Use our own lexer, not jison's

Summary:
Build our own lexer and inject it into jison's parser, because jison's
lexer notation is confusing and annoying, and it doesn't let us do some fun
stuff.

Test Plan: Run stuff, make sure it still works.

Reviewers: spicyj

Reviewed By: spicyj

Differential Revision: http://phabricator.benalpert.com/D40

lexer.js

@@ -0,0 +1,94 @@
+var DEFAULT_STATE = 0,
+    FUNC_STATE = 1;
+
+function Lexer() {
+};
+
+var funcs = [
+    'cdot', 'frac', 'lvert', 'rvert', 'pm', 'div'
+];
+
+var normals = [
+    [/^[/|a-zA-Z0-9.]/, 'ORD'],
+    [/^[*+-]/, 'BIN'],
+    [/^\^/, '^'],
+    [/^_/, '_'],
+    [/^{/, '{'],
+    [/^}/, '}'],
+    [/^[(\[]/, 'OPEN'],
+    [/^[)\]]/, 'CLOSE']
+];
+
+Lexer.prototype.doMatch = function(match) {
+    this.yytext = match;
+    this.yyleng = match.length;
+
+    this.yylloc.first_column = this._pos;
+    this.yylloc.last_column = this._pos + match.length;
+
+    this._pos += match.length;
+};
+
+Lexer.prototype.lex = function() {
+    // Get rid of whitespace
+    var whitespace = this._input.substr(this._pos).match(/^\s*/)[0];
+    this._pos += whitespace.length;
+
+    if (this._pos >= this._input.length) {
+        return 'EOF';
+    }
+
+    var toMatch = this._input.substr(this._pos);
+
+    if (this.state === DEFAULT_STATE) {
+        if (/^\\/.test(toMatch)) {
+            this.state = FUNC_STATE;
+            this.doMatch('\\');
+            return '\\';
+        } else {
+            for (var i = 0; i < normals.length; i++) {
+                var normal = normals[i];
+
+                var match = toMatch.match(normal[0]);
+                if (match) {
+                    this.doMatch(match[0]);
+                    return normal[1];
+                }
+            }
+        }
+    } else if (this.state === FUNC_STATE) {
+        for (var i = 0; i < funcs.length; i++) {
+            var func = funcs[i];
+
+            var regex = new RegExp('^' + func + '(?!a-zA-Z)');
+
+            var match = toMatch.match(regex);
+            if (match) {
+                this.doMatch(match[0]);
+                this.state = DEFAULT_STATE;
+                return func;
+            }
+        }
+    }
+
+    throw "Unexpected character: '" + toMatch[0] + "' at position " + this._pos;
+};
+
+Lexer.prototype.setInput = function(input) {
+    this._input = input;
+    this._pos = 0;
+
+    this.yyleng = 0;
+    this.yytext = "";
+    this.yylineno = 0;
+    this.yylloc = {
+        first_line: 1,
+        first_column: 0,
+        last_line: 1,
+        last_column: 0
+    };
+
+    this.state = DEFAULT_STATE;
+};
+
+module.exports = new Lexer();