--- @class Die
Die = {
    x = 0,
    y = 0,
    size = 16,
    dx = math.random(0, 1) == 0 and -1 or 1,
    dy = math.random(0, 1) == 0 and -1 or 1,
    value = nil,
    --
    box = nil,
    bouncing = false,
    angle = 0,
    scale = 1,
    --
    bg = nil,
    --
    ---
    ---@param self Die
    set_random_value = function(self)
        -- Don't change the value if the die is barely moving
        if (math.abs(self.dx)<0.25 or math.abs(self.dy)<0.25) then
            return
        end

        local n
        repeat
            n = math.random(1, 6)
        until n ~= self.value
        self.value = n
    end,
    ---
    --- @param self Die
    update = function(self)
        -- bounce off walls
        if math.abs(self.dx) < 0.05 then self.dx = 0 end
        if math.abs(self.dy) < 0.05 then self.dy = 0 end

        if self.box then
            if self.x < self.box.x then
                self.x = self.box.x
                self.dx = -self.dx
                self:set_random_value()
            end
            if self.x > self.box.x + self.box.width - self.size then
                self.x = self.box.x + self.box.width - self.size
                self.dx = -self.dx
                self:set_random_value()
            end
            if self.y < self.box.y then
                self.y = self.box.y
                self.dy = -self.dy
                self:set_random_value()
            end
            if self.y > self.box.y + self.box.height - self.size then
                self.y = self.box.y + self.box.height - self.size
                self.dy = -self.dy
                self:set_random_value()
            end
        end

        if not self.bouncing then
            -- reduce speed
            if self.dx ~= 0 then
                self.dx = self.dx * 0.85
            end
            if self.dy ~= 0 then
                self.dy = self.dy * 0.85
            end
        end

        self.x = self.x + self.dx
        self.y = self.y + self.dy
    end,
    ---
    ---@param self Die
    draw = function(self, colorkey)
        colorkey = colorkey or 0
        if self.bg then
            swap_color(12, self.bg)
        end
        swap_color(8, 0)

        -- aspr() uses the center as anchor point, so we offset the drawing position
        -- while keeping the scaling centered
        local offset = 8

        aspr(die_spr[self.value], self.x + offset, self.y + offset, colorkey, self.scale, self.scale, 0, self.angle, 2, 2)
        -- rectb(self.x, self.y, 16, 16, 2)
        reset_colors(12, 8)
    end
}

---comment
---@param o Die
---@return Die
function Die:new(o)
    o = o or {} -- create object if user does not provide one
    setmetatable(o, self)
    self.__index = self
    if o.box then
        o.angle = math.random() < .5 and 180 or -180
        o.x = o.box.x + math.random(0, o.box.width - o.size)
        o.y = o.box.y + math.random(0, o.box.height - o.size)
    end
    return o
end