feat: watch and live reload in development

2 files changed, 92 insertions, 3 deletions

diff --git a/internal/server/dev.go b/internal/server/dev.go
new file mode 100644
index 0000000..52ab29b
--- /dev/null
+++ b/internal/server/dev.go
@@ -0,0 +1,71 @@
+package server
+
+import (
+	"fmt"
+	"io/fs"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/pkg/errors"
+)
+
+type FileWatcher struct {
+	*fsnotify.Watcher
+}
+
+func NewFileWatcher() (*FileWatcher, error) {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, errors.WithMessage(err, "could not create watcher")
+	}
+
+	return &FileWatcher{watcher}, nil
+}
+
+func (watcher FileWatcher) AddRecursive(from string) error {
+	slog.Debug(fmt.Sprintf("watching files under %s", 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() {
+			slog.Debug(fmt.Sprintf("adding directory %s to watcher", 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()) {
+	for {
+		select {
+		case event := <-watcher.Events:
+			slog.Debug(fmt.Sprintf("event received: %s", event))
+			if event.Has(fsnotify.Create) || event.Has(fsnotify.Rename) {
+				f, err := os.Stat(event.Name)
+				if err != nil {
+					slog.Error(fmt.Sprintf("error handling %s event: %v", event.Op.String(), err))
+				} else if f.IsDir() {
+					err = watcher.Add(event.Name)
+					if err != nil {
+						slog.Error(fmt.Sprintf("error adding new folder to watcher: %v", err))
+					}
+				}
+			}
+			if event.Has(fsnotify.Rename) || event.Has(fsnotify.Write) {
+				callback()
+				time.Sleep(500 * time.Millisecond)
+			}
+		case err := <-watcher.Errors:
+			slog.Error(fmt.Sprintf("error in watcher: %v", err))
+		}
+	}
+}
diff --git a/internal/server/server.go b/internal/server/server.go
index fc56d47..04ee94c 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"context"
+	"fmt"
 	"html/template"
 	"io"
 	"log"
@@ -87,7 +88,8 @@ func New(runtimeConfig *Config) (*Server, error) {
 		Repanic: true,
 	})
 
-	tpl := template.Must(template.ParseGlob(path.Join("frontend", "templates", "*.tmpl")))
+	templatePaths := path.Join("frontend", "templates", "*.tmpl")
+	tpl := template.Must(template.ParseGlob(templatePaths))
 
 	top := http.NewServeMux()
 	mux := http.NewServeMux()
@@ -108,8 +110,24 @@ func New(runtimeConfig *Config) (*Server, error) {
 		applyDevModeOverrides(config)
 		liveReload := livereload.New()
 		liveReload.Start()
-		mux.Handle("/livereload", liveReload)
-		// liveReload.Reload()
+		top.Handle("/livereload", liveReload)
+		fw, err := NewFileWatcher()
+		if err != nil {
+			return nil, errors.WithMessage(err, "could not create file watcher")
+		}
+		err = fw.AddRecursive("frontend")
+		if err != nil {
+			return nil, errors.WithMessage(err, "could not add directory to file watcher")
+		}
+		go fw.Start(func() {
+			t, err := template.ParseGlob(path.Join("frontend", "templates", "*.tmpl"))
+			if err != nil {
+				slog.Error(fmt.Sprintf("could not parse template: %v", err))
+			} else {
+				tpl = t
+				liveReload.Reload()
+			}
+		})
 	}
 
 	var logWriter io.Writer