#!/usr/bin/lua5.2
telemver = "0.3 // 2018-05-04"

file = require("pl.file")
io = require("io")
lfs = require("lfs")
os = require("os")
path = require("pl.path")
string = require("string")
table = require("table")

_BBS_ROOT = "/var/bbs/"

-- Global var declarations
-- (Not actually required by Lua, just here to make the design clear/explicit)

username = os.getenv("USER")	-- TODO: This is, obviously, not secure and will need to be updated
boards = {}			-- Array of board names, alphaetically sorted
board_names = {}		-- Set of board names, must always be consistent with boards
current_board = ""		-- String, name of current board, must be in boards and board_names
current_board_threads = {}	-- Array of thread tables, containing threads associated with current_board
current_thread = {}		-- Active thread table, always an element of current_board_threads
current_thread_posts = {}	-- Array of post tables, containing posts associated with current_thread
current_post_index = nil	-- Integer index into current_thread_posts

-- Utility functions

function cat_file(filename)
	io.write(file.read(filename))
end

function getchar()
	os.execute("/bin/stty -icanon")
	local char = io.read(1)
	os.execute("/bin/stty icanon")
	return char
end

-- Internals

function update_boards()
	for board in lfs.dir(path.join(_BBS_ROOT, "boards")) do
		if string.sub(board, 1, 1) ~= "." and not board_names[board] then
			board_names[board] = true
			table.insert(boards, board)
		end
	end
	table.sort(boards)
end

function get_threads(board)
	local threads = {}
	for threaddir in lfs.dir(path.join(_BBS_ROOT, "boards", board)) do
		if string.sub(threaddir, 1,1) == "." then goto continue end
		if threaddir == "topic" then goto continue end
		local thread = {}
		thread.directory = path.join(_BBS_ROOT, "boards", board, threaddir)
		_, _, timestamp, thread.author = string.find(threaddir, "(%d+)-(%g+)")
		thread.timestamp = tonumber(timestamp)

		io.input(path.join(thread.directory, "subject"))
		thread.subject = io.read("*line")
		io.input(io.stdin)

		local posts = get_posts(thread)
		thread.post_count = #posts
		thread.updated = 0
		for _, post in ipairs(posts) do
			if post.timestamp > thread.updated then
				thread.updated = post.timestamp
			end
		end
		table.insert(threads, thread)
		::continue::
	end
	table.sort(threads, function(x,y) return x.updated > y.updated end)
	return threads
end

function get_posts(thread)
	local posts = {}
	for postfile in lfs.dir(thread.directory) do
		if string.sub(postfile, 1,1) == "." then goto continue end
		if postfile == "subject" then goto continue end
		local post = {}
		post.filename = path.join(thread.directory, postfile)
		_, _, timestamp, post.author = string.find(postfile, "(%d+)-(%a+)")
		post.timestamp = tonumber(timestamp)
		table.insert(posts, post)
		::continue::
	end
	table.sort(posts, function(x,y) return x.timestamp < y.timestamp end)
	return posts
end

-- Commands

function do_board()
	-- Creates a new (empty) board

	-- Get details
	io.write("New board name? (Max 18 chars) ")
	local board = string.upper(io.read())
	if string.len(board) > 18 then
		print("Board names must be 18 characters or less!")
		return
	end
	io.write("Description? ")
	local desc = io.read()
	-- Create directory
	local board_dir = path.join(_BBS_ROOT, "boards", board)
	lfs.mkdir(board_dir)
	-- Write topic file
	local topic_file = path.join(board_dir, "topic")
	file.write(topic_file, desc)
	-- Update representation of BBS
	board_names[board] = true
	table.insert(boards, board)
	table.sort(boards)
	-- Done!
	print("Board created.")
end

function do_go()
	io.write("Go to which board? ")
	local board = string.upper(io.read())
	if board == "" then
		do_list()
	elseif board_names[board] == nil then
		print("No such board!  Hit `l` to list boards.")
	else
		current_board = board
		current_board_threads = get_threads(current_board)
	end
end

function do_help()
	cat_file(path.join(_BBS_ROOT, "docs", "help"))
end

function do_help2()
	cat_file(path.join(_BBS_ROOT, "docs", "help2"))
end

function do_list()
	update_boards()
	for _,b in ipairs(boards) do
		local threads = -3 -- Don't want to count "topic" file or "." or ".."
		for topic in lfs.dir(path.join(_BBS_ROOT, "boards", b)) do
			threads = threads +1
		end
		print(string.format("%s    [%d threads]", b, threads))
	end
end

function do_messages()
	if current_board == "" then
		print("Not at any board!  Hit `l` to list boards, `g` to go to one.")
	else
		current_board_threads = get_threads(current_board)
		for i, thread in ipairs(current_board_threads) do
			print(tostring(i), os.date("%x %H:%M", thread.timestamp), thread.author, thread.subject, "("..tostring(thread.post_count).." posts)")
		end
	end
end

function do_new()
	if current_board == "" then
		print("Not at any board!")
		return
	end
	-- Get subject for new thread
	io.write("Subject? ")
	local subject = io.read()
	if string.len(subject) > 48 then
		print("Thread subjects must be 48 characters or less!")
		return
	end
	-- Save body of post to temp file
	local filename = os.tmpname()
	os.execute("$EDITOR " .. filename)
	-- TODO: show and confirm
	-- Make thread dir
	local timestamp = tostring(os.time())
	local thread_dir = timestamp .. "-" .. username
	local thread_path = path.join(_BBS_ROOT, "boards", current_board, thread_dir)
	lfs.mkdir(thread_path)
	-- Write subject file
	file.write(path.join(thread_path, "subject"),
		subject)
	-- Move post file
	local post_file = thread_dir -- first post and thread directory names are the same!
	local newpath = path.join(thread_path, post_file)
	local ret, str = file.move(filename, newpath)
	if not ret then
		print(str)
	end
	-- Done!
	print("Post submitted.")
end

-- The "type" command is implemented using multiple functions
-- do_type is the entry point, which runs a command dispatch loop that
-- runs various do_type_xxx functions.

function do_type_first()
	current_post_index = 1
	do_type_show_post()
end

function do_type_last()
	current_post_index = #current_thread_posts
	do_type_show_post()
end

function do_type_next()
	if current_post_index ~= #current_thread_posts then
		current_post_index = current_post_index + 1
	end
	do_type_show_post()
end

function do_type_prev()
	if current_post_index ~= 1 then
		current_post_index = current_post_index - 1
	end
	do_type_show_post()
end

function do_type_reply()
	local filename = os.tmpname()
	os.execute("$EDITOR " .. filename)
	local timestamp = tostring(os.time())
	local newfilename = timestamp .. "-" .. username
	local newpath = path.join(current_thread.directory, newfilename)
	local ret, str = file.move(filename, newpath)
	if not ret then
		print(str)
	end
	current_thread_posts = get_posts(current_thread)
	current_post_index = #current_thread_posts
	do_type_show_post()
end

function do_type_show_post()
	local post = current_thread_posts[current_post_index]
	print("SUBJECT:    " .. current_thread.subject)
	print("AUTHOR:     " .. post.author)
	print("POSTED:     " .. os.date("%H:%M %B %d, %Y", post.timestamp))
	print("--------------------------------")
	cat_file(post.filename)
	print("--------------------------------")
	print(string.format("Viewing post %d of %d in thread", current_post_index, #current_thread_posts))
end

type_dispatch = {}
type_dispatch["f"] = do_type_first
type_dispatch["l"] = do_type_last
type_dispatch["n"] = do_type_next
type_dispatch["p"] = do_type_prev
type_dispatch["r"] = do_type_reply
type_dispatch["d"] = function() return end

function do_type()
	io.write("Read which thread? ")
	local thread_id = tonumber(io.read())
	if not thread_id or thread_id < 0 or thread_id > #current_board_threads then
		print("Invalid thread index!")
		return
	end
	current_thread = current_board_threads[thread_id]
	current_thread_posts = get_posts(current_thread)
	current_post_index = #current_thread_posts
	do_type_show_post()
	repeat
		-- Show prompt and read one char
		io.write("[f]irst, [n]ext, [p]rev, [l]last, [r]eply, [d]one > ")
		c = getchar()
		if c ~= "\n" then io.write("\n") end
		-- Dispatch to sub-command
		if c == "\n" then
			-- pass
		elseif type_dispatch[c] == nil then
			print("Invalid command!")
		elseif c ~= "\n" then
			type_dispatch[c]()
		end
	until c == "d"
end

-- end of "type" command implementation

function do_quit()
	print("Goodbye!")
end

function do_reply()
	if current_board == "" then
		print("Not at any board!")
		return
	end
	io.write("Reply to which thread? ")
	local thread_id = tonumber(io.read())
	if not thread_id or thread_id < 0 or thread_id > #current_board_threads then
		print("Invalid thread index!")
		return
	end
	current_thread = current_board_threads[thread_id]
	current_thread_posts = get_posts(current_thread)
	current_post_index = #current_thread_posts
	do_type_reply()
end

function do_rules()
	cat_file(path.join(_BBS_ROOT, "docs", "rules"))
end

function do_unimplemented()
	print("Sorry, this command is not (yet) implemented!")
end

function do_who()
	os.execute("/usr/bin/w")
end

-- MAIN PROGRAM BODY BELOW

-- Show welcome message
print("::::::::::: This is telem ver."..telemver.." :::::::::::")
cat_file(path.join(_BBS_ROOT, "docs", "welcome"))

-- Initialise global vars representing BBS state
update_boards()

-- Build dispatch table mapping chars to functions
dispatch = {}
dispatch["h"] = do_help
dispatch["g"] = do_go
dispatch["l"] = do_list
dispatch["m"] = do_messages
dispatch["q"] = do_quit
dispatch["t"] = do_type
dispatch["?"] = do_help2
dispatch["!"] = do_rules
dispatch["w"] = do_who
dispatch["s"] = do_unimplemented
dispatch["="] = do_unimplemented
dispatch["M"] = do_unimplemented
dispatch["n"] = do_new
dispatch["r"] = do_reply
dispatch["b"] = do_board
dispatch["c"] = do_unimplemented

-- Infinite loop of command dispatch
repeat
	-- Show prompt and read 1 char from keyboard
	io.write("["..current_board.."] COMMAND :> ")
	c = getchar()
	if c ~= "\n" then io.write("\n") end
	-- Use char as index into dispatch table
	if c == "\n" then
		-- pass
	elseif dispatch[c] == nil then
		print("Unrecognised command, hit `h` for help.")
	else
		dispatch[c]()
	end
until c == "q"