http: Add the ability to serve a directory

http/handler.go

@@ -16,6 +16,11 @@ type ErrorData struct {
 	Message any
 }
 
+type DirectoryData struct {
+	Name    string
+	Entries []fs.DirEntry
+}
+
 type Handler struct {
 	Environment       *step.Environment
 	Directories       bool
@@ -79,10 +84,8 @@ func (this *Handler) ServeHTTP (res http.ResponseWriter, req *http.Request) {
 			return
 		}
 
-		// TODO: serve a directory and return
-		// have a custom directory listing document that takes in a list
-		// of the files in the directory and the path to the directory
-		// as data
+		this.serveDirectory(res, req, pat)
+		return
 	}
 
 	this.serveFile(res, req, pat)
@@ -102,6 +105,38 @@ func (this *Handler) serveFile (
 	this.serveDocument(res, req, name)	
 }
 
+func (this *Handler) serveDirectory (
+	res http.ResponseWriter,
+	req *http.Request,
+	pat string,
+) {
+	name := pathToName(pat)
+	entries, err := readDir(this.Environment.GetFS(), name)
+	if err != nil {
+		this.serveError(res, req, http.StatusInternalServerError, err, false)
+		return
+	}
+	if this.DirectoryDocument == "" {
+		this.serveFile(res, req, pat)
+		return
+	}
+	document, err := this.Environment.Parse(this.DirectoryDocument)
+	if err != nil {
+		this.serveError(res, req, http.StatusInternalServerError, err, false)
+		return
+	}
+	err = document.Execute(res, step.ExecutionData {
+		Data: DirectoryData {
+			Name:    name,
+			Entries: entries,
+		},
+	})
+	if err != nil {
+		this.serveError(res, req, http.StatusInternalServerError, err, false)
+		return
+	}
+}
+
 func (this *Handler) serveDocument (
 	res http.ResponseWriter,
 	req *http.Request,
@@ -214,3 +249,16 @@ func pathToName (pat string) string {
 	}
 	return pat
 }
+
+func readDir (filesystem fs.FS, name string) ([]fs.DirEntry, error) {
+	if filesystem, ok := filesystem.(fs.ReadDirFS); ok {
+		return filesystem.ReadDir(name)
+	}
+	dir, err := filesystem.Open(name)
+	if err != nil { return nil, err }
+	defer dir.Close()
+	if dir, ok := dir.(fs.ReadDirFile); ok {
+		return dir.ReadDir(0)
+	}
+	return nil, nil
+}