////////////////////////////////////////////////////////////////////////////////
/// @brief shape accessor
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2014 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Dr. Frank Celler
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2011-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "shape-accessor.h"
#include "Basics/logging.h"
#include "Basics/vector.h"
#include "VocBase/shaped-json.h"
#include "VocBase/VocShaper.h"

// #define DEBUG_SHAPE_ACCESSOR 1

// -----------------------------------------------------------------------------
// --SECTION--                                                     private types
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief shape accessor bytecode operations
////////////////////////////////////////////////////////////////////////////////

typedef enum {
  TRI_SHAPE_AC_DONE       = 1,
  TRI_SHAPE_AC_OFFSET_FIX = 2,
  TRI_SHAPE_AC_OFFSET_VAR = 3
}
TRI_shape_ac_bc_e;

// -----------------------------------------------------------------------------
// --SECTION--                                                 private functions
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief computes a byte-code sequence
////////////////////////////////////////////////////////////////////////////////

static bool BytecodeShapeAccessor (VocShaper* shaper, 
                                   TRI_shape_access_t* accessor) {
  // find the shape
  TRI_shape_t const* shape = shaper->lookupShapeId(accessor->_sid);

  if (shape == nullptr) {
    LOG_ERROR("unknown shape id %llu", (unsigned long long) accessor->_sid);
#ifdef TRI_ENABLE_MAINTAINER_MODE
    TRI_ASSERT(false);
#endif
    return false;
  }
  
  // we need at least 3 or 4 entries in the vector to store an accessor
  TRI_vector_pointer_t ops;

  if (TRI_InitVectorPointer(&ops, TRI_UNKNOWN_MEM_ZONE, 4) != TRI_ERROR_NO_ERROR) {
    return false;
  }

  // find the attribute path
  TRI_shape_path_t const* path = shaper->lookupAttributePathByPid(accessor->_pid);

  if (path == nullptr) {
    LOG_ERROR("unknown attribute path %llu", (unsigned long long) accessor->_pid);
#ifdef TRI_ENABLE_MAINTAINER_MODE
    TRI_ASSERT(false);
#endif
    return false;
  }

  TRI_shape_aid_t const* paids = (TRI_shape_aid_t*) (((char const*) path) + sizeof(TRI_shape_path_t));

  // and follow it
  for (size_t i = 0;  i < path->_aidLength;  ++i, ++paids) {
#ifdef DEBUG_SHAPE_ACCESSOR
    printf("%lu: aid: %lu, sid: %lu, type %lu\n",
           (unsigned long) i,
           (unsigned long) *paids,
           (unsigned long) shape->_sid,
           (unsigned long) shape->_type);
#endif

    if (shape->_type == TRI_SHAPE_ARRAY) {
      TRI_array_shape_t* s = (TRI_array_shape_t*) shape;
      TRI_shape_size_t const f = s->_fixedEntries;
      TRI_shape_size_t const v = s->_variableEntries;
      TRI_shape_size_t n = f + v;

      // find the aid within the shape
      char const* qtr = (char const*) shape;
      qtr += sizeof(TRI_array_shape_t);

      TRI_shape_sid_t const* sids = (TRI_shape_sid_t const*) qtr;
      qtr += n * sizeof(TRI_shape_sid_t);

      TRI_shape_aid_t const* aids = (TRI_shape_aid_t const*) qtr;
      qtr += n * sizeof(TRI_shape_aid_t);

      TRI_shape_size_t const* offsetsF = (TRI_shape_size_t const*) qtr;

      size_t j;

      // check for fixed size aid
      for (j = 0;  j < f;  ++j, ++sids, ++aids, ++offsetsF) {
        if (*paids == *aids) {
          TRI_shape_sid_t const sid = *sids;

          LOG_TRACE("found aid '%ld' as fixed entry with sid '%ld' and offset '%ld' - '%ld'",
                    (unsigned long) *paids,
                    (unsigned long) sid,
                    (unsigned long) offsetsF[0],
                    (unsigned long) offsetsF[1]);

          shape = shaper->lookupShapeId(sid);

          if (shape == nullptr) {
            LOG_ERROR("unknown shape id '%llu' for attribute id '%llu'",
                      (unsigned long long) accessor->_sid,
                      (unsigned long long) *paids);

            TRI_DestroyVectorPointer(&ops);
            return false;
          }

          // reserve a block big enough to hold the following 3 entries plus the final AC_DONE entry
          int res = TRI_ReserveVectorPointer(&ops, 4);

          if (res != TRI_ERROR_NO_ERROR) {
            LOG_ERROR("out of memory");
            TRI_DestroyVectorPointer(&ops);
            return false;
          }

          // this will always succeed as we reserve enough memory before
          TRI_PushBackVectorPointer(&ops, (void*) TRI_SHAPE_AC_OFFSET_FIX);
          TRI_PushBackVectorPointer(&ops, (void*) (uintptr_t) (offsetsF[0])); // offset is always smaller than 4 GByte
          TRI_PushBackVectorPointer(&ops, (void*) (uintptr_t) (offsetsF[1])); // offset is always smaller than 4 GByte
          break;
        }
      }

      if (j < f) {
        continue;
      }

      // check for variable size aid
      for (j = 0;  j < v;  ++j, ++sids, ++aids) {
        if (*paids == *aids) {
          TRI_shape_sid_t const sid = *sids;

          LOG_TRACE("found aid '%llu' as variable entry with sid '%llu'",
                    (unsigned long long) *paids,
                    (unsigned long long) sid);

          shape = shaper->lookupShapeId(sid);

          if (shape == nullptr) {
            LOG_ERROR("unknown shape id '%llu' for attribute id '%llu'",
                      (unsigned long long) accessor->_sid,
                      (unsigned long long) *paids);

            TRI_DestroyVectorPointer(&ops);
            return false;
          }

          // reserve a block big enough to hold the following 2 entries plus the final AC_DONE entry
          int res = TRI_ReserveVectorPointer(&ops, 3);
          
          if (res != TRI_ERROR_NO_ERROR) {
            LOG_ERROR("out of memory");
            TRI_DestroyVectorPointer(&ops);
            return false;
          }

          // this will always succeed as we reserved enough memory in the vector before
          TRI_PushBackVectorPointer(&ops, (void*) TRI_SHAPE_AC_OFFSET_VAR);
          TRI_PushBackVectorPointer(&ops, (void*) j);
          break;
        }
      }

      if (j < v) {
        continue;
      }

      LOG_TRACE("unknown attribute id '%llu'", (unsigned long long) *paids);
    }

    TRI_DestroyVectorPointer(&ops);

    accessor->_resultSid = TRI_SHAPE_ILLEGAL;
    accessor->_code = nullptr;

    return true;
  }

  // insert final "done" entry
  // note that this must always succeed as we reserved enough space before
  TRI_PushBackVectorPointer(&ops, (void*) TRI_SHAPE_AC_DONE);

  // remember resulting sid
  accessor->_resultSid = shape->_sid;

  // steal buffer from ops vector so we don't need to copy it
  accessor->_code = const_cast<void const**>(ops._buffer);

  // inform the vector that we took over ownership
  ops._buffer = nullptr;

  TRI_DestroyVectorPointer(&ops);
  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief executes a byte-code sequence
////////////////////////////////////////////////////////////////////////////////

static bool ExecuteBytecodeShapeAccessor (TRI_shape_access_t const* accessor,
                                          void** begin,
                                          void** end) {
  if (accessor->_resultSid == TRI_SHAPE_ILLEGAL) {
    return false;
  }

  void const** ops = static_cast<void const**>(accessor->_code);

  while (true) {
    TRI_shape_ac_bc_e op = *(TRI_shape_ac_bc_e*) ops;
    ++ops;

    switch (op) {
      case TRI_SHAPE_AC_DONE:
        return true;

      case TRI_SHAPE_AC_OFFSET_FIX: {
        TRI_shape_size_t b = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte
        TRI_shape_size_t e = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte

        *end   = ((char*) *begin) + e;
        *begin = ((char*) *begin) + b;
        break;
      }

      case TRI_SHAPE_AC_OFFSET_VAR: {
        TRI_shape_size_t pos = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte
        TRI_shape_size_t* offsetsV = (TRI_shape_size_t*) *begin;

        *end   = ((char*) *begin) + offsetsV[pos + 1];
        *begin = ((char*) *begin) + offsetsV[pos];
        break;
      }

      default:
        break;
    }
  }

  return false;
}

// -----------------------------------------------------------------------------
// --SECTION--                                                  public functions
// -----------------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////////////
/// @brief free a shape accessor
////////////////////////////////////////////////////////////////////////////////

void TRI_FreeShapeAccessor (TRI_shape_access_t* accessor) {
  TRI_ASSERT(accessor != nullptr);

  if (accessor->_code != nullptr) {
    TRI_Free(TRI_UNKNOWN_MEM_ZONE, (void*) accessor->_code);
  }

  TRI_Free(TRI_UNKNOWN_MEM_ZONE, accessor);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates a shape accessor
////////////////////////////////////////////////////////////////////////////////

TRI_shape_access_t* TRI_ShapeAccessor (VocShaper* shaper,
                                       TRI_shape_sid_t sid,
                                       TRI_shape_pid_t pid) {
  TRI_shape_access_t* accessor = static_cast<TRI_shape_access_t*>(TRI_Allocate(TRI_UNKNOWN_MEM_ZONE, sizeof(TRI_shape_access_t), false));

  if (accessor == nullptr) {
    TRI_set_errno(TRI_ERROR_OUT_OF_MEMORY);
    return nullptr;
  }

  accessor->_sid = sid;
  accessor->_pid = pid;
  accessor->_code = nullptr;

  bool ok = BytecodeShapeAccessor(shaper, accessor);

  if (ok) {
    return accessor;
  }

  TRI_FreeShapeAccessor(accessor);
  return nullptr;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief executes a shape accessor
////////////////////////////////////////////////////////////////////////////////

bool TRI_ExecuteShapeAccessor (TRI_shape_access_t const* accessor,
                               TRI_shaped_json_t const* shaped,
                               TRI_shaped_json_t* result) {
  void* begin = shaped->_data.data;
  void* end   = ((char*) begin) + shaped->_data.length;

  if (! ExecuteBytecodeShapeAccessor(accessor, &begin, &end)) {
    return false;
  }

  result->_sid         = accessor->_resultSid;
  result->_data.data   = (char*) begin;
  result->_data.length = (uint32_t) (((char const*) end) - ((char const*) begin));

  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief prints a TRI_shape_t for debugging
////////////////////////////////////////////////////////////////////////////////

void TRI_PrintShapeAccessor (TRI_shape_access_t* accessor) {
  TRI_shape_size_t b;
  TRI_shape_size_t e;
  TRI_shape_size_t pos;

  printf("shape accessor for sid: %lu, pid: %lu\n",
         (unsigned long) accessor->_sid,
         (unsigned long) accessor->_pid);

  if (accessor->_resultSid == TRI_SHAPE_ILLEGAL) {
    printf("  result shape: -\n");
    return;
  }

  printf("  result shape: %lu\n", (unsigned long) accessor->_resultSid);

  void const** ops = static_cast<void const**>(accessor->_code);

  while (true) {
    TRI_shape_ac_bc_e op = static_cast<TRI_shape_ac_bc_e>(*(TRI_shape_ac_bc_e*) ops);
    ops++;

    switch (op) {
      case TRI_SHAPE_AC_DONE:
        return;

      case TRI_SHAPE_AC_OFFSET_FIX:
        b = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte
        e = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte

        printf("  OP: fixed offset %lu - %lu\n",
               (unsigned long) b,
               (unsigned long) e);
        break;

      case TRI_SHAPE_AC_OFFSET_VAR:
        pos = (TRI_shape_size_t) (uintptr_t) *ops++; // offset is always smaller than 4 GByte

        printf("  OP: variable offset at position %lu\n",
               (unsigned long) pos);
        break;

      default:
        printf("  OP: unknown op code\n");
        return;
    }
  }
}

// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

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