Implement the ‘watch’ package

2 files changed, 65 insertions, 15 deletions

diff --git a/src/templates.go b/src/templates.go
index 8479759..de1f081 100644
--- a/src/templates.go
+++ b/src/templates.go
@@ -8,6 +8,8 @@ import (
 	"strings"
 
 	"git.thomasvoss.com/euro-cash.eu/src/dbx"
+	. "git.thomasvoss.com/euro-cash.eu/src/try"
+	"git.thomasvoss.com/euro-cash.eu/src/watch"
 )
 
 type templateData struct {
@@ -31,29 +33,36 @@ var (
 	}
 )
 
-func BuildTemplates(dir fs.FS) {
-	ents, err := fs.ReadDir(dir, ".")
-	if err != nil {
-		log.Fatal(err)
-	}
-
+func BuildTemplates(dir fs.FS, debugp bool) {
+	ents := Try2(fs.ReadDir(dir, "."))
 	notFoundTmpl = buildTemplate(dir, "-404")
 	errorTmpl = buildTemplate(dir, "-error")
-
 	templates = make(map[string]*template.Template, len(ents))
+
 	for _, e := range ents {
-		path := "/"
-		name := strings.TrimSuffix(e.Name(), ".html.tmpl")
-		switch {
-		case name[0] == '-':
-			continue
-		case name != "index":
-			path += strings.ReplaceAll(name, "-", "/")
+		name := e.Name()
+		buildAndSetTemplate(dir, name)
+		if debugp {
+			go watch.FileFS(dir, name, func() {
+				buildAndSetTemplate(dir, name)
+				log.Printf("Template ‘%s’ updated\n", name)
+			})
 		}
-		templates[path] = buildTemplate(dir, name)
 	}
 }
 
+func buildAndSetTemplate(dir fs.FS, name string) {
+	path := "/"
+	name = strings.TrimSuffix(name, ".html.tmpl")
+	switch {
+	case name[0] == '-':
+		return
+	case name != "index":
+		path += strings.ReplaceAll(name, "-", "/")
+	}
+	templates[path] = buildTemplate(dir, name)
+}
+
 func buildTemplate(dir fs.FS, name string) *template.Template {
 	names := [...]string{"-base", "-navbar", name}
 	for i, s := range names {
diff --git a/src/watch/watch.go b/src/watch/watch.go
new file mode 100644
index 0000000..84f9ed9
--- /dev/null
+++ b/src/watch/watch.go
@@ -0,0 +1,41 @@
+package watch
+
+import (
+	"errors"
+	"io/fs"
+	"log"
+	"os"
+	"time"
+
+	. "git.thomasvoss.com/euro-cash.eu/src/try"
+)
+
+func File(path string, f func()) {
+	impl(path, os.Stat, f)
+}
+
+func FileFS(dir fs.FS, path string, f func()) {
+	impl(path, func(path string) (os.FileInfo, error) {
+		return fs.Stat(dir, path)
+	}, f)
+}
+
+func impl(path string, statfn func(string) (os.FileInfo, error), f func()) {
+	ostat := Try2(statfn(path))
+
+	for {
+		nstat, err := statfn(path)
+		switch {
+		case errors.Is(err, os.ErrNotExist):
+			return
+		case err != nil:
+			log.Println(err)
+		}
+
+		if nstat.ModTime() != ostat.ModTime() {
+			f()
+			ostat = nstat
+		}
+		time.Sleep(1 * time.Second)
+	}
+}