#pragma once

#include <algorithm>
#include <cstdint>
#include <functional>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>

#include "secsgem/secs2/item.hpp"

namespace secsgem::gem {

namespace s2 = secsgem::secs2;

struct CollectionEvent {
  uint32_t id;
  std::string name;
};

struct Report {
  uint32_t id;
  std::vector<uint32_t> vids;
};

struct ReportData {
  uint32_t rptid;
  std::vector<s2::Item> values;
};

enum class DefineReportAck : uint8_t {
  Accept = 0,
  InsufficientSpace = 1,
  InvalidFormat = 2,
  RptidAlreadyDefined = 3,
  InvalidVid = 5,
};

enum class LinkEventAck : uint8_t {
  Accept = 0,
  InsufficientSpace = 1,
  InvalidFormat = 2,
  UnknownCeid = 3,
  UnknownRptid = 4,
  CeidAlreadyLinked = 5,
};

enum class EnableEventAck : uint8_t {
  Accept = 0,
  UnknownCeid = 1,
};

// VID resolver: a callable that maps a VID (which may be an SVID or DVID) to
// its current value, or std::nullopt if unknown. Injected at S2F33 validation
// and again at compose_reports_for emission time; that way the subscription
// service stays pure data (no back-reference to the SVID / DVID stores).
using VidLookup = std::function<std::optional<s2::Item>(uint32_t)>;
using VidExists = std::function<bool(uint32_t)>;

// E30 §6.6 dynamic event reporting state:
//   * the catalog of registered CEIDs (defined by the equipment),
//   * the host-defined reports (RPTID -> VID list),
//   * the CEID -> RPTID links,
//   * and the set of CEIDs the host has enabled.
//
// Pure data; no IO.
class EventReportSubscriptions {
 public:
  // --- CEID catalog -----------------------------------------------------
  void register_event(CollectionEvent ce) {
    by_ceid_.insert_or_assign(ce.id, std::move(ce));
  }
  bool has_event(uint32_t ceid) const { return by_ceid_.count(ceid) > 0; }
  std::vector<CollectionEvent> all_events() const {
    std::vector<CollectionEvent> out;
    out.reserve(by_ceid_.size());
    for (const auto& [_, e] : by_ceid_) out.push_back(e);
    return out;
  }

  // --- S2F33 define reports --------------------------------------------
  DefineReportAck define_reports(
      const std::vector<std::pair<uint32_t, std::vector<uint32_t>>>& rows,
      const VidExists& vid_exists) {
    if (rows.empty()) {
      reports_.clear();
      links_.clear();
      return DefineReportAck::Accept;
    }
    for (const auto& [rptid, vids] : rows) {
      if (vids.empty()) continue;
      for (auto v : vids)
        if (!vid_exists(v)) return DefineReportAck::InvalidVid;
    }
    for (const auto& [rptid, vids] : rows) {
      if (vids.empty()) {
        reports_.erase(rptid);
        for (auto& [_, rpts] : links_)
          rpts.erase(std::remove(rpts.begin(), rpts.end(), rptid), rpts.end());
      } else {
        reports_.insert_or_assign(rptid, Report{rptid, vids});
      }
    }
    return DefineReportAck::Accept;
  }

  std::vector<Report> all_reports() const {
    std::vector<Report> out;
    out.reserve(reports_.size());
    for (const auto& [_, r] : reports_) out.push_back(r);
    return out;
  }

  // --- S2F35 link event report -----------------------------------------
  LinkEventAck link_event_reports(
      const std::vector<std::pair<uint32_t, std::vector<uint32_t>>>& rows) {
    if (rows.empty()) {
      links_.clear();
      return LinkEventAck::Accept;
    }
    for (const auto& [ceid, rpts] : rows) {
      if (!has_event(ceid)) return LinkEventAck::UnknownCeid;
      for (auto r : rpts)
        if (!reports_.count(r)) return LinkEventAck::UnknownRptid;
    }
    for (const auto& [ceid, rpts] : rows) {
      if (rpts.empty()) links_.erase(ceid);
      else links_[ceid] = rpts;
    }
    return LinkEventAck::Accept;
  }

  // --- S2F37 enable / disable event -----------------------------------
  EnableEventAck enable_events(bool enable, const std::vector<uint32_t>& ceids) {
    if (ceids.empty()) {
      if (enable) for (const auto& [id, _] : by_ceid_) enabled_.insert(id);
      else enabled_.clear();
      return EnableEventAck::Accept;
    }
    for (auto id : ceids)
      if (!has_event(id)) return EnableEventAck::UnknownCeid;
    for (auto id : ceids) {
      if (enable) enabled_.insert(id);
      else enabled_.erase(id);
    }
    return EnableEventAck::Accept;
  }

  bool is_enabled(uint32_t ceid) const { return enabled_.count(ceid) > 0; }

  // --- S6F11 emission --------------------------------------------------
  std::vector<ReportData> compose_for(uint32_t ceid, const VidLookup& lookup) const {
    std::vector<ReportData> out;
    auto it = links_.find(ceid);
    if (it == links_.end()) return out;
    for (auto rptid : it->second) {
      auto rit = reports_.find(rptid);
      if (rit == reports_.end()) continue;
      ReportData rd{rptid, {}};
      for (auto vid : rit->second.vids) {
        auto v = lookup(vid);
        rd.values.push_back(v ? *v : s2::Item::list({}));
      }
      out.push_back(std::move(rd));
    }
    return out;
  }

 private:
  std::map<uint32_t, CollectionEvent> by_ceid_;
  std::map<uint32_t, Report> reports_;
  std::map<uint32_t, std::vector<uint32_t>> links_;
  std::set<uint32_t> enabled_;
};

}  // namespace secsgem::gem