local MODEL_URL = "#turret"
local TOUCH = hash("touch")
local SHOOT = hash("shoot")

local function play_animation(animation_id)
    model.play_anim(MODEL_URL, animation_id, go.PLAYBACK_ONCE_FORWARD)
end

function init(self)
    msg.post(".", "acquire_input_focus")

    self.camera_url = nil
    self.mouse_x = 0
    self.mouse_y = 0
    self.has_mouse = false
end

function on_message(self, message_id, message, sender)
    if message_id == hash("register_camera") then
        self.camera_url = message.url
        pprint("Camera registered: " .. tostring(self.camera_url))
    end
end

function on_input(self, action_id, action)
    if action.screen_x and action.screen_y then
        self.mouse_x = action.screen_x
        self.mouse_y = action.screen_y
        self.has_mouse = true
        if action_id == TOUCH and action.pressed then
            play_animation(SHOOT)
        end
    end
end

function update(self, dt)
    if not self.camera_url or not self.has_mouse then
        return
    end

    -- Get two points on the cursor's line of sight (near and far planes)
    -- z = 0 -> near plane, z = 1 -> far plane (normalized depth, not world units)
    local p0 = camera.screen_to_world(
        vmath.vector3(self.mouse_x, self.mouse_y, 0),
        self.camera_url
    )

    local p1 = camera.screen_to_world(
        vmath.vector3(self.mouse_x, self.mouse_y, 1),
        self.camera_url
    )
    -- Ray direction: from near plane towards far plane
    local ray = p1 - p0

    -- Get the turret's current world position (with parent transforms applied)
    go.update_world_transform()
    local gun_pos = go.get_world_position()

    -- Ray is parallel to the horizontal plane - no intersection
    if math.abs(ray.y) < 0.00001 then
        return
    end
    -- Intersect the ray with the horizontal plane at the gun's height (y = gun_pos.y)
    local t = (gun_pos.y - p0.y) / ray.y
    local target = p0 + ray * t

    -- Horizontal vector from turret to target
    local dx = target.x - gun_pos.x
    local dz = target.z - gun_pos.z

    -- Target is directly under/above the turret - direction is undefined
    if math.abs(dx) + math.abs(dz) < 0.00001 then
        return
    end

    -- Yaw angle. atan2(dx, dz) assumes the model faces +Z at angle 0
    local angle = math.atan2(dx, dz)

    -- Rotate the turret around the Y axis
    go.set_rotation(
        vmath.quat_rotation_y(angle)
    )
end

function init(self)
    msg.post("/turret#turret_controller", "register_camera", {
        url = msg.url("#camera")
    })
end