1 files changed, 207 insertions, 0 deletions
diff --git a/lib/command_parse.y b/lib/command_parse.y
new file mode 100644
index 0000000000..e7efb0d5a8
--- /dev/null
+++ b/lib/command_parse.y
@@ -0,0 +1,207 @@
+%{
+#include "cmdtree.h"
+
+extern int yylex(void);
+extern void yyerror(const char *);
+extern int cmd_parse_format(const char *, const char *);
+extern void set_buffer_string(const char *);
+
+// compile with debugging facilities
+#define YYDEBUG 1
+%}
+
+%union{
+  int integer;
+  char *string;
+  struct graph_node *node;
+}
+
+%{
+// last top-level node
+struct graph_node *topnode,         // command root node
+                  *currnode;        // current node
+
+struct graph_node *optnode_start,   // start node for option set
+                  *optnode_end,     // end node for option set
+                  *optnode_el;      // start node for an option set element
+
+struct graph_node *selnode_start,   // start node for selector set
+                  *selnode_end,     // end node for selector set
+                  *selnode_el;      // start node for an selector set element
+%}
+
+%token <string>  WORD
+%token <string>  IPV4
+%token <string>  IPV4_PREFIX
+%token <string>  IPV6
+%token <string>  IPV6_PREFIX
+%token <string>  VARIABLE
+%token <string>  RANGE
+%token <integer> NUMBER
+
+%type <node> start
+%type <node> sentence_root
+%type <node> literal_token
+%type <node> placeholder_token
+%type <node> option_token
+%type <node> selector_token
+%type <node> option
+%type <node> selector
+%type <node> selector_token_seq
+%type <node> option_token_seq
+
+%defines "command_parse.h"
+%output "command_parse.c"
+
+/* grammar proper */
+%%
+
+start: sentence_root
+       cmd_token_seq;
+
+sentence_root: WORD
+  {
+    currnode = new_node(WORD_GN);
+    currnode->is_root = 1;
+    add_node(topnode, currnode);
+  };
+
+/* valid top level tokens */
+cmd_token:
+  placeholder_token
+  { currnode = add_node(currnode, $1); }
+| literal_token
+  { currnode = add_node(currnode, $1); }
+| selector
+  {
+    add_node(currnode, selnode_start);
+    currnode = selnode_end;
+  }
+| option
+  {
+    add_node(currnode, optnode_start);
+    currnode = optnode_end;
+  }
+;
+
+cmd_token_seq:
+  %empty
+| cmd_token_seq cmd_token
+;
+
+placeholder_token:
+  IPV4                                  {$$ = new_node(IPV4_GN);}
+| IPV4_PREFIX                           {$$ = new_node(IPV4_PREFIX_GN);}
+| IPV6                                  {$$ = new_node(IPV6_GN);}
+| IPV6_PREFIX                           {$$ = new_node(IPV6_PREFIX_GN);}
+| VARIABLE                              {$$ = new_node(VARIABLE_GN);}
+| RANGE                                 {$$ = new_node(RANGE_GN);}
+;
+
+literal_token:
+  WORD                                  {$$ = new_node(WORD_GN);}
+| NUMBER                                {$$ = new_node(NUMBER_GN);}
+;
+
+/* <selector|token> productions */
+selector:
+  '<' selector_part '|'
+      selector_element '>'
+{
+  $$ = new_node(SELECTOR_GN);
+  // attach subtree here
+};
+
+selector_part:
+  selector_part '|' selector_element
+| selector_element
+;
+
+selector_element:
+  WORD selector_token_seq;
+
+selector_token_seq:
+  %empty                                {$$ = NULL;}
+| selector_token_seq selector_token
+{
+  currnode = add_node(currnode, $2);
+}
+;
+
+selector_token:
+  literal_token
+| placeholder_token
+| option
+;
+
+/* [option|set] productions */
+option: '[' option_part ']'
+{
+  $$ = new_node(OPTION_GN);
+  // attach subtree here
+};
+
+option_part:
+  option_part '|' option_token_seq
+| option_token_seq
+;
+
+option_token_seq:
+  option_token_seq option_token
+| option_token
+{
+  printf("Matched singular option token in sequence, type: %d\n", $1->type);
+}
+;
+
+option_token:
+  literal_token
+{
+  // optnode_el points to root of option element
+  if (optnode_el == NULL) {
+    optnode_el = $1;
+    currnode = $1;
+  }
+  else
+    add_node(currnode, $1);
+}
+| placeholder_token
+{
+  // optnode_el points to root of option element
+  if (optnode_el == NULL) {
+    optnode_el = $1;
+    currnode = $1;
+  }
+  else
+    add_node(currnode, $1);
+}
+;
+
+%%
+
+int
+main (void)
+{
+  yydebug = 1;
+  const char* input = "show [random conf NAME] thing";
+  printf("Parsing:\n\t%s\n", input);
+  return cmd_parse_format(input, "description");
+}
+
+void yyerror(char const *message) {
+  printf("Grammar error: %s\n", message);
+  exit(EXIT_FAILURE);
+}
+
+int
+cmd_parse_format(const char *string, const char *desc)
+{
+  // make flex read from a string
+  set_buffer_string(string);
+  // initialize the start node of this command dfa
+  topnode = new_node(NUL_GN);
+  // parse command into DFA
+  yyparse();
+  // topnode points to command DFA
+  return 0;
+}