Remove TOKENS constant and replace with Keywords

src/lexer/statements/select.ts

@@ -1,20 +1,22 @@
 import { Query } from "../../reader/query";
 import { ILexer } from "../interface";
 import { cleanUnquotedIdentifier } from "../lexer";
-import { TOKENS, Types } from "../tokens";
+import { Types } from "../tokens";
 import { Keyword } from "../keywords";
 import { Token } from "../token";
 
 class Select implements ILexer {
   public options: string[] = [];
 
   public tokenise(query: Query): Query {
+
+    const keywords = Object.keys(Keyword).map(keyword => keyword.toLowerCase());
     let lastToken = "";
     query.lines.forEach(line => {
       line.content.split(" ").forEach(word => {
         let item = word.toLowerCase();
 
-        if (TOKENS.keyword.includes(item)) {
+        if (keywords.includes(item)) {
           line.tokens.push(new Token(Types.Keyword, item));
         } else if (lastToken === Keyword.Select || lastToken === Keyword.From) {
           item = cleanUnquotedIdentifier(item);

src/lexer/tokens.ts

@@ -1,25 +1,3 @@
-export const TOKENS = {
-  keyword: [
-    "select",
-    "delete",
-    "update",
-    "from",
-    "where",
-    "set",
-    "join",
-    "having",
-    "limit",
-    "else",
-    "if",
-    "begin"
-  ],
-
-  comment: ["#", "--"],
-  boolean: ["true", "false", "null"],
-  conditional: ["and", "or"],
-  operator: ["+", "-", "/"]
-};
-
 export enum Types {
   Keyword = "keyword",
   TableReference = "table_reference",