Add a formatter for VyOS 1.x config files.

2 files changed, 84 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 7ce3047..e196d22 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,8 @@ LIBFILES=$(BUILDDIR)/lib/bindings.cmx			\
          $(BUILDDIR)/lib/apply_bindings.cmx		\
          $(BUILDDIR)/generated/vyosconfig.o		\
          $(BUILDDIR)/lib/vyos1x_parser.cmx		\
-         $(BUILDDIR)/lib/vyos1x_lexer.cmx
+         $(BUILDDIR)/lib/vyos1x_lexer.cmx		\
+         $(BUILDDIR)/lib/vyos1x_renderer.cmx
 
 CAML_INIT=$(BUILDDIR)/stub/init.o
 
diff --git a/lib/vyos1x_renderer.ml b/lib/vyos1x_renderer.ml
new file mode 100644
index 0000000..4a1f4a0
--- /dev/null
+++ b/lib/vyos1x_renderer.ml
@@ -0,0 +1,82 @@
+(* The renderer makes two assumptions about the invariants of the config files:
+   that top level nodes are never tag or leaf nodes,
+   and that immediate children of tag nodes are never themselves tag nodes.
+
+   They are true in all existing VyOS configs and configs with those invariant
+   broken will never load, so these assumptions are safe to make when
+   processing existing configs. In configs built from scratch, the user is
+   responsible for its validness.
+
+   The original loader behaviour with tag nodes is strange: deep down, after
+   config loading, they are indistinguishable from any other nodes, but at load
+   time, they fail to validate unless they are formatted as tag nodes in the
+   config file, that is, "ethernet eth0 { ..." as opposed to "ethernet { eth0 { ...".
+
+   Since Vyconf makes no distinction between normal nodes and tag nodes other than
+   at set command validation and formatting time, I reused the ephemeral flag
+   which is never used in VyOS 1.x for marking nodes as tag nodes at parsing time.
+
+ *)
+
+module CT = Config_tree
+module VT = Vytree
+
+let make_indent indent level = String.make (level * indent) ' '
+
+let render_values indent_str name values =
+    match values with
+    | [] -> Printf.sprintf "%s%s { }\n" indent_str name
+    | [v] -> Printf.sprintf "%s%s %s\n" indent_str name v
+    | _  -> 
+        let rendered = List.map (fun s -> Printf.sprintf "%s%s %s" indent_str name s) values in
+        String.concat "\n" rendered
+
+let render_comment indent c =
+    match c with
+    | None -> ""
+    | Some c ->  Printf.sprintf "%s/* %s */\n" indent c
+
+let rec render_node indent level node =
+    let open CT in
+    let indent_str = make_indent indent level in
+    let name = VT.name_of_node node in
+    let data = VT.data_of_node node in
+    let is_tag = data.ephemeral (* sic! look in the parser *) in 
+    let comment = render_comment indent_str data.comment in
+    let values = render_values indent_str name data.values in
+    let children = VT.children_of_node node in
+    match children with
+    | [] -> Printf.sprintf "%s\n%s" comment values
+    | _ ->
+        if is_tag then 
+            begin
+                let inner = List.map (render_tag_node indent (level + 1) name) children in
+                String.concat "\n" inner
+            end
+        else
+            begin
+                let inner = List.map (render_node indent (level + 1)) children in
+                let inner = String.concat "\n" inner in
+                Printf.sprintf "%s%s%s {\n%s\n%s}\n" indent_str comment name inner indent_str
+            end
+
+and render_tag_node indent level parent node =
+    let open CT in
+    let indent_str = make_indent indent level in
+    let name = VT.name_of_node node in
+    let data = VT.data_of_node node in
+    let comment = render_comment indent_str data.comment in
+    let values = render_values indent_str name data.values in
+    let children = VT.children_of_node node in
+    match children with
+    | [] -> Printf.sprintf "%s\n%s" comment values
+    | _ ->
+        (* Exploiting the fact that immediate children of tag nodes are
+           never themselves tag nodes *)
+        let inner = List.map (render_node indent (level + 1)) children in
+        let inner = String.concat "\n" inner in
+        Printf.sprintf "%s%s%s %s {\n%s\n%s}\n" indent_str comment parent name inner indent_str
+
+     
+
+