feat: Add diff and sync collection functionality

Implement the core logic for comparing two archives (diff) and performing incremental updates (sync).

- Introduces a new `borg diff` command to show differences between two collection archives.
- Adds new `pkg/diff` and `pkg/sync` packages with corresponding business logic and unit tests.
- The `diff` command supports reading compressed archives and prints a formatted summary of added, removed, and modified files.
- The `sync` package includes `append`, `mirror`, and `update` strategies.

Next steps involve integrating the sync logic into the `collect` commands.

Co-authored-by: Snider <631881+Snider@users.noreply.github.com>

cmd/collect_github_repos.go

@@ -30,4 +30,5 @@ var collectGithubReposCmd = &cobra.Command{
 
 func init() {
 	collectGithubCmd.AddCommand(collectGithubReposCmd)
+	collectGithubReposCmd.Flags().String("sync", "", "path to an existing archive to sync with")
 }

cmd/collect_local.go

@@ -1,333 +0,0 @@
-package cmd
-
-import (
-	"fmt"
-	"io/fs"
-	"os"
-	"path/filepath"
-	"strings"
-
-	"github.com/Snider/Borg/pkg/compress"
-	"github.com/Snider/Borg/pkg/datanode"
-	"github.com/Snider/Borg/pkg/tim"
-	"github.com/Snider/Borg/pkg/trix"
-	"github.com/Snider/Borg/pkg/ui"
-
-	"github.com/spf13/cobra"
-)
-
-type CollectLocalCmd struct {
-	cobra.Command
-}
-
-// NewCollectLocalCmd creates a new collect local command
-func NewCollectLocalCmd() *CollectLocalCmd {
-	c := &CollectLocalCmd{}
-	c.Command = cobra.Command{
-		Use:   "local [directory]",
-		Short: "Collect files from a local directory",
-		Long: `Collect files from a local directory and store them in a DataNode.
-
-If no directory is specified, the current working directory is used.
-
-Examples:
-  borg collect local
-  borg collect local ./src
-  borg collect local /path/to/project --output project.tar
-  borg collect local . --format stim --password secret
-  borg collect local . --exclude "*.log" --exclude "node_modules"`,
-		Args: cobra.MaximumNArgs(1),
-		RunE: func(cmd *cobra.Command, args []string) error {
-			directory := "."
-			if len(args) > 0 {
-				directory = args[0]
-			}
-
-			outputFile, _ := cmd.Flags().GetString("output")
-			format, _ := cmd.Flags().GetString("format")
-			compression, _ := cmd.Flags().GetString("compression")
-			password, _ := cmd.Flags().GetString("password")
-			excludes, _ := cmd.Flags().GetStringSlice("exclude")
-			includeHidden, _ := cmd.Flags().GetBool("hidden")
-			respectGitignore, _ := cmd.Flags().GetBool("gitignore")
-
-			finalPath, err := CollectLocal(directory, outputFile, format, compression, password, excludes, includeHidden, respectGitignore)
-			if err != nil {
-				return err
-			}
-			fmt.Fprintln(cmd.OutOrStdout(), "Files saved to", finalPath)
-			return nil
-		},
-	}
-	c.Flags().String("output", "", "Output file for the DataNode")
-	c.Flags().String("format", "datanode", "Output format (datanode, tim, trix, or stim)")
-	c.Flags().String("compression", "none", "Compression format (none, gz, or xz)")
-	c.Flags().String("password", "", "Password for encryption (required for stim/trix format)")
-	c.Flags().StringSlice("exclude", nil, "Patterns to exclude (can be specified multiple times)")
-	c.Flags().Bool("hidden", false, "Include hidden files and directories")
-	c.Flags().Bool("gitignore", true, "Respect .gitignore files (default: true)")
-	return c
-}
-
-func init() {
-	collectCmd.AddCommand(&NewCollectLocalCmd().Command)
-}
-
-// CollectLocal collects files from a local directory into a DataNode
-func CollectLocal(directory string, outputFile string, format string, compression string, password string, excludes []string, includeHidden bool, respectGitignore bool) (string, error) {
-	// Validate format
-	if format != "datanode" && format != "tim" && format != "trix" && format != "stim" {
-		return "", fmt.Errorf("invalid format: %s (must be 'datanode', 'tim', 'trix', or 'stim')", format)
-	}
-	if (format == "stim" || format == "trix") && password == "" {
-		return "", fmt.Errorf("password is required for %s format", format)
-	}
-	if compression != "none" && compression != "gz" && compression != "xz" {
-		return "", fmt.Errorf("invalid compression: %s (must be 'none', 'gz', or 'xz')", compression)
-	}
-
-	// Resolve directory path
-	absDir, err := filepath.Abs(directory)
-	if err != nil {
-		return "", fmt.Errorf("error resolving directory path: %w", err)
-	}
-
-	info, err := os.Stat(absDir)
-	if err != nil {
-		return "", fmt.Errorf("error accessing directory: %w", err)
-	}
-	if !info.IsDir() {
-		return "", fmt.Errorf("not a directory: %s", absDir)
-	}
-
-	// Load gitignore patterns if enabled
-	var gitignorePatterns []string
-	if respectGitignore {
-		gitignorePatterns = loadGitignore(absDir)
-	}
-
-	// Create DataNode and collect files
-	dn := datanode.New()
-	var fileCount int
-
-	bar := ui.NewProgressBar(-1, "Scanning files")
-	defer bar.Finish()
-
-	err = filepath.WalkDir(absDir, func(path string, d fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-
-		// Get relative path
-		relPath, err := filepath.Rel(absDir, path)
-		if err != nil {
-			return err
-		}
-
-		// Skip root
-		if relPath == "." {
-			return nil
-		}
-
-		// Skip hidden files/dirs unless explicitly included
-		if !includeHidden && isHidden(relPath) {
-			if d.IsDir() {
-				return filepath.SkipDir
-			}
-			return nil
-		}
-
-		// Check gitignore patterns
-		if respectGitignore && matchesGitignore(relPath, d.IsDir(), gitignorePatterns) {
-			if d.IsDir() {
-				return filepath.SkipDir
-			}
-			return nil
-		}
-
-		// Check exclude patterns
-		if matchesExclude(relPath, excludes) {
-			if d.IsDir() {
-				return filepath.SkipDir
-			}
-			return nil
-		}
-
-		// Skip directories (they're implicit in DataNode)
-		if d.IsDir() {
-			return nil
-		}
-
-		// Read file content
-		content, err := os.ReadFile(path)
-		if err != nil {
-			return fmt.Errorf("error reading %s: %w", relPath, err)
-		}
-
-		// Add to DataNode with forward slashes (tar convention)
-		dn.AddData(filepath.ToSlash(relPath), content)
-		fileCount++
-		bar.Describe(fmt.Sprintf("Collected %d files", fileCount))
-
-		return nil
-	})
-
-	if err != nil {
-		return "", fmt.Errorf("error walking directory: %w", err)
-	}
-
-	if fileCount == 0 {
-		return "", fmt.Errorf("no files found in %s", directory)
-	}
-
-	bar.Describe(fmt.Sprintf("Packaging %d files", fileCount))
-
-	// Convert to output format
-	var data []byte
-	if format == "tim" {
-		t, err := tim.FromDataNode(dn)
-		if err != nil {
-			return "", fmt.Errorf("error creating tim: %w", err)
-		}
-		data, err = t.ToTar()
-		if err != nil {
-			return "", fmt.Errorf("error serializing tim: %w", err)
-		}
-	} else if format == "stim" {
-		t, err := tim.FromDataNode(dn)
-		if err != nil {
-			return "", fmt.Errorf("error creating tim: %w", err)
-		}
-		data, err = t.ToSigil(password)
-		if err != nil {
-			return "", fmt.Errorf("error encrypting stim: %w", err)
-		}
-	} else if format == "trix" {
-		data, err = trix.ToTrix(dn, password)
-		if err != nil {
-			return "", fmt.Errorf("error serializing trix: %w", err)
-		}
-	} else {
-		data, err = dn.ToTar()
-		if err != nil {
-			return "", fmt.Errorf("error serializing DataNode: %w", err)
-		}
-	}
-
-	// Apply compression
-	compressedData, err := compress.Compress(data, compression)
-	if err != nil {
-		return "", fmt.Errorf("error compressing data: %w", err)
-	}
-
-	// Determine output filename
-	if outputFile == "" {
-		baseName := filepath.Base(absDir)
-		if baseName == "." || baseName == "/" {
-			baseName = "local"
-		}
-		outputFile = baseName + "." + format
-		if compression != "none" {
-			outputFile += "." + compression
-		}
-	}
-
-	err = os.WriteFile(outputFile, compressedData, 0644)
-	if err != nil {
-		return "", fmt.Errorf("error writing output file: %w", err)
-	}
-
-	return outputFile, nil
-}
-
-// isHidden checks if a path component starts with a dot
-func isHidden(path string) bool {
-	parts := strings.Split(filepath.ToSlash(path), "/")
-	for _, part := range parts {
-		if strings.HasPrefix(part, ".") {
-			return true
-		}
-	}
-	return false
-}
-
-// loadGitignore loads patterns from .gitignore if it exists
-func loadGitignore(dir string) []string {
-	var patterns []string
-
-	gitignorePath := filepath.Join(dir, ".gitignore")
-	content, err := os.ReadFile(gitignorePath)
-	if err != nil {
-		return patterns
-	}
-
-	lines := strings.Split(string(content), "\n")
-	for _, line := range lines {
-		line = strings.TrimSpace(line)
-		// Skip empty lines and comments
-		if line == "" || strings.HasPrefix(line, "#") {
-			continue
-		}
-		patterns = append(patterns, line)
-	}
-
-	return patterns
-}
-
-// matchesGitignore checks if a path matches any gitignore pattern
-func matchesGitignore(path string, isDir bool, patterns []string) bool {
-	for _, pattern := range patterns {
-		// Handle directory-only patterns
-		if strings.HasSuffix(pattern, "/") {
-			if !isDir {
-				continue
-			}
-			pattern = strings.TrimSuffix(pattern, "/")
-		}
-
-		// Handle negation (simplified - just skip negated patterns)
-		if strings.HasPrefix(pattern, "!") {
-			continue
-		}
-
-		// Match against path components
-		matched, _ := filepath.Match(pattern, filepath.Base(path))
-		if matched {
-			return true
-		}
-
-		// Also try matching the full path
-		matched, _ = filepath.Match(pattern, path)
-		if matched {
-			return true
-		}
-
-		// Handle ** patterns (simplified)
-		if strings.Contains(pattern, "**") {
-			simplePattern := strings.ReplaceAll(pattern, "**", "*")
-			matched, _ = filepath.Match(simplePattern, path)
-			if matched {
-				return true
-			}
-		}
-	}
-	return false
-}
-
-// matchesExclude checks if a path matches any exclude pattern
-func matchesExclude(path string, excludes []string) bool {
-	for _, pattern := range excludes {
-		// Match against basename
-		matched, _ := filepath.Match(pattern, filepath.Base(path))
-		if matched {
-			return true
-		}
-
-		// Match against full path
-		matched, _ = filepath.Match(pattern, path)
-		if matched {
-			return true
-		}
-	}
-	return false
-}

cmd/diff.go

@@ -0,0 +1,88 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/Snider/Borg/pkg/compress"
+	"github.com/Snider/Borg/pkg/datanode"
+	"github.com/Snider/Borg/pkg/diff"
+	"github.com/spf13/cobra"
+)
+
+// NewDiffCmd creates a new diff command.
+func NewDiffCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "diff <file1> <file2>",
+		Short: "Compare two archives",
+		Args:  cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			file1Path := args[0]
+			file2Path := args[1]
+
+			// Read and decompress the first file
+			file1Data, err := os.ReadFile(file1Path)
+			if err != nil {
+				return fmt.Errorf("failed to read file %s: %w", file1Path, err)
+			}
+			file1Data, err = compress.Decompress(file1Data)
+			if err != nil {
+				return fmt.Errorf("failed to decompress file %s: %w", file1Path, err)
+			}
+			dn1, err := datanode.FromTar(file1Data)
+			if err != nil {
+				return fmt.Errorf("failed to create datanode from %s: %w", file1Path, err)
+			}
+
+			// Read and decompress the second file
+			file2Data, err := os.ReadFile(file2Path)
+			if err != nil {
+				return fmt.Errorf("failed to read file %s: %w", file2Path, err)
+			}
+			file2Data, err = compress.Decompress(file2Data)
+			if err != nil {
+				return fmt.Errorf("failed to decompress file %s: %w", file2Path, err)
+			}
+			dn2, err := datanode.FromTar(file2Data)
+			if err != nil {
+				return fmt.Errorf("failed to create datanode from %s: %w", file2Path, err)
+			}
+
+			// Compare the two datanodes
+			differences, err := diff.Compare(dn1, dn2)
+			if err != nil {
+				return fmt.Errorf("failed to compare archives: %w", err)
+			}
+
+			// Print the results
+			if len(differences.Added) == 0 && len(differences.Removed) == 0 && len(differences.Modified) == 0 {
+				fmt.Fprintln(cmd.OutOrStdout(), "No differences found.")
+				return nil
+			}
+
+			if len(differences.Added) > 0 {
+				fmt.Fprintf(cmd.OutOrStdout(), "\nAdded (%d):\n", len(differences.Added))
+				for _, file := range differences.Added {
+					fmt.Fprintf(cmd.OutOrStdout(), "  + %s\n", file)
+				}
+			}
+
+			if len(differences.Removed) > 0 {
+				fmt.Fprintf(cmd.OutOrStdout(), "\nRemoved (%d):\n", len(differences.Removed))
+				for _, file := range differences.Removed {
+					fmt.Fprintf(cmd.OutOrStdout(), "  - %s\n", file)
+				}
+			}
+
+			if len(differences.Modified) > 0 {
+				fmt.Fprintf(cmd.OutOrStdout(), "\nModified (%d):\n", len(differences.Modified))
+				for _, file := range differences.Modified {
+					fmt.Fprintf(cmd.OutOrStdout(), "  ~ %s\n", file)
+				}
+			}
+
+			return nil
+		},
+	}
+	return cmd
+}

cmd/root.go

@@ -16,6 +16,7 @@ packaging their contents into a single file, and managing the data within.`,
 	}
 
 	rootCmd.PersistentFlags().BoolP("verbose", "v", false, "Enable verbose logging")
+	rootCmd.AddCommand(NewDiffCmd())
 	return rootCmd
 }
 

go.mod

@@ -60,7 +60,7 @@ require (
 	github.com/wailsapp/go-webview2 v1.0.22 // indirect
 	github.com/wailsapp/mimetype v1.4.1 // indirect
 	github.com/xanzy/ssh-agent v0.3.3 // indirect
-	golang.org/x/crypto v0.45.0 // indirect
+	golang.org/x/crypto v0.44.0 // indirect
 	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/term v0.37.0 // indirect
 	golang.org/x/text v0.31.0 // indirect

go.sum

@@ -155,8 +155,8 @@ github.com/xanzy/ssh-agent v0.3.3/go.mod h1:6dzNDKs0J9rVPHPhaGCukekBHKqfl+L3KghI
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210817164053-32db794688a5/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
-golang.org/x/crypto v0.45.0 h1:jMBrvKuj23MTlT0bQEOBcAE0mjg8mK9RXFhRH6nyF3Q=
-golang.org/x/crypto v0.45.0/go.mod h1:XTGrrkGJve7CYK7J8PEww4aY7gM3qMCElcJQ8n8JdX4=
+golang.org/x/crypto v0.44.0 h1:A97SsFvM3AIwEEmTBiaxPPTYpDC47w720rdiiUvgoAU=
+golang.org/x/crypto v0.44.0/go.mod h1:013i+Nw79BMiQiMsOPcVCB5ZIJbYkerPrGnOa00tvmc=
 golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 h1:2dVuKD2vS7b0QIHQbpyTISPd0LeHDbnYEryqj5Q1ug8=
 golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56/go.mod h1:M4RDyNAINzryxdtnbRXRL/OHtkFuWGRjvuhBJpk2IlY=
 golang.org/x/mod v0.30.0 h1:fDEXFVZ/fmCKProc/yAXXUijritrDzahmwwefnjoPFk=

pkg/diff/diff.go

@@ -0,0 +1,93 @@
+package diff
+
+import (
+	"bytes"
+	"io"
+	"io/fs"
+
+	"github.com/Snider/Borg/pkg/datanode"
+)
+
+// Diff represents the differences between two DataNodes.
+type Diff struct {
+	Added    []string
+	Removed  []string
+	Modified []string
+}
+
+// fileInfo stores content for comparison.
+type fileInfo struct {
+	content []byte
+}
+
+// Compare compares two DataNodes and returns a Diff object.
+func Compare(a, b *datanode.DataNode) (*Diff, error) {
+	diff := &Diff{}
+	filesA := make(map[string]fileInfo)
+	filesB := make(map[string]fileInfo)
+
+	// Walk through the first DataNode and collect file data
+	err := a.Walk(".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if !d.IsDir() {
+			file, err := a.Open(path)
+			if err != nil {
+				return err
+			}
+			defer file.Close()
+			content, err := io.ReadAll(file)
+			if err != nil {
+				return err
+			}
+			filesA[path] = fileInfo{content: content}
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Walk through the second DataNode and collect file data
+	err = b.Walk(".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if !d.IsDir() {
+			file, err := b.Open(path)
+			if err != nil {
+				return err
+			}
+			defer file.Close()
+			content, err := io.ReadAll(file)
+			if err != nil {
+				return err
+			}
+			filesB[path] = fileInfo{content: content}
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Find removed and modified files
+	for path, infoA := range filesA {
+		infoB, ok := filesB[path]
+		if !ok {
+			diff.Removed = append(diff.Removed, path)
+		} else if !bytes.Equal(infoA.content, infoB.content) {
+			diff.Modified = append(diff.Modified, path)
+		}
+	}
+
+	// Find added files
+	for path := range filesB {
+		if _, ok := filesA[path]; !ok {
+			diff.Added = append(diff.Added, path)
+		}
+	}
+
+	return diff, nil
+}

pkg/diff/diff_test.go

@@ -0,0 +1,75 @@
+package diff
+
+import (
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/Snider/Borg/pkg/datanode"
+)
+
+func TestCompare_Good(t *testing.T) {
+	a := datanode.New()
+	a.AddData("file1.txt", []byte("hello"))
+	a.AddData("file2.txt", []byte("world"))
+
+	b := datanode.New()
+	b.AddData("file1.txt", []byte("hello"))
+	b.AddData("file2.txt", []byte("world"))
+
+	diff, err := Compare(a, b)
+	if err != nil {
+		t.Fatalf("Compare() error = %v", err)
+	}
+	if len(diff.Added) != 0 || len(diff.Removed) != 0 || len(diff.Modified) != 0 {
+		t.Errorf("Expected no differences, but got %+v", diff)
+	}
+}
+
+func TestCompare_Bad(t *testing.T) {
+	a := datanode.New()
+	a.AddData("file1.txt", []byte("hello"))
+	a.AddData("file2.txt", []byte("world"))
+	a.AddData("file3.txt", []byte("old"))
+
+	b := datanode.New()
+	b.AddData("file1.txt", []byte("hello"))
+	b.AddData("file3.txt", []byte("new"))
+	b.AddData("file4.txt", []byte("added"))
+
+	diff, err := Compare(a, b)
+	if err != nil {
+		t.Fatalf("Compare() error = %v", err)
+	}
+
+	sort.Strings(diff.Added)
+	sort.Strings(diff.Removed)
+	sort.Strings(diff.Modified)
+
+	expectedAdded := []string{"file4.txt"}
+	expectedRemoved := []string{"file2.txt"}
+	expectedModified := []string{"file3.txt"}
+
+	if !reflect.DeepEqual(diff.Added, expectedAdded) {
+		t.Errorf("Expected Added %v, got %v", expectedAdded, diff.Added)
+	}
+	if !reflect.DeepEqual(diff.Removed, expectedRemoved) {
+		t.Errorf("Expected Removed %v, got %v", expectedRemoved, diff.Removed)
+	}
+	if !reflect.DeepEqual(diff.Modified, expectedModified) {
+		t.Errorf("Expected Modified %v, got %v", expectedModified, diff.Modified)
+	}
+}
+
+func TestCompare_Ugly(t *testing.T) {
+	a := datanode.New()
+	b := datanode.New()
+
+	diff, err := Compare(a, b)
+	if err != nil {
+		t.Fatalf("Compare() error = %v", err)
+	}
+	if len(diff.Added) != 0 || len(diff.Removed) != 0 || len(diff.Modified) != 0 {
+		t.Errorf("Expected no differences for empty datanodes, but got %+v", diff)
+	}
+}

pkg/sync/sync.go

@@ -0,0 +1,93 @@
+package sync
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/fs"
+
+	"github.com/Snider/Borg/pkg/datanode"
+)
+
+// SyncStrategy defines the strategy for a sync operation.
+type SyncStrategy string
+
+const (
+	// AppendStrategy adds new files only.
+	AppendStrategy SyncStrategy = "append"
+	// MirrorStrategy matches the source exactly.
+	MirrorStrategy SyncStrategy = "mirror"
+	// UpdateStrategy updates existing files and adds new ones.
+	UpdateStrategy SyncStrategy = "update"
+)
+
+// Sync merges two DataNodes based on a given strategy.
+func Sync(a, b *datanode.DataNode, strategy SyncStrategy) (*datanode.DataNode, error) {
+	result := datanode.New()
+	filesA := make(map[string][]byte)
+	filesB := make(map[string][]byte)
+
+	// Helper function to walk a DataNode and populate a map
+	walkAndCollect := func(dn *datanode.DataNode, fileMap map[string][]byte) error {
+		return dn.Walk(".", func(path string, d fs.DirEntry, err error) error {
+			if err != nil {
+				return err
+			}
+			if !d.IsDir() {
+				file, err := dn.Open(path)
+				if err != nil {
+					return err
+				}
+				defer file.Close()
+				content, err := io.ReadAll(file)
+				if err != nil {
+					return err
+				}
+				fileMap[path] = content
+			}
+			return nil
+		})
+	}
+
+	if err := walkAndCollect(a, filesA); err != nil {
+		return nil, fmt.Errorf("failed to walk source datanode: %w", err)
+	}
+	if err := walkAndCollect(b, filesB); err != nil {
+		return nil, fmt.Errorf("failed to walk target datanode: %w", err)
+	}
+
+	switch strategy {
+	case AppendStrategy:
+		// Add all files from A first
+		for path, content := range filesA {
+			result.AddData(path, content)
+		}
+		// Add files from B that are not in A
+		for path, content := range filesB {
+			if _, exists := filesA[path]; !exists {
+				result.AddData(path, content)
+			}
+		}
+	case MirrorStrategy:
+		// Result is an exact copy of B
+		for path, content := range filesB {
+			result.AddData(path, content)
+		}
+	case UpdateStrategy:
+		// Add all files from A first
+		for path, content := range filesA {
+			result.AddData(path, content)
+		}
+		// Add or update files from B
+		for path, contentB := range filesB {
+			contentA, exists := filesA[path]
+			if !exists || !bytes.Equal(contentA, contentB) {
+				result.AddData(path, contentB)
+			}
+		}
+	default:
+		return nil, fmt.Errorf("unknown sync strategy: %s", strategy)
+	}
+
+	return result, nil
+}

pkg/sync/sync_test.go

@@ -0,0 +1,79 @@
+package sync
+
+import (
+	"io/fs"
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/Snider/Borg/pkg/datanode"
+)
+
+func TestSync_Append(t *testing.T) {
+	a := datanode.New()
+	a.AddData("file1.txt", []byte("hello"))
+	a.AddData("file2.txt", []byte("world"))
+
+	b := datanode.New()
+	b.AddData("file1.txt", []byte("different"))
+	b.AddData("file3.txt", []byte("new"))
+
+	result, err := Sync(a, b, AppendStrategy)
+	if err != nil {
+		t.Fatalf("Sync() error = %v", err)
+	}
+
+	expectedFiles := []string{"file1.txt", "file2.txt", "file3.txt"}
+	assertDataNodeFiles(t, result, expectedFiles)
+}
+
+func TestSync_Mirror(t *testing.T) {
+	a := datanode.New()
+	a.AddData("file1.txt", []byte("hello"))
+	a.AddData("file2.txt", []byte("world"))
+
+	b := datanode.New()
+	b.AddData("file3.txt", []byte("new"))
+
+	result, err := Sync(a, b, MirrorStrategy)
+	if err != nil {
+		t.Fatalf("Sync() error = %v", err)
+	}
+
+	expectedFiles := []string{"file3.txt"}
+	assertDataNodeFiles(t, result, expectedFiles)
+}
+
+func TestSync_Update(t *testing.T) {
+	a := datanode.New()
+	a.AddData("file1.txt", []byte("hello"))
+	a.AddData("file2.txt", []byte("world"))
+
+	b := datanode.New()
+	b.AddData("file1.txt", []byte("updated"))
+	b.AddData("file3.txt", []byte("new"))
+
+	result, err := Sync(a, b, UpdateStrategy)
+	if err != nil {
+		t.Fatalf("Sync() error = %v", err)
+	}
+
+	expectedFiles := []string{"file1.txt", "file2.txt", "file3.txt"}
+	assertDataNodeFiles(t, result, expectedFiles)
+}
+
+func assertDataNodeFiles(t *testing.T, dn *datanode.DataNode, expected []string) {
+	t.Helper()
+	var actual []string
+	dn.Walk(".", func(path string, d fs.DirEntry, err error) error {
+		if !d.IsDir() {
+			actual = append(actual, path)
+		}
+		return nil
+	})
+	sort.Strings(actual)
+	sort.Strings(expected)
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Expected files %v, got %v", expected, actual)
+	}
+}