Adds optional paren matching to keyboard input

config.h

@@ -9,6 +9,9 @@
 // Set global tab width for the editor here
 static const int tabwidth = 4;
 
+// Turn on or off paren matching for: (, {, [
+static const int MATCH_PARENS = 1;
+
 /* 
  * Values from 1 to 256 representing 256 color/8-bit pallate
  * see: https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit

hermes.c

@@ -353,6 +353,19 @@ void editorUpdateSyntax(erow *row) {
     editorUpdateSyntax(&E.row[row->idx + 1]);
 }
 
+char editorGetMatchingParen(char c) {
+  switch (c) {
+    case '{':
+      return '}';
+    case '(':    
+      return ')';
+    case '[':
+      return ']';
+    default:
+      return ' ';
+  }
+}
+
 int editorSyntaxToColor(int hl) {
   switch (hl) {
     case HL_NUMBER:    return HL_NUMBER_COLOR;
@@ -1152,6 +1165,16 @@ void editorInputKp(int c) {
       if (c == DEL_KEY) editorMoveCursor(ARROW_RIGHT);
       editorDeleteChar();
       break;
+    case '(':
+    case '{':
+    case '[':
+      editorInsertChar(c);
+      if (MATCH_PARENS) {
+        char match = editorGetMatchingParen(c);
+        editorInsertChar(match);
+        editorMoveCursor(ARROW_LEFT);
+      }
+      break;
     default:
       editorInsertChar(c);
       break;