// Copyright (c) 2008-2022 the Urho3D project
// License: MIT

#include <Urho3D/Core/CoreEvents.h>
#include <Urho3D/Engine/Engine.h>
#include <Urho3D/Graphics/Camera.h>
#include <Urho3D/Graphics/DebugRenderer.h>
#include <Urho3D/Graphics/DecalSet.h>
#include <Urho3D/Graphics/Graphics.h>
#include <Urho3D/Graphics/Light.h>
#include <Urho3D/Graphics/Material.h>
#include <Urho3D/Graphics/Model.h>
#include <Urho3D/Graphics/Octree.h>
#include <Urho3D/Graphics/Renderer.h>
#include <Urho3D/Graphics/StaticModel.h>
#include <Urho3D/Graphics/Zone.h>
#include <Urho3D/Input/Input.h>
#include <Urho3D/Resource/ResourceCache.h>
#include <Urho3D/Scene/Scene.h>
#include <Urho3D/UI/Font.h>
#include <Urho3D/UI/Text.h>
#include <Urho3D/UI/UI.h>

#include "Decals.h"

#include <Urho3D/DebugNew.h>

URHO3D_DEFINE_APPLICATION_MAIN(Decals)

Decals::Decals(Context* context) :
    Sample(context),
    drawDebug_(false)
{
}

void Decals::Start()
{
    // Execute base class startup
    Sample::Start();

    // Create the scene content
    CreateScene();

    // Create the UI content
    CreateUI();

    // Setup the viewport for displaying the scene
    SetupViewport();

    // Hook up to the frame update and render post-update events
    SubscribeToEvents();

    // Set the mouse mode to use in the sample
    Sample::InitMouseMode(MM_RELATIVE);
}

void Decals::CreateScene()
{
    auto* cache = GetSubsystem<ResourceCache>();

    scene_ = new Scene(context_);

    // Create octree, use default volume (-1000, -1000, -1000) to (1000, 1000, 1000)
    // Also create a DebugRenderer component so that we can draw debug geometry
    scene_->CreateComponent<Octree>();
    scene_->CreateComponent<DebugRenderer>();

    // Create scene node & StaticModel component for showing a static plane
    Node* planeNode = scene_->CreateChild("Plane");
    planeNode->SetScale(Vector3(100.0f, 1.0f, 100.0f));
    auto* planeObject = planeNode->CreateComponent<StaticModel>();
    planeObject->SetModel(cache->GetResource<Model>("Models/Plane.mdl"));
    planeObject->SetMaterial(cache->GetResource<Material>("Materials/StoneTiled.xml"));

    // Create a Zone component for ambient lighting & fog control
    Node* zoneNode = scene_->CreateChild("Zone");
    auto* zone = zoneNode->CreateComponent<Zone>();
    zone->SetBoundingBox(BoundingBox(-1000.0f, 1000.0f));
    zone->SetAmbientColor(Color(0.15f, 0.15f, 0.15f));
    zone->SetFogColor(Color(0.5f, 0.5f, 0.7f));
    zone->SetFogStart(100.0f);
    zone->SetFogEnd(300.0f);

    // Create a directional light to the world. Enable cascaded shadows on it
    Node* lightNode = scene_->CreateChild("DirectionalLight");
    lightNode->SetDirection(Vector3(0.6f, -1.0f, 0.8f));
    auto* light = lightNode->CreateComponent<Light>();
    light->SetLightType(LIGHT_DIRECTIONAL);
    light->SetCastShadows(true);
    light->SetShadowBias(BiasParameters(0.00025f, 0.5f));
    // Set cascade splits at 10, 50 and 200 world units, fade shadows out at 80% of maximum shadow distance
    light->SetShadowCascade(CascadeParameters(10.0f, 50.0f, 200.0f, 0.0f, 0.8f));

    // Create some mushrooms
    const unsigned NUM_MUSHROOMS = 240;
    for (unsigned i = 0; i < NUM_MUSHROOMS; ++i)
    {
        Node* mushroomNode = scene_->CreateChild("Mushroom");
        mushroomNode->SetPosition(Vector3(Random(90.0f) - 45.0f, 0.0f, Random(90.0f) - 45.0f));
        mushroomNode->SetRotation(Quaternion(0.0f, Random(360.0f), 0.0f));
        mushroomNode->SetScale(0.5f + Random(2.0f));
        auto* mushroomObject = mushroomNode->CreateComponent<StaticModel>();
        mushroomObject->SetModel(cache->GetResource<Model>("Models/Mushroom.mdl"));
        mushroomObject->SetMaterial(cache->GetResource<Material>("Materials/Mushroom.xml"));
        mushroomObject->SetCastShadows(true);
    }

    // Create randomly sized boxes. If boxes are big enough, make them occluders. Occluders will be software rasterized before
    // rendering to a low-resolution depth-only buffer to test the objects in the view frustum for visibility
    const unsigned NUM_BOXES = 20;
    for (unsigned i = 0; i < NUM_BOXES; ++i)
    {
        Node* boxNode = scene_->CreateChild("Box");
        float size = 1.0f + Random(10.0f);
        boxNode->SetPosition(Vector3(Random(80.0f) - 40.0f, size * 0.5f, Random(80.0f) - 40.0f));
        boxNode->SetScale(size);
        auto* boxObject = boxNode->CreateComponent<StaticModel>();
        boxObject->SetModel(cache->GetResource<Model>("Models/Box.mdl"));
        boxObject->SetMaterial(cache->GetResource<Material>("Materials/Stone.xml"));
        boxObject->SetCastShadows(true);
        if (size >= 3.0f)
            boxObject->SetOccluder(true);
    }

    // Create the camera. Limit far clip distance to match the fog
    cameraNode_ = scene_->CreateChild("Camera");
    auto* camera = cameraNode_->CreateComponent<Camera>();
    camera->SetFarClip(300.0f);

    // Set an initial position for the camera scene node above the plane
    cameraNode_->SetPosition(Vector3(0.0f, 5.0f, 0.0f));
}

void Decals::CreateUI()
{
    auto* cache = GetSubsystem<ResourceCache>();
    auto* ui = GetSubsystem<UI>();

    // Create a Cursor UI element because we want to be able to hide and show it at will. When hidden, the mouse cursor will
    // control the camera, and when visible, it will point the raycast target
    auto* style = cache->GetResource<XMLFile>("UI/DefaultStyle.xml");
    SharedPtr<Cursor> cursor(new Cursor(context_));
    cursor->SetStyleAuto(style);
    ui->SetCursor(cursor);
    // Set starting position of the cursor at the rendering window center
    auto* graphics = GetSubsystem<Graphics>();
    cursor->SetPosition(graphics->GetWidth() / 2, graphics->GetHeight() / 2);

    // Construct new Text object, set string to display and font to use
    auto* instructionText = ui->GetRoot()->CreateChild<Text>();
    instructionText->SetText(
        "Use WASD keys to move\n"
        "LMB to paint decals, RMB to rotate view\n"
        "Space to toggle debug geometry\n"
        "7 to toggle occlusion culling"
    );
    instructionText->SetFont(cache->GetResource<Font>("Fonts/Anonymous Pro.ttf"), 15);
    // The text has multiple rows. Center them in relation to each other
    instructionText->SetTextAlignment(HA_CENTER);

    // Position the text relative to the screen center
    instructionText->SetHorizontalAlignment(HA_CENTER);
    instructionText->SetVerticalAlignment(VA_CENTER);
    instructionText->SetPosition(0, ui->GetRoot()->GetHeight() / 4);
}

void Decals::SetupViewport()
{
    auto* renderer = GetSubsystem<Renderer>();

    // Set up a viewport to the Renderer subsystem so that the 3D scene can be seen
    SharedPtr<Viewport> viewport(new Viewport(context_, scene_, cameraNode_->GetComponent<Camera>()));
    renderer->SetViewport(0, viewport);
}

void Decals::SubscribeToEvents()
{
    // Subscribe HandleUpdate() function for processing update events
    SubscribeToEvent(E_UPDATE, URHO3D_HANDLER(Decals, HandleUpdate));

    // Subscribe HandlePostRenderUpdate() function for processing the post-render update event, during which we request
    // debug geometry
    SubscribeToEvent(E_POSTRENDERUPDATE, URHO3D_HANDLER(Decals, HandlePostRenderUpdate));
}

void Decals::MoveCamera(float timeStep)
{
    // Right mouse button controls mouse cursor visibility: hide when pressed
    auto* ui = GetSubsystem<UI>();
    auto* input = GetSubsystem<Input>();
    ui->GetCursor()->SetVisible(!input->GetMouseButtonDown(MOUSEB_RIGHT));

    // Do not move if the UI has a focused element (the console)
    if (ui->GetFocusElement())
        return;

    // Movement speed as world units per second
    const float MOVE_SPEED = 20.0f;
    // Mouse sensitivity as degrees per pixel
    const float MOUSE_SENSITIVITY = 0.1f;

    // Use this frame's mouse motion to adjust camera node yaw and pitch. Clamp the pitch between -90 and 90 degrees
    // Only move the camera when the cursor is hidden
    if (!ui->GetCursor()->IsVisible())
    {
        IntVector2 mouseMove = input->GetMouseMove();
        yaw_ += MOUSE_SENSITIVITY * mouseMove.x_;
        pitch_ += MOUSE_SENSITIVITY * mouseMove.y_;
        pitch_ = Clamp(pitch_, -90.0f, 90.0f);

        // Construct new orientation for the camera scene node from yaw and pitch. Roll is fixed to zero
        cameraNode_->SetRotation(Quaternion(pitch_, yaw_, 0.0f));
    }

    // Read WASD keys and move the camera scene node to the corresponding direction if they are pressed
    if (input->GetKeyDown(KEY_W))
        cameraNode_->Translate(Vector3::FORWARD * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_S))
        cameraNode_->Translate(Vector3::BACK * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_A))
        cameraNode_->Translate(Vector3::LEFT * MOVE_SPEED * timeStep);
    if (input->GetKeyDown(KEY_D))
        cameraNode_->Translate(Vector3::RIGHT * MOVE_SPEED * timeStep);

    // Toggle debug geometry with space
    if (input->GetKeyPress(KEY_SPACE))
        drawDebug_ = !drawDebug_;

    // Paint decal with the left mousebutton; cursor must be visible
    if (ui->GetCursor()->IsVisible() && input->GetMouseButtonPress(MOUSEB_LEFT))
        PaintDecal();
}

void Decals::PaintDecal()
{
    Vector3 hitPos;
    Drawable* hitDrawable;

    if (Raycast(250.0f, hitPos, hitDrawable))
    {
        // Check if target scene node already has a DecalSet component. If not, create now
        Node* targetNode = hitDrawable->GetNode();
        auto* decal = targetNode->GetComponent<DecalSet>();
        if (!decal)
        {
            auto* cache = GetSubsystem<ResourceCache>();

            decal = targetNode->CreateComponent<DecalSet>();
            decal->SetMaterial(cache->GetResource<Material>("Materials/UrhoDecal.xml"));
        }
        // Add a square decal to the decal set using the geometry of the drawable that was hit, orient it to face the camera,
        // use full texture UV's (0,0) to (1,1). Note that if we create several decals to a large object (such as the ground
        // plane) over a large area using just one DecalSet component, the decals will all be culled as one unit. If that is
        // undesirable, it may be necessary to create more than one DecalSet based on the distance
        decal->AddDecal(hitDrawable, hitPos, cameraNode_->GetRotation(), 0.5f, 1.0f, 1.0f, Vector2::ZERO,
            Vector2::ONE);
    }
}

bool Decals::Raycast(float maxDistance, Vector3& hitPos, Drawable*& hitDrawable)
{
    hitDrawable = nullptr;

    auto* ui = GetSubsystem<UI>();
    IntVector2 pos = ui->GetCursorPosition();
    // Check the cursor is visible and there is no UI element in front of the cursor
    if (!ui->GetCursor()->IsVisible() || ui->GetElementAt(pos, true))
        return false;

    auto* graphics = GetSubsystem<Graphics>();
    auto* camera = cameraNode_->GetComponent<Camera>();
    Ray cameraRay = camera->GetScreenRay((float)pos.x_ / graphics->GetWidth(), (float)pos.y_ / graphics->GetHeight());
    // Pick only geometry objects, not eg. zones or lights, only get the first (closest) hit
    PODVector<RayQueryResult> results;
    RayOctreeQuery query(results, cameraRay, RAY_TRIANGLE, maxDistance, DRAWABLE_GEOMETRY);
    scene_->GetComponent<Octree>()->RaycastSingle(query);
    if (results.Size())
    {
        RayQueryResult& result = results[0];
        hitPos = result.position_;
        hitDrawable = result.drawable_;
        return true;
    }

    return false;
}

void Decals::HandleUpdate(StringHash eventType, VariantMap& eventData)
{
    using namespace Update;

    // Take the frame time step, which is stored as a float
    float timeStep = eventData[P_TIMESTEP].GetFloat();

    // Move the camera, scale movement with time step
    MoveCamera(timeStep);
}

void Decals::HandlePostRenderUpdate(StringHash eventType, VariantMap& eventData)
{
    // If draw debug mode is enabled, draw viewport debug geometry. Disable depth test so that we can see the effect of occlusion
    if (drawDebug_)
        GetSubsystem<Renderer>()->DrawDebugGeometry(false);
}