// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab

#include "librbd/io/ReadResult.h"
#include "include/buffer.h"
#include "common/dout.h"
#include "librbd/io/AioCompletion.h"
#include <boost/variant/apply_visitor.hpp>
#include <boost/variant/static_visitor.hpp>

#define dout_subsys ceph_subsys_rbd
#undef dout_prefix
#define dout_prefix *_dout << "librbd::io::ReadResult: " << this \
                           << " " << __func__ << ": "

namespace librbd {
namespace io {

struct ReadResult::SetClipLengthVisitor : public boost::static_visitor<void> {
  size_t length;

  SetClipLengthVisitor(size_t length) : length(length) {
  }

  void operator()(Linear &linear) const {
    assert(length <= linear.buf_len);
    linear.buf_len = length;
  }

  template <typename T>
  void operator()(T &t) const {
  }
};

struct ReadResult::AssembleResultVisitor : public boost::static_visitor<void> {
  CephContext *cct;
  Striper::StripedReadResult &destriper;

  AssembleResultVisitor(CephContext *cct, Striper::StripedReadResult &destriper)
    : cct(cct), destriper(destriper) {
  }

  void operator()(Empty &empty) const {
    ldout(cct, 20) << "dropping read result" << dendl;
  }

  void operator()(Linear &linear) const {
    ldout(cct, 20) << "copying resulting bytes to "
                   << reinterpret_cast<void*>(linear.buf) << dendl;
    destriper.assemble_result(cct, linear.buf, linear.buf_len);
  }

  void operator()(Vector &vector) const {
    bufferlist bl;
    destriper.assemble_result(cct, bl, true);

    ldout(cct, 20) << "copying resulting " << bl.length() << " bytes to iovec "
                   << reinterpret_cast<const void*>(vector.iov) << dendl;

    bufferlist::iterator it = bl.begin();
    size_t length = bl.length();
    size_t offset = 0;
    int idx = 0;
    for (; offset < length && idx < vector.iov_count; idx++) {
      size_t len = MIN(vector.iov[idx].iov_len, length - offset);
      it.copy(len, static_cast<char *>(vector.iov[idx].iov_base));
      offset += len;
    }
    assert(offset == bl.length());
  }

  void operator()(Bufferlist &bufferlist) const {
    bufferlist.bl->clear();
    destriper.assemble_result(cct, *bufferlist.bl, true);

    ldout(cct, 20) << "moved resulting " << bufferlist.bl->length() << " "
                   << "bytes to bl " << reinterpret_cast<void*>(bufferlist.bl)
                   << dendl;
  }
};

ReadResult::C_ReadRequest::C_ReadRequest(AioCompletion *aio_completion)
  : aio_completion(aio_completion) {
  aio_completion->add_request();
}

void ReadResult::C_ReadRequest::finish(int r) {
  aio_completion->complete_request(r);
}

void ReadResult::C_ImageReadRequest::finish(int r) {
  CephContext *cct = aio_completion->ictx->cct;
  ldout(cct, 10) << "C_ImageReadRequest: r=" << r
                 << dendl;
  if (r >= 0) {
    size_t length = 0;
    for (auto &image_extent : image_extents) {
      length += image_extent.second;
    }
    assert(length == bl.length());

    aio_completion->lock.Lock();
    aio_completion->read_result.m_destriper.add_partial_result(
      cct, bl, image_extents);
    aio_completion->lock.Unlock();
    r = length;
  }

  C_ReadRequest::finish(r);
}

void ReadResult::C_SparseReadRequestBase::finish(ExtentMap &extent_map,
                                                 const Extents &buffer_extents,
                                                 uint64_t offset, size_t length,
                                                 bufferlist &bl, int r) {
  aio_completion->lock.Lock();
  CephContext *cct = aio_completion->ictx->cct;
  ldout(cct, 10) << "C_SparseReadRequestBase: r = " << r
                 << dendl;

  if (r >= 0 || r == -ENOENT) { // this was a sparse_read operation
    ldout(cct, 10) << " got " << extent_map
                   << " for " << buffer_extents
                   << " bl " << bl.length() << dendl;
    // reads from the parent don't populate the m_ext_map and the overlap
    // may not be the full buffer.  compensate here by filling in m_ext_map
    // with the read extent when it is empty.
    if (extent_map.empty()) {
      extent_map[offset] = bl.length();
    }

    aio_completion->read_result.m_destriper.add_partial_sparse_result(
      cct, bl, extent_map, offset, buffer_extents);
    r = length;
  }
  aio_completion->lock.Unlock();

  C_ReadRequest::finish(r);
}

ReadResult::ReadResult() : m_buffer(Empty()) {
}

ReadResult::ReadResult(char *buf, size_t buf_len)
  : m_buffer(Linear(buf, buf_len)) {
}

ReadResult::ReadResult(const struct iovec *iov, int iov_count)
  : m_buffer(Vector(iov, iov_count)) {
}

ReadResult::ReadResult(ceph::bufferlist *bl)
  : m_buffer(Bufferlist(bl)) {
}

void ReadResult::set_clip_length(size_t length) {
  boost::apply_visitor(SetClipLengthVisitor(length), m_buffer);
}

void ReadResult::assemble_result(CephContext *cct) {
  boost::apply_visitor(AssembleResultVisitor(cct, m_destriper), m_buffer);
}

} // namespace io
} // namespace librbd