1 files changed, 109 insertions, 0 deletions
diff --git a/internal/server/dev.go b/internal/server/dev.go
new file mode 100644
index 0000000..6fcc93e
--- /dev/null
+++ b/internal/server/dev.go
@@ -0,0 +1,109 @@
+package server
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"slices"
+	"time"
+
+	"go.alanpearce.eu/x/log"
+
+	"github.com/fsnotify/fsnotify"
+	"gitlab.com/tozd/go/errors"
+)
+
+type FileWatcher struct {
+	*fsnotify.Watcher
+}
+
+var (
+	l       *log.Logger
+	ignores = []string{
+		"*.templ",
+		"*.go",
+	}
+	checkSettleInterval = 200 * time.Millisecond
+)
+
+func matches(name string) func(string) bool {
+	return func(pattern string) bool {
+		matched, err := path.Match(pattern, name)
+		if err != nil {
+			l.Warn("error checking watcher ignores", "error", err)
+		}
+
+		return matched
+	}
+}
+
+func ignored(pathname string) bool {
+	return slices.ContainsFunc(ignores, matches(path.Base(pathname)))
+}
+
+func NewFileWatcher(log *log.Logger) (*FileWatcher, error) {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, errors.WithMessage(err, "could not create watcher")
+	}
+	l = log
+
+	return &FileWatcher{watcher}, nil
+}
+
+func (watcher FileWatcher) AddRecursive(from string) error {
+	l.Debug("walking directory tree", "root", from)
+	err := filepath.WalkDir(from, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return errors.WithMessagef(err, "could not walk directory %s", path)
+		}
+		if entry.IsDir() {
+			l.Debug("adding directory to watcher", "path", path)
+			if err = watcher.Add(path); err != nil {
+				return errors.WithMessagef(err, "could not add directory %s to watcher", path)
+			}
+		}
+
+		return nil
+	})
+
+	return errors.WithMessage(err, "error walking directory tree")
+}
+
+func (watcher FileWatcher) Start(callback func(string)) {
+	var timer *time.Timer
+	for {
+		select {
+		case event := <-watcher.Events:
+			if !ignored(event.Name) {
+				l.Debug("watcher event", "name", event.Name, "op", event.Op.String())
+				if event.Has(fsnotify.Create) || event.Has(fsnotify.Rename) {
+					f, err := os.Stat(event.Name)
+					if err != nil {
+						l.Error(
+							fmt.Sprintf("error handling %s event: %v", event.Op.String(), err),
+						)
+					} else if f.IsDir() {
+						err = watcher.Add(event.Name)
+						if err != nil {
+							l.Error(fmt.Sprintf("error adding new folder to watcher: %v", err))
+						}
+					}
+				}
+				if event.Has(fsnotify.Rename) || event.Has(fsnotify.Write) ||
+					event.Has(fsnotify.Create) || event.Has(fsnotify.Chmod) {
+					if timer == nil {
+						timer = time.AfterFunc(checkSettleInterval, func() {
+							callback(event.Name)
+						})
+					}
+					timer.Reset(checkSettleInterval)
+				}
+			}
+		case err := <-watcher.Errors:
+			l.Error("error in watcher", "error", err)
+		}
+	}
+}