From e2235c24231f8c33fa0b727b4b25fcd62729ccee Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Tue, 8 Apr 2025 15:51:46 -0700
Subject: Copy recursive

---
 internal/cp/cp.go | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 internal/cp/cp.go

(limited to 'internal')

diff --git a/internal/cp/cp.go b/internal/cp/cp.go
new file mode 100644
index 0000000..c19627f
--- /dev/null
+++ b/internal/cp/cp.go
@@ -0,0 +1,172 @@
+package cp
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+type Progress interface {
+	Max(int64)
+	Progress(int64)
+	FileStart(string)
+	FileDone(string, error)
+}
+
+func size(files []string) int64 {
+	var n int64 = 0
+	for _, f := range files {
+		filepath.WalkDir(f, func(path string, d fs.DirEntry, err error) error {
+			if err != nil {
+				return nil
+			}
+			switch d.Type() {
+			case 0: // regular file
+				stat, err := d.Info()
+				if err != nil {
+					return nil
+				}
+				n += 1 + stat.Size()
+			case os.ModeSymlink, os.ModeDir:
+				n++
+			}
+			return nil
+		})
+	}
+	return n
+}
+
+func fileExists(path string) bool {
+	_, err := os.Lstat(path)
+	return !errors.Is(err, os.ErrNotExist)
+}
+
+func copyRegularFile(src, dst string, force bool, progress Progress) (err error) {
+	progress.FileStart(src)
+
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	stat, err := in.Stat()
+	if err != nil {
+		return err
+	}
+	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, stat.Mode().Perm())
+	if err != nil {
+		if !force || !fileExists(dst) {
+			return err
+		}
+		if err := os.RemoveAll(dst); err != nil {
+			return err
+		}
+		out, err = os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, stat.Mode().Perm())
+		if err != nil {
+			return err
+		}
+	}
+	defer out.Close()
+	for {
+		n, err := io.CopyN(out, in, 1024*1024)
+		if n > 0 {
+			progress.Progress(n)
+		}
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+	}
+	if err := out.Close(); err != nil {
+		return err
+	}
+	progress.Progress(1)
+	return nil
+}
+
+func copySpecialFile(src string, d fs.DirEntry, dst string, force bool, progress Progress) error {
+	switch d.Type() {
+	case fs.ModeSymlink:
+		target, err := os.Readlink(src)
+		if err != nil {
+			return err
+		}
+		if err := os.Symlink(target, dst); err != nil {
+			if !force || !fileExists(dst) {
+				return err
+			}
+			if err := os.RemoveAll(dst); err != nil {
+				return err
+			}
+			if err := os.Symlink(target, dst); err != nil {
+				return err
+			}
+		}
+		progress.Progress(1)
+	case fs.ModeDir:
+		stat, err := d.Info()
+		if err != nil {
+			return err
+		}
+		if err := os.Mkdir(dst, stat.Mode().Perm()); err != nil {
+			if !force || !fileExists(dst) {
+				return err
+			}
+			if err := os.RemoveAll(dst); err != nil {
+				return err
+			}
+			if err := os.Mkdir(dst, stat.Mode().Perm()); err != nil {
+				return err
+			}
+		}
+		progress.Progress(1)
+	default:
+		return fmt.Errorf("%s: unknown file type %s", src, d.Type())
+	}
+	return nil
+}
+
+func Copy(srcs []string, dstRoot string, force bool, progress Progress) {
+	go func() {
+		progress.Max(size(srcs))
+	}()
+	const maxConcurrency = 10
+	// sem acts as a semaphore to limit the number of concurrent file copies
+	sem := make(chan struct{}, maxConcurrency)
+	for _, srcRoot := range srcs {
+		filepath.WalkDir(srcRoot, func(src string, d fs.DirEntry, err error) error {
+			if err != nil {
+				progress.FileDone(src, err)
+				return nil
+			}
+			relPath, err := filepath.Rel(srcRoot, src)
+			if err != nil {
+				progress.FileDone(src, err)
+				return nil
+			}
+			dst := filepath.Join(dstRoot, relPath)
+			if d.Type().IsRegular() {
+				sem <- struct{}{}
+				go func() {
+					defer func() { <-sem }()
+					err := copyRegularFile(src, dst, force, progress)
+					progress.FileDone(src, err)
+				}()
+			} else {
+				if err := copySpecialFile(src, d, dst, force, progress); err != nil {
+					progress.FileDone(src, err)
+					return nil
+				}
+			}
+			return nil
+		})
+	}
+	for range maxConcurrency {
+		sem <- struct{}{}
+	}
+}
-- 
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