1 files changed, 134 insertions, 0 deletions
diff --git a/shelf/shelf.go b/shelf/shelf.go
new file mode 100644
index 0000000..6df46fc
--- /dev/null
+++ b/shelf/shelf.go
@@ -0,0 +1,134 @@
+package shelf
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"io/fs"
+	"path/filepath"
+	"runtime"
+	"slices"
+	"strings"
+	"sync"
+
+	"golang.org/x/sync/errgroup"
+)
+
+var Root = ".shelf"
+
+type Sum map[Item]string
+
+func Index(ignore []byte) (Sum, error) {
+	sum := make(Sum)
+
+	var rw sync.RWMutex
+
+	g, ctx := errgroup.WithContext(context.Background())
+
+	sem := make(chan struct{}, max(1, runtime.NumCPU()-1))
+
+	ign := newIgnore(ignore)
+
+	rootPath := filepath.Clean(Root)
+
+	walkErr := filepath.WalkDir(rootPath, func(abs string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return nil
+		}
+
+		rel, relErr := filepath.Rel(rootPath, abs)
+
+		if relErr != nil {
+			return err
+		}
+
+		if rel == "." {
+			return nil
+		}
+
+		if ign.Match(rel, d.IsDir()) {
+			if d.IsDir() {
+				return fs.SkipDir
+			}
+
+			return nil
+		}
+
+		if d.IsDir() || !d.Type().IsRegular() {
+			return nil
+		}
+
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case sem <- struct{}{}:
+		}
+
+		g.Go(func() error {
+			defer func() { <-sem }()
+
+			hash, hashErr := hashFile(abs)
+
+			if hashErr != nil {
+				return hashErr
+			}
+
+			rw.Lock()
+
+			sum[Item(rel)] = hash
+
+			rw.Unlock()
+
+			return nil
+		})
+
+		return nil
+	})
+
+	if err := g.Wait(); err != nil {
+		return nil, err
+	}
+
+	return sum, walkErr
+}
+
+func Serialize(s Sum, w io.Writer) error {
+	items := make([]Item, 0, len(s))
+
+	for item := range s {
+		items = append(items, item)
+	}
+
+	slices.SortFunc(items, func(a, b Item) int {
+		return strings.Compare(string(a), string(b))
+	})
+
+	for _, item := range items {
+		if _, err := fmt.Fprintf(w, "%s  %s\n", s[item], item); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func Deserialize(r io.Reader) (Sum, error) {
+	sum := make(Sum)
+
+	s := bufio.NewScanner(r)
+
+	for s.Scan() {
+		line := s.Text()
+
+		parts := strings.SplitN(line, "  ", 2)
+
+		if len(parts) != 2 {
+			return nil, fmt.Errorf("malformed line: %q", line)
+		}
+
+		sum[Item(parts[1])] = parts[0]
+	}
+
+	return sum, s.Err()
+}