#include <destrum/Components/Animator.h>
#include <destrum/Graphics/Pipelines/SkinningPipeline.h>
#include <destrum/ObjectModel/GameObject.h>

#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/quaternion.hpp>
#include <destrum/Util/DeltaTime.h>

#include "spdlog/spdlog.h"

Animator::Animator(GameObject& parent)
    : Component(parent, "Animator") {}

void Animator::Update() {
    if (!m_current.clip) return;

    const float dt = Time::GetInstance().DeltaTime();

    m_current.time += dt * m_current.speed;
    if (m_current.clip->looped)
        m_current.time = std::fmod(m_current.time, m_current.clip->duration);
    else
        m_current.time = std::min(m_current.time, m_current.clip->duration);

    if (m_previous.clip) {
        m_previous.time += dt * m_previous.speed;
        if (m_previous.clip->looped)
            m_previous.time = std::fmod(m_previous.time, m_previous.clip->duration);

        m_blendT += dt / m_blendDuration;
        if (m_blendT >= 1.f) {
            m_blendT   = 1.f;
            m_previous = {};
        }
    }
}

void Animator::ImGuiInspector() {
    // ImGui::Text("Clip:  %s", m_currentClipName.empty() ? "(none)" : m_currentClipName.c_str());
    // ImGui::Text("Time:  %.2f", m_current.time);
    // ImGui::Text("Blend: %.2f", m_blendT);
    //
    // if (!isPlaying()) {
    //     ImGui::BeginDisabled();
    //     ImGui::Button("Stop");
    //     ImGui::EndDisabled();
    // } else if (ImGui::Button("Stop")) {
    //     stop();
    // }
    //
    // ImGui::Separator();
    // ImGui::Text("Clips:");
    // for (auto& [name, _] : m_clips) {
    //     if (ImGui::Selectable(name.c_str(), name == m_currentClipName))
    //         play(name);
    // }
}

void Animator::addClip(std::shared_ptr<SkeletalAnimation> clip) {
    m_clips[clip->name] = std::move(clip);
}

void Animator::play(const std::string& name, float blendTime) {
    auto it = m_clips.find(name);
    if (it == m_clips.end()) return;

    if (m_current.clip && blendTime > 0.f) {
        m_previous      = m_current;
        m_blendT        = 0.f;
        m_blendDuration = blendTime;
    } else {
        m_previous = {};
        m_blendT   = 1.f;
    }

    m_current        = { it->second.get(), 0.f, 1.f };
    m_currentClipName = name;
}

void Animator::stop() {
    m_current         = {};
    m_previous        = {};
    m_currentClipName = {};
}

std::size_t Animator::uploadJointMatrices(const RenderContext& ctx, const Skeleton& skeleton, std::size_t frameIndex) {
    auto matrices = computeJointMatrices(skeleton);
    return ctx.renderer.getSkinningPipeline().appendJointMatrices(matrices, frameIndex);
}

std::vector<glm::mat4> Animator::computeJointMatrices(const Skeleton& skeleton) {
    const std::size_t numJoints = skeleton.joints.size();
    std::vector<glm::mat4> global(numJoints, glm::mat4{1.f});
    std::vector<glm::mat4> result(numJoints, glm::mat4{1.f});

    auto findTrack = [](const SkeletalAnimation* clip,
                     std::uint32_t idx) -> const SkeletalAnimation::Track* {
        if (!clip) return nullptr;
        for (auto& t : clip->tracks)
            if (t.jointIndex == idx) return &t;
        return nullptr;
    };

    for (std::uint32_t i = 0; i < numJoints; ++i) {
        glm::vec3 tr  = {0.f, 0.f, 0.f};
        glm::quat rot = glm::identity<glm::quat>();
        glm::vec3 sc  = {1.f, 1.f, 1.f};

        // Sample current clip if one is playing
        if (m_current.clip) {
            if (const auto* track = findTrack(m_current.clip, i)) {
                tr  = sampleTranslation(*track, m_current.time);
                rot = sampleRotation   (*track, m_current.time);
                sc  = sampleScale      (*track, m_current.time);
            }

            if (m_previous.clip && m_blendT < 1.f) {
                if (const auto* prev = findTrack(m_previous.clip, i)) {
                    tr  = glm::mix  (sampleTranslation(*prev, m_previous.time), tr,  m_blendT);
                    rot = glm::slerp(sampleRotation   (*prev, m_previous.time), rot, m_blendT);
                    sc  = glm::mix  (sampleScale      (*prev, m_previous.time), sc,  m_blendT);
                }
            }
        }
        // If no clip: tr/rot/sc stay as identity → rest pose

        glm::mat4 local = glm::translate(glm::mat4{1.f}, tr)
                        * glm::mat4_cast(rot)
                        * glm::scale(glm::mat4{1.f}, sc);

        const int parent = skeleton.parentIndex[i];
        global[i] = (parent < 0) ? skeleton.rootPreTransform * local
                                  : global[parent] * local;

        result[i] = global[i] * skeleton.inverseBindMatrices[i];
    }

    return result;
}

// ─── Keyframe sampling ────────────────────────────────────────────────────────

glm::vec3 Animator::sampleTranslation(const SkeletalAnimation::Track& track, float t) {
    const auto& kf = track.keyframes;
    if (kf.size() == 1) return kf[0].translation;
    for (std::size_t i = 0; i + 1 < kf.size(); ++i) {
        if (t <= kf[i + 1].time) {
            float f = (t - kf[i].time) / (kf[i + 1].time - kf[i].time);
            return glm::mix(kf[i].translation, kf[i + 1].translation, f);
        }
    }
    return kf.back().translation;
}

glm::quat Animator::sampleRotation(const SkeletalAnimation::Track& track, float t) {
    const auto& kf = track.keyframes;
    if (kf.size() == 1) return kf[0].rotation;
    for (std::size_t i = 0; i + 1 < kf.size(); ++i) {
        if (t <= kf[i + 1].time) {
            float f = (t - kf[i].time) / (kf[i + 1].time - kf[i].time);
            return glm::slerp(kf[i].rotation, kf[i + 1].rotation, f);
        }
    }
    return kf.back().rotation;
}

glm::vec3 Animator::sampleScale(const SkeletalAnimation::Track& track, float t) {
    const auto& kf = track.keyframes;
    if (kf.size() == 1) return kf[0].scale;
    for (std::size_t i = 0; i + 1 < kf.size(); ++i) {
        if (t <= kf[i + 1].time) {
            float f = (t - kf[i].time) / (kf[i + 1].time - kf[i].time);
            return glm::mix(kf[i].scale, kf[i + 1].scale, f);
        }
    }
    return kf.back().scale;
}