---
-- This Real Time Streaming Protocol (RTSP) library implements only a minimal
-- subset of the protocol needed by the current scripts.
--
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
-- @author Patrik Karlsson <patrik@cqure.net>
--
-- The library contains the following classes:
--
-- * <code>Request</code>
-- ** This class contains the functions needed to create the RTSP request
--
-- * <code>Response</code>
-- ** This class contains the functions needed to parse the RTSP response
--
-- * <code>Client</code>
-- ** This class contains the RTSP client, a class responsible for sending
--    and receiving requests and responses to/from the server
--
-- * <code>Helper</code>
-- ** This class serves as the main interface for script writers
--
-- The following sample code shows how to use the library:
-- <code>
--   local helper = rtsp.Helper:new(host, port)
--   local status = helper:connect()
--   local response
--   status, response = helper:describe(url)
--   helper:close()
-- </code>

--
-- Version 0.1
-- Created 10/23/2011 - v0.1 - Created by Patrik Karlsson
--

module(... or "rtsp", package.seeall)

-- The RTSP Request object
Request = {
	
	--- Creates a new Request instance
	-- @return o instance of Request
	new = function(self, url, headers)
		local o = { url = url, req = {}, headers = headers or {} }
       	setmetatable(o, self)
        self.__index = self
		return o
	end,
		
	--- Sets the RTSP Request method
	-- @param method string containing the RTSP method
	setMethod = function(self, method)
		self.method = method
	end,
	
	--- Sets the RTSP sequence number
	-- @param cseq number containing the sequence number
	setCSeq = function(self, cseq)
		self.cseq = cseq
	end,
	
	--- Adds an optional header to the RTSP request
	-- @param header string containing the header name
	-- @param value string containing the header value
	addHeader = function(self, header, value)
		table.insert( self.headers, { header = value } )
	end,
	
	--- Converts the Request to a string
	--
	-- @return req string containing the request as a string
	__tostring = function(self)
		assert(self.cseq, "Request is missing required header CSeq")
		assert(self.url, "Request is missing URL")
		
		local req = stdnse.strjoin("\r\n", { 
			("%s %s RTSP/1.0"):format(self.method, self.url), 
			("CSeq: %d"):format(self.cseq)
		} ) .. "\r\n"
		if ( #self.headers > 0 ) then
			req = req .. stdnse.strjoin("\r\n", self.headers) .. "\r\n"
		end
		
		return req .. "\r\n"
	end,	
}

-- The RTSP response instance
Response = {
	
	--- Creates a new Response instance
	-- @param data string containing the unparsed data 
	new = function(self, data)
		assert(data, "No data was supplied")
		local o = { 
			raw = data,
			status = tonumber(data:match("^RTSP%/1%.0 (%d*) "))
		 }

		-- Split the response into a temporary array
		local tmp = stdnse.strsplit("\r\n", data)
		if ( not(tmp) )	then return nil end
		
		-- we should have atleas one entry
		if ( #tmp > 1 ) then
			o.headers = {}
			for i=2, #tmp do
				-- if we have an empty line, this should be the end of headers
				if ( #tmp[i] == 0 ) then break end
				local key, val = tmp[i]:match("^(.-): (.*)$")
				-- create a key per header name
				o.headers[key] = val
			end
		end

       	setmetatable(o, self)
        self.__index = self
		return o
	end,
		
}


-- RTSP Client class
Client = {
	
	-- Creates a new Client instance
	-- @param host table as received by the action method
	-- @param port table as received by the action method
	-- @return o instance of Client
	new = function(self, host, port)
		local o = { 
			host = host,
			port = port,
			cseq = 0,
			headers = { },
			retries = 3,
			timeout = 10 * 1000,
		}
       	setmetatable(o, self)
        self.__index = self
		return o
	end,
	
	--- Sets the number of retries for socket reads
	-- @param retries number containing the number of retries
	setRetries = function(self, retries) self.retries = retries end,
	
	--- Sets the socket connection timeout in ms
	-- @param timeout number containing the timeout in ms
	setTimeout = function(self, timeout) self.timeout = timeout end,
	
	--- Adds a RTSP header to the request
	-- @param header string containing the header name
	-- @param value string containing the header value
	addHeader = function(self, header, value)
		table.insert(self.headers, { ("%s: %s"):format(header,value) } )
	end,
	
	--- Connects to the RTSP server
	-- @return status true on success, false on failure
	-- @return err string containing the error message on failure
	connect = function(self)
		self.socket = nmap.new_socket()
		self.socket:set_timeout(self.timeout)
		local status = self.socket:connect(self.host, self.port)
		if ( not(status) ) then
			stdnse.print_debug(2, "Failed to connect to the server: %s", self.host.ip)
			return false, ("Failed to connect to the server: %s"):format(self.host.ip)
		end
		return true
	end,	
	
	--- Sends a DESCRIBE request to the server and receives the response
	-- @param url string containing the RTSP URL
	-- @return status true on success, false on failure
	-- @return response Response instance on success
	--         err string containing the error message on failure
	describe = function(self, url)
		local req = Request:new(url, self.headers)
		req:setMethod("DESCRIBE")
		return self:exch(req)
	end,
	
	options = function(self, url)
		local req = Request:new(url, self.headers)
		req:setMethod("OPTIONS")
		return self:exch(req)
	end,
	
	--- Sends a request to the server and receives the response and attempts
	--  to retry if either send or receive fails. 
	-- @param request instance of Request
	-- @return status true on success, false on failure
	-- @return response Response instance on success
	--         err string containing the error message on failure
	exch = function(self, req)
		local retries = self.retries
		local status, data
		self.cseq = self.cseq + 1
		req:setCSeq( self.cseq )
		
		repeat
			local err
			status, err = self.socket:send( tostring(req) )
			-- check if send was successfull, in case it wasn't AND
			-- this is our last retry, ABORT
			if ( not(status) and 0 == retries - 1 ) then
				stdnse.print_debug(2, "Failed to send request to server (%s)", err)
				return false, ("Failed to send request to server (%s)"):format(err)
			-- if send was successfull, attempt to receive the response
			elseif ( status ) then
				status, data = self.socket:receive()
				-- if we got the response allright, break out of retry loop
				if ( status ) then break end
			end			
			-- if either send or receive fails, re-connect the socket
			if ( not(status) ) then
				self:close()
				local status, err = self:connect()
				-- if re-connect fails, BAIL out of here
				if ( not(status) ) then
					stdnse.print_debug(2, "Failed to reconnect socket to server (%s)", err)
					return false, ("Failed to reconnect socket to server (%s)"):format(err)
				end
			end	
			retries = retries - 1
		until( status or retries == 0 )

		if( not(status) ) then
			stdnse.print_debug(2, "Failed to receive response from server (%s)", data)
			return false, ("Failed to receive response from server (%s)"):format(data)
		end
			
		return true, Response:new(data)
	end,
		
	--- Closes the RTSP socket with the server
	close = function(self)
		return self.socket:close()
	end,
	
}

-- The Helper class is the main script interface
Helper = {
	
	-- Creates a new Helper instance
	-- @param host table as received by the action method
	-- @param port table as received by the action method
	-- @return o instance of Client
	new = function(self, host, port)
		local o = { host = host, port = port, client = Client:new(host, port) }
       	setmetatable(o, self)
        self.__index = self
		return o
	end,
	
	-- Connects to the RTSP server
	-- @return status true on success, false on failure
	-- @return err string containing the error message on failure
	connect = function(self)
		return self.client:connect()
	end,
	
	-- Closes the RTSP socket with the server
	close = function(self)
		return self.client:close()
	end,
	
	-- Sends a DESCRIBE request to the server and receives the response
	--
	-- @param url string containing the RTSP URL
	-- @return status true on success, false on failure
	-- @return response string containing the unparsed RTSP response on success
	--         err string containing the error message on failure
	describe = function(self, url)
		return self.client:describe(url)
	end,
	
	options = function(self, url)
		return self.client:options(url)
	end,
	
}