-- Multiplier applied to the touch->block direction vector.
local force_factor = 30

-- Debug line color used by @render:draw_line.
local debug_line_color = vmath.vector4(0, 0.5, 1, 1)

-- Game object ids of dynamic blocks controlled by this script.
-- The script is attached to the "controller" object in the collection.
local blocks = {
    [1] = "block1",
    [2] = "block2",
    [3] = "block3",
    [4] = "block4",
}

function init(self)
    -- <1> Receive touch/mouse input in on_input().
    msg.post(".", "acquire_input_focus")
end

-- Pre-hashed action id for the touch action.
local touch_action_id = hash("touch")

function on_input(self, action_id, action)
    -- <2> Built-in "touch" also maps mouse clicks on desktop.
    if action_id == touch_action_id then
        -- <3> Iterate over all blocks and apply force to each.
        for _, block in pairs(blocks) do
            -- <4> Compute the force vector by subtracting the block center from the touch position.
            local center = go.get_world_position(block)
            local touch = vmath.vector3(action.x, action.y, center.z)
            local force = (touch - center) * force_factor

            -- <5> Send force to the block's dynamic collision object.
            msg.post(block, "apply_force", {
                force = force,
                position = center
            })

            -- <6> Visualize direction from touch point to block center.
            msg.post("@render:", "draw_line", {
                start_point = touch,
                end_point = center,
                color = debug_line_color
            })
        end
    end
end

function final(self)
    -- Stop receiving input when the controller is destroyed.
    msg.post(".", "release_input_focus")
end