//===--- SerializedModuleLoader.cpp - Import Swift modules ------*- c++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "swift/Serialization/SerializedModuleLoader.h"
#include "ModuleFile.h"
#include "swift/Subsystems.h"
#include "swift/AST/AST.h"
#include "swift/AST/Component.h"
#include "swift/AST/Diagnostics.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/system_error.h"

using namespace swift;

namespace {
class SerializedModule : public LoadedModule {
public:
  SerializedModule(ASTContext &ctx, SerializedModuleLoader &owner,
                   Identifier name, Component *comp)
    : LoadedModule(DeclContextKind::SerializedModule, name, comp, ctx, owner) {}

  static bool classof(const DeclContext *DC) {
    return DC->getContextKind() == DeclContextKind::SerializedModule;
  }
};

typedef std::pair<Identifier, SourceLoc> AccessPathElem;
}

// FIXME: Copied from SourceLoader. Not bothering to fix until we decide that
// the source loader search path should be the same as the module loader search
// path.
static llvm::error_code findModule(ASTContext &ctx, AccessPathElem moduleID,
                                   llvm::OwningPtr<llvm::MemoryBuffer> &buffer){
  llvm::SmallString<64> moduleFilename(moduleID.first.str());
  moduleFilename += ".sm";

  llvm::SmallString<128> inputFilename;

  // First, search in the directory corresponding to the import location.
  // FIXME: This screams for a proper FileManager abstraction.
  llvm::SMLoc rawLoc = moduleID.second.Value;
  int currentBufferID = ctx.SourceMgr.FindBufferContainingLoc(rawLoc);
  if (currentBufferID >= 0) {
    const llvm::MemoryBuffer *importingBuffer
      = ctx.SourceMgr.getBufferInfo(currentBufferID).Buffer;
    StringRef currentDirectory
      = llvm::sys::path::parent_path(importingBuffer->getBufferIdentifier());
    if (!currentDirectory.empty()) {
      inputFilename = currentDirectory;
      llvm::sys::path::append(inputFilename, moduleFilename.str());
      llvm::error_code err = llvm::MemoryBuffer::getFile(inputFilename, buffer);
      if (!err)
        return err;
    }
  }

  // Second, search in the current directory.
  llvm::error_code err = llvm::MemoryBuffer::getFile(moduleFilename, buffer);
  if (!err)
    return err;

  // If we fail, search each import search path.
  for (auto Path : ctx.ImportSearchPaths) {
    inputFilename = Path;
    llvm::sys::path::append(inputFilename, moduleFilename.str());
    err = llvm::MemoryBuffer::getFile(inputFilename, buffer);
    if (!err)
      return err;
  }

  return err;
}

static Module *makeTU(ASTContext &ctx, AccessPathElem moduleID,
                      ArrayRef<StringRef> inputPaths) {
  Component *comp = new (ctx.Allocate<Component>(1)) Component();
  TranslationUnit *TU = new (ctx) TranslationUnit(moduleID.first, comp, ctx,
                                                  /*IsMainModule=*/false,
                                                  /*IsReplModule=*/false);

  ctx.LoadedModules[moduleID.first.str()] = TU;

  std::vector<unsigned> BufferIDs;
  for (auto &path : inputPaths) {
    // Open the input file.
    llvm::OwningPtr<llvm::MemoryBuffer> InputFile;
    if (llvm::MemoryBuffer::getFileOrSTDIN(path, InputFile))
      return nullptr;

    // Transfer ownership of the MemoryBuffer to the SourceMgr.
    // FIXME: include location
    llvm::SMLoc rawLoc = moduleID.second.Value;
    BufferIDs.push_back(ctx.SourceMgr.AddNewSourceBuffer(InputFile.take(),
                                                         rawLoc));
  }

  for (auto &BufferID : BufferIDs) {
    unsigned BufferOffset = 0;
    const llvm::MemoryBuffer *Buffer =
      ctx.SourceMgr.getMemoryBuffer(BufferID);
    do {
      parseIntoTranslationUnit(TU, BufferID, &BufferOffset, 0, /*SIL=*/nullptr);
    } while (BufferOffset != Buffer->getBufferSize());
  }

  performNameBinding(TU);
  performTypeChecking(TU);

  return TU;
}


static Module *error(SerializedModuleLoader &owner, ASTContext &ctx,
                     AccessPathElem moduleID, ModuleStatus reason) {
  switch (reason) {
  case ModuleStatus::Valid:
  case ModuleStatus::FallBackToTranslationUnit:
    llvm_unreachable("not an error");
  case ModuleStatus::Malformed:
    ctx.Diags.diagnose(moduleID.second, diag::serialization_malformed_module);
    break;
  case ModuleStatus::FormatTooNew:
    ctx.Diags.diagnose(moduleID.second, diag::serialization_module_too_new);
    break;
  }

  // Return a dummy module to avoid future errors.
  auto comp = new (ctx.Allocate<Component>(1)) Component();
  auto module = new (ctx) SerializedModule(ctx, owner, moduleID.first, comp);

  ctx.LoadedModules[moduleID.first.str()] = module;
  return module;
}

Module *SerializedModuleLoader::loadModule(SourceLoc importLoc,
                                           Module::AccessPathTy path) {

  // FIXME: Swift submodules?
  if (path.size() > 1)
    return nullptr;

  auto moduleID = path[0];

  llvm::OwningPtr<llvm::MemoryBuffer> inputFile;
  if (llvm::error_code err = findModule(Ctx, moduleID, inputFile)) {
    if (err.value() != llvm::errc::no_such_file_or_directory) {
      Ctx.Diags.diagnose(moduleID.second, diag::sema_opening_import,
                         moduleID.first.str(), err.message());
    }

    return nullptr;
  }
  assert(inputFile);
  
  Module *result;
  llvm::OwningPtr<ModuleFile> loadedModuleFile;
  ModuleStatus err = ModuleFile::load(std::move(inputFile), loadedModuleFile);
  switch (err) {
  case ModuleStatus::Valid:
    llvm_unreachable("non-fallback modules not supported yet!");
  case ModuleStatus::FallBackToTranslationUnit:
    result = makeTU(Ctx, moduleID, loadedModuleFile->getInputSourcePaths());
    break;
  case ModuleStatus::FormatTooNew:
  case ModuleStatus::Malformed:
    return error(*this, Ctx, moduleID, err);
  }

  return result;
}