local Util = require("common.util")
local Dim = require("common.dimensions")

require "common.globals"
require "common.class"

local PageManager = require "api.page.pagemanager"

local Page = require "api.page.page"
local KShootManiaPage = require "titlescreen.splash.kshootmaniapage"
local USCPage = require "titlescreen.splash.uscpage"
local TeamExceedPage = require "titlescreen.splash.teamexceedpage"
local CreditsPage = require "titlescreen.splash.creditspage"

---@class SplashPage : Page
---@field pages Page[]
---@field currentPage integer
---@field _isTransitioning boolean # actively fading between pages
---@field _isFadeOut boolean # fading out between pages
local SplashPage = {
    __name = "SplashScreen",
    BACKGROUND_COLOR = {255, 255, 255},
    FADE_DURATION = 0.25
}

---Create a new SplashScreen instance
---@param params? SplashPage
---@return SplashPage
function SplashPage.new(params)
    local self = CreateInstance(SplashPage, params, Page)

    local pageManager = PageManager.get()

    self.currentPage = 0 -- start on nil page
    self.content = {
        pageManager:getPage(KShootManiaPage),
        pageManager:getPage(USCPage),
        pageManager:getPage(TeamExceedPage),
        pageManager:getPage(CreditsPage),
    }

    self._isTransitioning = true -- immediately transition to first page
    self._isFadeOut = false

    -- set callbacks
    for index, page in ipairs(self.content) do
        if index < #self.content then
            page.onInvalidation = function (page_inst)
                self._isTransitioning = true
            end
        else -- last index
            page.onInvalidation = function (page_inst)
                self:onInvalidation()
            end
        end
    end
    return self
end

function SplashPage:init()
    self.currentPage = 0
    self._isTransitioning = true
    for _, page in ipairs(self.content) do
        page:init()
    end
    Page.init(self)
end

function SplashPage:handleButtonInput(button)
    if button == game.BUTTON_STA then
        game.StopSample(KShootManiaPage.SAMPLE_PATH) -- hack to stop splash screen sample from playing when skipping
        self:onInvalidation()
    end
end

---Fade between pages
function SplashPage:fadeTransition(deltaTime)
    local fadeDuration = self.FADE_DURATION
    local fadeColor = self.BACKGROUND_COLOR

    -- reset variables on first call
    if not self["__fadeStarted"] then
        self.__fadeTimer = 0.0
        self.__fadeStarted = true
    end

    local fadeAlpha = 0.0
    local halfDuration = fadeDuration / 2
    if self.__fadeTimer < halfDuration then
        fadeAlpha = math.ceil(Util.lerp(self.__fadeTimer, 0, 0, halfDuration, 255)) -- fade out

        self._isFadeOut = true

    elseif self.__fadeTimer < fadeDuration then
        fadeAlpha = math.ceil(Util.lerp(self.__fadeTimer, halfDuration, 255, fadeDuration, 0)) -- fade in

        if self._isFadeOut then -- just switched to fading in, swap to new page
            self.currentPage = self.currentPage + 1
        end

        self._isFadeOut = false

    else
        self.__fadeStarted = false -- fade done, reset variable
        self._isTransitioning = false
        self._isFadeOut = false

    end

    local fillColor = {table.unpack(fadeColor, 1, 3)} -- copy color table
    table.insert(fillColor, fadeAlpha) -- add alpha

    gfx.BeginPath()
    gfx.FillColor(table.unpack(fillColor))
    gfx.Rect(0, 0, Dim.design.width, Dim.design.height)
    gfx.Fill()

    self.__fadeTimer = self.__fadeTimer + deltaTime
end

function SplashPage:drawBackground(deltaTime)
    gfx.BeginPath()
    gfx.FillColor(table.unpack(self.BACKGROUND_COLOR))
    gfx.Rect(0, 0, Dim.design.width, Dim.design.height)
    gfx.Fill()
end

function SplashPage:drawContent(deltaTime)
    if self.content[self.currentPage] then
        self.content[self.currentPage]:render(deltaTime)
    end
end

function SplashPage:drawForeground(deltaTime)
    local textFillColor = {0, 0, 0}
    if self.currentPage <= 1 then
        textFillColor = {255, 255, 255}
    end

    if self._isTransitioning then
        self:fadeTransition(deltaTime)
    end

    gfx.LoadSkinFont("segoeui.ttf")
    gfx.FillColor(table.unpack(textFillColor))
    gfx.TextAlign(gfx.TEXT_ALIGN_LEFT + gfx.TEXT_ALIGN_BOTTOM)
    gfx.FontSize(28)
    gfx.Text("Press START to skip...", 10, Dim.design.height - 10)
end

return SplashPage