From 3fd46f3977fb650974e5e936cba362c787c00637 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Sat, 7 Feb 2026 16:32:10 +0200
Subject: reimport this PoC

---
 internal/watcher/file_watcher.go | 86 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 internal/watcher/file_watcher.go

(limited to 'internal/watcher')

diff --git a/internal/watcher/file_watcher.go b/internal/watcher/file_watcher.go
new file mode 100644
index 0000000..63ccb08
--- /dev/null
+++ b/internal/watcher/file_watcher.go
@@ -0,0 +1,86 @@
+package watcher
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"time"
+)
+
+// FileWatcher monitors a file for changes based on modification time.
+type FileWatcher struct {
+	filePath       string
+	pollInterval   time.Duration
+	lastModTime    time.Time
+}
+
+// NewFileWatcher creates a new file watcher.
+func NewFileWatcher(filePath string, pollInterval time.Duration) *FileWatcher {
+	return &FileWatcher{
+		filePath:     filePath,
+		pollInterval: pollInterval,
+	}
+}
+
+// Watch starts watching the file and returns a channel that signals changes.
+// If the file doesn't exist yet, it will wait until it appears.
+func (fw *FileWatcher) Watch(ctx context.Context) (<-chan struct{}, error) {
+	changeChan := make(chan struct{}, 1)
+
+	go func() {
+		defer close(changeChan)
+		ticker := time.NewTicker(fw.pollInterval)
+		defer ticker.Stop()
+
+		fileExists := false
+		
+		// Wait for file to exist
+		for !fileExists {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+				info, err := os.Stat(fw.filePath)
+				if err != nil {
+					// File doesn't exist yet, keep waiting
+					fmt.Printf("Waiting for file to exist: %s\n", fw.filePath)
+					continue
+				}
+				
+				// File now exists!
+				fileExists = true
+				fw.lastModTime = info.ModTime()
+				// Send initial change to process file
+				changeChan <- struct{}{}
+				fmt.Printf("File detected, starting watch: %s\n", fw.filePath)
+			}
+		}
+
+		// Now watch for changes
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+				info, err := os.Stat(fw.filePath)
+				if err != nil {
+					// File might have been deleted or is temporarily unavailable
+					continue
+				}
+
+				modTime := info.ModTime()
+				if modTime.After(fw.lastModTime) {
+					fw.lastModTime = modTime
+					changeChan <- struct{}{}
+				}
+			}
+		}
+	}()
+
+	return changeChan, nil
+}
+
+// GetLastModTime returns the last known modification time of the file.
+func (fw *FileWatcher) GetLastModTime() time.Time {
+	return fw.lastModTime
+}
-- 
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