//===--- 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 "ModuleFormat.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;
  }
};
}

// 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, StringRef moduleID,
                                   SourceLoc importLoc,
                                   llvm::OwningPtr<llvm::MemoryBuffer> &buffer){
  llvm::SmallString<64> moduleFilename(moduleID);
  moduleFilename += ".sm";

  llvm::SmallString<128> inputFilename;

  // First, search in the directory corresponding to the import location.
  // FIXME: This screams for a proper FileManager abstraction.
  int currentBufferID = ctx.SourceMgr.FindBufferContainingLoc(importLoc.Value);
  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;
}


Module *SerializedModuleLoader::loadModule(
    SourceLoc importLoc,
    ArrayRef<std::pair<Identifier, SourceLoc>> 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.first.str(),
                                        moduleID.second, 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);
  if (!inputFile->getBuffer().startswith(serialization::SIGNATURE)) {
    // FIXME: Diagnose malformed module? Right now we silently skip it and
    // continue searching.
    return nullptr;
  }

  // For now, treat all separate modules as unique components.
  auto comp = new (Ctx.Allocate<Component>(1)) Component();
  auto module = new (Ctx) SerializedModule(Ctx, *this, moduleID.first, comp);

  Ctx.LoadedModules[module->Name.str()] = module;
  return module;
}