---------------------------------------- System initialization ----------------------------------------

-- Obtaining boot filesystem component proxy
local bootFilesystemProxy = component.proxy(component.proxy(component.list("eeprom")()).getData())

-- Executes file from boot HDD during OS initialization (will be overriden in filesystem library later)
function dofile(path)
	local stream, reason = bootFilesystemProxy.open(path, "r")
	if stream then
		local data, chunk = ""
		while true do
			chunk = bootFilesystemProxy.read(stream, math.huge)
			if chunk then
				data = data .. chunk
			else
				break
			end
		end

		bootFilesystemProxy.close(stream)

		local result, reason = load(data, "=" .. path)
		if result then
			return result()
		else
			error(reason)
		end
	else
		error(reason)
	end
end

-- Initializing global package system
package = {
	paths = {["/Libraries/"] = true},
	loaded = {},
	loading = {},
}

-- Checks existense of specified path. It will be overriden after filesystem library initialization
local function requireExists(path)
	return bootFilesystemProxy.exists(path)
end

-- Works the similar way as native Lua require() function
function require(module)
	-- For non-case-sensitive filesystems
	local lowerModule = unicode.lower(module)

	if package.loaded[lowerModule] then
		return package.loaded[lowerModule]
	elseif package.loading[lowerModule] then
		error("recursive require() call found: library \"" .. module .. "\" is trying to require another library that requires it\n" .. debug.traceback())
	else
		local errors = {}

		local function checkVariant(variant)
			if requireExists(variant) then
				return variant
			else
				table.insert(errors, "  variant \"" .. variant .. "\" not exists")
			end
		end

		local function checkVariants(path, module)
			return
				checkVariant(path .. module .. ".lua") or
				checkVariant(path .. module) or
				checkVariant(module)
		end

		local modulePath
		for path in pairs(package.paths) do
			modulePath =
				checkVariants(path, module) or
				checkVariants(path, unicode.upper(unicode.sub(module, 1, 1)) .. unicode.sub(module, 2, -1))
			
			if modulePath then
				package.loading[lowerModule] = true
				local result = dofile(modulePath)
				package.loaded[lowerModule] = result or true
				package.loading[lowerModule] = nil
				
				return result
			end
		end

		error("unable to locate library \"" .. module .. "\":\n" .. table.concat(errors, "\n"))
	end
end

local GPUProxy = component.proxy(component.list("gpu")())
local screenWidth, screenHeight = GPUProxy.getResolution()

-- Displays title and currently required library when booting OS
local UIRequireTotal, UIRequireCounter = 13, 1

local function UIRequire(module)
	local function centrize(width)
		return math.floor(screenWidth / 2 - width / 2)
	end
	
	local title, width, total = "MineOS", 26, 14
	local x, y, part = centrize(width), math.floor(screenHeight / 2 - 1), math.ceil(width * UIRequireCounter / UIRequireTotal)
	UIRequireCounter = UIRequireCounter + 1
	
	-- Title
	GPUProxy.setForeground(0x2D2D2D)
	GPUProxy.set(centrize(#title), y, title)

	-- Progressbar
	GPUProxy.setForeground(0x878787)
	GPUProxy.set(x, y + 2, string.rep("─", part))
	GPUProxy.setForeground(0xC3C3C3)
	GPUProxy.set(x + part, y + 2, string.rep("─", width - part))

	return require(module)
end

-- Preparing screen for loading libraries
GPUProxy.setBackground(0xE1E1E1)
GPUProxy.fill(1, 1, screenWidth, screenHeight, " ")

-- Loading libraries
bit32 = bit32 or UIRequire("Bit32")
local paths = UIRequire("Paths")
local event = UIRequire("Event")
local filesystem = UIRequire("Filesystem")

-- Setting main filesystem proxy too what are we booting from
filesystem.setProxy(bootFilesystemProxy)

-- Redeclaring requireExists function after filesystem library initialization
requireExists = function(variant)
	return filesystem.exists(variant)
end

-- Loading other libraries
UIRequire("Component")
UIRequire("Keyboard")
UIRequire("Color")
UIRequire("Text")
UIRequire("Number")
local image = UIRequire("Image")
UIRequire("Screen")
local GUI = UIRequire("GUI")
local system = UIRequire("System")
UIRequire("Network")

---------------------------------------- Main loop ----------------------------------------

-- "double_touch" event handler
local doubleTouchInterval, doubleTouchX, doubleTouchY, doubleTouchButton, doubleTouchUptime, doubleTouchScreenAddress = 0.3
if not event.doubleTouchHandler then
	event.doubleTouchHandler = event.addHandler(
		function(signalType, screenProxyAddress, x, y, button, user)
			if signalType == "touch" then
				local uptime = computer.uptime()
				
				if doubleTouchX == x and doubleTouchY == y and doubleTouchButton == button and doubleTouchScreenAddress == screenProxyAddress and uptime - doubleTouchUptime <= doubleTouchInterval then
					computer.pushSignal("double_touch", screenProxyAddress, x, y, button, user)
					event.skip("touch")
				end

				doubleTouchX, doubleTouchY, doubleTouchButton, doubleTouchUptime, doubleTouchScreenAddress = x, y, button, uptime, screenProxyAddress
			end
		end
	)
end

-- Creating main OS workspace, which contains every window/menu/etc.
local workspace = GUI.workspace()
system.setWorkspace(workspace)

-- Logging in
system.authorize()

-- Main loop with UI regeneration after errors 
while true do
	local success, path, line, traceback = system.call(workspace.start, workspace, 0)
	if success then
		break
	else
		system.updateWorkspace()
		system.updateDesktop()
		workspace:draw()
		
		system.error(path, line, traceback)
		workspace:draw()
	end
end