local tArgs = { ... }
if #tArgs == 0 then
	print( "Usage: nano <path>" )
	return
end

local sPath = shell.resolve( tArgs[1] )
local bReadOnly = fs.isReadOnly( sPath )
if fs.exists( sPath ) and fs.isDir( sPath ) then
	print( "Cannot edit a directory" )
	return
end

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

local bMenu = false
local nMenuItem = 1

local sStatus = ""
local tLines = {}
local tabWidth = 2

function explode(div,str)
	if (div=='') then return false end
	local pos,arr = 0,{}
	
	for st,sp in function() return string.find(str,div,pos,true) end do
		table.insert(arr,string.sub(str,pos,st-1))
		pos = sp + 1
	end
	table.insert(arr,string.sub(str,pos)) -- Attach chars right of last divider
	return arr
end

local function load()
	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()
	else
		table.insert( tLines, "" )
	end
end

local function save( path )
	if not path then path = sPath end
	local file = io.open( path, "w" )
	if file then
		for n, sLine in ipairs( tLines ) do
			file:write( sLine .. "\n" )
		end
		file:close()
		return true
	end
	return false
end

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

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

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

local tMenuItems = { "Save", "Save&Exit", "Save Copy As", "Exit" }

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

	if not bMenu then
		term.write( sStatus )
	else
		for n,sItem in ipairs( tMenuItems ) do
			if n == nMenuItem then
				term.write( "["..sItem.."]" )
			else
				term.write( " "..sItem.." " )
			end
		end
	end
	
    term.setCursorPos( x - scrollX, y - scrollY )
end

local function setStatus( _sText )
	sStatus = _sText .. "    ["..x..":"..y.."]"
	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 )
end

load()

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

redrawText()
setStatus( "Press CTRL for menu" )

local menux, menuprompt, menuinput, promptcallback = nil, "", "", function() end

local function redrawMenuPrompt()
	menux = 1 + #menuprompt + #menuinput
	term.setCursorPos(1,h)
	term.clearLine()
	local minput =  menuinput
	if #minput + #menuprompt > w then minput = string.sub(minput,#minput-w+#menuprompt+1) end
	term.write(menuprompt..minput)
	term.setCursorBlink(true)
	term.setCursorPos(menux, h)
end

local function setupMenuPrompt( prompt, defaultval )
	if not defaultval then defaultval = "" end
	menuinput = defaultval
	menuprompt = prompt
	redrawMenuPrompt()
end


local function saveAs( prompt )
	term.setCursorPos(1,h-1)
	term.clearLine()
	term.write( prompt )
	setupMenuPrompt("File: ", "/"..sPath)
	promptcallback = function( fname )
		if #fname == 0 then
			setStatus( "error: invalid filename" )
			term.setCursorPos(1,h-1)
			term.clearLine()
			term.write( "error: invalid filename" )
			return false
		end
		if string.sub( fname, 1, 1 ) ~= "/" then
			fname = shell.resove(fname)
		end
		if save(fname) then
			return true
		else
			setStatus( "error: couldn't write to file" )
			term.setCursorPos(1,h-1)
			term.clearLine()
			term.write( "error: couldn't write to file" )
			return false
		end
	end
end

local bRunning = true
local tMenuFunctions = {
	["Exit"] = function()
		bRunning = false
	end,
	["Save&Exit"] = function()
		if save() then
			bRunning = false
		else
			while true do
				if saveAs( "error: Access denied" ) then
					bRunning = false
					break
				end
			end
		end
	end,
	["Save"] = function()
		if save() then
			setStatus( "Saved to "..sPath )
		else
			while true do
				if saveAs( "error: Access denied" ) then
					bRunning = false
					break
				end
			end
		end
	end,
	["Save Copy As"] = function()
		saveAs( "Choose new location: " )
	end,
}

local function doMenuItem( _n )
	local fnMenu = tMenuFunctions[ tMenuItems[_n] ]
	if fnMenu then
		fnMenu()
	end

	bMenu = false
	term.setCursorBlink( true )
	redrawMenu()
end


-- KEYS: 
-- up 200; down 208; left 203; right 205;
-- bspace 14; enter 28; Tab 15; Ctrl 29;
-- Del 211; PgUp 201; PgDn 209;  Ins 210

while bRunning do
  local sEvent, param = os.pullEvent()
  if sEvent == "key" then
    if param == 200 then
		-- Up
		if not bMenu then
			-- Move cursor up
			if y > 1 then
				y = y - 1
				x = math.min( x, string.len( tLines[y] ) + 1 )
				setCursor( x, y )
			end
		end
		
	elseif param == 208 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 == 203 then
		-- Left
		if not bMenu then
			-- Move cursor left
			if x > 1 then
				x = x - 1
				setCursor( x, y )
			end
		else
			-- Move menu left
			nMenuItem = nMenuItem - 1
			if nMenuItem < 1 then
				nMenuItem = #tMenuItems
			end
			redrawMenu()
		end
			
		
	elseif param == 205 then
		-- Right
		if not bMenu then
			-- Move cursor right
   		 	if x < string.len( tLines[y] ) + 1 then
				x = x + 1
				setCursor( x, y )
		  	end
		else
			-- Move menu right
			nMenuItem = nMenuItem + 1
		  	if nMenuItem > #tMenuItems then
				nMenuItem = 1
		  	end
		  	redrawMenu()
		end
	elseif param == 211 then
		if not bMenu then
			local sLine = tLines[y]
			if x < #sLine then
				tLines[y] = string.sub(sLine,1,x-1) .. string.sub(sLine,x+1)
				redrawLine()
			end
		end
	elseif param == 14 then
		-- Backspace
		if menux then
			menuinput = string.sub( menuinput, 1, #menuinput - 1 )
		elseif 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()
		
				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 == 28 then
		-- Enter
		if menux then
			menux = nil
			promptcallback( menuinput )
		elseif not bMenu then
			-- Newline
			local sLine = tLines[y]
			local sLineStart = string.sub(sLine,1,x-1)
			tLines[y] = sLineStart
			local tx = 1
			local spaces = -1
			while tx <= #sLineStart do
				if string.sub(sLineStart,tx,tx) ~= " " then spaces = tx - 1 break end 
				tx = tx + 1
			end
			if spaces == -1 then spaces = #sLineStart end
			
			local blocks = {
				["function"] = "end", 
				["then"] = "end", 
				["do"] = "end",
				["--[["] = "]]"
			}
			sLineStart = sLineStart:gsub("[,.:(){}]"," ")
			local ids = explode(" ", sLineStart)
			local tobeclosed = {}
			for k,v in pairs(ids) do 
				if blocks[v] then 
					spaces = spaces + tabWidth
					tobeclosed[#tobeclosed] = blocks[v]
				end
			end
			for k,v in pairs(ids) do
				for k2,v2 in pairs(tobeclosed) do
					if v2 == v then
						spaces = spaces - tabWidth
						tobeclosed[k2] = nil
						break
					end
				end
			end
			if string.sub( sLineStart, #sLineStart-2 ) == "end" then
				local c = 1
				while c < #sLineStart-2 do
					if string.sub( sLineStart, c, c ) ~= " " then
						c = -1
						break
					end
					c = c + 1
				end
				if #sLineStart-2>tabWidth then
					tLines[y] = string.rep(" ",#sLineStart-3-tabWidth).."end"
					spaces = spaces - tabWidth
				end
			end
					
			table.insert( tLines, y+1, string.rep(" ",spaces) .. string.sub(sLine,x) )
			redrawText()

			x = 1+spaces
			y = y + 1
			setCursor( x, y )		
			
		else
			-- Menu selection
			doMenuItem( nMenuItem )
		end
		
	elseif param == 15 then
		-- Tab
		if not bMenu then
			local sLine = tLines[y]
			tLines[y] = string.sub(sLine,1,x-1) .. string.rep( " ", tabWidth - (x-1)%tabWidth ) .. string.sub(sLine,x)
			redrawLine()
			x = x + tabWidth - (x-1)%tabWidth
			setCursor( x, y )
		end
	elseif param == 29 then
		-- Menu toggle
		bMenu = not bMenu
		if bMenu then
			term.setCursorBlink( false )
			nMenuItem = 1
		else
			term.setCursorBlink( true )
		end
		redrawMenu()
	end
	setStatus("Press CTRL for menu")
  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()
		
		x = x + string.len( param )
		setCursor( x, y )
		setStatus("Press CTRL for menu")
	else
		if menux then
			menuinput = menuinput .. param
			redrawMenuPrompt()
		else
			if(tostring(tonumber(param)) == param) and tMenuItems[tonumber(param)] then
				doMenuItem(tonumber(param))
			end
			-- 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
	end
  end
end



term.clear()
term.setCursorBlink( false )
term.setCursorPos( 1, 1 )