#include "pg_meta.h"

#include <string_view>

#include "crimson/os/cyan_collection.h"
#include "crimson/os/cyan_store.h"

// prefix pgmeta_oid keys with _ so that PGLog::read_log_and_missing() can
// easily skip them

static const string_view infover_key = "_infover"sv;
static const string_view info_key = "_info"sv;
static const string_view biginfo_key = "_biginfo"sv;
static const string_view epoch_key = "_epoch"sv;
static const string_view fastinfo_key = "_fastinfo"sv;

using ceph::os::CyanStore;

PGMeta::PGMeta(CyanStore* store, spg_t pgid)
  : store{store},
    pgid{pgid}
{}

namespace {
  template<typename T>
  std::optional<T> find_value(const CyanStore::omap_values_t& values,
                              string_view key)
  {
    auto found = values.find(key);
    if (found == values.end()) {
      return {};
    }
    auto p = found->second.cbegin();
    T value;
    decode(value, p);
    return std::make_optional(std::move(value));
  }
}
seastar::future<epoch_t> PGMeta::get_epoch()
{
  auto ch = store->open_collection(coll_t{pgid});
  return store->omap_get_values(ch,
                                pgid.make_pgmeta_oid(),
                                {string{infover_key},
                                 string{epoch_key}}).then(
    [](auto&& values) {
      {
        // sanity check
        auto infover = find_value<__u8>(values, infover_key);
        assert(infover);
        if (*infover < 10) {
          throw std::runtime_error("incompatible pg meta");
        }
      }
      {
        auto epoch = find_value<epoch_t>(values, epoch_key);
        assert(epoch);
        return seastar::make_ready_future<epoch_t>(*epoch);
      }
    });
}

seastar::future<pg_info_t, PastIntervals> PGMeta::load()
{
  auto ch = store->open_collection(coll_t{pgid});
  return store->omap_get_values(ch,
                                pgid.make_pgmeta_oid(),
                                {string{infover_key},
                                 string{info_key},
                                 string{biginfo_key},
                                 string{fastinfo_key}}).then(
    [this](auto&& values) {
      {
        // sanity check
        auto infover = find_value<__u8>(values, infover_key);
        assert(infover);
        if (infover < 10) {
          throw std::runtime_error("incompatible pg meta");
        }
      }
      pg_info_t info;
      {
        auto found = find_value<pg_info_t>(values, info_key);
        assert(found);
        info = *std::move(found);
      }
      PastIntervals past_intervals;
      {
        using biginfo_t = std::pair<PastIntervals, decltype(info.purged_snaps)>;
        auto big_info = find_value<biginfo_t>(values, biginfo_key);
        assert(big_info);
        past_intervals = std::move(big_info->first);
        info.purged_snaps = std::move(big_info->second);
      }
      {
        auto fast_info = find_value<pg_fast_info_t>(values, fastinfo_key);
        assert(fast_info);
        fast_info->try_apply_to(&info);
      }
      return seastar::make_ready_future<pg_info_t, PastIntervals>(
        std::move(info),
        std::move(past_intervals));
    });
}