// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2026 Martino Ferrari

#include "search.hpp"

#include <chrono>
#include <cmath>
#include <mutex>

namespace udpscope {

namespace {
double ms_since(const std::chrono::steady_clock::time_point& t0) {
  const std::chrono::duration<double, std::milli> d = std::chrono::steady_clock::now() - t0;
  return d.count();
}
}  // namespace

void BufferSearch::start(const EventCondition& c, int channel, double dt) {
  clear();
  channel_ = channel;
  detector_.reset();
  detector_.configure(c, dt);
  // `configure()` is a no-op for an unchanged condition, so the explicit reset above is what
  // makes a re-run of the *same* search start from a clean machine.
  detector_.reset();
  state_ = State::Running;
  t_scratch_.resize(static_cast<std::size_t>(kChunk));
  v_scratch_.resize(static_cast<std::size_t>(kChunk));
}

void BufferSearch::cancel() noexcept {
  if (state_ == State::Running) state_ = State::Cancelled;
}

void BufferSearch::clear() noexcept {
  state_ = State::Idle;
  started_ = false;
  truncated_ = false;
  at_ = 0;
  end_ = 0;
  first_s_ = 0.0;
  scanned_s_ = 0.0;
  total_s_ = 0.0;
  hits_.clear();
  cursor_ = -1;
  chunks_ = 0;
  worst_chunk_ms_ = 0.0;
  total_ms_ = 0.0;
}

void BufferSearch::select(int i) noexcept {
  if (hits_.empty()) {
    cursor_ = -1;
    return;
  }
  if (i < 0) i = 0;
  if (static_cast<std::size_t>(i) >= hits_.size()) i = static_cast<int>(hits_.size()) - 1;
  cursor_ = i;
}

bool BufferSearch::next() noexcept {
  if (hits_.empty() || cursor_ + 1 >= static_cast<int>(hits_.size())) return false;
  ++cursor_;
  return true;
}

bool BufferSearch::prev() noexcept {
  if (hits_.empty() || cursor_ <= 0) return false;
  --cursor_;
  return true;
}

bool BufferSearch::pump(ScopeModel& model) {
  if (state_ != State::Running) return false;
  const auto chunk_t0 = std::chrono::steady_clock::now();
  u64 n = 0;
  {
    std::lock_guard<std::mutex> lock(model.mutex());
    if (channel_ < 0 || static_cast<std::size_t>(channel_) >= model.channel_count()) {
      state_ = State::Cancelled;
      return false;
    }
    BufferStore& store = model.live();
    if (!started_) {
      // The whole retained buffer: the bounds are deliberately absurd, because
      // `live_window_locked()` clamps them to the time ring and to *every* value ring, which
      // is the one cut that keeps the stamps and the values index-aligned by construction.
      u64 first = 0;
      u64 last = 0;
      model.live_window_locked(-1.0e300, 1.0e300, first, last);
      at_ = first;
      end_ = last;
      started_ = true;
      if (end_ > at_) {
        f64 stamp = 0.0;
        store.time().copy_from(at_, 1, &stamp);
        first_s_ = static_cast<double>(stamp);
        store.time().copy_from(end_ - 1, 1, &stamp);
        total_s_ = static_cast<double>(stamp) - first_s_;
      }
    }
    // The producer keeps pushing while we scan, so the oldest samples go. `copy_from()` fixes
    // *which* indices are read, not that the slots still hold them -- a read behind the base
    // would silently return whatever overwrote it, which would be a hit at a time that never
    // existed. Skipping forward and reporting `Truncated` is the honest answer.
    const u64 base = store.time().base();
    if (base > at_) {
      at_ = base;
      truncated_ = true;
      detector_.reset();  // the sequence has a gap in it; no pulse spans it
    }
    if (at_ >= end_) {
      state_ = truncated_ ? State::Truncated : State::Done;
      total_ms_ += ms_since(chunk_t0);
      return false;
    }
    n = end_ - at_ < kChunk ? end_ - at_ : kChunk;
    store.time().copy_from(at_, n, t_scratch_.data());
    store.values(static_cast<std::size_t>(channel_)).copy_from(at_, n, v_scratch_.data());
  }
  // The evaluation is outside the lock: it is the expensive half, and it touches only the
  // copies above.
  for (u64 i = 0; i < n; ++i) {
    const double t = static_cast<double>(t_scratch_[static_cast<std::size_t>(i)]);
    const double e =
        detector_.feed(static_cast<double>(v_scratch_[static_cast<std::size_t>(i)]), t);
    if (std::isfinite(e)) {
      hits_.push_back(e);
      if (hits_.size() >= kHitsMax) {
        at_ += i + 1;
        scanned_s_ = t - first_s_;
        state_ = State::Capped;
        ++chunks_;
        const double cost = ms_since(chunk_t0);
        if (cost > worst_chunk_ms_) worst_chunk_ms_ = cost;
        total_ms_ += cost;
        return false;
      }
    }
    scanned_s_ = t - first_s_;
  }
  at_ += n;
  ++chunks_;
  const double cost = ms_since(chunk_t0);
  if (cost > worst_chunk_ms_) worst_chunk_ms_ = cost;
  total_ms_ += cost;
  if (at_ >= end_) {
    state_ = truncated_ ? State::Truncated : State::Done;
    return false;
  }
  return true;
}

}  // namespace udpscope