Initial commit

internal/template/service.go

@@ -0,0 +1,90 @@
+package template
+
+import (
+	"fmt"
+	"html/template"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"strings"
+)
+
+type Service struct {
+	baseDir string
+	cache   map[string]*template.Template
+}
+
+func createFuncMap() template.FuncMap {
+	funcMap := template.FuncMap{
+		"dict": func(pairs ...any) (map[string]any, error) {
+			if len(pairs)%2 != 0 {
+				return nil, fmt.Errorf("dict requires an even number of arguments")
+			}
+			m := make(map[string]any)
+			for i := 0; i < len(pairs); i += 2 {
+				key, ok := pairs[i].(string)
+				if !ok {
+					return nil, fmt.Errorf("dict keys must be strings")
+				}
+				m[key] = pairs[i+1]
+			}
+			return m, nil
+		},
+		"default": func(fallback string, value any) any {
+			if value == nil {
+				return fallback
+			}
+			return value
+		},
+	}
+
+	return funcMap
+}
+
+func NewService(uiDir string) (*Service, error) {
+	cache := make(map[string]*template.Template)
+
+	uiFS := os.DirFS(uiDir)
+
+	funcMap := createFuncMap()
+
+	err := fs.WalkDir(uiFS, "pages", func(filePath string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			return nil
+		}
+		if !strings.HasSuffix(filePath, ".html") {
+			return nil
+		}
+
+		// Key by the relative path under pages/, e.g. "auth/signin.html".
+		relPath := strings.TrimPrefix(filePath, "pages/")
+
+		tmpl, err := template.New(path.Base(filePath)).Funcs(funcMap).ParseFS(uiFS, filePath, "layouts/*.html")
+		if err != nil {
+			return fmt.Errorf("can't parse filesystem: %w", err)
+		}
+		cache[relPath] = tmpl
+
+		return nil
+	})
+	if err != nil {
+		return nil, fmt.Errorf("can't walk 'pages' in '%s': %w", uiDir, err)
+	}
+
+	return &Service{
+		baseDir: uiDir,
+		cache:   cache,
+	}, nil
+}
+
+func (e *Service) Render(w io.Writer, pageName string, data any) error {
+	tmpl, ok := e.cache[pageName]
+	if !ok {
+		return fmt.Errorf("no such template: %s", pageName)
+	}
+	return tmpl.Execute(w, data)
+}