feat: add html.append helper

2 files changed, 111 insertions, 14 deletions

diff --git a/examples/site/build.lua b/examples/site/build.lua
index e18124e..7a9dfd4 100644
--- a/examples/site/build.lua
+++ b/examples/site/build.lua
@@ -11,7 +11,7 @@ local features = {
 
 local feature_list = assert(html.find_by_class(page, "feature-list"))
 for _, feature in ipairs(features) do
-  table.insert(feature_list.children, html.element("li", nil, feature))
+  feature_list:append(html.element("li", nil, feature))
 end
 
 local entries = {}
@@ -25,7 +25,7 @@ summary.text = tostring(#entries) .. " entries"
 
 local file_list = assert(html.find_by_class(page, "file-list"))
 for _, entry in ipairs(entries) do
-  table.insert(file_list.children, html.element("li", nil,
+  html.append(file_list, html.element("li", nil,
     html.element("code", nil, entry.path),
     " (", entry.type, ")"))
 end
diff --git a/src/Dom/Dom.c b/src/Dom/Dom.c
index 4eb3ad4..67817aa 100644
--- a/src/Dom/Dom.c
+++ b/src/Dom/Dom.c
@@ -6,10 +6,18 @@
 #include <string.h>
 #include <strings.h>
 
+#define HTML_NODE_METATABLE "yapssg.html_node"
+
 static int absolute_index(lua_State *lua, int index) {
   return index < 0 ? lua_gettop(lua) + index + 1 : index;
 }
 
+static void set_html_node_metatable(lua_State *lua, int table_index) {
+  table_index = absolute_index(lua, table_index);
+  luaL_getmetatable(lua, HTML_NODE_METATABLE);
+  lua_setmetatable(lua, table_index);
+}
+
 static int table_is_node(lua_State *lua, int table_index) {
   int is_node;
 
@@ -25,15 +33,16 @@ static int table_is_node(lua_State *lua, int table_index) {
   return is_node;
 }
 
-static void append_element_child(lua_State *lua, int children_index,
-                                 int child_index, size_t *child_count,
-                                 unsigned int depth) {
+static void append_normalized_child(lua_State *lua, int children_index,
+                                    int child_index, size_t *child_count,
+                                    unsigned int depth,
+                                    const char *function_name) {
   size_t array_length;
   size_t index;
   int child_type;
 
   if (!lua_checkstack(lua, 2)) {
-    luaL_error(lua, "html.element children are nested too deeply");
+    luaL_error(lua, "%s children are nested too deeply", function_name);
   }
   children_index = absolute_index(lua, children_index);
   child_index = absolute_index(lua, child_index);
@@ -45,7 +54,7 @@ static void append_element_child(lua_State *lua, int children_index,
   if (child_type == LUA_TSTRING ||
       (child_type == LUA_TTABLE && table_is_node(lua, child_index))) {
     if (*child_count == INT_MAX) {
-      luaL_error(lua, "html.element has too many children");
+      luaL_error(lua, "%s has too many children", function_name);
     }
     ++*child_count;
     lua_pushvalue(lua, child_index);
@@ -54,21 +63,22 @@ static void append_element_child(lua_State *lua, int children_index,
   }
   if (child_type != LUA_TTABLE) {
     luaL_error(lua,
-               "html.element child must be a string, node, child array, or "
-               "nil (got %s)",
-               lua_typename(lua, child_type));
+               "%s child must be a string, node, child array, or nil (got "
+               "%s)",
+               function_name, lua_typename(lua, child_type));
   }
   if (depth == 100) {
-    luaL_error(lua, "html.element children are nested too deeply");
+    luaL_error(lua, "%s children are nested too deeply", function_name);
   }
 
   array_length = lua_objlen(lua, child_index);
   if (array_length > INT_MAX) {
-    luaL_error(lua, "html.element child array is too large");
+    luaL_error(lua, "%s child array is too large", function_name);
   }
   for (index = 1; index <= array_length; ++index) {
     lua_rawgeti(lua, child_index, (int)index);
-    append_element_child(lua, children_index, -1, child_count, depth + 1);
+    append_normalized_child(lua, children_index, -1, child_count, depth + 1,
+                            function_name);
     lua_pop(lua, 1);
   }
 }
@@ -104,10 +114,84 @@ static int html_element(lua_State *lua) {
   lua_newtable(lua);
   children_index = lua_gettop(lua);
   for (index = 3; index <= argument_count; ++index) {
-    append_element_child(lua, children_index, index, &child_count, 0);
+    append_normalized_child(lua, children_index, index, &child_count, 0,
+                            "html.element");
   }
   lua_setfield(lua, -2, "children");
+  set_html_node_metatable(lua, -1);
+
+  return 1;
+}
+
+static int html_append(lua_State *lua) {
+  size_t new_child_count = 0;
+  size_t existing_child_count;
+  size_t index;
+  int argument_count = lua_gettop(lua);
+  int new_children_index;
+  int children_index;
+  const char *tag;
+
+  luaL_checktype(lua, 1, LUA_TTABLE);
+  lua_getfield(lua, 1, "tag");
+  tag = lua_tostring(lua, -1);
+  if (tag == NULL || tag[0] == '\0') {
+    return luaL_argerror(lua, 1, "element expected");
+  }
+  lua_pop(lua, 1);
+
+  lua_newtable(lua);
+  new_children_index = lua_gettop(lua);
+  for (index = 2; index <= (size_t)argument_count; ++index) {
+    append_normalized_child(lua, new_children_index, (int)index,
+                            &new_child_count, 0, "html.append");
+  }
+  if (new_child_count == 0) {
+    lua_pushvalue(lua, 1);
+    return 1;
+  }
 
+  lua_getfield(lua, 1, "children");
+  if (lua_isnil(lua, -1)) {
+    lua_pop(lua, 1);
+    lua_newtable(lua);
+    lua_pushvalue(lua, -1);
+    lua_setfield(lua, 1, "children");
+  } else if (!lua_istable(lua, -1)) {
+    return luaL_error(lua, "html.append element children must be a table");
+  }
+  children_index = lua_gettop(lua);
+  existing_child_count = lua_objlen(lua, children_index);
+  if (existing_child_count > INT_MAX) {
+    return luaL_error(lua, "html.append element has too many children");
+  }
+
+  if (existing_child_count == 0) {
+    size_t text_length;
+
+    lua_getfield(lua, 1, "text");
+    if (lua_type(lua, -1) == LUA_TSTRING) {
+      lua_tolstring(lua, -1, &text_length);
+      if (text_length > 0) {
+        lua_pushvalue(lua, -1);
+        lua_rawseti(lua, children_index, 1);
+        existing_child_count = 1;
+      }
+    }
+    lua_pop(lua, 1);
+  }
+
+  if (new_child_count > INT_MAX - existing_child_count) {
+    return luaL_error(lua, "html.append element has too many children");
+  }
+  for (index = 1; index <= new_child_count; ++index) {
+    lua_rawgeti(lua, new_children_index, (int)index);
+    lua_rawseti(lua, children_index, (int)(existing_child_count + index));
+  }
+  lua_pushnil(lua);
+  lua_setfield(lua, 1, "text");
+
+  lua_pushvalue(lua, 1);
   return 1;
 }
 
@@ -222,9 +306,21 @@ static int html_find_by_class(lua_State *lua) {
 }
 
 void dom_register_html(lua_State *lua) {
+  if (luaL_newmetatable(lua, HTML_NODE_METATABLE)) {
+    lua_newtable(lua);
+    lua_pushcfunction(lua, html_append);
+    lua_setfield(lua, -2, "append");
+    lua_setfield(lua, -2, "__index");
+    lua_pushboolean(lua, 0);
+    lua_setfield(lua, -2, "__metatable");
+  }
+  lua_pop(lua, 1);
+
   lua_newtable(lua);
   lua_pushcfunction(lua, html_element);
   lua_setfield(lua, -2, "element");
+  lua_pushcfunction(lua, html_append);
+  lua_setfield(lua, -2, "append");
   lua_pushcfunction(lua, html_find_by_class);
   lua_setfield(lua, -2, "find_by_class");
   lua_setglobal(lua, "html");
@@ -357,6 +453,7 @@ static void push_element(lua_State *lua, const xmlNode *node) {
 
   lua_newtable(lua);
   element_index = lua_gettop(lua);
+  set_html_node_metatable(lua, element_index);
   set_string_field(lua, element_index, "tag", (const char *)node->name);
   push_attributes(lua, node, element_index);
   push_children(lua, node, element_index, structured_children);