#include "fgc/CaptureScheduler.h"

#include "fgc/CommandParser.h"
#include "fgc/Logger.h"

#include <chrono>
#include <cstdint>
#include <cstdlib>
#include <iomanip>
#include <optional>
#include <sstream>

namespace fgc {

namespace {

long long steadyNowMs() {
    using namespace std::chrono;
    return duration_cast<milliseconds>(steady_clock::now().time_since_epoch()).count();
}

// How close (encoder counts) an axis must be to its target, in addition to
// reporting standstill, to count as "settled". Generous vs. the firmware hold
// deadband (~200 counts).
constexpr long kSettleTolCounts = 600;

// Seconds with one decimal, for the overrun warning.
std::string seconds(double ms) {
    std::ostringstream o;
    o << std::fixed << std::setprecision(1) << ms / 1000.0 << " s";
    return o.str();
}

}  // namespace

CaptureScheduler::CaptureScheduler(IMotorController& motor, ICameraSource& camera,
                                   double image_rate, Geometry geometry, ScanGrid& grid,
                                   std::function<long long()> now_ms)
    : motor_(motor),
      camera_(camera),
      geometry_(geometry),
      grid_(grid),
      now_ms_(now_ms ? std::move(now_ms) : steadyNowMs),
      image_rate_(image_rate),
      interval_ms_(image_rate > 0.0 ? 1000.0 / image_rate : 0.0) {
    timer_start_ = now_ms_();
}

void CaptureScheduler::setMode(Mode mode, const PanSpec& pan) {
    mode_ = mode;
    pan_  = pan;
    pan_headings_ = mode == Mode::Pan ? panHeadings(pan, pan_step_deg_) : std::vector<double>{};
    pan_index_    = 0;
    pan_unreachable_warned_ = false;
    moving_ = false;  // restart the move/settle cycle cleanly
    hold_   = {};
    // The first move goes from wherever the gimbal is, so it may be long: no
    // overrun warning for it.
    first_move_   = true;
    rule_started_ = false;
    // Drop any armed snapshot: a scan starting means the operator moved on, and
    // keeping it would fire an image at some unrelated later moment when the scan
    // stops - attributed to whatever the gimbal happened to be pointing at then.
    snapshot_pending_ = false;
    // Continuous capture is a manual-mode activity: any mode change ends it, so
    // a later return to manual never resumes shooting nobody asked for.
    continuous_      = false;
    continuous_hold_ = {};
    // The first frame comes no sooner than one interval after the mode starts.
    resetTimer();
}

void CaptureScheduler::setContinuous(bool on) {
    continuous_      = on;
    continuous_hold_ = {};
    // The first frame comes one interval after switching on, as the first scan
    // waypoint does after `mode auto`.
    resetTimer();
}

void CaptureScheduler::setSettleRule(bool on, const SettleRule::Params& params) {
    use_rule_ = on;
    rule_.setParams(params);
    rule_started_ = false;
}

void CaptureScheduler::setSettleWait(int settle_ms, int timeout_ms) {
    settle_wait_ms_   = settle_ms < 0 ? 0 : settle_ms;
    frame_timeout_ms_ = timeout_ms < 0 ? 0 : timeout_ms;
}

long long CaptureScheduler::elapsedMs() const { return now_ms_() - timer_start_; }
void      CaptureScheduler::resetTimer() { timer_start_ = now_ms_(); }

void CaptureScheduler::sendMove() {
    // On a 1-axis (yaw-only) rig the firmware rejects the two-axis `MOVE y,p`
    // form ("ERR axis not present") and moves nothing, so address yaw alone.
    motor_.sendCommand(moveCommand(yaw_target_, pitch_present_ ? std::optional<long>(pitch_target_)
                                                               : std::nullopt));
}

bool CaptureScheduler::settledAt(const MotorTelemetry& t) const {
    bool yaw_ok = t.yaw.standstill && std::labs(t.yaw.xenc - yaw_target_) <= kSettleTolCounts;
    // A 1-axis rig never reports pitch standstill, so don't gate the capture on it.
    if (!t.pitch_present) return yaw_ok;
    return yaw_ok && t.pitch.standstill &&
           std::labs(t.pitch.xenc - pitch_target_) <= kSettleTolCounts;
}

bool CaptureScheduler::roomToSave() {
    const bool room = !can_save_ || can_save_();
    if (!room && !holding_) {
        holding_ = true;
        LOG_WARN << "saving is behind: holding the scan here until it catches up";
    } else if (room && holding_) {
        holding_ = false;
        LOG_INFO << "saving caught up: the scan carries on";
    }
    return room;
}

const char* CaptureScheduler::phase() const {
    if (!moving_ || hold_.settled_ms == 0) return "moving";
    return hold_.ready_ms == 0 ? "settling" : "waiting";
}

std::string CaptureScheduler::waypointLabel() const {
    if (mode_ == Mode::Pan)
        return "pan position " + std::to_string(pan_index_ + 1) + "/" +
               std::to_string(pan_headings_.size());
    return "waypoint " + std::to_string(grid_.index() + 1) + "/" + std::to_string(grid_.size());
}

void CaptureScheduler::requestSnapshot() {
    snapshot_pending_ = true;
    snapshot_hold_    = {};
}

void CaptureScheduler::beginHold(Hold& h) {
    h = {};
    h.settled_ms = now_ms_();
}

// From here on, watch the frames the camera delivers until brightness says the
// image has settled, or the frame budget runs out.
bool CaptureScheduler::ruleDecided(long long since_settled) {
    if (!rule_started_) {
        rule_started_ = true;
        rule_.reset();
        rule_seq_ = camera_.frameSeq();
        // No frame data from this camera: keep the fixed wait's behaviour.
        if (rule_seq_ == 0) rule_seq_ = UINT64_MAX;
    }
    if (rule_seq_ == UINT64_MAX) return true;
    SettleRule::Verdict v = SettleRule::Verdict::Waiting;
    for (const auto& f : camera_.framesSince(rule_seq_)) {
        rule_seq_ = f.seq;
        v         = rule_.add(f);
        if (v != SettleRule::Verdict::Waiting) break;
    }
    if (v == SettleRule::Verdict::Waiting) {
        if (since_settled < settle_wait_ms_ + frame_timeout_ms_) return false;  // keep watching
        LOG_WARN << waypointLabel() << ": the image did not settle within " << frame_timeout_ms_
                 << " ms of standstill; keeping the newest frame";
    } else {
        LOG_TRACE_CAT(LogCat::Control)
            << "image settled after " << since_settled << " ms"
            << (v == SettleRule::Verdict::AtLimit ? " (exposure and gain at their limit)" : "");
    }
    rule_seq_ = UINT64_MAX;  // decided
    return true;
}

bool CaptureScheduler::dwellOver(Hold& h, bool keep_rule) {
    if (h.ready_ms != 0) return true;
    const long long since = now_ms_() - h.settled_ms;
    if (since < settle_wait_ms_) return false;
    if (keep_rule && use_rule_ && !ruleDecided(since)) return false;
    h.ready_ms = now_ms_();
    return true;
}

CaptureScheduler::Shot CaptureScheduler::fire(Hold& h) {
    if (h.due_ms == 0) h.due_ms = now_ms_();
    if (camera_.trigger()) return Shot::Captured;
    if (now_ms_() - h.due_ms >= frame_timeout_ms_) return Shot::TimedOut;
    return Shot::Waiting;  // no fresh frame yet; retry next tick
}

// Wait for rest and the exposure, then shoot - the tail of a scan waypoint
// without the move. A snapshot and a continuous-capture frame both come through
// here, so either is exactly what a scan waypoint produces: same file, same
// CamEvent.
//
// Standstill only, no target check: the operator aims, so there is no target.
// Movement restarts the wait. The frame budget is measured from when the trigger
// fell due, not from the request - a request made mid-slew must not spend the
// camera's budget on the slew.
CaptureScheduler::Shot CaptureScheduler::shootAtRest(const MotorTelemetry& t, Hold& h,
                                                     bool wait_interval) {
    const bool standstill = t.yaw.standstill && (!pitch_present_ || t.pitch.standstill);
    if (!standstill) {
        h = {};  // still slewing (e.g. a jog is in flight)
        return Shot::Waiting;
    }
    if (h.settled_ms == 0) {
        beginHold(h);
        return Shot::Waiting;
    }
    if (!dwellOver(h, false)) return Shot::Waiting;
    if (wait_interval) {
        if (interval_ms_ <= 0.0 || elapsedMs() < interval_ms_) return Shot::Waiting;
        // Continuous capture holds, as the scan does, while saving is behind.
        if (h.due_ms == 0 && !roomToSave()) return Shot::Waiting;
    }
    return fire(h);
}

void CaptureScheduler::serviceSnapshot(const MotorTelemetry& t) {
    switch (shootAtRest(t, snapshot_hold_, false)) {
        case Shot::Waiting:
            return;
        case Shot::Captured:
            LOG_INFO << "snapshot captured";
            break;
        case Shot::TimedOut:
            LOG_WARN << "snapshot: no frame within " << frame_timeout_ms_
                     << " ms; send 'snapshot' (Space) again";
            break;
    }
    snapshot_pending_ = false;
    snapshot_hold_    = {};
}

// The scan's cycle without the move: one frame per interval since the last,
// once at rest and the exposure has settled.
void CaptureScheduler::serviceContinuous(const MotorTelemetry& t) {
    switch (shootAtRest(t, continuous_hold_, true)) {
        case Shot::Waiting:
            return;
        case Shot::Captured:
            LOG_INFO << "continuous capture: captured";
            break;
        case Shot::TimedOut:
            LOG_WARN << "continuous capture: no frame within " << frame_timeout_ms_
                     << " ms; trying again next interval";
            break;
    }
    continuous_hold_ = {};
    resetTimer();
}

// Pick the next target, skipping unreachable ones in this same tick (a skip
// costs no time and does not restart the interval), and MOVE there.
bool CaptureScheduler::startNextMove() {
    // A move that starts a pass again - back from the last waypoint to the first -
    // is long by nature and the interval is not expected to hold for it; nor for
    // the first move after a mode starts, from wherever the gimbal was.
    bool                pass_start = false;
    std::optional<long> yc;
    if (mode_ == Mode::Auto) {
        if (grid_.empty()) return false;
        pass_start = grid_.index() == 0 && grid_.size() > 1;
        // Yaw travel is under a full turn, so some bearings are unreachable.
        // Skip such a waypoint rather than clamping to the nearest limit, which
        // would image a direction nobody asked for and label it with the one
        // they did. Try each at most once per tick, so a grid with none reachable
        // just idles.
        for (size_t tries = 0; tries < grid_.size(); ++tries) {
            yc = geometry_.yaw.headingToCounts(grid_.current().yaw_deg);
            if (yc) break;
            if (!unreachable_warned_) {
                unreachable_warned_ = true;
                LOG_WARN << "scan waypoint " << (grid_.index() + 1) << "/" << grid_.size()
                         << " heading " << grid_.current().yaw_deg
                         << " deg is outside the reachable yaw arc; skipping it (further "
                            "unreachable waypoints are skipped silently)";
            }
            grid_.advance();
        }
        if (!yc) return false;
        const ScanPoint& p = grid_.current();
        yaw_target_   = *yc;
        pitch_target_ = geometry_.pitch.toCounts(p.pitch_deg);
        // One INFO line per move so the operator can follow the scan in the
        // log without enabling the control wire-trace.
        LOG_INFO << "scan move " << (grid_.index() + 1) << "/" << grid_.size()
                 << ": yaw " << p.yaw_deg << " pitch " << p.pitch_deg << " (deg)";
    } else {  // pan: the next position, left to right, at the pan's pitch
        if (pan_headings_.empty()) return false;
        pass_start = pan_index_ == 0 && pan_headings_.size() > 1;
        // Skip positions outside the reachable arc, as the sweep does.
        for (size_t tries = 0; tries < pan_headings_.size(); ++tries) {
            yc = geometry_.yaw.headingToCounts(pan_headings_[pan_index_]);
            if (yc) break;
            if (!pan_unreachable_warned_) {
                pan_unreachable_warned_ = true;
                LOG_WARN << "pan position " << (pan_index_ + 1) << "/" << pan_headings_.size()
                         << " heading " << pan_headings_[pan_index_]
                         << " deg is outside the reachable yaw arc; skipping it (further "
                            "unreachable positions are skipped silently)";
            }
            pan_index_ = (pan_index_ + 1) % pan_headings_.size();
        }
        if (!yc) return false;
        yaw_target_   = *yc;
        pitch_target_ = geometry_.pitch.toCounts(pan_.pitch);
        LOG_INFO << "pan move " << (pan_index_ + 1) << "/" << pan_headings_.size()
                 << ": yaw " << pan_headings_[pan_index_] << " pitch " << pan_.pitch
                 << " (deg)";
    }
    // Time spent waiting for saving is already announced, so not an overrun.
    quiet_overrun_ = first_move_ || pass_start || save_held_;
    first_move_    = false;
    save_held_     = false;
    sendMove();
    moving_       = true;
    hold_         = {};
    rule_started_ = false;
    move_sent_ms_ = now_ms_();
    return true;
}

// The waypoint's frame is kept or given up: on to the next, and the interval
// counts from now.
void CaptureScheduler::finishWaypoint() {
    moving_       = false;
    hold_         = {};
    rule_started_ = false;
    if (mode_ == Mode::Auto) grid_.advance();
    else if (!pan_headings_.empty()) pan_index_ = (pan_index_ + 1) % pan_headings_.size();
    resetTimer();
}

void CaptureScheduler::tick() {
    // 1. Telemetry.
    MotorTelemetry t = motor_.telemetry();
    pitch_present_ = t.pitch_present;

    // 2. Manual: a snapshot, else continuous capture. Only in manual, so a
    //    request can never inject a frame into a running sweep or fight it for
    //    the settle window. A snapshot goes first; continuous capture resumes
    //    on its own clock afterwards.
    if (mode_ == Mode::Manual) {
        if (snapshot_pending_) serviceSnapshot(t);
        else if (continuous_) serviceContinuous(t);
        return;
    }

    // 3. Capture cycle: the next scan waypoint (auto) or pan position (pan).
    //    Move straight away - while there is room to save what it will capture -
    //    and wait out what is left of the interval at the end.
    if (interval_ms_ <= 0.0) return;
    if (!moving_) {
        if (!roomToSave()) {
            save_held_ = true;
            return;
        }
        startNextMove();
        return;
    }

    // Moving: wait for standstill at the target.
    if (hold_.settled_ms == 0) {
        if (!settledAt(t)) return;
        beginHold(hold_);
        LOG_TRACE_CAT(LogCat::Control)
            << "settled at yaw=" << t.yaw.xenc << " pitch=" << t.pitch.xenc
            << "; waiting " << settle_wait_ms_ << " ms"
            << (use_rule_ ? " and for the image to settle" : "") << " before capture";
        return;
    }

    // The camera free-runs, so this wait is what makes the kept frame one that
    // was exposed with the gimbal at rest (no slew blur) and with the on-camera
    // auto exposure settled on this waypoint's light.
    if (hold_.ready_ms == 0) {
        if (!dwellOver(hold_, true)) return;
        const long long used = hold_.ready_ms - timer_start_;
        if (static_cast<double>(used) > interval_ms_ && !quiet_overrun_) {
            ++overruns_;
            LOG_WARN << waypointLabel() << ": " << seconds(static_cast<double>(used))
                     << " since the last picture, over the " << seconds(interval_ms_)
                     << " interval (move "
                     << seconds(static_cast<double>(hold_.settled_ms - move_sent_ms_))
                     << ", exposure "
                     << seconds(static_cast<double>(hold_.ready_ms - hold_.settled_ms)) << ")";
        }
    }

    // Then whatever is left of the interval.
    if (static_cast<double>(elapsedMs()) < interval_ms_) return;

    switch (fire(hold_)) {
        case Shot::Waiting:
            return;
        case Shot::Captured:
            LOG_INFO << "captured " << waypointLabel();
            break;
        case Shot::TimedOut:
            // Never park on one waypoint: a stalled camera would otherwise stop
            // the whole sweep rather than costing it a single image.
            LOG_WARN << "no frame within " << frame_timeout_ms_ << " ms; skipping "
                     << waypointLabel();
            break;
    }
    finishWaypoint();
}

}  // namespace fgc