jserver.d

import vibe.d;
import core.time;
import std.stdio;


TCPConnection[] workers;
bool logging;

shared static this()
{
    logging = false;
    runTask({
        writeln("Start worker connector");
        listenTCP_s(8011, &worker_handler);
    });

    writeln("Start client connector");
    listenTCP_s(8010, &handler);
}

struct Block {
    ubyte code;
    uint size;
    ubyte[] buf;
}

uint readBlock(TCPConnection conn, Block *block) {
    ubyte[4] buf;
    if(!conn.waitForData(dur!"seconds"(100L))) {
        writeln("Read head timeout");
        return 1;
    }
    conn.read(buf);    

    block.code = buf[0];
    block.size = buf[1] + (buf[2] << 8) + (buf[3] << 16);
    block.buf = new ubyte[block.size];

    if(!conn.waitForData(dur!"seconds"(100L))) {
        writeln("Read body timeout");
        return 1;
    }

    conn.read(block.buf);
    return 0;
};


uint writeBlock(TCPConnection conn, Block *block) {
    ubyte[4] head;
    uint size = block.size;

    head[0] = block.code;
    head[1] = size & 0xff;
    head[2] = (size & 0xff00) >> 8;
    head[3] = (size & 0xff0000) >> 16;

    conn.write(head);
    conn.write(block.buf);
    return 0;
}

void worker_handler(TCPConnection conn) {
    writeln("Worker connected");

    Block block;
    if(readBlock(conn, &block)) return;

    workers ~= conn;

    while(conn.connected){
        sleep(500.msecs);
    }
    writeln("Worker disconected");
}

void handler(TCPConnection conn) {
    writeln("Client connected");
    TCPConnection worker;
    while(conn.connected){
        Block req;
        if(logging) { writeln("Read client"); }
        
        if(readBlock(conn, &req)) return;
        req.code = 15;

        if(logging) { writeln(1, workers); }
        // wait worker
        while(workers.length == 0) {
            sleep(1.msecs);
        }
        worker = workers[$-1];
        workers.length -= 1;
        if(logging) { writeln(2, workers); }

        if(logging) { writeln("Write worker"); }
        writeBlock(worker, &req);

        if(logging) { writeln("read worker"); }
        Block resp;
        if(readBlock(worker, &resp)) {
            writeln("Error read worker");
            return;
        }
        workers ~= worker;  // send worker to queue
        if(logging) { writeln("Write client"); }
        writeBlock(conn, &resp);

        if(logging) { writeln("loop end"); }
    }

}