more initial changes

internal/util/fileutil.go

@@ -0,0 +1,60 @@
+package util
+
+import (
+    "os"
+    "path/filepath"
+    "strings"
+    "time"
+)
+
+// HasExt reports whether path has one of the provided extensions (case-insensitive, with or without dot).
+func HasExt(path string, exts []string) bool {
+    if len(exts) == 0 {
+        return true
+    }
+    ext := strings.ToLower(filepath.Ext(path))
+    for _, e := range exts {
+        e = strings.ToLower(e)
+        if !strings.HasPrefix(e, ".") {
+            e = "." + e
+        }
+        if ext == e {
+            return true
+        }
+    }
+    return false
+}
+
+// WaitForStable waits until the file size has not changed for stableFor duration.
+func WaitForStable(path string, stableFor time.Duration, timeout time.Duration) error {
+    start := time.Now()
+    var lastSize int64 = -1
+    var stableStart time.Time
+
+    for {
+        info, err := os.Stat(path)
+        if err != nil {
+            return err
+        }
+        size := info.Size()
+
+        if size == lastSize {
+            if stableStart.IsZero() {
+                stableStart = time.Now()
+            }
+            if time.Since(stableStart) >= stableFor {
+                return nil
+            }
+        } else {
+            stableStart = time.Time{}
+        }
+
+        lastSize = size
+
+        if time.Since(start) > timeout {
+            return os.ErrDeadlineExceeded
+        }
+
+        time.Sleep(2 * time.Second)
+    }
+}