# Sample ruby DSL to create a game window.
# reference of what the engine should build up to.

width, height = 720, 480
image = Image.new "assets/loading.png"

window = Window.new width, height, title: "My Game", loading_bg: image

window.map_key ?w, :forward
window.map_key ?s, :backward
window.map_key ?a, :left
window.map_key ?d, :right

menu_scene = Scene.new

default_font = Font.new "assets/DejaVuSans.ttf", 12, italic: true

start_button = ElementText.new "Start Game", font: default_font, position: {x: 100, y: 100}

start_button.on_click do
  window.start :game_scene
end

menu_scene.add_element start_button

game_scene = Scene.new

world = ElementWorld.new

# world.cam # camera object to control the view of the world, has position, zoom, rotation

# can define any components with name and groups it is part of, systems will apply behaviour based on their groups
# there are 5 inbuilt groups that have systems written for them, but you can create more component groups and systems for whatever you want
# these groups are unique: true, meaning only on of it can be added to an entity and can be accesed using entity.group_name

world.new_component :sample_body, [:body] do
  # these properties exist in the dsl, and are used by the physics engine, but you can also add any custom properties you want to the body and use them in your controller code or whatever
  shape = :rectangle
  size = {width: 50, height: 50}
  angle = 0
  mass = 1 # this can be set to 0 for static bodies that should not be affected by physics, these bodies will not move but can still collide with other bodies (velocity will be ignored for static bodies)
  velocity = {x: 1, y: 0}
  collision = true
  # whether this body should collide with other bodies, if false it will not collide with anything and will not be affected by physics, but can still be moved by setting the position directly or by using a controller, useful for things like ghosts or whatever
end

world.new_component :sample_sprite, [:sprite] do
  tiles = Tiles.from "assets/sprite.png", tile_width: 50, tile_height: 50
  animation1 = {tiles: 5..6, frame_rate: 10, loop: true}
  animations = {idle: animation1}
  current_animation = :idle
end

world.new_component :sample_light, [:light] do
  color = {r: 255, g: 255, b: 255, a: 255}
  intensity = 1.0
  radius = 100

  # useful if using inbuilt fog light shader only
  # mostly cuz i need it though most engines wouldnt have such a feature explicitly (it is dumb addition but i added it cuz i want to)
  # it could be achived using other methods / custom properties but this is just a convenient way to do it
end

world.new_component :sample_render, [:render] do
  # for extra rendering options like speech bubbles, health bars, etc
  z_index = 0 # by default all are y-sorted, but can override with z_index for more control in here
  renderer = do
    draw_rect 0, 0, 50, 50, {r: 255, g: 0, b: 0, a: 255} # example of custom rendering code for this entity (0,0 is the position of the entity)
    draw_text "Hello World", default_font, 0, 0, {r: 255, g: 255, b: 255, a: 255}
  end
  # offset from the position of the entity, useful for things like speech bubbles or health bars that should be above the entity, etc
  offset = {x: 0, y: 0}
end

world.new_component :sample_controller, [:controller] do
  # these are defined in the window and mapped to the actual keys, so you can use whatever keys you want and just map them to these actions in the window
  # teh user can also remap them in the settings of the game
  keyboard_inputs = [
    :forward, :backward, :left, :right
  ]
  # direct means only clicks on this entity will trigger the mouse inputs, useful for like chests or doors or whatever
  # global means mouse inputs will be triggered as long as the mouse is within the window, useful for like aiming or whatever
  # none means mouse inputs will not be triggered for this entity, useful for when the entity should not be interactable with the mouse
  # on direct and global mouse mode, you can also get the mouse position relative to the entity or the world
  mouse_input_mode = :direct
  mouse_position_mode = :relative
  mouse_inputs = [:left, :right, :hover]
  # when multiple entities match the mouse input, the one with the highest priority will receive the input, useful for when you have multiple entities on top of each other and you want to control which one should receive the mouse input
  mouse_priority = 100
  # doesnt work without a body component (as they have no size)
  
  update = do |delta_time|
    # example of custom controller code for this entity, delta_time is the time since the last update in ms, useful for making movement frame rate independent
    if key_down?(:forward)
      # move the entity forward, you can access the body component of the entity to move it with physics, or you can set the position directly for more arcade style movement, etc
      # if the entity has a body component, you can also apply forces or impulses to it for more realistic physics interactions
      # if the entity has a sprite component, you can also change the current animation based on the input or whatever
      entity.body.velocity.x = 0
    elsif key_down?(:backward)
      entity.body.velocity.y = 1
    else
      entity.body.velocity.y = 0
    end

    if colliding_with?([:enemies]) # list of groups to check collisions with
      puts "Colliding with an enemy!"
    end

    if mouse_down?(:left)
      # example of getting the mouse position relative to the entity or the world
      puts "Mouse position relative to entity: #{mouse_position}"
    end
  end
end

# this is a custom compoenent group and component

world.define_group type: :component, name: :health, unique: false

world.new_component :enemy_health, [:health] do
  health = 100

  # event subscriptions work like this, you can trigger events on the entity itself, or on the world
  on_event = {
    :damage => do |amount|
      health -= amount
      puts "Enemy took #{amount} damage, remaining health: #{health}"
    end
  }
end

world.define_group type: :entity, name: :enemies

world.add_entity "Enemy1" do # Name is optional (as entities can be referenced by group or name)
  groups = [:enemies]

  position = {x: 100, y: 100} # entities always have a position, even if they don't have a body component, this is useful for rendering and for entities that don't need physics but still need to be positioned in the world
  components = [:sample_body, :sample_sprite, :sample_light, :sample_render, :sample_controller, :enemy_health]
end

world.add_entity "Trap Preview" do
  position = {x: 0, y: 0}
  components = [:sample_sprite]

  disabled = true # this entity will not be updated or rendered normally
end

# systems are called on the world every update frame, some systems are built into the engine for things like physics, rendering, etc, but you can also create your own custom systems for things like trap placement, enemy spawning, etc

world.add_system :health_regen do |dt|
  # example of a custom system that regenerates health for all entities with a health component, dt is the time since the last update in ms, useful for making things frame rate independent
  world.entities_query(:health).each do |entity|
    health_component = entity.healths.first # get the first health compoenent of teh entity (uses entity.group_names to access the component group - s or es added appropriately)
    health_component.health += 0.1 * dt # regenerate 0.1 health per second
  end
end

world.add_system :trap_placement do |dt| # example from teh game mist trying to be made with this engine
  # do trap placement logic when a trap is held
  if world.fetch(:holding_trap, false) # example of using the world's store to keep track of global state like whether the player is currently holding a trap or not
    if mouse_down?(:left)
      # place a trap at the mouse position, you can use the mouse position relative to the world for this
      world.add_entity "Trap" do
        groups = [:traps]

        position = mouse_position_world

        components = [:trap_body, :trap_sprite, :trap_render, :trap_controller]
      end

      world.store :holding_trap, false # stop placing traps until the player picks up another one
    else
      # show a preview of the trap at the mouse position, you can use the mouse position relative to the world for this
      world.entity("Trap Preview").update do
        position = mouse_position_world
        disabled = false # enable the trap preview entity to show it at the mouse position
      end
    end
  else
    # hide the trap preview when not holding a trap
    world.entity("Trap Preview").update do
      disabled = true
    end
  end
end

# this is used by teh engine like so
# when a bunch of enities reuse the same components, you can define the components once and then just add them to the entities, which is more efficient than defining the components for each entity separately
# and also for example all the entites that have a body component can be packed and calculated together in the physics engine, all the entities that have a sprite component can be packed and rendered together in the rendering engine, etc.

world.add_shader :fog do |shader|
  # shaders are per world
  vertex "assets/fog.vert"
  fragment "assets/fog.frag"

  data_format = {
    name: :float,
    time: :float,
    resolution: :vec2
    # data required by teh shader is defined here once
  }

  frame do |shader|
    # example of custom shader code for this shader, this is called every frame and is where you would update the shader data based on the current state of the world or whatever
    shader.set_data :time, Time.now.to_f
    shader.set_data :resolution, {x: width, y: height}
  end

  z = 100 # shaders always appear above normal sprites but z is used to sort them relative to each other, so a shader with z 100 will appear above a shader with z 50, but both will appear above normal sprites
end

window.add_scene :menu_scene => menu_scene
window.add_scene :game_scene => game_scene

window.start :menu_scene # first scene to show when the game starts, stops the loading bg