#include "source/server/admin/stats_render.h"

#include "source/common/stats/histogram_impl.h"

#include "absl/strings/str_format.h"

namespace Envoy {

namespace Server {

StatsTextRender::StatsTextRender(const StatsParams& params)

    : histogram_buckets_mode_(params.histogram_buckets_mode_) {}

void StatsTextRender::generate(Buffer::Instance& response, const std::string& name,

                               uint64_t value) {

  response.addFragments({name, ": ", absl::StrCat(value), "\n"});

}

void StatsTextRender::generate(Buffer::Instance& response, const std::string& name,

                               const std::string& value) {

  response.addFragments({name, ": \"", value, "\"\n"});

}

void StatsTextRender::generate(Buffer::Instance& response, const std::string& name,

                               const Stats::ParentHistogram& histogram) {

  if (!histogram.used()) {

    response.addFragments({name, ": No recorded values\n"});

    return;

  }

  switch (histogram_buckets_mode_) {

  case Utility::HistogramBucketsMode::Unset:

  case Utility::HistogramBucketsMode::Summary:

    response.addFragments({name, ": ", histogram.quantileSummary(), "\n"});

    break;

  case Utility::HistogramBucketsMode::Cumulative:

    response.addFragments({name, ": ", histogram.bucketSummary(), "\n"});

    break;

  case Utility::HistogramBucketsMode::Disjoint:

    addDisjointBuckets(name, histogram, response);

    break;

  case Utility::HistogramBucketsMode::Detailed:

    response.addFragments({name, ":\n  totals="});

    addDetail(histogram.detailedTotalBuckets(), response);

    response.add("\n  intervals=");

    addDetail(histogram.detailedIntervalBuckets(), response);

    response.addFragments({"\n  summary=", histogram.quantileSummary(), "\n"});

    break;

  }

}

void StatsTextRender::finalize(Buffer::Instance&) {}

void StatsTextRender::addDetail(const std::vector<Stats::ParentHistogram::Bucket>& buckets,

                                Buffer::Instance& response) {

  absl::string_view delim = "";

  for (const Stats::ParentHistogram::Bucket& bucket : buckets) {

    response.addFragments({delim, absl::StrFormat("%.15g,%.15g:%lu", bucket.lower_bound_,

                                                  bucket.width_, bucket.count_)});

    delim = ", ";

  }

}

// Computes disjoint buckets as text and adds them to the response buffer.

void StatsTextRender::addDisjointBuckets(const std::string& name,

                                         const Stats::ParentHistogram& histogram,

                                         Buffer::Instance& response) {

  if (!histogram.used()) {

    response.addFragments({name, ": No recorded values\n"});

    return;

  }

  response.addFragments({name, ": "});

  std::vector<absl::string_view> bucket_summary;

  const Stats::HistogramStatistics& interval_statistics = histogram.intervalStatistics();

  Stats::ConstSupportedBuckets& supported_buckets = interval_statistics.supportedBuckets();

  const std::vector<uint64_t> disjoint_interval_buckets =

      interval_statistics.computeDisjointBuckets();

  const std::vector<uint64_t> disjoint_cumulative_buckets =

      histogram.cumulativeStatistics().computeDisjointBuckets();

  // Make sure all vectors are the same size.

  ASSERT(disjoint_interval_buckets.size() == disjoint_cumulative_buckets.size());

  ASSERT(disjoint_cumulative_buckets.size() == supported_buckets.size());

  const size_t min_size = std::min({disjoint_interval_buckets.size(),

                                    disjoint_cumulative_buckets.size(), supported_buckets.size()});

  std::vector<std::string> bucket_strings;

  bucket_strings.reserve(min_size);

  for (size_t i = 0; i < min_size; ++i) {

    if (i != 0) {

      bucket_summary.push_back(" ");

    }

    bucket_strings.push_back(fmt::format("B{:g}({},{})", supported_buckets[i],

                                         disjoint_interval_buckets[i],

                                         disjoint_cumulative_buckets[i]));

    bucket_summary.push_back(bucket_strings.back());

  }

  bucket_summary.push_back("\n");

  response.addFragments(bucket_summary);

}

StatsJsonRender::StatsJsonRender(Http::ResponseHeaderMap& response_headers,

                                 Buffer::Instance& response, const StatsParams& params)

    : histogram_buckets_mode_(params.histogram_buckets_mode_),

      json_(std::make_unique<JsonContext>(response)), response_(response) {

  response_headers.setReferenceContentType(Http::Headers::get().ContentTypeValues.Json);

}

StatsJsonRender::JsonContext::JsonContext(Buffer::Instance& response)

    : streamer_(response), stats_map_(streamer_.makeRootMap()) {

  // We don't create a JSON data model for the stats output, as that makes

  // streaming difficult. Instead we emit the preamble in the constructor here,

  // and create json models for each stats entry.

  stats_map_->addKey("stats");

  stats_array_ = stats_map_->addArray();

}

void StatsJsonRender::drainIfNeeded(Buffer::Instance& response) {

  if (&response_ != &response) {

    response.move(response_);

  }

}

// Buffers a JSON fragment for a numeric stats, flushing to the response

// buffer once we exceed JsonStatsFlushCount stats.

void StatsJsonRender::generate(Buffer::Instance& response, const std::string& name,

                               uint64_t value) {

  ASSERT(!histograms_initialized_);

  json_->stats_array_->addMap()->addEntries({{"name", name}, {"value", value}});

  drainIfNeeded(response);

}

// Buffers a JSON fragment for a text-readout stat, flushing to the response

// buffer once we exceed JsonStatsFlushCount stats.

void StatsJsonRender::generate(Buffer::Instance& response, const std::string& name,

                               const std::string& value) {

  ASSERT(!histograms_initialized_);

  json_->stats_array_->addMap()->addEntries({{"name", name}, {"value", value}});

  drainIfNeeded(response);

}

// In JSON we buffer all histograms and don't write them immediately, so we

// can, in one JSON structure, emit shared attributes of all histograms and

// each individual histogram.

//

// This is counter to the goals of streaming and chunked interfaces, but

// usually there are far fewer histograms than counters or gauges.

//

// We can further optimize this by streaming out the histograms object, one

// histogram at a time, in case buffering all the histograms in Envoy

// buffers up too much memory.

void StatsJsonRender::generate(Buffer::Instance& response, const std::string& name,

                               const Stats::ParentHistogram& histogram) {

  if (!histograms_initialized_) {

    renderHistogramStart();

  }

  switch (histogram_buckets_mode_) {

  case Utility::HistogramBucketsMode::Unset:

  case Utility::HistogramBucketsMode::Summary: {

    Json::Streamer::MapPtr map = json_->histogram_array_->addMap();

    map->addEntries({{"name", name}});

    map->addKey("values");

    populatePercentiles(histogram, *map);

    break;

  }

  case Utility::HistogramBucketsMode::Cumulative: {

    const Stats::HistogramStatistics& interval_statistics = histogram.intervalStatistics();

    const std::vector<uint64_t>& interval_buckets = interval_statistics.computedBuckets();

    const std::vector<uint64_t>& cumulative_buckets =

        histogram.cumulativeStatistics().computedBuckets();

    collectBuckets(name, histogram, interval_buckets, cumulative_buckets);

    break;

  }

  case Utility::HistogramBucketsMode::Disjoint: {

    const Stats::HistogramStatistics& interval_statistics = histogram.intervalStatistics();

    const std::vector<uint64_t> interval_buckets = interval_statistics.computeDisjointBuckets();

    const std::vector<uint64_t> cumulative_buckets =

        histogram.cumulativeStatistics().computeDisjointBuckets();

    collectBuckets(name, histogram, interval_buckets, cumulative_buckets);

    break;

  }

  case Utility::HistogramBucketsMode::Detailed: {

    generateHistogramDetail(name, histogram, *json_->histogram_array_->addMap());

    break;

  }

  }

  drainIfNeeded(response);

}

void StatsJsonRender::populateSupportedPercentiles(Json::Streamer::Array& array) {

  Stats::HistogramStatisticsImpl empty_statistics;

  std::vector<double> supported = empty_statistics.supportedQuantiles();

  std::vector<Json::Streamer::Value> views(supported.size());

  for (uint32_t i = 0, n = supported.size(); i < n; ++i) {

    views[i] = supported[i] * 100;

  }

  array.addEntries(views);

}

void StatsJsonRender::populatePercentiles(const Stats::ParentHistogram& histogram,

                                          Json::Streamer::Map& map) {

  Json::Streamer::ArrayPtr array = map.addArray();

  std::vector<double> totals = histogram.cumulativeStatistics().computedQuantiles(),

                      intervals = histogram.intervalStatistics().computedQuantiles();

  uint32_t min_size = std::min(totals.size(), intervals.size());

  ASSERT(totals.size() == min_size);

  ASSERT(intervals.size() == min_size);

  for (uint32_t i = 0; i < min_size; ++i) {

    array->addMap()->addEntries({{"cumulative", totals[i]}, {"interval", intervals[i]}});

  }

};

void StatsJsonRender::renderHistogramStart() {

  histograms_initialized_ = true;

  json_->histogram_map1_ = json_->stats_array_->addMap();

  json_->histogram_map1_->addKey("histograms");

  switch (histogram_buckets_mode_) {

  case Utility::HistogramBucketsMode::Detailed:

    json_->histogram_map2_ = json_->histogram_map1_->addMap();

    json_->histogram_map2_->addKey("supported_percentiles");

    { populateSupportedPercentiles(*json_->histogram_map2_->addArray()); }

    json_->histogram_map2_->addKey("details");

    json_->histogram_array_ = json_->histogram_map2_->addArray();

    break;

  case Utility::HistogramBucketsMode::Unset:

  case Utility::HistogramBucketsMode::Summary:

    json_->histogram_map2_ = json_->histogram_map1_->addMap();

    json_->histogram_map2_->addKey("supported_quantiles");

    { populateSupportedPercentiles(*json_->histogram_map2_->addArray()); }

    json_->histogram_map2_->addKey("computed_quantiles");

    json_->histogram_array_ = json_->histogram_map2_->addArray();

    break;

  case Utility::HistogramBucketsMode::Cumulative:

  case Utility::HistogramBucketsMode::Disjoint:

    json_->histogram_array_ = json_->histogram_map1_->addArray();

    break;

  }

}

void StatsJsonRender::generateHistogramDetail(const std::string& name,

                                              const Stats::ParentHistogram& histogram,

                                              Json::Streamer::Map& map) {

  // Now we produce the stream-able histogram records, without using the json intermediate

  // representation or serializer.

  map.addEntries({{"name", name}});

  map.addKey("totals");

  populateBucketsVerbose(histogram.detailedTotalBuckets(), map);

  map.addKey("intervals");

  populateBucketsVerbose(histogram.detailedIntervalBuckets(), map);

  map.addKey("percentiles");

  populatePercentiles(histogram, map);

}

void StatsJsonRender::populateBucketsVerbose(

    const std::vector<Stats::ParentHistogram::Bucket>& buckets, Json::Streamer::Map& map) {

  Json::Streamer::ArrayPtr buckets_array = map.addArray();

  for (const Stats::ParentHistogram::Bucket& bucket : buckets) {

    buckets_array->addMap()->addEntries(

        {{"lower_bound", bucket.lower_bound_}, {"width", bucket.width_}, {"count", bucket.count_}});

  }

}

// Since histograms are buffered (see above), the finalize() method generates

// all of them.

void StatsJsonRender::finalize(Buffer::Instance& response) {

  json_.reset();

  drainIfNeeded(response);

}

// Collects the buckets from the specified histogram, using either the

// cumulative or disjoint views, as controlled by buckets_fn.

void StatsJsonRender::collectBuckets(const std::string& name,

                                     const Stats::ParentHistogram& histogram,

                                     const std::vector<uint64_t>& interval_buckets,

                                     const std::vector<uint64_t>& cumulative_buckets) {

  const Stats::HistogramStatistics& interval_statistics = histogram.intervalStatistics();

  Stats::ConstSupportedBuckets& supported_buckets = interval_statistics.supportedBuckets();

  // Make sure all vectors are the same size.

  ASSERT(interval_buckets.size() == cumulative_buckets.size());

  ASSERT(cumulative_buckets.size() == supported_buckets.size());

  size_t min_size =

      std::min({interval_buckets.size(), cumulative_buckets.size(), supported_buckets.size()});

  Json::Streamer::MapPtr map = json_->histogram_array_->addMap();

  map->addEntries({{"name", name}});

  map->addKey("buckets");

  Json::Streamer::ArrayPtr buckets = map->addArray();

  for (uint32_t i = 0; i < min_size; ++i) {

    Json::Streamer::MapPtr bucket_map = buckets->addMap();

    bucket_map->addEntries({{"upper_bound", supported_buckets[i]},

                            {"interval", interval_buckets[i]},

                            {"cumulative", cumulative_buckets[i]}});

  }

}

} // namespace Server

} // namespace Envoy