackPaths)-1]
-
-		// get the next element that's lexicographically smallest, and drain it from
-		// the current directory on top of the stack.
-		nextNode := drainNextNode(topOfStack)
-
-		// If nextNode returns nil, there's nothing left in the directory node, so we
-		// can emit it from the stack.
-		// Contrary to the import case, we don't emit the node popping from the stack, but when pushing.
-		if nextNode == nil {
-			// pop off stack
-			stackDirectories = stackDirectories[:len(stackDirectories)-1]
-			stackPaths = stackPaths[:len(stackPaths)-1]
-
-			continue
-		}
-
-		switch n := (nextNode).(type) {
-		case *castorev1pb.DirectoryNode:
-			err := narWriter.WriteHeader(&nar.Header{
-				Path: path.Join(topOfStackPath, string(n.GetName())),
-				Type: nar.TypeDirectory,
-			})
-			if err != nil {
-				return fmt.Errorf("unable to write nar header: %w", err)
-			}
-
-			d, err := directoryLookupFn(n.GetDigest())
-			if err != nil {
-				return fmt.Errorf("unable to lookup directory: %w", err)
-			}
-
-			// add to stack
-			stackDirectories = append(stackDirectories, d)
-			stackPaths = append(stackPaths, path.Join(topOfStackPath, string(n.GetName())))
-		case *castorev1pb.FileNode:
-			err := narWriter.WriteHeader(&nar.Header{
-				Path:       path.Join(topOfStackPath, string(n.GetName())),
-				Type:       nar.TypeRegular,
-				Size:       int64(n.GetSize()),
-				Executable: n.GetExecutable(),
-			})
-			if err != nil {
-				return fmt.Errorf("unable to write nar header: %w", err)
-			}
-
-			// copy file contents
-			contentReader, err := blobLookupFn(n.GetDigest())
-			if err != nil {
-				return fmt.Errorf("unable to get blob: %w", err)
-			}
-			defer contentReader.Close()
-
-			_, err = io.Copy(narWriter, contentReader)
-			if err != nil {
-				return fmt.Errorf("unable to copy contents from contentReader: %w", err)
-			}
-
-			err = contentReader.Close()
-			if err != nil {
-				return fmt.Errorf("unable to close content reader: %w", err)
-			}
-		case *castorev1pb.SymlinkNode:
-			err := narWriter.WriteHeader(&nar.Header{
-				Path:       path.Join(topOfStackPath, string(n.GetName())),
-				Type:       nar.TypeSymlink,
-				LinkTarget: string(n.GetTarget()),
-			})
-			if err != nil {
-				return fmt.Errorf("unable to write nar header: %w", err)
-			}
-		}
-	}
-}
-
-// TODO: add validation functions to Directory in both rust and golang, to
-// validate the keys in directories, files and symlinks are sorted.
-
-// drainNextNode will drain a directory message with one of its child nodes,
-// whichever comes first alphabetically.
-func drainNextNode(d *castorev1pb.Directory) interface{} {
-	switch v := (smallestNode(d)).(type) {
-	case *castorev1pb.DirectoryNode:
-		d.Directories = d.Directories[1:]
-		return v
-	case *castorev1pb.FileNode:
-		d.Files = d.Files[1:]
-		return v
-	case *castorev1pb.SymlinkNode:
-		d.Symlinks = d.Symlinks[1:]
-		return v
-	case nil:
-		return nil
-	default:
-		panic("invalid type encountered")
-	}
-}
-
-// smallestNode will return the node from a directory message,
-// whichever comes first alphabetically.
-func smallestNode(d *castorev1pb.Directory) interface{} {
-	childDirectories := d.GetDirectories()
-	childFiles := d.GetFiles()
-	childSymlinks := d.GetSymlinks()
-
-	if len(childDirectories) > 0 {
-		if len(childFiles) > 0 {
-			if len(childSymlinks) > 0 {
-				// directories,files,symlinks
-				return smallerNode(smallerNode(childDirectories[0], childFiles[0]), childSymlinks[0])
-			} else {
-				// directories,files,!symlinks
-				return smallerNode(childDirectories[0], childFiles[0])
-			}
-		} else {
-			// directories,!files
-			if len(childSymlinks) > 0 {
-				// directories,!files,symlinks
-				return smallerNode(childDirectories[0], childSymlinks[0])
-			} else {
-				// directories,!files,!symlinks
-				return childDirectories[0]
-			}
-		}
-	} else {
-		// !directories
-		if len(childFiles) > 0 {
-			// !directories,files
-			if len(childSymlinks) > 0 {
-				// !directories,files,symlinks
-				return smallerNode(childFiles[0], childSymlinks[0])
-			} else {
-				// !directories,files,!symlinks
-				return childFiles[0]
-			}
-		} else {
-			//!directories,!files
-			if len(childSymlinks) > 0 {
-				//!directories,!files,symlinks
-				return childSymlinks[0]
-			} else {
-				//!directories,!files,!symlinks
-				return nil
-			}
-		}
-	}
-}
-
-// smallerNode compares two nodes by their name,
-// and returns the one with the smaller name.
-// both nodes may not be nil, we do check for these cases in smallestNode.
-func smallerNode(a interface{ GetName() []byte }, b interface{ GetName() []byte }) interface{ GetName() []byte } {
-	if string(a.GetName()) < string(b.GetName()) {
-		return a
-	} else {
-		return b
-	}
-}