feat(Parser): implement Parser

Add a simple parser implementation that supports only field reads.

modules/change_detection/src/parser/parser.js

@@ -1,2 +1,81 @@
+import {FIELD, int} from 'facade/lang';
+import {ListWrapper, List} from 'facade/collection';
+import {Lexer, EOF, Token, $PERIOD} from './lexer';
+import {ClosureMap} from './closure_map';
+import {AST, ImplicitReceiver, FieldRead} from './ast';
+
+var _implicitReceiver = new ImplicitReceiver();
+
 export class Parser {
+  @FIELD('final _lexer:Lexer')
+  @FIELD('final _closureMap:ClosureMap')
+  constructor(lexer:Lexer, closureMap:ClosureMap){
+    this._lexer = lexer;
+    this._closureMap = closureMap;
+  }
+
+  parse(input:string):AST {
+    var tokens = this._lexer.tokenize(input);
+    return new _ParseAST(tokens, this._closureMap).parseChain();
+  }
 }
+
+class _ParseAST {
+  @FIELD('final tokens:List<Token>')
+  @FIELD('final closureMap:ClosureMap')
+  @FIELD('index:int')
+  constructor(tokens:List, closureMap:ClosureMap) {
+    this.tokens = tokens;
+    this.index = 0;
+    this.closureMap = closureMap;
+  }
+
+  peek(offset:int):Token {
+    var i = this.index + offset;
+    return i < this.tokens.length ? this.tokens[i] : EOF;
+  }
+
+  get next():Token {
+    return this.peek(0);
+  }
+
+  advance() {
+    this.index ++;
+  }
+
+  optionalCharacter(code:int):boolean {
+    if (this.next.isCharacter(code)) {
+      this.advance();
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  parseChain():AST {
+    var exprs = [];
+    while (this.index < this.tokens.length) {
+      ListWrapper.push(exprs, this.parseAccess());
+    }
+    return ListWrapper.first(exprs);
+  }
+
+  parseAccess():AST {
+    var result = this.parseFieldRead(_implicitReceiver);
+    while(this.optionalCharacter($PERIOD)) {
+      result = this.parseFieldRead(result);
+    }
+    return result;
+  }
+
+  parseFieldRead(receiver):AST {
+    var id = this.parseIdentifier();
+    return new FieldRead(receiver, id, this.closureMap.getter(id));
+  }
+
+  parseIdentifier():string {
+    var n = this.next;
+    this.advance();
+    return n.toString();
+  }
+}