module redis.connection;

import std.socket : TcpSocket;

import std.array : appender, back, popBack;
import std..string : format;
public import redis;
import redis.response;

debug(redis) {
	import std.stdio : writeln;
	import redis.encoder : escape;
}

public:

/**
 * Sends a pre-encoded string
 *
 * Params:
 *   conn     	 = Connection to redis server.
 *   encoded_cmd = The command to be sent.
 *
 * Throws: $(D ConnectionException) if sending fails.
 */
void send(TcpSocket conn, string encoded_cmd)
{
	debug(redis) { writeln("Request : '", escape(encoded_cmd) ~ "'"); }

	auto sent = conn.send(encoded_cmd);
	if (sent != (cast(byte[])encoded_cmd).length)
		throw new ConnectionException("Error while sending request");
}

/**
 * Receive responses from redis server
 *
 * Params:
 *   conn    	  = Connection to redis server.
 *   minResponses = The number of multibulks you expect
 *
 * Throws: $(D ConnectionException) if there is a socket error or server closes the connection.
 */
Response[] receiveResponses(TcpSocket conn, size_t minResponses = 0)
{
	byte[] buffer;
	Response[] responses;
	Response*[] MultiBulks; //Stack of pointers to multibulks
	Response[]* stackPtr = &responses;

	while(true)
	{
		receive(conn, buffer);

		debug(redis) { writeln("BUFFER : ", escape(cast(string)buffer)); }

		while(buffer.length > 0)
		{
			auto r = parseResponse(buffer);
			debug(redis) { writeln(__FUNCTION__,"\t",r.type,"\t",typeid(r));}	
			if(r.type == ResponseType.Invalid)
				break;

			*stackPtr ~= r;
			if(r.isMoved)
			{
				break;
			}
			if(r.type == ResponseType.MultiBulk)
			{
				auto mb = &((*stackPtr)[$-1]);
				if(mb.count > 0)
				{
					MultiBulks ~= mb;
					stackPtr = &((*mb).values);
				}
			}
			else
				while(MultiBulks.length > 0)
				{
					auto mb = *(MultiBulks.back);

					if(mb.count == mb.values.length)
					{
						MultiBulks.popBack();

						if(MultiBulks.length > 0)
							stackPtr = &((*MultiBulks.back).values);
						else
							stackPtr = &responses;
					}
					else
						break;
				}
		}

		if(buffer.length == 0 && MultiBulks.length == 0) //Make sure all the multi bulks got their data
		{
			debug(redis) {
				if(minResponses > 1 && responses.length < minResponses)
					writeln("WAITING FOR MORE RESPONSES ... ");
			}

			if(responses.length < minResponses)
				continue;

			break;
		}

	}

	debug(redis) { writeln(__FUNCTION__,"\tlen:",responses.length,"\t",responses);}
	return responses;
}

/* -------- EXCEPTIONS ------------- */

class ConnectionException : Exception {
	this(string msg) { super(msg); }
}


private :

void receive(TcpSocket conn, ref byte[] buffer)
{
	byte[1024 * 16] buff;
	size_t len = conn.receive(buff);

	if (conn.blocking)
	{
		if(len == 0)
			throw new ConnectionException("Server closed the connection!");
		else if(len == TcpSocket.ERROR)
			throw new ConnectionException("A socket error occurred!");
	}
	else
	{
		if (len == -1)
		{
			import core.stdc.errno;

			if (errno == EWOULDBLOCK)
			{
				len = 0;
				errno = 0;
			}
			else
				throw new ConnectionException(format("A socket error occurred! errno: %s", errno));
		}
	}

	buffer ~= buff[0 .. len];
	debug(redis) { writeln("Response : ", "'" ~ escape(cast(string)buffer) ~ "'", " Length : ", len); }
}