From 04a4a4fa7eb1c8d1044d717a657606ee58b2778f Mon Sep 17 00:00:00 2001
From: Felicitas Pojtinger <felicitas@pojtinger.com>
Date: Mon, 27 Dec 2021 17:12:19 +0100
Subject: [PATCH] feat: Add support for `O_TRUNC` and `O_APPEND` flags

---
 cmd/stfs/cmd/serve_ftp.go  |  1 +
 cmd/stfs/cmd/serve_http.go |  5 +++--
 internal/fs/file.go        | 15 ++++++++-------
 internal/fs/filesystem.go  | 16 ++++++++++++----
 4 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/cmd/stfs/cmd/serve_ftp.go b/cmd/stfs/cmd/serve_ftp.go
index 5dc5d8a..30508a6 100644
--- a/cmd/stfs/cmd/serve_ftp.go
+++ b/cmd/stfs/cmd/serve_ftp.go
@@ -203,6 +203,7 @@ var serveFTPCmd = &cobra.Command{
 					viper.GetString(cacheWriteFlag),
 				)
 			},
+			true, // FTP needs read permission for `STOR` command even if O_WRONLY is set
 
 			logger.PrintHeader,
 		)
diff --git a/cmd/stfs/cmd/serve_http.go b/cmd/stfs/cmd/serve_http.go
index 0feeebd..0cc1953 100644
--- a/cmd/stfs/cmd/serve_http.go
+++ b/cmd/stfs/cmd/serve_http.go
@@ -125,8 +125,9 @@ var serveHTTPCmd = &cobra.Command{
 				Metadata: metadataPersister,
 			},
 
-			"",  // We never write
-			nil, // We never write
+			"",    // We never write
+			nil,   // We never write
+			false, // We never write
 
 			logger.PrintHeader,
 		)
diff --git a/internal/fs/file.go b/internal/fs/file.go
index 5dc8228..5a7db3d 100644
--- a/internal/fs/file.go
+++ b/internal/fs/file.go
@@ -199,8 +199,6 @@ func (f *File) closeWithoutLocking() error {
 }
 
 func (f *File) enterWriteMode() error {
-	log.Println("File.enterWriteMode")
-
 	if f.readOpReader != nil || f.readOpWriter != nil {
 		if err := f.closeWithoutLocking(); err != nil {
 			return err
@@ -253,13 +251,16 @@ func (f *File) enterWriteMode() error {
 			}
 		}
 
-		// TODO: Don't do this if O_APPEND is set
-		if err := f.writeBuf.Truncate(0); err != nil {
-			return err
+		if f.flags.truncate {
+			if err := f.writeBuf.Truncate(0); err != nil {
+				return err
+			}
 		}
 
-		if _, err := f.writeBuf.Seek(0, io.SeekStart); err != nil {
-			return err
+		if !f.flags.append {
+			if _, err := f.writeBuf.Seek(0, io.SeekStart); err != nil {
+				return err
+			}
 		}
 	}
 
diff --git a/internal/fs/filesystem.go b/internal/fs/filesystem.go
index 473b784..b73ddbe 100644
--- a/internal/fs/filesystem.go
+++ b/internal/fs/filesystem.go
@@ -30,8 +30,9 @@ type FileSystem struct {
 
 	metadata config.MetadataConfig
 
-	compressionLevel string
-	getFileBuffer    func() (WriteCache, func() error, error)
+	compressionLevel       string
+	getFileBuffer          func() (WriteCache, func() error, error)
+	relaxedReadPermissions bool
 
 	onHeader func(hdr *models.Header)
 }
@@ -44,6 +45,7 @@ func NewFileSystem(
 
 	compressionLevel string,
 	getFileBuffer func() (WriteCache, func() error, error),
+	ignorePermissionFlags bool,
 
 	onHeader func(hdr *models.Header),
 ) afero.Fs {
@@ -53,8 +55,9 @@ func NewFileSystem(
 
 		metadata: metadata,
 
-		compressionLevel: compressionLevel,
-		getFileBuffer:    getFileBuffer,
+		compressionLevel:       compressionLevel,
+		getFileBuffer:          getFileBuffer,
+		relaxedReadPermissions: ignorePermissionFlags,
 
 		onHeader: onHeader,
 	}
@@ -196,6 +199,11 @@ func (f *FileSystem) OpenFile(name string, flag int, perm os.FileMode) (afero.Fi
 		flags.write = true
 	}
 
+	if flags.write && !flags.read && f.relaxedReadPermissions {
+		flags.read = true
+		flags.write = true
+	}
+
 	if flag&os.O_APPEND != 0 {
 		flags.append = true
 	}