// src/game/transport_clock_sync.cpp
// Clock synchronization and yaw correction for transports.
// Extracted from TransportManager (Phase 3a of spline refactoring).
#include "game/transport_clock_sync.hpp"
#include "game/transport_manager.hpp"
#include "game/transport_path_repository.hpp"
#include "math/spline.hpp"
#include "core/logger.hpp"
#include <glm/gtc/constants.hpp>
#include <cmath>

namespace wowee::game {

bool TransportClockSync::computePathTime(
    ActiveTransport& transport,
    const math::CatmullRomSpline& spline,
    double elapsedTime,
    float deltaTime,
    uint32_t& outPathTimeMs) const
{
    uint32_t nowMs = static_cast<uint32_t>(elapsedTime * 1000.0);
    uint32_t durationMs = spline.durationMs();

    if (transport.hasServerClock) {
        // Predict server time using clock offset (works for both client and server-driven modes)
        int64_t serverTimeMs = static_cast<int64_t>(nowMs) + transport.serverClockOffsetMs;
        int64_t mod = static_cast<int64_t>(durationMs);
        int64_t wrapped = serverTimeMs % mod;
        if (wrapped < 0) wrapped += mod;
        outPathTimeMs = static_cast<uint32_t>(wrapped);
        return true;
    }

    if (transport.useClientAnimation) {
        // Pure local clock (no server sync yet, client-driven)
        uint32_t dtMs = static_cast<uint32_t>(deltaTime * 1000.0f);
        if (!transport.clientAnimationReverse) {
            transport.localClockMs += dtMs;
        } else {
            if (dtMs > durationMs) {
                dtMs %= durationMs;
            }
            if (transport.localClockMs >= dtMs) {
                transport.localClockMs -= dtMs;
            } else {
                transport.localClockMs = durationMs - (dtMs - transport.localClockMs);
            }
        }
        outPathTimeMs = transport.localClockMs % durationMs;
        return true;
    }

    // Strict server-authoritative mode: do not guess movement between server snapshots.
    return false;
}

void TransportClockSync::processServerUpdate(
    ActiveTransport& transport,
    const PathEntry* pathEntry,
    const glm::vec3& position,
    float orientation,
    double elapsedTime)
{
    const bool hadPrevUpdate = (transport.serverUpdateCount > 0);
    const double prevUpdateTime = transport.lastServerUpdate;
    const glm::vec3 prevPos = transport.position;

    const bool hasPath = (pathEntry != nullptr);
    const bool isZOnlyPath = (hasPath && pathEntry->fromDBC && pathEntry->zOnly && pathEntry->spline.durationMs() > 0);
    const bool isWorldCoordPath = (hasPath && pathEntry->worldCoords && pathEntry->spline.durationMs() > 0);

    // Don't let (0,0,0) server updates override a TaxiPathNode world-coordinate path
    if (isWorldCoordPath && glm::dot(position, position) < 1.0f) {
        transport.serverUpdateCount++;
        transport.lastServerUpdate = elapsedTime;
        transport.serverYaw = orientation;
        transport.hasServerYaw = true;
        return;
    }

    // Track server updates
    transport.serverUpdateCount++;
    transport.lastServerUpdate = elapsedTime;
    // Z-only elevators and world-coordinate paths (TaxiPathNode) always stay client-driven.
    // For other DBC paths (trams, ships): only switch to server-driven mode when the server
    // sends a position that actually differs from the current position, indicating it's
    // actively streaming movement data (not just echoing the spawn position).
    if (isZOnlyPath || isWorldCoordPath) {
        transport.useClientAnimation = true;
    } else if (transport.useClientAnimation && hasPath && pathEntry->fromDBC) {
        glm::vec3 pd = position - transport.position;
        float posDeltaSq = glm::dot(pd, pd);
        if (posDeltaSq > 1.0f) {
            // Server sent a meaningfully different position — it's actively driving this transport
            transport.useClientAnimation = false;
            LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                     " switching to server-driven (posDeltaSq=", posDeltaSq, ")");
        }
        // Otherwise keep client animation (server just echoed spawn pos or sent small jitter)
    } else if (!hasPath || !pathEntry->fromDBC) {
        // No DBC path — purely server-driven
        transport.useClientAnimation = false;
    }
    transport.clientAnimationReverse = false;

    // Server-authoritative transport mode:
    // Trust explicit server world position/orientation directly for all moving transports.
    transport.hasServerClock = false;
    if (transport.serverUpdateCount == 1) {
        // Seed once from first authoritative update; keep stable base for fallback phase estimation.
        // For z-only elevator paths, keep the spawn-derived basePosition (the DBC path is local offsets).
        if (!isZOnlyPath) {
            transport.basePosition = position;
        }
    }
    transport.position = position;
    transport.serverYaw = orientation;
    transport.hasServerYaw = true;
    float effectiveYaw = transport.serverYaw + (transport.serverYawFlipped180 ? glm::pi<float>() : 0.0f);
    transport.rotation = glm::angleAxis(effectiveYaw, glm::vec3(0.0f, 0.0f, 1.0f));

    if (hadPrevUpdate) {
        const double dt = elapsedTime - prevUpdateTime;
        if (dt > 0.001) {
            glm::vec3 v = (position - prevPos) / static_cast<float>(dt);
            float speedSq = glm::dot(v, v);
            constexpr float kMinAuthoritativeSpeed = 0.15f;
            constexpr float kMaxSpeed = 60.0f;
            if (speedSq >= kMinAuthoritativeSpeed * kMinAuthoritativeSpeed) {
                updateYawAlignment(transport, v);

                if (speedSq > kMaxSpeed * kMaxSpeed) {
                    v *= (kMaxSpeed * glm::inversesqrt(speedSq));
                }

                transport.serverLinearVelocity = v;
                transport.serverAngularVelocity = 0.0f;
                transport.hasServerVelocity = true;

                // Re-apply potentially corrected yaw this frame after alignment check.
                effectiveYaw = transport.serverYaw + (transport.serverYawFlipped180 ? glm::pi<float>() : 0.0f);
                transport.rotation = glm::angleAxis(effectiveYaw, glm::vec3(0.0f, 0.0f, 1.0f));
            }
        }
    } else {
        // Seed fallback path phase from nearest waypoint to the first authoritative sample.
        if (pathEntry && pathEntry->spline.keyCount() > 0 && pathEntry->spline.durationMs() > 0) {
            glm::vec3 local = position - transport.basePosition;
            size_t bestIdx = pathEntry->spline.findNearestKey(local);
            transport.localClockMs = pathEntry->spline.keys()[bestIdx].timeMs % pathEntry->spline.durationMs();
        }

        // Bootstrap velocity from mapped DBC path on first authoritative sample.
        if (transport.allowBootstrapVelocity && pathEntry && pathEntry->spline.keyCount() >= 2 && pathEntry->spline.durationMs() > 0) {
            bootstrapVelocityFromPath(transport, *pathEntry);
        } else if (!transport.allowBootstrapVelocity) {
            LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                     " DBC bootstrap velocity disabled for this transport");
        }
    }
}

void TransportClockSync::updateYawAlignment(
    ActiveTransport& transport,
    const glm::vec3& velocity) const
{
    // Auto-detect 180-degree yaw mismatch by comparing heading to movement direction.
    // Some transports appear to report yaw opposite their actual travel direction.
    glm::vec2 horizontalV(velocity.x, velocity.y);
    float hLenSq = glm::dot(horizontalV, horizontalV);
    if (hLenSq > 0.04f) {
        horizontalV *= glm::inversesqrt(hLenSq);
        glm::vec2 heading(std::cos(transport.serverYaw), std::sin(transport.serverYaw));
        float alignDot = glm::dot(heading, horizontalV);

        if (alignDot < -0.35f) {
            transport.serverYawAlignmentScore = std::max(transport.serverYawAlignmentScore - 1, -12);
        } else if (alignDot > 0.35f) {
            transport.serverYawAlignmentScore = std::min(transport.serverYawAlignmentScore + 1, 12);
        }

        if (!transport.serverYawFlipped180 && transport.serverYawAlignmentScore <= -4) {
            transport.serverYawFlipped180 = true;
            LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                     " enabled 180-degree yaw correction (alignScore=",
                     transport.serverYawAlignmentScore, ")");
        } else if (transport.serverYawFlipped180 &&
                   transport.serverYawAlignmentScore >= 4) {
            transport.serverYawFlipped180 = false;
            LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                     " disabled 180-degree yaw correction (alignScore=",
                     transport.serverYawAlignmentScore, ")");
        }
    }
}

void TransportClockSync::bootstrapVelocityFromPath(
    ActiveTransport& transport,
    const PathEntry& pathEntry) const
{
    // Bootstrap velocity from nearest DBC path segment on first authoritative sample.
    // This avoids "stalled at dock" when server sends sparse transport snapshots.
    const auto& keys = pathEntry.spline.keys();
    glm::vec3 local = transport.position - transport.basePosition;
    size_t bestIdx = pathEntry.spline.findNearestKey(local);

    float bestDistSq = 0.0f;
    {
        glm::vec3 d = keys[bestIdx].position - local;
        bestDistSq = glm::dot(d, d);
    }

    constexpr float kMaxBootstrapNearestDist = 80.0f;
    if (bestDistSq > (kMaxBootstrapNearestDist * kMaxBootstrapNearestDist)) {
        LOG_WARNING("Transport 0x", std::hex, transport.guid, std::dec,
                    " skipping DBC bootstrap velocity: nearest path point too far (dist=",
                    std::sqrt(bestDistSq), ", path=", transport.pathId, ")");
        return;
    }

    size_t n = keys.size();
    uint32_t durMs = pathEntry.spline.durationMs();
    constexpr float kMinBootstrapSpeed = 0.25f;
    constexpr float kMaxSpeed = 60.0f;

    auto tryApplySegment = [&](size_t a, size_t b) {
        uint32_t t0 = keys[a].timeMs;
        uint32_t t1 = keys[b].timeMs;
        if (b == 0 && t1 <= t0 && durMs > 0) {
            t1 = durMs;
        }
        if (t1 <= t0) return;
        glm::vec3 seg = keys[b].position - keys[a].position;
        float dtSeg = static_cast<float>(t1 - t0) / 1000.0f;
        if (dtSeg <= 0.001f) return;
        glm::vec3 v = seg / dtSeg;
        float speedSq = glm::dot(v, v);
        if (speedSq < kMinBootstrapSpeed * kMinBootstrapSpeed) return;
        if (speedSq > kMaxSpeed * kMaxSpeed) {
            v *= (kMaxSpeed * glm::inversesqrt(speedSq));
        }
        transport.serverLinearVelocity = v;
        transport.serverAngularVelocity = 0.0f;
        transport.hasServerVelocity = true;
    };

    // Prefer nearest forward meaningful segment from bestIdx.
    for (size_t step = 1; step < n && !transport.hasServerVelocity; ++step) {
        size_t a = (bestIdx + step - 1) % n;
        size_t b = (bestIdx + step) % n;
        tryApplySegment(a, b);
    }
    // Fallback: nearest backward meaningful segment.
    for (size_t step = 1; step < n && !transport.hasServerVelocity; ++step) {
        size_t b = (bestIdx + n - step + 1) % n;
        size_t a = (bestIdx + n - step) % n;
        tryApplySegment(a, b);
    }

    if (transport.hasServerVelocity) {
        LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                 " bootstrapped velocity from DBC path ", transport.pathId,
                 " v=(", transport.serverLinearVelocity.x, ", ",
                 transport.serverLinearVelocity.y, ", ",
                 transport.serverLinearVelocity.z, ")");
    } else {
        LOG_INFO("Transport 0x", std::hex, transport.guid, std::dec,
                 " skipped DBC bootstrap velocity (segment too short/static)");
    }
}

} // namespace wowee::game