local chats = {}

-- File path for saving chats
filePath = "chats.txt"
userFilePath = "users.txt"

adminu = "username"
adminp = "password"

local function getFirstWord(str)
    local firstWord = str:match("^(%S+)")
    return firstWord
end

function twoInputStrip(str)
    first, second = str:match("(%S+)%s+(%S+)")
    return first, second
end

function threeInputStrip(str)
    first, second, third = str:match("(%S+)%s+(%S+)%s+(%S+)")
    return first, second, third
end

function fourInputStrip(str)
    local first, second, third, fourth = str:match("(%S+)%s+(%S+)%s+(%S+)%s+(.*)")
    return first, second, third, fourth
end

local function cutSpaces(str)
    local substrings = {}
    for substring in str:gmatch("%S+") do
        table.insert(substrings, substring)
    end
    return substrings
end

-- Function to save chats to a file
local function saveChats()
    local file = fs.open(filePath, "w")
    file.write(textutils.serialize(chats))
    file.close()
    print("Chats saved.")
end

-- Function to print the first key of each sub-array
local function getChannelIds()
	chatnames = {}
    for _, subArray in ipairs(chats) do
        for chatname, _ in pairs(subArray) do
			print(chatname)
            table.insert(chatnames, chatname)
            break  -- Only print the first key
        end
    end
	return chatnames
end

-- Function to save chats to a file
local function addUser(user, userID)
    local file = fs.open(userFilePath, "a")
    file.writeLine(user .. " " .. userID)
    file.close()
    print("Users saved.")
end

-- Function to save chats to a file
local function removeUser(user, userID)
    success = false
	if fs.exists(userFilePath) then
		local file = fs.open(userFilePath, "r")
		local line = file.readLine()
    	while line do
			print(line)
			name = twoInputStrip(line)
			if name == user then
				success = true
			else
				table.insert(newfile, line)
			end
			line = file.readLine()
		end
		file.close()
		file = fs.open(userFilePath, "w")
		for _, line in pairs(newfile) do
			file.writeLine(line)
		end
		file.close()
	end
	return success
end

local function findUser(user)
    if fs.exists(userFilePath) then
        local file = fs.open(userFilePath, "r")
        if file then
            line = file.readLine()
            while line do
                local name, nid = twoInputStrip(line)
                if name ~= nil and name == user then
                    file.close()
                    return nid
                end
				line = file.readLine()
            end
            file.close()
        end
    end
    return nil
end

local function checkChat(chat, ruser)
    users = cutSpaces(chat[1])
    for _, user in pairs(users) do
	    if user == ruser then
	        return true
        end
	end
    return false
end

local function getUsersChats(chats, newruser)
	userchats = {}
	newid = findUser(newruser)
    if newid == nil then
	    return "no"
	end
	for chatname, array in pairs(chats) do
		if checkChat(chats[chatname], newruser) then
			table.insert(userchats, chatname)
		end
	end
	if userchats == nil then
    	return "none"
    else
	    return userchats
   	end
	return nil
end

local function ping(chatID)
	users = cutSpaces(chats[chatID][1])
	for _, user in pairs(users) do
		userid = findUser(user)
		if userid ~= nil then
			rednet.send(tonumber(userid), "update")
		end
	end
end

-- Function to load chats from a file
local function loadChats()
    if fs.exists(filePath) then
        local file = fs.open(filePath, "r")
        local content = file.readAll()
        chats = textutils.unserialize(content) or {}
        file.close()
        print("Chats loaded.")
		return chats
    else
        print("No saved chats found.")
		return nil
    end
end

-- Function to handle creating a new chat
local function handleCreateChat(chatID, username)
    if not chats[chatID] and username ~= nil then
        chats[chatID] = {username .. " "}
        print("Chat " .. chatID .. " created.")
        saveChats()
		return "true"
    else
        print("Chat " .. chatID .. " already exists.")
		return "exists"
    end
end

-- Function to save chats to a file
local function handleAddUser(user, chatID)
	if chats[chatID] then
    	chats[chatID][1] = chats[chatID][1] .. user .. " "
		local wfile = fs.open(filePath, "w")
    	wfile.write(textutils.serialize(chats))
    	wfile.close()
		return "true"
    end
	return nil
end

-- Function to save chats to a file
local function handleRemoveUser(username, ruser, chatID)
	print(chats[chatID][1])
	owner = getFirstWord(chats[chatID][1])
	if owner ~= nil and owner == username then
		if chats[chatID] then
    		users = cutSpaces(chats[chatID][1])
			for _, user in pairs(users) do
				if user == ruser then
					chats[chatID][1] = chats[chatID][1]:gsub("%f[%a]" .. user .. "%f[%A]%s*", "")
					local wfile = fs.open(filePath, "w")
	    			wfile.write(textutils.serialize(chats))
    				wfile.close()
					return "true"
				end
			end
		end
    end
	return nil
end

-- Function to handle deleting a chat
local function handleDeleteChat(chatID, username)
    if chats[chatID] then
		owner = getFirstWord(chats[chatID][1])
		if owner ~= nil and owner == username then
        	chats[chatID] = nil
        	print("Chat " .. chatID .. " deleted.")
        	saveChats()
			return "true"
		end
		return "denied"
    else
        print("Chat " .. chatID .. " does not exist.")
		return nil
    end
end

-- Function to handle incoming messages
local function handleIncomingMessage(chatID, username, text)
    if not chats[chatID] then
        print("Chat " .. chatID .. " does not exist.")
        return nil
    end
    table.insert(chats[chatID], username .. ": " .. text)
    print("Message in chat " .. chatID .. " from " .. username .. ": " .. text)
    saveChats()
	return "true"
end

-- Function to print all messages in a chat
local function printChatMessages(chatID)
    if not chats[chatID] then
        print("Chat " .. chatID .. " does not exist.")
        return nil
    end

    term.clear()
    term.setCursorPos(1, 1)
    for _, line in ipairs(chats[chatID]) do
        print(line)
    end
	return "true"
end

local function messageRequests()
	-- Main server loop
	while true do
	    id, message = rednet.receive()
    	command = twoInputStrip(message)
	    if command == "create" then
			command, chatid, username = threeInputStrip(message)
			newid = findUser(username)
        	if newid == nil then
				addUser(username, id)
			elseif newid ~= id then
				removeUser(username, newid)
				addUser(username, id)
			end
			success = handleCreateChat(chatid, username)
			rednet.send(id, success)
		elseif command == "add" then
			success = nil
			command, chatid, username, nusername = fourInputStrip(message)
			if findUser(nusername) == nil then
				print("User does not Exist")
			end
			print(handleAddUser(nusername, chatid))
			rednet.send(id, success)
	
		elseif command == "remove" then
			command, chatid, username, ruser = fourInputStrip(message)
			success = handleRemoveUser(username, ruser, chatid)
			rednet.send(id, success)

	    elseif command == "delete" then
			command, chatid, username, dusername = fourInputStrip(message)
			success = handleDeleteChat(chatid, dusername)
			rednet.send(id, success)

	    elseif command == "send" then
			command, chatid, username, text = fourInputStrip(message)
        	success = handleIncomingMessage(chatid, username, text)
	        if success == "true" then
				ping(chatid)
			end
			rednet.send(id, success)

    	elseif command == "retrieve" then
			command, chatid, ruser = threeInputStrip(message)
	        if chats[chatid] then
				rsuccess = false
				users = cutSpaces(chats[chatid][1])
            	for _, user in pairs(users) do
                	if user == ruser then
    	        		rednet.send(id, chats[chatid])
						rsuccess = true
						break
					end
				end
				if not rsuccess then
					rednet.send(id, "false")
				end
        	else
            	rednet.send(id, nil)
        	end
		elseif command == "find" then
			command, user = twoInputStrip(message)
			rednet.send(id, findUser(user))		
    	elseif command == "chats" then
			command, user = twoInputStrip(message)
			rednet.send(id, getUsersChats(chats, user))
		end
	end
end

local function displayOptions()
	print("1. Display ChatID's")
	print("2. Display Chat")
	print("3. Display Users")
	print("4. Add User to Chat")
	print("5. Remove User to Chat")
	print("6. Get User's Chats")
	print("7. Exit to Login")
	print("8. Exit to OS")
end

local function userSwitch(choice, chats)
	if choice == 1 then
		print("\n")
		for idname, array in pairs(chats) do
			print(idname)
		end
		read()
		return 1
	elseif choice == 2 then
		print("Input Chat ID")
		newid = read()
		
		scrollPosition = 1
		maxLines = 15
    	local startIndex = math.max(1, scrollPosition)
    	local endIndex = math.min(#chats[newid], scrollPosition + maxLines - 1)
    	
    	while true do
        	term.clear()
	
    	    -- Display the database content after the instruction
    	    for i = startIndex, endIndex do
    	        print(chats[newid][i])
        	end
        
	        local event, key = os.pullEvent("key")
    	    if key == keys.up then
        	    scrollPosition = math.max(1, scrollPosition - 1)
 	       elseif key == keys.down then
    	        scrollPosition = math.min(#chats[newid] - maxLines + 1, scrollPosition + 1)
    	    elseif key == keys.backspace then
        	    break  -- Exit loop on backspace key press
      		end
 
        	startIndex = math.max(1, scrollPosition)
        	endIndex = math.min(#chats[newid], scrollPosition + maxLines - 1)
    	end
		return 2
	elseif choice == 3 then
		if fs.exists(userFilePath) then
			local file = fs.open(userFilePath, "r")
			local line = file.readLine()
    		while line do
				print(line)
				line = file.readLine()
			end
		end
		read()
		return 3
	elseif choice == 4 then
		print("User to Add")
		nusername = read()
		print("Chat ID: ")
		chatid = read()
		print(handleAddUser(nusername, chatid))
		read()
		return 4
	elseif choice == 5 then
		print("User to Remove")
		ruser = read()
		print("Chat ID: ")
		chatid = read()
		handleRemoveUser(getFirstWord(chats[chatid][1]), ruser, chatid)
		read()
		return 5
	elseif choice == 6 then
		print("Enter Username: ")
		newruser = read()
		chatnames = getUsersChats(chats, newruser)
		if chatnames == "no" then
			print("No User Found")
			read()
		elseif chatnames == "none" then
			print("No Chat's Found")
			read()
		else
			for _, chatname in pairs(chatnames) do
   				print(chatname)
    		end
			read()
		end
		return 6
	elseif choice == 7 then
		term.clear()
		return 7
	elseif choice == 8 then
		term.clear()
		return 8
	else
		print("Incorrect Input")
		return -1
	end
end

local function login(chats)
	while true do
		print("Enter Username: ")
		u = read()
		print("Enter Password: ")
		p = read('*')
		if u == adminu and p == adminp then
			while true do
				displayOptions()
				result = tonumber(read())
				userSwitch(result, chats)
				if result == 7 or result == 8 then
					break
				end
				shell.run("clear")
			end
			if result == 8 then
				break
			end
		end
	end
end

shell.run("clear")
loadChats()
rednet.open("top")
parallel.waitForAny(
	function() messageRequests() end,
	function() login(chats) end
)