local mt = {}

mt.newPool = function(pool_options)
	pool_options = pool_options or {}
	local pool = {}
	pool.threads = {} -- indexed by coroutines, contains their metadata
	pool.namedThreads = {} -- indexed by coroutine names, contains their metadata also.
	pool.byID = {} -- aaaa bees
	-- coroutines are named if their metadata has a name field.
	pool.threadcount = 0 -- used for detecting when all things in a pool are depleted
	pool.id = math.random(1,99999999999999)
	pool.clear = function()
		pool.threads = {}
		pool.namedThreads = {}
		pool.threadcount = 0
	end
	local idcount = 0
	
	pool.add = function(fn, options)
		options = options or {}
		options.co = coroutine.create(function() local retv = fn(options) if retv~=nil then options.retv=retv end os.queueEvent("ignore_this") end)
		options.fn = fn
		options.id = idcount
		idcount = idcount + 1
		pool.threads[options.co] = options
		if options.name then
			pool.namedThreads[options.name] = options
		end
		pool.byID[options.id] = options
		pool.threadcount = pool.threadcount + 1
		os.queueEvent("pool_fn_added",options,pool)
		return options.co
	end
	
	pool.rm = function(name)
		local tr = nil
		if type(name) == "string" then
			if not pool.namedThreads[name] then
				error("no thread with name "..name)
			end
			tr = pool.namedThreads[name]
		elseif type(name)=="number" then
			if not pool.byID[name] then
				error("no thread with ID "..name)
			end
			tr = pool.byID[name]
		else
			tr = name
		end
		tr = pool.byID[tr.id]
		os.queueEvent("pool_fn_end",tr.id,pool.id) 		
		pool.threads[tr.co] = nil
		if type(name)=="string" then pool.namedThreads[name] = nil end
		pool.byID[name] = nil
		pool.threadcount = pool.threadcount - 1
		
		return true
	end
	
	pool.addFile = function(filename, options)
		pool.add(function()
			dofile(filename)
		end,options)
	end
	
	pool.run = function(terminable)
		terminable = terminable or true -- if false, terminate events will be echoed to coroutines instead of 
		-- terminating this pool
		while true do
			local event = {coroutine.yield()}
			if event[1] == "terminate" and terminable then
				return
			end
			for thread, options in pairs(pool.threads) do
				if coroutine.status(thread) ~= "dead" then
					if event[1] == options.filter or options.filter == nil then
						local x,e,y = coroutine.resume(thread,unpack(event))
						options.filter = y
						if not x then
							os.queueEvent("pool_fn_crash",options.id,pool.id,e)
							pool.rm(options)
							if pool_options.crash_on_error then
								error(e)
							end
						end
					end
				else
					pool.rm(options)
				end
			end
			if pool.threadcount == 0 then return end
		end
	end
	
	pool.await = function(...)
		local args = {...}
		local retv = {}
		for i,v in ipairs(args) do
			local to_match = nil
			if type(v) == "table" then
				to_match = v.id
			elseif type(name)=="number" then
				if not pool.byID[name] then
					error("no thread with ID "..name)
				end
				to_match = name
			else
				if not pool.namedThreads[v] then
					error("no thread named "..v)
					return
				end
				to_match = pool.namedThreads[v].id
			end
			if coroutine.status(pool.byID[to_match].co) == "dead" then
				table.insert(retv, pool.byID[to_match].retv)
			else
				while true do
					local e, b, c, d = os.pullEvent()
					if (e=="pool_fn_end" or e=="pool_fn_crash") then
						if c == pool.id and b == to_match then
							table.insert(retv, pool.byID[b].retv)
							break
						end
					end
				end
			end
		end
		return unpack(retv)
	end
	pool.await_any = function(...)
		local args = {...}
		local match = {}
		for i,v in ipairs(args) do
			local to_match = nil
			if type(v) == "table" then
				to_match = v.id
			elseif type(name)=="number" then
				if not pool.byID[name] then
					error("no thread with ID "..name)
				end
				to_match = name
			else
				if not pool.namedThreads[v] then
					error("no thread named "..v)
					return
				end
				to_match = pool.namedThreads[v].id
			end
			if coroutine.status(pool.byID[to_match].co) == "dead" then
				return pool.byID[to_match].retv
			end
			table.insert(match,to_match)
		end
		while true do
			local e, b, c, d = os.pullEvent()
			if e=="pool_fn_end" and c == pool.id then
				for i,v in ipairs(match) do
					if b == v then
						return pool.byID[v].retv
					end
				end
			end
		end
	end
	return pool
end

return mt