//===--- Parser.cpp - Swift Language Parser -------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
//  This file implements the Swift parser.
//
//===----------------------------------------------------------------------===//

#include "swift/Subsystems.h"
#include "swift/AST/Verifier.h"
#include "swift/Basic/Diagnostics.h"
#include "Parser.h"
#include "Lexer.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/Twine.h"
using namespace swift;
  
/// parseTranslationUnit - Entrypoint for the parser.
TranslationUnit *swift::parseTranslationUnit(unsigned BufferID,
                                             ASTContext &Ctx) {
  TranslationUnit *TU = Parser(BufferID, Ctx).parseTranslationUnit();
  if (TU) verify(TU, VerificationKind::Parsed);
  return TU;
}
  
//===----------------------------------------------------------------------===//
// Setup and Helper Methods
//===----------------------------------------------------------------------===//

Parser::Parser(unsigned BufferID, ASTContext &Context)
  : SourceMgr(Context.SourceMgr),
    Diags(Context.Diags),
    L(*new Lexer(BufferID, Context)),
    Context(Context),
    ScopeInfo(*this) {
}

Parser::~Parser() {
  delete &L;
}

/// peekToken - Return the next token that will be installed by consumeToken.
const Token &Parser::peekToken() {
  return L.peekNextToken();
}

SourceLoc Parser::consumeToken() {
  SourceLoc Loc = Tok.getLoc();
  assert(Tok.isNot(tok::eof) && "Lexing past eof!");
  L.lex(Tok);
  return Loc;
}

/// skipUntil - Read tokens until we get to the specified token, then return.
/// Because we cannot guarantee that the token will ever occur, this skips to
/// some likely good stopping point.
///
void Parser::skipUntil(tok T1, tok T2) {
  // tok::unknown is a sentinel that means "don't skip".
  if (T1 == tok::unknown && T2 == tok::unknown) return;
  
  while (Tok.isNot(tok::eof) && Tok.isNot(T1) && Tok.isNot(T2)) {
    switch (Tok.getKind()) {
    default: consumeToken(); break;
    // TODO: Handle paren/brace/bracket recovery.
    }
  }
}


//===----------------------------------------------------------------------===//
// Primitive Parsing
//===----------------------------------------------------------------------===//

/// parseIdentifier - Consume an identifier if present and return its name in
/// Result.  Otherwise, emit an error and return true.
bool Parser::parseIdentifier(Identifier &Result, DiagID Message,
                             ArrayRef<DiagnosticArgument> Args) {
  if (Tok.is(tok::identifier) || Tok.is(tok::oper)) {
    Result = Context.getIdentifier(Tok.getText());
    consumeToken();
    return false;
  }
  
  Diags.diagnose(Tok.getLoc(), Message, Args);
  return true;
}

/// parseToken - The parser expects that 'K' is next in the input.  If so, it is
/// consumed and false is returned.
///
/// If the input is malformed, this emits the specified error diagnostic.
/// Next, if SkipToTok is specified, it calls skipUntil(SkipToTok).  Finally,
/// true is returned.
bool Parser::parseToken(tok K, const char *Message, tok SkipToTok) {
  if (Tok.is(K)) {
    consumeToken(K);
    return false;
  }
  
  error(Tok.getLoc(), Message);
  skipUntil(SkipToTok);
  
  // If we skipped ahead to the missing token and found it, consume it as if
  // there were no error.
  if (K == SkipToTok && Tok.is(SkipToTok))
    consumeToken();
  return true;
}

/// value-specifier:
///   ':' type
///   ':' type '=' expr
///   '=' expr
bool Parser::parseValueSpecifier(Type &Ty, NullablePtr<Expr> &Init,
                                 bool SingleInit) {
  // Diagnose when we don't have a type or an expression.
  if (Tok.isNot(tok::colon) && Tok.isNot(tok::equal)) {
    diagnose(Tok, diags::expected_type_or_init);
    // TODO: Recover better by still creating var, but making it have
    // 'invalid' type so that uses of the identifier are not errors.
    return true;
  }
  
  // Parse the type if present.
  if (consumeIf(tok::colon) &&
      parseType(Ty, diags::expected_type))
    return true;
  
  // Parse the initializer, if present.
  if (consumeIf(tok::equal)) {
    ParseResult<Expr> Tmp;
    if (SingleInit) {
      Tmp = parseSingleExpr("expected expression in value specifier");
    } else {
      Tmp = parseExpr("expected expression in value specifier");
    }
    if (Tmp)
      return true;
    
    if (!Tmp.isSemaError())
      Init = Tmp.get();
    
    // If there was an expression, but it had a parse error, give the var decl
    // an artificial int type to avoid chained errors.
    // FIXME: We really need to distinguish erroneous expr from missing expr in
    // ActOnVarDecl.
    if (Tmp.isSemaError() && Ty.isNull())
      Ty = Context.TheInt32Type;
  }
  
  return false;
}