#include "rive/animation/state_machine_instance.hpp"
#include "rive/animation/state_machine_input.hpp"
#include "rive/animation/state_machine_bool.hpp"
#include "rive/animation/state_machine_number.hpp"
#include "rive/animation/state_machine_trigger.hpp"
#include "rive/animation/state_machine_input_instance.hpp"
#include "rive/animation/state_machine.hpp"
#include "rive/animation/state_machine_layer.hpp"
#include "rive/animation/any_state.hpp"
#include "rive/animation/entry_state.hpp"
#include "rive/animation/state_transition.hpp"
#include "rive/animation/transition_condition.hpp"
#include "rive/animation/animation_state.hpp"
#include "rive/animation/state_instance.hpp"
#include "rive/animation/animation_state_instance.hpp"
#include "rive/animation/state_machine_event.hpp"
#include "rive/shapes/shape.hpp"
#include "rive/math/aabb.hpp"
#include "rive/math/hit_test.hpp"
#include <unordered_map>

using namespace rive;
namespace rive {
    class StateMachineLayerInstance {
    private:
        static const int maxIterations = 100;
        const StateMachineLayer* m_Layer = nullptr;
        ArtboardInstance* m_ArtboardInstance = nullptr;

        StateInstance* m_AnyStateInstance = nullptr;
        StateInstance* m_CurrentState = nullptr;
        StateInstance* m_StateFrom = nullptr;

        // const LayerState* m_CurrentState = nullptr;
        // const LayerState* m_StateFrom = nullptr;
        const StateTransition* m_Transition = nullptr;

        bool m_HoldAnimationFrom = false;
        // LinearAnimationInstance* m_AnimationInstance = nullptr;
        // LinearAnimationInstance* m_AnimationInstanceFrom = nullptr;
        float m_Mix = 1.0f;
        float m_MixFrom = 1.0f;
        bool m_StateChangedOnAdvance = false;

        bool m_WaitingForExit = false;
        /// Used to ensure a specific animation is applied on the next apply.
        const LinearAnimation* m_HoldAnimation = nullptr;
        float m_HoldTime = 0.0f;

    public:
        ~StateMachineLayerInstance() {
            delete m_AnyStateInstance;
            delete m_CurrentState;
            delete m_StateFrom;
        }

        void init(const StateMachineLayer* layer, ArtboardInstance* instance) {
            m_ArtboardInstance = instance;
            assert(m_Layer == nullptr);
            m_AnyStateInstance = layer->anyState()->makeInstance(instance).release();
            m_Layer = layer;
            changeState(m_Layer->entryState());
        }

        void updateMix(float seconds) {
            if (m_Transition != nullptr && m_StateFrom != nullptr && m_Transition->duration() != 0)
            {
                m_Mix = std::min(
                    1.0f,
                    std::max(0.0f,
                             (m_Mix + seconds / m_Transition->mixTime(m_StateFrom->state()))));
            } else {
                m_Mix = 1.0f;
            }
        }

        bool advance(/*Artboard* artboard, */ float seconds, Span<SMIInput*> inputs) {
            m_StateChangedOnAdvance = false;

            if (m_CurrentState != nullptr) {
                m_CurrentState->advance(seconds, inputs);
            }

            updateMix(seconds);

            if (m_StateFrom != nullptr && m_Mix < 1.0f && !m_HoldAnimationFrom) {
                // This didn't advance during our updateState, but it should now
                // that we realize we need to mix it in.
                m_StateFrom->advance(seconds, inputs);
            }

            for (int i = 0; updateState(inputs, i != 0); i++) {
                apply();

                if (i == maxIterations) {
                    fprintf(stderr, "StateMachine exceeded max iterations.\n");
                    return false;
                }
            }

            apply();

            return m_Mix != 1.0f || m_WaitingForExit ||
                   (m_CurrentState != nullptr && m_CurrentState->keepGoing());
        }

        bool isTransitioning() {
            return m_Transition != nullptr && m_StateFrom != nullptr &&
                   m_Transition->duration() != 0 && m_Mix < 1.0f;
        }

        bool updateState(Span<SMIInput*> inputs, bool ignoreTriggers) {
            // Don't allow changing state while a transition is taking place
            // (we're mixing one state onto another).
            if (isTransitioning()) {
                return false;
            }

            m_WaitingForExit = false;

            if (tryChangeState(m_AnyStateInstance, inputs, ignoreTriggers)) {
                return true;
            }

            return tryChangeState(m_CurrentState, inputs, ignoreTriggers);
        }

        bool changeState(const LayerState* stateTo) {
            if ((m_CurrentState == nullptr ? nullptr : m_CurrentState->state()) == stateTo) {
                return false;
            }
            m_CurrentState =
                stateTo == nullptr ? nullptr : stateTo->makeInstance(m_ArtboardInstance).release();
            return true;
        }

        bool tryChangeState(StateInstance* stateFromInstance,
                            Span<SMIInput*> inputs,
                            bool ignoreTriggers) {
            if (stateFromInstance == nullptr) {
                return false;
            }
            auto stateFrom = stateFromInstance->state();
            auto outState = m_CurrentState;
            for (size_t i = 0, length = stateFrom->transitionCount(); i < length; i++) {
                auto transition = stateFrom->transition(i);
                auto allowed = transition->allowed(stateFromInstance, inputs, ignoreTriggers);
                if (allowed == AllowTransition::yes && changeState(transition->stateTo())) {
                    m_StateChangedOnAdvance = true;
                    // state actually has changed
                    m_Transition = transition;
                    if (m_StateFrom != m_AnyStateInstance) {
                        // Old state from is done.
                        delete m_StateFrom;
                    }
                    m_StateFrom = outState;

                    // If we had an exit time and wanted to pause on exit, make
                    // sure to hold the exit time. Delegate this to the
                    // transition by telling it that it was completed.
                    if (outState != nullptr && transition->applyExitCondition(outState)) {
                        // Make sure we apply this state. This only returns true
                        // when it's an animation state instance.
                        auto instance =
                            static_cast<AnimationStateInstance*>(m_StateFrom)->animationInstance();

                        m_HoldAnimation = instance->animation();
                        m_HoldTime = instance->time();
                    }
                    m_MixFrom = m_Mix;

                    // Keep mixing last animation that was mixed in.
                    if (m_Mix != 0.0f) {
                        m_HoldAnimationFrom = transition->pauseOnExit();
                    }
                    if (m_StateFrom != nullptr && m_StateFrom->state()->is<AnimationState>() &&
                        m_CurrentState != nullptr)
                    {
                        auto instance =
                            static_cast<AnimationStateInstance*>(m_StateFrom)->animationInstance();

                        auto spilledTime = instance->spilledTime();
                        m_CurrentState->advance(spilledTime, inputs);
                    }
                    m_Mix = 0.0f;
                    updateMix(0.0f);
                    m_WaitingForExit = false;
                    return true;
                } else if (allowed == AllowTransition::waitingForExit) {
                    m_WaitingForExit = true;
                }
            }
            return false;
        }

        void apply(/*Artboard* artboard*/) {
            if (m_HoldAnimation != nullptr) {
                m_HoldAnimation->apply(m_ArtboardInstance, m_HoldTime, m_MixFrom);
                m_HoldAnimation = nullptr;
            }

            if (m_StateFrom != nullptr && m_Mix < 1.0f) {
                m_StateFrom->apply(m_MixFrom);
            }
            if (m_CurrentState != nullptr) {
                m_CurrentState->apply(m_Mix);
            }
        }

        bool stateChangedOnAdvance() const { return m_StateChangedOnAdvance; }

        const LayerState* currentState() {
            return m_CurrentState == nullptr ? nullptr : m_CurrentState->state();
        }

        const LinearAnimationInstance* currentAnimation() const {
            if (m_CurrentState == nullptr || !m_CurrentState->state()->is<AnimationState>()) {
                return nullptr;
            }
            return static_cast<AnimationStateInstance*>(m_CurrentState)->animationInstance();
        }
    };

    /// Representation of a Shape from the Artboard Instance and all the events it
    /// triggers. Allows tracking hover and performing hit detection only once on
    /// shapes that trigger multiple events.
    class HitShape {
    private:
        Shape* m_Shape;

    public:
        Shape* shape() const { return m_Shape; }
        HitShape(Shape* shape) : m_Shape(shape) {}
        bool isHovered = false;
        std::vector<const StateMachineEvent*> events;
    };
} // namespace rive

void StateMachineInstance::processEvent(Vec2D position, EventType hitEvent) {
    position -= Vec2D(m_ArtboardInstance->originX() * m_ArtboardInstance->width(),
                      m_ArtboardInstance->originY() * m_ArtboardInstance->height());

    const float hitRadius = 2;
    auto hitArea = AABB(position.x - hitRadius,
                        position.y - hitRadius,
                        position.x + hitRadius,
                        position.y + hitRadius)
                       .round();

    for (const auto& hitShape : m_HitShapes) {

        // TODO: quick reject.

        bool isOver = hitShape->shape()->hitTest(hitArea);

        bool hoverChange = hitShape->isHovered != isOver;
        hitShape->isHovered = isOver;

        // iterate all events associated with this hit shape
        for (auto event : hitShape->events) {
            // Always update hover states regardless of which specific event type
            // we're trying to trigger.
            if (hoverChange) {
                if (isOver && event->eventType() == EventType::enter) {
                    event->performChanges(this);
                    markNeedsAdvance();
                } else if (!isOver && event->eventType() == EventType::exit) {
                    event->performChanges(this);
                    markNeedsAdvance();
                }
            }
            if (isOver && hitEvent == event->eventType()) {
                event->performChanges(this);
                markNeedsAdvance();
            }
        }
    }
}

void StateMachineInstance::pointerMove(Vec2D position) {
    processEvent(position, EventType::updateHover);
}
void StateMachineInstance::pointerDown(Vec2D position) { processEvent(position, EventType::down); }
void StateMachineInstance::pointerUp(Vec2D position) { processEvent(position, EventType::up); }

StateMachineInstance::StateMachineInstance(const StateMachine* machine,
                                           ArtboardInstance* instance) :
    Scene(instance), m_Machine(machine) {
    const auto count = machine->inputCount();
    m_InputInstances.resize(count);
    for (size_t i = 0; i < count; i++) {
        auto input = machine->input(i);
        if (input == nullptr) {
            continue;
        }
        switch (input->coreType()) {
            case StateMachineBool::typeKey:
                m_InputInstances[i] = new SMIBool(input->as<StateMachineBool>(), this);
                break;
            case StateMachineNumber::typeKey:
                m_InputInstances[i] = new SMINumber(input->as<StateMachineNumber>(), this);
                break;
            case StateMachineTrigger::typeKey:
                m_InputInstances[i] = new SMITrigger(input->as<StateMachineTrigger>(), this);
                break;
            default:
                // Sanity check.
                break;
        }
    }

    m_LayerCount = machine->layerCount();
    m_Layers = new StateMachineLayerInstance[m_LayerCount];
    for (size_t i = 0; i < m_LayerCount; i++) {
        m_Layers[i].init(machine->layer(i), m_ArtboardInstance);
    }

    // Initialize events. Store a lookup table of shape id to hit shape
    // representation (an object that stores all the events triggered by the
    // shape producing an event).
    std::unordered_map<uint32_t, HitShape*> hitShapeLookup;
    for (std::size_t i = 0; i < machine->eventCount(); i++) {
        auto event = machine->event(i);

        // Iterate actual leaf hittable shapes tied to this event and resolve
        // corresponding ones in the artboard instance.
        for (auto id : event->hitShapeIds()) {
            HitShape* hitShape;
            auto itr = hitShapeLookup.find(id);
            if (itr == hitShapeLookup.end()) {
                auto shape = m_ArtboardInstance->resolve(id);
                if (shape != nullptr && shape->is<Shape>()) {
                    auto hs = std::make_unique<HitShape>(shape->as<Shape>());
                    hitShapeLookup[id] = hitShape = hs.get();
                    m_HitShapes.push_back(std::move(hs));
                } else {
                    // No object or not a shape...
                    continue;
                }
            } else {
                hitShape = itr->second;
            }
            hitShape->events.push_back(event);
        }
    }
}

StateMachineInstance::~StateMachineInstance() {
    for (auto inst : m_InputInstances) {
        delete inst;
    }
    delete[] m_Layers;
}

bool StateMachineInstance::advance(float seconds) {
    m_NeedsAdvance = false;
    for (size_t i = 0; i < m_LayerCount; i++) {
        if (m_Layers[i].advance(seconds, toSpan(m_InputInstances))) {
            m_NeedsAdvance = true;
        }
    }

    for (auto inst : m_InputInstances) {
        inst->advanced();
    }

    return m_NeedsAdvance;
}

bool StateMachineInstance::advanceAndApply(float seconds) {
    bool more = this->advance(seconds);
    m_ArtboardInstance->advance(seconds);
    return more;
}

void StateMachineInstance::markNeedsAdvance() { m_NeedsAdvance = true; }
bool StateMachineInstance::needsAdvance() const { return m_NeedsAdvance; }

std::string StateMachineInstance::name() const { return m_Machine->name(); }

SMIInput* StateMachineInstance::input(size_t index) const {
    if (index < m_InputInstances.size()) {
        return m_InputInstances[index];
    }
    return nullptr;
}

template <typename SMType, typename InstType>
InstType* StateMachineInstance::getNamedInput(const std::string& name) const {
    for (const auto inst : m_InputInstances) {
        auto input = inst->input();
        if (input->is<SMType>() && input->name() == name) {
            return static_cast<InstType*>(inst);
        }
    }
    return nullptr;
}

SMIBool* StateMachineInstance::getBool(const std::string& name) const {
    return getNamedInput<StateMachineBool, SMIBool>(name);
}
SMINumber* StateMachineInstance::getNumber(const std::string& name) const {
    return getNamedInput<StateMachineNumber, SMINumber>(name);
}
SMITrigger* StateMachineInstance::getTrigger(const std::string& name) const {
    return getNamedInput<StateMachineTrigger, SMITrigger>(name);
}

size_t StateMachineInstance::stateChangedCount() const {
    size_t count = 0;
    for (size_t i = 0; i < m_LayerCount; i++) {
        if (m_Layers[i].stateChangedOnAdvance()) {
            count++;
        }
    }
    return count;
}

const LayerState* StateMachineInstance::stateChangedByIndex(size_t index) const {
    size_t count = 0;
    for (size_t i = 0; i < m_LayerCount; i++) {
        if (m_Layers[i].stateChangedOnAdvance()) {
            if (count == index) {
                return m_Layers[i].currentState();
            }
            count++;
        }
    }
    return nullptr;
}

const size_t StateMachineInstance::currentAnimationCount() const {
    size_t count = 0;
    for (size_t i = 0; i < m_LayerCount; i++) {
        if (m_Layers[i].currentAnimation() != nullptr) {
            count++;
        }
    }
    return count;
}

const LinearAnimationInstance* StateMachineInstance::currentAnimationByIndex(size_t index) const {
    size_t count = 0;
    for (size_t i = 0; i < m_LayerCount; i++) {
        if (m_Layers[i].currentAnimation() != nullptr) {
            if (count == index) {
                return m_Layers[i].currentAnimation();
            }
            count++;
        }
    }
    return nullptr;
}