/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-

 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "FileSystemModule.h"

#include "sqlite3.h"

#include "nsString.h"

#include "nsIDirectoryEnumerator.h"

#include "nsIFile.h"

namespace {

struct VirtualTableCursorBase

{

  VirtualTableCursorBase()

  {

    memset(&mBase, 0, sizeof(mBase));

  }

  sqlite3_vtab_cursor mBase;

};

struct VirtualTableCursor : public VirtualTableCursorBase

{

public:

  VirtualTableCursor()

  : mRowId(-1)

  {

    mCurrentFileName.SetIsVoid(true);

  }

  const nsString& DirectoryPath() const

  {

    return mDirectoryPath;

  }

  const nsString& CurrentFileName() const

  {

    return mCurrentFileName;

  }

  int64_t RowId() const

  {

    return mRowId;

  }

  nsresult Init(const nsAString& aPath);

  nsresult NextFile();

private:

  nsCOMPtr<nsIDirectoryEnumerator> mEntries;

  nsString mDirectoryPath;

  nsString mCurrentFileName;

  int64_t mRowId;

};

nsresult

VirtualTableCursor::Init(const nsAString& aPath)

{

  nsCOMPtr<nsIFile> directory =

    do_CreateInstance(NS_LOCAL_FILE_CONTRACTID);

  NS_ENSURE_TRUE(directory, NS_ERROR_FAILURE);

  nsresult rv = directory->InitWithPath(aPath);

  NS_ENSURE_SUCCESS(rv, rv);

  rv = directory->GetPath(mDirectoryPath);

  NS_ENSURE_SUCCESS(rv, rv);

  rv = directory->GetDirectoryEntries(getter_AddRefs(mEntries));

  NS_ENSURE_SUCCESS(rv, rv);

  rv = NextFile();

  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;

}

nsresult

VirtualTableCursor::NextFile()

{

  bool hasMore;

  nsresult rv = mEntries->HasMoreElements(&hasMore);

  NS_ENSURE_SUCCESS(rv, rv);

  if (!hasMore) {

    mCurrentFileName.SetIsVoid(true);

    return NS_OK;

  }

  nsCOMPtr<nsISupports> entry;

  rv = mEntries->GetNext(getter_AddRefs(entry));

  NS_ENSURE_SUCCESS(rv, rv);

  nsCOMPtr<nsIFile> file = do_QueryInterface(entry);

  NS_ENSURE_TRUE(file, NS_ERROR_FAILURE);

  rv = file->GetLeafName(mCurrentFileName);

  NS_ENSURE_SUCCESS(rv, rv);

  mRowId++;

  return NS_OK;

}

int Connect(sqlite3* aDB, void* aAux, int aArgc, const char* const* aArgv,

            sqlite3_vtab** aVtab, char** aErr)

{

  static const char virtualTableSchema[] =

    "CREATE TABLE fs ("

      "name TEXT, "

      "path TEXT"

    ")";

  int rc = sqlite3_declare_vtab(aDB, virtualTableSchema);

  if (rc != SQLITE_OK) {

    return rc;

  }

  sqlite3_vtab* vt = new sqlite3_vtab();

  memset(vt, 0, sizeof(*vt));

  *aVtab = vt;

  return SQLITE_OK;

}

int Disconnect(sqlite3_vtab* aVtab )

{

  delete aVtab;

  return SQLITE_OK;

}

int BestIndex(sqlite3_vtab* aVtab, sqlite3_index_info* aInfo)

{

  // Here we specify what index constraints we want to handle. That is, there

  // might be some columns with particular constraints in which we can help

  // SQLite narrow down the result set.

  //

  // For example, take the "path = x" where x is a directory. In this case,

  // we can narrow our search to just this directory instead of the entire file

  // system. This can be a significant optimization. So, we want to handle that

  // constraint. To do so, we would look for two specific input conditions:

  //

  // 1. aInfo->aConstraint[i].iColumn == 1

  // 2. aInfo->aConstraint[i].op == SQLITE_INDEX_CONSTRAINT_EQ

  //

  // The first states that the path column is being used in one of the input

  // constraints and the second states that the constraint involves the equal

  // operator.

  //

  // An even more specific search would be for name='xxx', in which case we

  // can limit the search to a single file, if it exists.

  //

  // What we have to do here is look for all of our index searches and select

  // the narrowest. We can only pick one, so obviously we want the one that

  // is the most specific, which leads to the smallest result set.

  for(int i = 0; i < aInfo->nConstraint; i++) {

    if (aInfo->aConstraint[i].iColumn == 1 && aInfo->aConstraint[i].usable) {

      if (aInfo->aConstraint[i].op & SQLITE_INDEX_CONSTRAINT_EQ) {

        aInfo->aConstraintUsage[i].argvIndex = 1;

      }

      break;

    }

    // TODO: handle single files (constrained also by the name column)

  }

  return SQLITE_OK;

}

int Open(sqlite3_vtab* aVtab, sqlite3_vtab_cursor** aCursor)

{

  VirtualTableCursor* cursor = new VirtualTableCursor();

  *aCursor = reinterpret_cast<sqlite3_vtab_cursor*>(cursor);

  return SQLITE_OK;

}

int Close(sqlite3_vtab_cursor* aCursor)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  delete cursor;

  return SQLITE_OK;

}

int Filter(sqlite3_vtab_cursor* aCursor, int aIdxNum, const char* aIdxStr,

           int aArgc, sqlite3_value** aArgv)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  if(aArgc <= 0) {

    return SQLITE_OK;

  }

  nsDependentString path(

    reinterpret_cast<const char16_t*>(::sqlite3_value_text16(aArgv[0])));

  nsresult rv = cursor->Init(path);

  NS_ENSURE_SUCCESS(rv, SQLITE_ERROR);

  return SQLITE_OK;

}

int Next(sqlite3_vtab_cursor* aCursor)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  nsresult rv = cursor->NextFile();

  NS_ENSURE_SUCCESS(rv, SQLITE_ERROR);

  return SQLITE_OK;

}

int Eof(sqlite3_vtab_cursor* aCursor)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  return cursor->CurrentFileName().IsVoid() ? 1 : 0;

}

int Column(sqlite3_vtab_cursor* aCursor, sqlite3_context* aContext,

           int aColumnIndex)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  switch (aColumnIndex) {

    // name

    case 0: {

      const nsString& name = cursor->CurrentFileName();

      sqlite3_result_text16(aContext, name.get(),

                            name.Length() * sizeof(char16_t),

                            SQLITE_TRANSIENT);

      break;

    }

    // path

    case 1: {

      const nsString& path = cursor->DirectoryPath();

      sqlite3_result_text16(aContext, path.get(),

                            path.Length() * sizeof(char16_t),

                            SQLITE_TRANSIENT);

      break;

    }

    default:

      MOZ_ASSERT_UNREACHABLE("Unsupported column!");

  }

  return SQLITE_OK;

}

int RowId(sqlite3_vtab_cursor* aCursor, sqlite3_int64* aRowid)

{

  VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);

  *aRowid = cursor->RowId();

  return SQLITE_OK;

}

} // namespace

namespace mozilla {

namespace storage {

int RegisterFileSystemModule(sqlite3* aDB, const char* aName)

{

  static sqlite3_module module = {

    1,

    Connect,

    Connect,

    BestIndex,

    Disconnect,

    Disconnect,

    Open,

    Close,

    Filter,

    Next,

    Eof,

    Column,

    RowId,

    nullptr,

    nullptr,

    nullptr,

    nullptr,

    nullptr,

    nullptr,

    nullptr

  };

  return sqlite3_create_module(aDB, aName, &module, nullptr);

}

} // namespace storage

} // namespace mozilla