local parentShell = shell
local x,y = term.getSize()

local bExit = false
local sDir = (parentShell and parentShell.dir()) or ""
local sPath = (parentShell and parentShell.path()) or ".:/rom/programs"
local tAliases = (parentShell and parentShell.aliases()) or {}
local tProgramStack = {}

local shell = {}
local tEnv = {
	["shell"] = shell,
}

local function cPrint(text)
	local x2,y2 = term.getCursorPos()
	term.setCursorPos(math.ceil((x / 2) - (text:len() / 2)), y2)
	print(text)
end

local function lPrint(text)
	local x2,y2 = term.getCursorPos()
	term.setCursorPos(x - text:len(), y2)
	write(text)
end

-- Install shell API

function shell.error( _sError )
	term.clear()
	term.setCursorPos(1,4)
	cPrint("BSoD")
	print()
	print("  An error has occured. To continue:\n")
	print("  Press Ctrl+S to shutdown, or\n")
	print("  Press Ctrl+R to restart your computer.")
	print("  You will lose all unsaved information.")
	print("\n  Error: " .._sError)
	print()
	cPrint("Press any key to continue")
	os.pullEventRaw( "key" )
	os.reboot()
end


function shell.run( _sCommand, ... )
	local sPath = shell.resolveProgram( _sCommand )
	if sPath ~= nil then
		tProgramStack[#tProgramStack + 1] = sPath
   		local result = os.run( tEnv, sPath, ... )
		tProgramStack[#tProgramStack] = nil
		return result
   	else
    	print( "No such program" )
    	return false
    end
end

function shell.exit()
    bExit = true
end

function shell.dir()
	return sDir
end

function shell.setDir( _sDir )
	sDir = _sDir
end

function shell.path()
	return sPath
end

function shell.setPath( _sPath )
	sPath = _sPath
end

function shell.resolve( _sPath )
	local sStartChar = string.sub( _sPath, 1, 1 )
	if sStartChar == "/" or sStartChar == "\\" then
		return fs.combine( "", _sPath )
	else
		return fs.combine( sDir, _sPath )
	end
end

function shell.resolveProgram( _sCommand )
	-- Substitute aliases firsts
	if tAliases[ _sCommand ] ~= nil then
		_sCommand = tAliases[ _sCommand ]
	end

    -- If the path is a global path, use it directly
    local sStartChar = string.sub( _sCommand, 1, 1 )
    if sStartChar == "/" or sStartChar == "\\" then
    	local sPath = fs.combine( "", _sCommand )
    	if fs.exists( sPath ) and not fs.isDir( sPath ) then
			return sPath
    	end
		return nil
    end

 	-- Otherwise, look on the path variable
    for sPath in string.gmatch(sPath, "[^:]+") do
    	sPath = fs.combine( shell.resolve( sPath ), _sCommand )
    	if fs.exists( sPath ) and not fs.isDir( sPath ) then
			return sPath
    	end
    end

	-- Not found
	return nil
end

function shell.programs( _bIncludeHidden )
	local tItems = {}

	-- Add programs from the path
    for sPath in string.gmatch(sPath, "[^:]+") do
    	sPath = shell.resolve( sPath )
		if fs.isDir( sPath ) then
			local tList = fs.list( sPath )
			for n,sFile in pairs( tList ) do
				if not fs.isDir( fs.combine( sPath, sFile ) ) and
				   (_bIncludeHidden or string.sub( sFile, 1, 1 ) ~= ".") then
					tItems[ sFile ] = true
				end
			end
		end
    end

	-- Sort and return
	local tItemList = {}
	for sItem, b in pairs( tItems ) do
		table.insert( tItemList, sItem )
	end
	table.sort( tItemList )
	return tItemList
end

function shell.getRunningProgram()
	if #tProgramStack > 0 then
		return tProgramStack[#tProgramStack]
	end
	return nil
end

function shell.setAlias( _sCommand, _sProgram )
	tAliases[ _sCommand ] = _sProgram
end

function shell.clearAlias( _sCommand )
	tAliases[ _sCommand ] = nil
end

function shell.aliases()
	-- Add aliases
	local tCopy = {}
	for sAlias, sCommand in pairs( tAliases ) do
		tCopy[sAlias] = sCommand
	end
	return tCopy
end

-- Attempt to boot the disks bios.
local sUserStartup = nil

for n,sSide in pairs( redstone.getSides() ) do
	if disk.isPresent( sSide ) and disk.hasData( sSide ) then
		local sDiskStartup = shell.resolveProgram( fs.combine(disk.getMountPath( sSide ), "bios.lua") )
		if sDiskStartup then
			sUserStartup = sDiskStartup
			break
		end
	end
end

-- Boot your PC
lPrint("F12 = Boot Menu")
term.setCursorPos(1,y)
write("Loading...")


local timer = os.startTimer( 3 )
while true do
	local sEvent, param = os.pullEventRaw()
	if param == timer and sEvent == "timer" then
		break
	elseif sEvent == "key" and param == 88 then
		term.setCursorPos(1,4)
		cPrint("+-----------------+")
		cPrint("|    Boot Menu    |")
		cPrint("+-----------------+")
		cPrint("| 1.   DISK       |")
		cPrint("| 2.   Hard Drive |")
		cPrint("|                 |")
		cPrint("|                 |")
		cPrint("|                 |")
		cPrint("+-----------------+")
		while true do
			local sEvent, param = os.pullEventRaw( "key" )
			if param == 2 then
				break --It already boots out of the disk :P
			elseif param == 3 then
				sHardStartup = shell.resolveProgram( "/bios.lua" )
				if sHardStartup then
					sUserStartup = sHardStartup
					break
				else
					shell.error( "BIOS undetected in hard drive!" )
				end
			end
		end

		break
	end
end

if sUserStartup then
	--Store each line as a table
	local tLines = {}
	local file = io.open(sUserStartup, "r")
	local line
	while true do
		line = file:read()
		if not line then break end
		tLines[#tLines+1] = line
	end
	file:close()

	if tLines[1]:find("#") then
		fs.delete(".bios.lua.new")
		local BIOS = fs.open(".bios.lua.new", "w")
		for i = 3, #tLines do
			BIOS.writeLine(tLines[i])
		end
		BIOS.close()
		shell.run("rom/programs/clear")
		shell.run(".bios.lua.new")
		if string.sub(sUserStartup, 1, 5) == "disk/" then
			shell.run("disk/" ..string.sub(tLines[1], 2, string.len(tLines[1])))
		else
			shell.run(string.sub(tLines[1], 2, string.len(tLines[1])))
		end
	else
		shell.error( "Unsupported/Corrupted BIOS!" )
	end
else
	shell.error( "BIOS undetected! Please insert a boot   disk" )
end