/.EnderOS/.edit

function reset()
term.clear()
term.setCursorPos(1,1)
end

reset()
term.setTextColor(colors.orange)
print("What file do you wish to edit?")
-- Get file to edit
term.setTextColor(colors.white)
local input = read()
reset()

-- Error checking
local sPath = shell.resolve(input)
local bReadOnly = fs.isReadOnly( sPath )
if fs.exists( sPath ) and fs.isDir( sPath ) then
	term.setTextColor(colors.red)
	print( "Cannot edit a directory." )
	term.setTextColor(colors.white)
	sleep(3)
	Edit()
end

if fs.exists( sPath ) and sPath == shell.getRunningProgram() then
	term.setTextColor(colors.red)
	print( "Cannot edit the file EnderOS is contained in!" )
	term.setTextColor(colors.white)
	sleep(3)
	Edit()
end

local x,y = 1,1
local w,h = term.getSize()
local scrollX, scrollY = 0,0

local tLines = {}
local bRunning = true

-- Colours
local highlightColour, keywordColour, commentColour, textColour, bgColour
if term.isColour() then
	bgColour = colours.black
	textColour = colours.white
	highlightColour = colours.orange
	keywordColour = colours.lightBlue
	commentColour = colours.lime
	stringColour = colours.red
else
	bgColour = colours.black
	textColour = colours.white
	highlightColour = colours.white
	keywordColour = colours.white
	commentColour = colours.white
	stringColour = colours.white
end

-- Menus
local bMenu = false
local nMenuItem = 1
local tMenuItems = {"Save", "Exit", "Print"}
local sStatus = "Press Ctrl to access menu"

local function load(_sPath)
	tLines = {}
	if fs.exists( _sPath ) then
		local file = io.open( _sPath, "r" )
		local sLine = file:read()
		while sLine do
			table.insert( tLines, sLine )
			sLine = file:read()
		end
		file:close()
	end

	if #tLines == 0 then
		table.insert( tLines, "" )
	end
end

local function save( _sPath )
	-- Create intervening folder
	local sDir = sPath:sub(1, sPath:len() - fs.getName(sPath):len() )
	if not fs.exists( sDir ) then
		fs.makeDir( sDir )
	end

	-- Save
	local file = nil
	local function innerSave()
		file = fs.open( _sPath, "w" )
		if file then
			for n, sLine in ipairs( tLines ) do
				file.write( sLine .. "\n" )
			end
		else
			term.setTextColor(colors.red)
			error( "EnderOS failed to open ".._sPath )
			term.setTextColor(colors.white)
		end
	end

	local ok = pcall( innerSave )
	if file then
		file.close()
	end
	return ok
end

local tKeywords = {
	["and"] = true,
	["break"] = true,
	["do"] = true,
	["else"] = true,
	["elseif"] = true,
	["end"] = true,
	["false"] = true,
	["for"] = true,
	["function"] = true,
	["if"] = true,
	["in"] = true,
	["local"] = true,
	["nil"] = true,
	["not"] = true,
	["or"] = true,
	["repeat"] = true,
	["return"] = true,
	["then"] = true,
	["true"] = true,
	["until"]= true,
	["while"] = true,
}

local function tryWrite( sLine, regex, colour )
	local match = string.match( sLine, regex )
	if match then
		if type(colour) == "number" then
			term.setTextColour( colour )
		else
			term.setTextColour( colour(match) )
		end
		term.write( match )
		term.setTextColour( textColour )
		return string.sub( sLine, string.len(match) + 1 )
	end
	return nil
end

local function writeHighlighted( sLine )
	while string.len(sLine) > 0 do
		sLine =
			tryWrite( sLine, "^%-%-%[%[.-%]%]", commentColour ) or
			tryWrite( sLine, "^%-%-.*", commentColour ) or
			tryWrite( sLine, "^\".-[^\\]\"", stringColour ) or
			tryWrite( sLine, "^\'.-[^\\]\'", stringColour ) or
			tryWrite( sLine, "^%[%[.-%]%]", stringColour ) or
			tryWrite( sLine, "^[%w_]+", function( match )
				if tKeywords[ match ] then
					return keywordColour
				end
				return textColour
			end ) or
			tryWrite( sLine, "^[^%w_]", textColour )
	end
end

local function redrawText()
	for y=1,h-1 do
		term.setCursorPos( 1 - scrollX, y )
		term.clearLine()

		local sLine = tLines[ y + scrollY ]
		if sLine ~= nil then
			writeHighlighted( sLine )
		end
	end
	term.setCursorPos( x - scrollX, y - scrollY )
end

local function redrawLine(_nY)
	local sLine = tLines[_nY]
	term.setCursorPos( 1 - scrollX, _nY - scrollY )
	term.clearLine()
	writeHighlighted( sLine )
	term.setCursorPos( x - scrollX, _nY - scrollY )
end

local function setLeftStatus()
end

local function redrawMenu()
    term.setCursorPos( 1, h )
	term.clearLine()

	local sLeft, sRight
	local nLeftColour, nLeftHighlight1, nLeftHighlight2
	if bMenu then
		local sMenu = ""
		for n,sItem in ipairs( tMenuItems ) do
			if n == nMenuItem then
				nLeftHighlight1 = sMenu:len() + 1
				nLeftHighlight2 = sMenu:len() + sItem:len() + 2
			end
			sMenu = sMenu.." "..sItem.." "
		end
		sLeft = sMenu
		nLeftColour = textColour
	else
		sLeft = sStatus
		nLeftColour = highlightColour
	end

	-- Left goes last so that it can overwrite the line numbers.
	sRight = "Ln "..y
	term.setTextColour( highlightColour )
	term.setCursorPos( w-sRight:len() + 1, h )
	term.write(sRight)

	sRight = tostring(y)
	term.setTextColour( textColour )
	term.setCursorPos( w-sRight:len() + 1, h )
	term.write(sRight)

	if sLeft then
		term.setCursorPos( 1, h )
		term.setTextColour( nLeftColour )
		term.write(sLeft)
		if nLeftHighlight1 then
			term.setTextColour( highlightColour )
			term.setCursorPos( nLeftHighlight1, h )
			term.write( "[" )
			term.setCursorPos( nLeftHighlight2, h )
			term.write( "]" )
		end
		term.setTextColour( textColour )
	end

	-- Cursor highlights selection
	term.setCursorPos( x - scrollX, y - scrollY )
end

local tMenuFuncs = {
	Save=function()
		if bReadOnly then
			sStatus = "You cannot access this file!"
		else
			local ok, err = save( sPath )
			if ok then
				sStatus="EnderOS saved this file to "..sPath
			else
				sStatus="EnderOS could not save this file to "..sPath
			end
		end
		redrawMenu()
	end,
	Print=function()
		local sPrinterSide = nil
		for n,sSide in ipairs(rs.getSides()) do
			if peripheral.isPresent(sSide) and peripheral.getType(sSide) == "printer" then
				sPrinterSide = sSide
				break
			end
		end

		if not sPrinterSide then
			sStatus = "EnderOS could not find any printers!"
			return
		end

		local nPage = 0
		local sName = fs.getName( sPath )
		local printer = peripheral.wrap(sPrinterSide)
		if printer.getInkLevel() < 1 then
			sStatus = "EnderOS detected no ink!"
			return
		elseif printer.getPaperLevel() < 1 then
			sStatus = "EnderOS detected no paper!"
			return
		end

		local terminal = {
			getCursorPos = printer.getCursorPos,
			setCursorPos = printer.setCursorPos,
			getSize = printer.getPageSize,
			write = printer.write,
		}
		terminal.scroll = function()
			if nPage == 1 then
				printer.setPageTitle( sName.." (page "..nPage..")" )
			end

			while not printer.newPage()	do
				if printer.getInkLevel() < 1 then
					sStatus = "EnderOS has detected low ink levels, please refill"
				elseif printer.getPaperLevel() < 1 then
					sStatus = "EnderOS has detected low paper levels, please refill"
				else
					sStatus = "EnderOS has detected a full output tray, please empty"
				end

				term.restore()
				redrawMenu()
				term.redirect( terminal )

				local timer = os.startTimer(0.5)
				sleep(0.5)
			end

			nPage = nPage + 1
			if nPage == 1 then
				printer.setPageTitle( sName )
			else
				printer.setPageTitle( sName.." (page "..nPage..")" )
			end
		end

		bMenu = false
		term.redirect( terminal )
		local ok, error = pcall( function()
			term.scroll()
			for n, sLine in ipairs( tLines ) do
				print( sLine )
			end
		end )
		term.restore()
		if not ok then
			print( error )
		end

		while not printer.endPage() do
			sStatus = "EnderOS has detected a full output tray, please empty"
			redrawMenu()
			sleep( 0.5 )
		end
		bMenu = true

		if nPage > 1 then
			sStatus = "EnderOS printed "..nPage.." Pages"
		else
			sStatus = "EnderOS printed 1 Page"
		end
		redrawMenu()
	end,
	Exit=function()
		bRunning = false
	end
}

local function doMenuItem( _n )
	tMenuFuncs[tMenuItems[_n]]()
	if bMenu then
		bMenu = false
		term.setCursorBlink( true )
	end
	redrawMenu()
end

local function setCursor( x, y )
	local screenX = x - scrollX
	local screenY = y - scrollY

	local bRedraw = false
	if screenX < 1 then
		scrollX = x - 1
		screenX = 1
		bRedraw = true
	elseif screenX > w then
		scrollX = x - w
		screenX = w
		bRedraw = true
	end

	if screenY < 1 then
		scrollY = y - 1
		screenY = 1
		bRedraw = true
	elseif screenY > h-1 then
		scrollY = y - (h-1)
		screenY = h-1
		bRedraw = true
	end

	if bRedraw then
		redrawText()
	end
	term.setCursorPos( screenX, screenY )

	-- Statusbar now pertains to menu, it would probably be safe to redraw the menu on every key event.
	redrawMenu()
end

-- Actual program functionality begins
load(sPath)

term.setBackgroundColour( bgColour )
term.clear()
term.setCursorPos(x,y)
term.setCursorBlink( true )

redrawText()
redrawMenu()

-- Handle input
while bRunning do
	local sEvent, param, param2, param3 = os.pullEvent()
	if sEvent == "key" then
		if param == keys.up then
			-- Up
			if not bMenu then
				if y > 1 then
					-- Move cursor up
					y = y - 1
					x = math.min( x, string.len( tLines[y] ) + 1 )
					setCursor( x, y )
				end
			end
		elseif param == keys.down then
			-- Down
			if not bMenu then
				-- Move cursor down
				if y < #tLines then
					y = y + 1
					x = math.min( x, string.len( tLines[y] ) + 1 )
					setCursor( x, y )
				end
			end
		elseif param == keys.tab then
			-- Tab
			if not bMenu then
				local sLine = tLines[y]

				-- Indent line
				-- IN CASE OF INSERT TAB IN PLACE:
				-- tLines[y] = string.sub(sLine,1,x-1) .. "  " .. string.sub(sLine,x)
				tLines[y]="  "..tLines[y]
				x = x + 2
				setCursor( x, y )
				redrawLine(y)
			end
		elseif param == keys.pageUp then
			-- Page Up
			if not bMenu then
				-- Move up a page
				local sx,sy=term.getSize()
				y=y-sy-1
				if y<1 then	y=1 end
				x = math.min( x, string.len( tLines[y] ) + 1 )
				setCursor( x, y )
			end
		elseif param == keys.pageDown then
			-- Page Down
			if not bMenu then
				-- Move down a page
				local sx,sy=term.getSize()
				if y<#tLines-sy-1 then
					y = y+sy-1
				else
					y = #tLines
				end
				x = math.min( x, string.len( tLines[y] ) + 1 )
				setCursor( x, y )
			end
		elseif param == keys.home then
			-- Home
			if not bMenu then
				-- Move cursor to the beginning
				x=1
				setCursor(x,y)
			end
		elseif param == keys["end"] then
			-- End
			if not bMenu then
				-- Move cursor to the end
				x = string.len( tLines[y] ) + 1
				setCursor(x,y)
			end
		elseif param == keys.left then
			-- Left
			if not bMenu then
				if x > 1 then
					-- Move cursor left
					x = x - 1
				elseif x==1 and y>1 then
					x = string.len( tLines[y-1] ) + 1
					y = y - 1
				end
				setCursor( x, y )
			else
				-- Move menu left
				nMenuItem = nMenuItem - 1
				if nMenuItem < 1 then
					nMenuItem = #tMenuItems
				end
				redrawMenu()
			end
		elseif param == keys.right then
			-- Right
			if not bMenu then
				if x < string.len( tLines[y] ) + 1 then
					-- Move cursor right
					x = x + 1
				elseif x==string.len( tLines[y] ) + 1 and y<#tLines then
					x = 1
					y = y + 1
				end
				setCursor( x, y )
			else
				-- Move menu right
				nMenuItem = nMenuItem + 1
				if nMenuItem > #tMenuItems then
					nMenuItem = 1
				end
				redrawMenu()
			end
		elseif param == keys.delete then
			-- Delete
			if not bMenu then
				if  x < string.len( tLines[y] ) + 1 then
					local sLine = tLines[y]
					tLines[y] = string.sub(sLine,1,x-1) .. string.sub(sLine,x+1)
					redrawLine(y)
				elseif y<#tLines then
					tLines[y] = tLines[y] .. tLines[y+1]
					table.remove( tLines, y+1 )
					redrawText()
					redrawMenu()
				end
			end
		elseif param == keys.backspace then
			-- Backspace
			if not bMenu then
				if x > 1 then
					-- Remove character
					local sLine = tLines[y]
					tLines[y] = string.sub(sLine,1,x-2) .. string.sub(sLine,x)
					redrawLine(y)

					x = x - 1
					setCursor( x, y )
				elseif y > 1 then
					-- Remove newline
					local sPrevLen = string.len( tLines[y-1] )
					tLines[y-1] = tLines[y-1] .. tLines[y]
					table.remove( tLines, y )
					redrawText()

					x = sPrevLen + 1
					y = y - 1
					setCursor( x, y )
				end
			end
		elseif param == keys.enter then
			-- Enter
			if not bMenu then
				-- Newline
				local sLine = tLines[y]
				local _,spaces=string.find(sLine,"^[ ]+")
				if not spaces then
					spaces=0
				end
				tLines[y] = string.sub(sLine,1,x-1)
				table.insert( tLines, y+1, string.rep(' ',spaces)..string.sub(sLine,x) )
				redrawText()

				x = spaces+1
				y = y + 1
				setCursor( x, y )
			else
				-- Menu selection
				doMenuItem( nMenuItem )
			end
		elseif param == keys.leftCtrl or param == keys.rightCtrl then
			-- Menu toggle
			bMenu = not bMenu
			if bMenu then
				term.setCursorBlink( false )
				nMenuItem = 1
			else
				term.setCursorBlink( true )
			end
			redrawMenu()
		end

	elseif sEvent == "char" then
		if not bMenu then
			-- Input text
			local sLine = tLines[y]
			tLines[y] = string.sub(sLine,1,x-1) .. param .. string.sub(sLine,x)
			redrawLine(y)

			x = x + string.len( param )
			setCursor( x, y )
		else
			-- Select menu items
			for n,sMenuItem in ipairs( tMenuItems ) do
				if string.lower(string.sub(sMenuItem,1,1)) == string.lower(param) then
					doMenuItem( n )
					break
				end
			end
		end

	elseif sEvent == "mouse_click" then
		if not bMenu then
			if param == 1 then
				-- Left click
				local cx,cy = param2, param3
				if cy < h then
					y = math.min( math.max( scrollY + cy, 1 ), #tLines )
					x = math.min( math.max( scrollX + cx, 1 ), string.len( tLines[y] ) + 1 )
					setCursor( x, y )
				end
			end
		end

	elseif sEvent == "mouse_scroll" then
		if not bMenu then
			if param == -1 then
				-- Scroll up
				if scrollY > 0 then
					-- Move cursor up
					scrollY = scrollY - 1
					redrawText()
				end

			elseif param == 1 then
				-- Scroll down
				local nMaxScroll = #tLines - (h-1)
				if scrollY < nMaxScroll then
					-- Move cursor down
					scrollY = scrollY + 1
					redrawText()
				end

			end
		end
	end
end

-- Cleanup
term.clear()
term.setCursorBlink( false )
term.setCursorPos( 1, 1 )
startScreen()