initial

internal/bsdaily/copy.go

@@ -0,0 +1,49 @@
+package bsdaily
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+)
+
+func CopyFile(src, dst string) (err error) {
+	slog.Info("copying file", "src", src, "dst", dst)
+
+	srcFile, err := os.Open(src)
+	if err != nil {
+		return fmt.Errorf("opening source %s: %w", src, err)
+	}
+	defer srcFile.Close()
+
+	srcInfo, err := srcFile.Stat()
+	if err != nil {
+		return fmt.Errorf("stat source %s: %w", src, err)
+	}
+
+	dstFile, err := os.Create(dst)
+	if err != nil {
+		return fmt.Errorf("creating destination %s: %w", dst, err)
+	}
+	defer func() {
+		if cerr := dstFile.Close(); cerr != nil && err == nil {
+			err = fmt.Errorf("closing destination %s: %w", dst, cerr)
+		}
+	}()
+
+	written, err := io.Copy(dstFile, srcFile)
+	if err != nil {
+		return fmt.Errorf("copying data: %w", err)
+	}
+
+	if written != srcInfo.Size() {
+		return fmt.Errorf("short copy: wrote %d bytes, expected %d", written, srcInfo.Size())
+	}
+
+	if err := dstFile.Sync(); err != nil {
+		return fmt.Errorf("syncing destination %s: %w", dst, err)
+	}
+
+	slog.Info("file copied", "dst", dst, "bytes", written)
+	return nil
+}