local Constraints = require "lib.simple_ui.core.constraints"
local Rect = require "lib.simple_ui.core.rect"
local StatefulElement = require "lib.simple_ui.core.stateful_element"


--- @class ScreenArea : StatefulElement
--- @field dimensions Rect
--- @field filter "nearest" | "linear"
local element = setmetatable({}, StatefulElement)
element.__index = element
element.type = "ScreenArea"

function element:build()
    local cw, ch = self.state.canvas:getDimensions()
    if cw ~= self.dimensions.width or ch ~= self.dimensions.height then
        self.state.canvas = self:initState().canvas -- в реальном мире оно не будет пересоздаваться каждый кадр
    end
    return self.child
end

function element:layout()
    local screenW, screenH = self.state.canvas:getDimensions()

    self._constraints_ = Constraints {
        maxWidth = screenW,
        maxHeight = screenH
    }
    self._size_ = Vec3 { screenW, screenH }

    if not self._child_ then return end
    self._child_._constraints_ = Constraints(self._constraints_)
    self._child_:layout()
    self._child_._offset_ = Vec3 {}
end

function element:draw()
    local oldCanvas = love.graphics.getCanvas()

    love.graphics.push()
    love.graphics.origin()
    love.graphics.setCanvas(self.state.canvas)
    love.graphics.clear()
    if self._child_ then self._child_:draw() end
    love.graphics.pop()

    love.graphics.setCanvas(oldCanvas)
    love.graphics.push("transform")
    love.graphics.translate(self._offset_.x, self._offset_.y)
    love.graphics.draw(self.state.canvas)
    love.graphics.pop()
end

function element:initState()
    local canvas = love.graphics.newCanvas(self.dimensions.width, self.dimensions.height)
    canvas:setFilter(self.filter, self.filter)
    return {
        canvas = canvas
    }
end

--- @return ScreenArea
--- @param values {key: any, dimensions: Rect?, filter: "nearest" | "linear" | nil,  child: UIElement?}
function element:new(values)
    if not values.dimensions then values.dimensions = Rect { width = love.graphics.getWidth(), height = love.graphics.getHeight() } end
    if not values.filter then values.filter = "linear" end
    return StatefulElement.new(self, values)
end

return element