-- Decals example.
-- This sample demonstrates:
--     - Performing a raycast to the octree and adding a decal to the hit location
--     - Defining a Cursor UI element which stays inside the window and can be shown/hidden
--     - Marking suitable (large) objects as occluders for occlusion culling
--     - Displaying renderer debug geometry to see the effect of occlusion

require "LuaScripts/Utilities/Sample"

function Start()
    -- Execute the common startup for samples
    SampleStart()

    -- 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()
end

function CreateScene()
    scene_ = Scene()

    -- 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
    local planeNode = scene_:CreateChild("Plane")
    planeNode.scale = Vector3(100.0, 1.0, 100.0)
    local planeObject = planeNode:CreateComponent("StaticModel")
    planeObject.model = cache:GetResource("Model", "Models/Plane.mdl")
    planeObject.material = cache:GetResource("Material", "Materials/StoneTiled.xml")

    -- Create a Zone component for ambient lighting & fog control
    local zoneNode = scene_:CreateChild("Zone")
    local zone = zoneNode:CreateComponent("Zone")
    zone.boundingBox = BoundingBox(-1000.0, 1000.0)
    zone.ambientColor = Color(0.15, 0.15, 0.15)
    zone.fogColor = Color(0.5, 0.5, 0.7)
    zone.fogStart = 100.0
    zone.fogEnd = 300.0

    -- Create a directional light to the world. Enable cascaded shadows on it
    local lightNode = scene_:CreateChild("DirectionalLight")
    lightNode.direction = Vector3(0.6, -1.0, 0.8)
    local light = lightNode:CreateComponent("Light")
    light.lightType = LIGHT_DIRECTIONAL
    light.castShadows = true
    light.shadowBias = BiasParameters(0.00025, 0.5)
    -- Set cascade splits at 10, 50 and 200 world units, fade shadows out at 80% of maximum shadow distance
    light.shadowCascade = CascadeParameters(10.0, 50.0, 200.0, 0.0, 0.8)

    -- Create some mushrooms
    local NUM_MUSHROOMS = 240
    for i = 1, NUM_MUSHROOMS do
        local mushroomNode = scene_:CreateChild("Mushroom")
        mushroomNode.position = Vector3(Random(90.0) - 45.0, 0.0, Random(90.0) - 45.0)
        mushroomNode.rotation = Quaternion(0.0, Random(360.0), 0.0)
        mushroomNode:SetScale(0.5 + Random(2.0))
        local mushroomObject = mushroomNode:CreateComponent("StaticModel")
        mushroomObject.model = cache:GetResource("Model", "Models/Mushroom.mdl")
        mushroomObject.material = cache:GetResource("Material", "Materials/Mushroom.xml")
        mushroomObject.castShadows = true
    end

    -- 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
    local NUM_BOXES = 20
    for i = 1, NUM_BOXES do
        local boxNode = scene_:CreateChild("Box")
        local size = 1.0 + Random(10.0)
        boxNode.position = Vector3(Random(80.0) - 40.0, size * 0.5, Random(80.0) - 40.0)
        boxNode:SetScale(size)
        local boxObject = boxNode:CreateComponent("StaticModel")
        boxObject.model = cache:GetResource("Model", "Models/Box.mdl")
        boxObject.material = cache:GetResource("Material", "Materials/Stone.xml")
        boxObject.castShadows = true
        if size >= 3.0 then
            boxObject.occluder = true
        end
    end

    -- Create the camera. Limit far clip distance to match the fog
    cameraNode = scene_:CreateChild("Camera")
    local camera = cameraNode:CreateComponent("Camera")
    camera.farClip = 300.0

    -- Set an initial position for the camera scene node above the plane
    cameraNode.position = Vector3(0.0, 5.0, 0.0)
end

function CreateUI()
    -- 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
    local style = cache:GetResource("XMLFile", "UI/DefaultStyle.xml")
    local cursor = ui.root:CreateChild("Cursor")
    cursor:SetStyleAuto(style)
    ui.cursor = cursor
    -- Set starting position of the cursor at the rendering window center
    cursor:SetPosition(graphics.width / 2, graphics.height / 2)

    -- Construct new Text object, set string to display and font to use
    local instructionText = ui.root:CreateChild("Text")
    instructionText.text =
        "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.textAlignment = HA_CENTER

    -- Position the text relative to the screen center
    instructionText.horizontalAlignment = HA_CENTER
    instructionText.verticalAlignment = VA_CENTER
    instructionText:SetPosition(0, ui.root.height / 4)
end

function SetupViewport()
    -- Set up a viewport to the Renderer subsystem so that the 3D scene can be seen
    local viewport = Viewport:new(scene_, cameraNode:GetComponent("Camera"))
    renderer:SetViewport(0, viewport)
end

function SubscribeToEvents()
    -- Subscribe HandleUpdate() function for processing update events
    SubscribeToEvent("Update", "HandleUpdate")

    -- Subscribe HandlePostRenderUpdate() function for processing the post-render update event, during which we request
    -- debug geometry
    SubscribeToEvent("PostRenderUpdate", "HandlePostRenderUpdate")
end

function MoveCamera(timeStep)
    -- Right mouse button controls mouse cursor visibility: hide when pressed
    ui.cursor.visible = not input:GetMouseButtonDown(MOUSEB_RIGHT)

    -- Do not move if the UI has a focused element (the console)
    if ui.focusElement ~= nil then
        return
    end

    -- Movement speed as world units per second
    local MOVE_SPEED = 20.0
    -- Mouse sensitivity as degrees per pixel
    local MOUSE_SENSITIVITY = 0.1

    -- 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 not ui.cursor.visible then
        local mouseMove = input.mouseMove
        yaw = yaw + MOUSE_SENSITIVITY * mouseMove.x
        pitch = pitch + MOUSE_SENSITIVITY * mouseMove.y
        pitch = Clamp(pitch, -90.0, 90.0)

        -- Construct new orientation for the camera scene node from yaw and pitch. Roll is fixed to zero
        cameraNode.rotation = Quaternion(pitch, yaw, 0.0)
    end

    -- Read WASD keys and move the camera scene node to the corresponding direction if they are pressed
    if input:GetKeyDown(KEY_W) then
        cameraNode:Translate(Vector3(0.0, 0.0, 1.0) * MOVE_SPEED * timeStep)
    end
    if input:GetKeyDown(KEY_S) then
        cameraNode:Translate(Vector3(0.0, 0.0, -1.0) * MOVE_SPEED * timeStep)
    end
    if input:GetKeyDown(KEY_A) then
        cameraNode:Translate(Vector3(-1.0, 0.0, 0.0) * MOVE_SPEED * timeStep)
    end
    if input:GetKeyDown(KEY_D) then
        cameraNode:Translate(Vector3(1.0, 0.0, 0.0) * MOVE_SPEED * timeStep)
    end

    -- Toggle debug geometry with space
    if input:GetKeyPress(KEY_SPACE) then
        drawDebug = not drawDebug
    end

    -- Paint decal with the left mousebutton cursor must be visible
    if ui.cursor.visible and input:GetMouseButtonPress(MOUSEB_LEFT) then
        PaintDecal()
    end
end

function PaintDecal()
    local result, hitPos, hitDrawable = Raycast(250.0)
    if result then
        -- Check if target scene node already has a DecalSet component. If not, create now
        local targetNode = hitDrawable:GetNode()
        local decal = targetNode:GetComponent("DecalSet")
        if decal == nil then
            decal = targetNode:CreateComponent("DecalSet")
            decal.material = cache:GetResource("Material", "Materials/UrhoDecal.xml")
        end
        -- 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.rotation, 0.5, 1.0, 1.0, Vector2(0.0, 0.0), Vector2(1.0, 1.0))
    end
end

function Raycast(maxDistance)
    local hitPos = nil
    local hitDrawable = nil

    local pos = ui.cursorPosition
    -- Check the cursor is visible and there is no UI element in front of the cursor
    if (not ui.cursor.visible) or (ui:GetElementAt(pos, true) ~= nil) then
        return false, nil, nil
    end

    local camera = cameraNode:GetComponent("Camera")
    local cameraRay = camera:GetScreenRay(pos.x / graphics.width, pos.y / graphics.height)
    -- Pick only geometry objects, not eg. zones or lights, only get the first (closest) hit
    local octree = scene_:GetComponent("Octree")
    local result = octree:RaycastSingle(cameraRay, RAY_TRIANGLE, maxDistance, DRAWABLE_GEOMETRY)
    if result.drawable ~= nil then
        -- Calculate hit position in world space
        hitPos = cameraRay.origin + cameraRay.direction * result.distance
        hitDrawable = result.drawable
        return true, hitPos, hitDrawable
    end

    return false, nil, nil
end

function HandleUpdate(eventType, eventData)
    -- Take the frame time step, which is stored as a float
    local timeStep = eventData:GetFloat("TimeStep")

    -- Move the camera, scale movement with time step
    MoveCamera(timeStep)
end

function HandlePostRenderUpdate(eventType, 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 then
        renderer:DrawDebugGeometry(false)
    end
end

-- Create XML patch instructions for screen joystick layout specific to this sample app
function GetScreenJoystickPatchString()
    return
        "<patch>" ..
        "    <remove sel=\"/element/element[./attribute[@name='Name' and @value='Button0']]/attribute[@name='Is Visible']\" />" ..
        "    <replace sel=\"/element/element[./attribute[@name='Name' and @value='Button0']]/element[./attribute[@name='Name' and @value='Label']]/attribute[@name='Text']/@value\">Paint</replace>" ..
        "    <add sel=\"/element/element[./attribute[@name='Name' and @value='Button0']]\">" ..
        "        <element type=\"Text\">" ..
        "            <attribute name=\"Name\" value=\"MouseButtonBinding\" />" ..
        "            <attribute name=\"Text\" value=\"LEFT\" />" ..
        "        </element>" ..
        "    </add>" ..
        "    <remove sel=\"/element/element[./attribute[@name='Name' and @value='Button1']]/attribute[@name='Is Visible']\" />" ..
        "    <replace sel=\"/element/element[./attribute[@name='Name' and @value='Button1']]/element[./attribute[@name='Name' and @value='Label']]/attribute[@name='Text']/@value\">Debug</replace>" ..
        "    <add sel=\"/element/element[./attribute[@name='Name' and @value='Button1']]\">" ..
        "        <element type=\"Text\">" ..
        "            <attribute name=\"Name\" value=\"KeyBinding\" />" ..
        "            <attribute name=\"Text\" value=\"SPACE\" />" ..
        "        </element>" ..
        "    </add>" ..
        "</patch>"
end
