/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * 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.
 */

#include "src/trace_processor/perfetto_sql/intrinsics/table_functions/connected_flow.h"

#include <cstddef>
#include <cstdint>
#include <memory>
#include <optional>
#include <queue>
#include <string>
#include <unordered_set>
#include <utility>
#include <vector>

#include "perfetto/base/logging.h"
#include "perfetto/base/status.h"
#include "perfetto/trace_processor/basic_types.h"
#include "src/trace_processor/core/dataframe/specs.h"
#include "src/trace_processor/perfetto_sql/intrinsics/table_functions/ancestor.h"
#include "src/trace_processor/perfetto_sql/intrinsics/table_functions/descendant.h"
#include "src/trace_processor/perfetto_sql/intrinsics/table_functions/static_table_function.h"
#include "src/trace_processor/perfetto_sql/intrinsics/table_functions/tables_py.h"
#include "src/trace_processor/storage/trace_storage.h"
#include "src/trace_processor/tables/flow_tables_py.h"
#include "src/trace_processor/tables/slice_tables_py.h"
#include "src/trace_processor/types/trace_processor_context.h"

namespace perfetto::trace_processor {

namespace {

enum FlowVisitMode : uint8_t {
  VISIT_INCOMING = 1 << 0,
  VISIT_OUTGOING = 1 << 1,
  VISIT_INCOMING_AND_OUTGOING = VISIT_INCOMING | VISIT_OUTGOING,
};

enum RelativesVisitMode : uint8_t {
  VISIT_NO_RELATIVES = 0,
  VISIT_ANCESTORS = 1 << 0,
  VISIT_DESCENDANTS = 1 << 1,
  VISIT_ALL_RELATIVES = VISIT_ANCESTORS | VISIT_DESCENDANTS,
};

// Searches through the slice table recursively to find connected flows.
// Usage:
//  BFS bfs = BFS(context);
//  bfs
//    // Add list of slices to start with.
//    .Start(start_id).Start(start_id2)
//    // Additionally include relatives of |another_id| in search space.
//    .GoToRelatives(another_id, VISIT_ANCESTORS)
//    // Visit all connected slices to the above slices.
//    .VisitAll(VISIT_INCOMING, VISIT_NO_RELATIVES);
//
//  bfs.TakeResultingFlows();
class BFS {
 public:
  explicit BFS(const TraceStorage* storage,
               const FlowGraph& flow_graph,
               tables::SliceTable::ConstCursor& descendant_cursor)
      : storage_(storage),
        flow_graph_(flow_graph),
        descendant_cursor_(descendant_cursor) {}

  std::vector<tables::FlowTable::RowNumber> TakeResultingFlows() && {
    return std::move(flow_rows_);
  }

  // Includes a starting slice ID to search.
  BFS& Start(SliceId start_id) {
    slices_to_visit_.emplace(start_id, VisitType::START);
    known_slices_.insert(start_id);
    return *this;
  }

  // Visits all slices that can be reached from the given starting slices.
  void VisitAll(FlowVisitMode visit_flow, RelativesVisitMode visit_relatives) {
    while (!slices_to_visit_.empty()) {
      SliceId slice_id = slices_to_visit_.front().first;
      VisitType visit_type = slices_to_visit_.front().second;
      slices_to_visit_.pop();

      // If the given slice is being visited due to being ancestor or descendant
      // of a previous one, do not compute ancestors or descendants again as the
      // result is going to be the same.
      if (visit_type != VisitType::VIA_RELATIVE) {
        GoToRelatives(slice_id, visit_relatives);
      }

      // If the slice was visited by a flow, do not try to go back.
      if ((visit_flow & VISIT_INCOMING) &&
          visit_type != VisitType::VIA_OUTGOING_FLOW) {
        GoByFlow(slice_id, FlowDirection::INCOMING);
      }
      if ((visit_flow & VISIT_OUTGOING) &&
          visit_type != VisitType::VIA_INCOMING_FLOW) {
        GoByFlow(slice_id, FlowDirection::OUTGOING);
      }
    }
  }

  // Includes the relatives of |slice_id| to the list of slices to visit.
  BFS& GoToRelatives(SliceId slice_id, RelativesVisitMode visit_relatives) {
    const auto& slice_table = storage_->slice_table();
    if (visit_relatives & VISIT_ANCESTORS) {
      slice_rows_.clear();
      if (Ancestor::GetAncestorSlices(slice_table, slice_id, slice_rows_,
                                      status_)) {
        GoToRelativesImpl(slice_rows_);
      }
    }
    if (visit_relatives & VISIT_DESCENDANTS) {
      slice_rows_.clear();
      if (Descendant::GetDescendantSlices(slice_table, descendant_cursor_,
                                          slice_id, slice_rows_, status_)) {
        GoToRelativesImpl(slice_rows_);
      }
    }
    return *this;
  }

  const base::Status& status() const { return status_; }

 private:
  enum class FlowDirection : uint8_t {
    INCOMING,
    OUTGOING,
  };
  enum class VisitType : uint8_t {
    START,
    VIA_INCOMING_FLOW,
    VIA_OUTGOING_FLOW,
    VIA_RELATIVE,
  };

  void GoByFlow(SliceId slice_id, FlowDirection flow_direction) {
    PERFETTO_DCHECK(known_slices_.count(slice_id) != 0);

    const auto& flow_map = flow_direction == FlowDirection::OUTGOING
                               ? flow_graph_.outgoing_flows
                               : flow_graph_.incoming_flows;
    auto* flows = flow_map.Find(slice_id);
    if (!flows) {
      return;
    }

    const auto& flow_table = storage_->flow_table();
    for (tables::FlowTable::RowNumber row : *flows) {
      flow_rows_.push_back(row);

      auto ref = row.ToRowReference(flow_table);
      SliceId next_slice_id = flow_direction == FlowDirection::OUTGOING
                                  ? ref.slice_in()
                                  : ref.slice_out();
      if (known_slices_.count(next_slice_id)) {
        continue;
      }

      known_slices_.insert(next_slice_id);
      slices_to_visit_.emplace(next_slice_id,
                               flow_direction == FlowDirection::INCOMING
                                   ? VisitType::VIA_INCOMING_FLOW
                                   : VisitType::VIA_OUTGOING_FLOW);
    }
  }

  void GoToRelativesImpl(
      const std::vector<tables::SliceTable::RowNumber>& rows) {
    const auto& slice = storage_->slice_table();
    for (tables::SliceTable::RowNumber row : rows) {
      auto relative_slice_id = row.ToRowReference(slice).id();
      if (known_slices_.count(relative_slice_id))
        continue;
      known_slices_.insert(relative_slice_id);
      slices_to_visit_.emplace(relative_slice_id, VisitType::VIA_RELATIVE);
    }
  }

  const TraceStorage* storage_;
  const FlowGraph& flow_graph_;
  tables::SliceTable::ConstCursor& descendant_cursor_;

  std::queue<std::pair<SliceId, VisitType>> slices_to_visit_;
  std::unordered_set<SliceId> known_slices_;
  std::vector<tables::FlowTable::RowNumber> flow_rows_;
  std::vector<tables::SliceTable::RowNumber> slice_rows_;
  base::Status status_;
};

}  // namespace

ConnectedFlow::Cursor::Cursor(Mode mode, TraceStorage* storage)
    : mode_(mode),
      storage_(storage),
      table_(storage->mutable_string_pool()),
      descendant_cursor_(Descendant::MakeCursor(storage->slice_table())) {}

bool ConnectedFlow::Cursor::Run(const std::vector<SqlValue>& arguments) {
  PERFETTO_DCHECK(arguments.size() == 1);

  // Clear all our temporary state.
  table_.Clear();

  const auto& flow = storage_->flow_table();
  const auto& slice = storage_->slice_table();

  if (arguments[0].type == SqlValue::Type::kNull) {
    // Nothing matches a null id so return an empty table.
    return OnSuccess(&table_.dataframe());
  }
  if (arguments[0].type != SqlValue::Type::kLong) {
    return OnFailure(base::ErrStatus("start id should be an integer."));
  }
  SliceId start_id{static_cast<uint32_t>(arguments[0].AsLong())};
  if (!slice.FindById(start_id)) {
    return OnFailure(base::ErrStatus("invalid slice id %u", start_id.value));
  }

  // Use cached graph if available, otherwise build a new one.
  FlowGraph graph = cached_flow_graph_.has_value()
                        ? std::move(cached_flow_graph_).value()
                        : FlowGraph::Build(flow);

  BFS bfs(storage_, graph, descendant_cursor_);
  switch (mode_) {
    case Mode::kDirectlyConnectedFlow:
      bfs.Start(start_id).VisitAll(VISIT_INCOMING_AND_OUTGOING,
                                   VISIT_NO_RELATIVES);
      break;
    case Mode::kFollowingFlow:
      bfs.Start(start_id).VisitAll(VISIT_OUTGOING, VISIT_DESCENDANTS);
      break;
    case Mode::kPrecedingFlow:
      bfs.Start(start_id).VisitAll(VISIT_INCOMING, VISIT_ANCESTORS);
      break;
  }
  if (!bfs.status().ok()) {
    return OnFailure(bfs.status());
  }
  std::vector<tables::FlowTable::RowNumber> result_rows =
      std::move(bfs).TakeResultingFlows();
  for (auto row : result_rows) {
    auto ref = row.ToRowReference(flow);
    table_.Insert(tables::ConnectedFlowTable::Row{
        ref.slice_out(),
        ref.slice_in(),
        ref.trace_id(),
        ref.arg_set_id(),
    });
  }

  // Cache the graph if the table is finalized.
  if (flow.dataframe().finalized()) {
    cached_flow_graph_ = std::move(graph);
  }

  return OnSuccess(&table_.dataframe());
}

ConnectedFlow::ConnectedFlow(Mode mode, TraceStorage* storage)
    : mode_(mode), storage_(storage) {}

ConnectedFlow::~ConnectedFlow() = default;

std::unique_ptr<StaticTableFunction::Cursor> ConnectedFlow::MakeCursor() {
  return std::make_unique<Cursor>(mode_, storage_);
}

dataframe::DataframeSpec ConnectedFlow::CreateSpec() {
  return tables::ConnectedFlowTable::kSpec.ToUntypedDataframeSpec();
}

std::string ConnectedFlow::TableName() {
  switch (mode_) {
    case Mode::kDirectlyConnectedFlow:
      return "directly_connected_flow";
    case Mode::kFollowingFlow:
      return "following_flow";
    case Mode::kPrecedingFlow:
      return "preceding_flow";
  }
  PERFETTO_FATAL("Unexpected ConnectedFlowType");
}

uint32_t ConnectedFlow::GetArgumentCount() const {
  return 1;
}

}  // namespace perfetto::trace_processor
