PrefabPreviewEditorWindow = EditorWindow:New({
    Title = "Prefab Previewer",
    Submenu = "Witchy Project" -- This tells the engine where to place it in the View menu
})

function PrefabPreviewEditorWindow:Initialize()
    -- the behavior of this window assumes the assets obtained here
    -- won't be deleted while the window is active, so in a more
    -- robust scenario the code would be a bit more complex
    self.prefabs = AssetManager.GetAssetsOfType(AssetType.Prefab)

    -- this shows the relative path to the currently selected asset
    self.pathLabel = self:CreateLabel("Select a Prefab")

    -- the MVP, it's a default SceneView so it has an empty scene
    -- loaded in. One could also load an existing scene into it,
    -- or create several scene views if desired, in the same window.
    -- we provide an Update function which mimics the Update loop
    -- in the engine proper
    self.sceneView = self:CreateSceneView()
    self.sceneView.Update = function(deltaTime)
        self:SceneUpdate(deltaTime)
    end

    -- the list box that will hold our prefabs
    -- we will instantiate the selected prefab in the SceneView's
    -- scene for previewing purposes.
    self.prefabListBox = self:CreateListBox("Prefabs")
    for i = 1, #self.prefabs do
        self.prefabListBox:AddItem(self.prefabs[i].FileName)
    end
    self.prefabListBox.OnSelectionChanged = function(newIndex)
        self:OnSelectedPrefabChanged(newIndex)
    end
end

function PrefabPreviewEditorWindow:SceneUpdate(deltaTime)
    -- if we've instantiated a prefab, rotate the entity so it looks cool
    if self.activeEntity ~= nil then
        self.activeEntity:RotateRight(80.0 * deltaTime)
    end
end

function PrefabPreviewEditorWindow:OnSelectedPrefabChanged(newIndex)
    if newIndex > 0 then
        -- we only want at most one instantiated prefab in the scene
        -- so delete the current one, if exists.
        if self.activeEntity ~= nil then
            self.sceneView:DestroyEntity(self.activeEntity)
            self.activeEntity = nil
        end

        self.pathLabel:SetText(self.prefabs[newIndex].FilePath)

        self.activeEntity = self.sceneView:InstantiatePrefab(self.prefabs[newIndex].Id)
        self.activeEntity:SetWorldPosition(Vec3:new(0.0, 0.0, 0.0))
        self.activeEntity:ClearRotation()

        -- this long named function travels the entity's hierarchy and tries to build a
        -- bounding sphere that covers its, and its children's, bounding spheres.
        local boundingSphere = self.activeEntity:GetBoundingSphereCoveringHierarchyInWorldSpace()
        if boundingSphere then
            local targetPos = boundingSphere.Origin + Vec3:new(
                boundingSphere.Radius + boundingSphere.Radius * 0.2,
                0.1,
                0.1
            )
            self.sceneView:SetCameraPosition(targetPos)
            self.sceneView:SetCameraLookAt(boundingSphere.Origin)
        else
            self.sceneView:SetCameraPosition(Vec3:new(0.2, 0.0, 0.0))
            self.sceneView:SetCameraLookAt(Vec3:new(0.0, 0.0, 0.0))
        end
    else
        if self.activeEntity ~= nil then
            self.sceneView:DestroyEntity(self.activeEntity)
            self.activeEntity = nil
        end
        self.pathLabel:SetText("Select a Prefab")
    end
end

function PrefabPreviewEditorWindow:OnContentAreaResized(newWidth, newHeight)
    -- Stuck with absolute positioning/sizing until I figure out what layouts should work like
    local labelHeight = 20
    local leftRightMargin = 10
    local contentWidthWithoutMargins = newWidth - leftRightMargin - leftRightMargin
    local sceneViewWidth = 0.8 * contentWidthWithoutMargins
    local prefabListWidth = contentWidthWithoutMargins - sceneViewWidth
    local sceneAndListHeight = newHeight - labelHeight

    self.pathLabel:SetPosition(leftRightMargin, 0)
    self.pathLabel:SetSize(contentWidthWithoutMargins, labelHeight)

    self.sceneView:SetPosition(leftRightMargin, labelHeight)
    self.sceneView:SetSize(sceneViewWidth, sceneAndListHeight)

    self.prefabListBox:SetPosition(leftRightMargin + sceneViewWidth, labelHeight)
    self.prefabListBox:SetSize(prefabListWidth, sceneAndListHeight)
end