#pragma once

#include "types.h"

// Unix domain sockets.
//
// These exist for Schcom. A compositor and its clients have to exchange
// messages, and a pipe cannot do it: a pipe is one-directional, has no
// notion of a connection, and gives no way for a server to be *found* by a
// client that starts later. A socket with a name in the filesystem is
// exactly the missing piece.
//
// AF_INET is deliberately absent. The socket layer is being built around the
// local case first because that is the one the GUI needs and the one whose
// semantics are simplest; a network stack plugs in underneath the same
// syscalls later rather than reshaping them.

#define AF_UNIX         1
#define AF_LOCAL        1
#define AF_INET         2       // recognised so it can be refused honestly

#define SOCK_STREAM     1
#define SOCK_DGRAM      2

#define UNIX_PATH_MAX   108

#define SHUT_RD         0
#define SHUT_WR         1
#define SHUT_RDWR       2

struct sockaddr_un {
  uint16 sun_family;
  char   sun_path[UNIX_PATH_MAX];
};

// The generic form syscalls take. Same shape as Linux's, so a musl-linked
// program's struct lines up byte for byte.
struct sockaddr {
  uint16 sa_family;
  char   sa_data[UNIX_PATH_MAX];
};

#ifdef _KERNEL_SOCKET_INTERNALS

#define NSOCK       32          // sockets in the system
#define SOCKBUF     4096        // receive buffer per connected socket
#define NBACKLOG    8

enum sockstate {
  SS_FREE = 0,
  SS_UNBOUND,
  SS_BOUND,
  SS_LISTENING,
  SS_CONNECTED,
};

// Every field here is protected by the socket table's single lock in
// kernel/net/unix.c -- there is deliberately no per-socket lock; see the
// comment at the top of that file for why.
struct socket {
  int   ref;
  int   type;
  int   state;

  char  name[UNIX_PATH_MAX];    // the bound path, for a listener

  // A connected socket's peer. Writing to a socket appends to the *peer's*
  // buffer, which is what makes one buffer per socket enough for a
  // bidirectional connection.
  struct socket *peer;
  int   peer_closed;

  char  data[SOCKBUF];
  uint  nread, nwrite;

  // Connections waiting to be accepted, on a listener.
  struct socket *queue[NBACKLOG];
  int   nqueue;
};

#endif