//===- IdentifierResolver.cpp - Lexical Scope Name lookup -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the IdentifierResolver class, which is used for lexical
// scoped lookup, based on identifier.
//
//===----------------------------------------------------------------------===//

#include "IdentifierResolver.h"
#include <list>
#include <vector>

using namespace clang;

//===----------------------------------------------------------------------===//
// IdDeclInfoMap class
//===----------------------------------------------------------------------===//

/// IdDeclInfoMap - Associates IdDeclInfos with Identifiers.
/// Allocates 'pools' (vectors of IdDeclInfos) to avoid allocating each
/// individual IdDeclInfo to heap.
class IdentifierResolver::IdDeclInfoMap {
  static const unsigned int VECTOR_SIZE = 512;
  // Holds vectors of IdDeclInfos that serve as 'pools'.
  // New vectors are added when the current one is full.
  std::list< std::vector<IdDeclInfo> > IDIVecs;
  unsigned int CurIndex;
  
public:
  IdDeclInfoMap() : CurIndex(VECTOR_SIZE) {}

  /// Returns the IdDeclInfo associated to the IdentifierInfo.
  /// It creates a new IdDeclInfo if one was not created before for this id.
  IdDeclInfo &operator[](IdentifierInfo *II);
};


//===----------------------------------------------------------------------===//
// LookupContext Implementation
//===----------------------------------------------------------------------===//

/// getContext - Returns translation unit context for non ScopedDecls and
/// for EnumConstantDecls returns the parent context of their EnumDecl.
DeclContext *IdentifierResolver::LookupContext::getContext(Decl *D) {
  DeclContext *Ctx;

  if (CXXFieldDecl *FD = dyn_cast<CXXFieldDecl>(D))
    return FD->getParent();

  if (EnumConstantDecl *EnumD = dyn_cast<EnumConstantDecl>(D)) {
    Ctx = EnumD->getDeclContext()->getParent();
  } else if (ScopedDecl *SD = dyn_cast<ScopedDecl>(D))
    Ctx = SD->getDeclContext();
  else
    return TUCtx();

  if (isa<TranslationUnitDecl>(Ctx))
    return TUCtx();

  return Ctx;
}

/// isEqOrContainedBy - Returns true of the given context is the same or a
/// parent of this one.
bool IdentifierResolver::LookupContext::isEqOrContainedBy(
                                                const LookupContext &PC) const {
  if (PC.isTU()) return true;

  for (LookupContext Next = *this; !Next.isTU();  Next = Next.getParent())
    if (Next.Ctx == PC.Ctx) return true;

  return false;
}


//===----------------------------------------------------------------------===//
// IdDeclInfo Implementation
//===----------------------------------------------------------------------===//

/// FindContext - Returns an iterator pointing just after the decl that is
/// in the given context or in a parent of it. The search is in reverse
/// order, from end to begin.
IdentifierResolver::IdDeclInfo::DeclsTy::iterator
IdentifierResolver::IdDeclInfo::FindContext(const LookupContext &Ctx,
                                            const DeclsTy::iterator &Start) {
  for (DeclsTy::iterator I = Start; I != Decls.begin(); --I) {
    if (Ctx.isEqOrContainedBy(LookupContext(*(I-1))))
      return I;
  }

  return Decls.begin();
}

/// AddShadowed - Add a decl by putting it directly above the 'Shadow' decl.
/// Later lookups will find the 'Shadow' decl first. The 'Shadow' decl must
/// be already added to the scope chain and must be in the same context as
/// the decl that we want to add.
void IdentifierResolver::IdDeclInfo::AddShadowed(NamedDecl *D,
                                                 NamedDecl *Shadow) {
  assert(LookupContext(D) == LookupContext(Shadow) &&
    "Decl and Shadow not in same context!");

  for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {
    if (Shadow == *(I-1)) {
      Decls.insert(I-1, D);
      return;
    }
  }

  assert(0 && "Shadow wasn't in scope chain!");
}

/// RemoveDecl - Remove the decl from the scope chain.
/// The decl must already be part of the decl chain.
void IdentifierResolver::IdDeclInfo::RemoveDecl(NamedDecl *D) {
  for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {
    if (D == *(I-1)) {
      Decls.erase(I-1);
      return;
    }
  }

  assert(0 && "Didn't find this decl on its identifier's chain!");
}


//===----------------------------------------------------------------------===//
// IdentifierResolver Implementation
//===----------------------------------------------------------------------===//

IdentifierResolver::IdentifierResolver() : IdDeclInfos(new IdDeclInfoMap) {}
IdentifierResolver::~IdentifierResolver() {
  delete IdDeclInfos;
}

/// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true
/// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns
/// true if 'D' belongs to the given declaration context.
bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S) {
  if (Ctx->isFunctionOrMethod())
    return S->isDeclScope(D);

  return LookupContext(D) == LookupContext(Ctx);
}

/// AddDecl - Link the decl to its shadowed decl chain.
void IdentifierResolver::AddDecl(NamedDecl *D) {
  IdentifierInfo *II = D->getIdentifier();
  void *Ptr = II->getFETokenInfo<void>();

  if (!Ptr) {
    II->setFETokenInfo(D);
    return;
  }

  IdDeclInfo *IDI;

  if (isDeclPtr(Ptr)) {
    II->setFETokenInfo(NULL);
    IDI = &(*IdDeclInfos)[II];
    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
    IDI->AddDecl(PrevD);
  } else
    IDI = toIdDeclInfo(Ptr);

  IDI->AddDecl(D);
}

/// AddShadowedDecl - Link the decl to its shadowed decl chain putting it
/// after the decl that the iterator points to, thus the 'Shadow' decl will be
/// encountered before the 'D' decl.
void IdentifierResolver::AddShadowedDecl(NamedDecl *D, NamedDecl *Shadow) {
  assert(D->getIdentifier() == Shadow->getIdentifier() && "Different ids!");
  assert(LookupContext(D) == LookupContext(Shadow) && "Different context!");

  IdentifierInfo *II = D->getIdentifier();
  void *Ptr = II->getFETokenInfo<void>();
  assert(Ptr && "No decl from Ptr ?");

  IdDeclInfo *IDI;

  if (isDeclPtr(Ptr)) {
    II->setFETokenInfo(NULL);
    IDI = &(*IdDeclInfos)[II];
    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
    assert(PrevD == Shadow && "Invalid shadow decl ?");
    IDI->AddDecl(D);
    IDI->AddDecl(PrevD);
    return;
  }

  IDI = toIdDeclInfo(Ptr);
  IDI->AddShadowed(D, Shadow);
}

/// RemoveDecl - Unlink the decl from its shadowed decl chain.
/// The decl must already be part of the decl chain.
void IdentifierResolver::RemoveDecl(NamedDecl *D) {
  assert(D && "null param passed");
  IdentifierInfo *II = D->getIdentifier();
  void *Ptr = II->getFETokenInfo<void>();

  assert(Ptr && "Didn't find this decl on its identifier's chain!");

  if (isDeclPtr(Ptr)) {
    assert(D == Ptr && "Didn't find this decl on its identifier's chain!");
    II->setFETokenInfo(NULL);
    return;
  }
  
  return toIdDeclInfo(Ptr)->RemoveDecl(D);
}

/// begin - Returns an iterator for decls of identifier 'II', starting at
/// declaration context 'Ctx'. If 'LookInParentCtx' is true, it will walk the
/// decls of parent declaration contexts too.
IdentifierResolver::iterator
IdentifierResolver::begin(const IdentifierInfo *II, DeclContext *Ctx,
                          bool LookInParentCtx) {
  assert(Ctx && "null param passed");

  void *Ptr = II->getFETokenInfo<void>();
  if (!Ptr) return end();

  LookupContext LC(Ctx);

  if (isDeclPtr(Ptr)) {
    NamedDecl *D = static_cast<NamedDecl*>(Ptr);
    LookupContext DC(D);

    if (( LookInParentCtx && LC.isEqOrContainedBy(DC)) ||
        (!LookInParentCtx && LC == DC))
      return iterator(D);
    else
      return end();
  }

  IdDeclInfo *IDI = toIdDeclInfo(Ptr);

  IdDeclInfo::DeclsTy::iterator I;
  if (LookInParentCtx)
    I = IDI->FindContext(LC);
  else {
    for (I = IDI->decls_end(); I != IDI->decls_begin(); --I)
      if (LookupContext(*(I-1)) == LC)
        break;
  }

  if (I != IDI->decls_begin())
    return iterator(I-1, LookInParentCtx);
  else // No decls found.
    return end();
}

/// PreIncIter - Do a preincrement when 'Ptr' is a BaseIter.
void IdentifierResolver::iterator::PreIncIter() {
  NamedDecl *D = **this;
  LookupContext Ctx(D);
  void *InfoPtr = D->getIdentifier()->getFETokenInfo<void>();
  assert(!isDeclPtr(InfoPtr) && "Decl with wrong id ?");
  IdDeclInfo *Info = toIdDeclInfo(InfoPtr);

  BaseIter I = getIterator();
  if (LookInParentCtx())
    I = Info->FindContext(Ctx, I);
  else {
    if (I != Info->decls_begin() && LookupContext(*(I-1)) != Ctx) {
      // The next decl is in different declaration context.
      // Skip remaining decls and set the iterator to the end.
      I = Info->decls_begin();
    }
  }

  if (I != Info->decls_begin())
    *this = iterator(I-1, LookInParentCtx());
  else // No more decls.
    *this = end();
}


//===----------------------------------------------------------------------===//
// IdDeclInfoMap Implementation
//===----------------------------------------------------------------------===//

/// Returns the IdDeclInfo associated to the IdentifierInfo.
/// It creates a new IdDeclInfo if one was not created before for this id.
IdentifierResolver::IdDeclInfo &
IdentifierResolver::IdDeclInfoMap::operator[](IdentifierInfo *II) {
  assert (II && "null IdentifierInfo passed");
  void *Ptr = II->getFETokenInfo<void>();

  if (Ptr) return *toIdDeclInfo(Ptr);

  if (CurIndex == VECTOR_SIZE) {
    // Add a IdDeclInfo vector 'pool'
    IDIVecs.push_back(std::vector<IdDeclInfo>());
    // Fill the vector
    IDIVecs.back().resize(VECTOR_SIZE);
    CurIndex = 0;
  }
  IdDeclInfo *IDI = &IDIVecs.back()[CurIndex];
  II->setFETokenInfo(reinterpret_cast<void*>(
                              reinterpret_cast<uintptr_t>(IDI) | 0x1)
                                                                     );
  ++CurIndex;
  return *IDI;
}