#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>

#include <patty/ax25.h>

struct _patty_ax25_server {
    patty_list *ifaces;

    patty_dict *socks_by_fd,
               *socks_bound,
               *socks_pending_accept,
               *socks_pending_connect,
               *socks_established;

    int fd_max;

    fd_set fds_watch,
           fds_r,
           fds_w;
};

int patty_ax25_server_init(patty_ax25_server *server) {
    memset(server, '\0', sizeof(*server));

    if ((server->ifaces = patty_list_new()) == NULL) {
        goto error_list_new_ifaces;
    }

    if ((server->socks_by_fd = patty_dict_new()) == NULL) {
        goto error_dict_new_socks_by_fd;
    }

    if ((server->socks_bound = patty_dict_new()) == NULL) {
        goto error_dict_new_socks_bound;
    }

    if ((server->socks_pending_accept = patty_dict_new()) == NULL) {
        goto error_dict_new_socks_pending_accept;
    }

    if ((server->socks_pending_connect = patty_dict_new()) == NULL) {
        goto error_dict_new_socks_pending_connect;
    }

    if ((server->socks_established = patty_dict_new()) == NULL) {
        goto error_dict_new_socks_established;
    }

    return 0;

error_dict_new_socks_established:
    patty_dict_destroy(server->socks_pending_connect);

error_dict_new_socks_pending_connect:
    patty_dict_destroy(server->socks_pending_accept);

error_dict_new_socks_pending_accept:
    patty_dict_destroy(server->socks_bound);

error_dict_new_socks_bound:
    patty_dict_destroy(server->socks_by_fd);

error_dict_new_socks_by_fd:
    patty_list_destroy(server->ifaces);

error_list_new_ifaces:
    return -1;
}

static int destroy_if(patty_ax25_if *iface, void *ctx) {
    patty_ax25_if_destroy(iface);

    return 0;
}

void patty_ax25_server_stop(patty_ax25_server *server) {
    patty_dict_destroy(server->socks_established);
    patty_dict_destroy(server->socks_pending_connect);
    patty_dict_destroy(server->socks_pending_accept);
    patty_dict_destroy(server->socks_bound);
    patty_dict_destroy(server->socks_by_fd);

    patty_ax25_server_each_if(server, destroy_if, NULL);
    patty_list_destroy(server->ifaces);
}

static void sock_init(patty_ax25_sock *sock, enum patty_ax25_sock_type type) {
    memset(sock, '\0', sizeof(*sock));

    sock->status   = PATTY_AX25_SOCK_CLOSED;
    sock->mode     = PATTY_AX25_SOCK_DM;
    sock->type     = type;
    sock->n_maxlen = PATTY_AX25_FRAME_DEFAULT_MAXLEN;
    sock->n_window = PATTY_AX25_FRAME_DEFAULT_WINDOW;
}

static inline void hash_init(uint32_t *hash) {
    *hash = 0xffffffdf;
}

static inline void hash_byte(uint32_t *hash, uint8_t c) {
    *hash += c;
    *hash += (*hash << 10);
    *hash ^= (*hash >>  6);
}

static inline void hash_addr(uint32_t *hash, patty_ax25_addr *addr) {
    int i;

    for (i=0; i<PATTY_AX25_CALLSIGN_LEN; i++) {
        hash_byte(hash, addr->callsign[i] >> 1);
    }

    hash_byte(hash, PATTY_AX25_ADDRESS_SSID_NUMBER(addr->ssid));
}

static inline void hash_end(uint32_t *hash) {
    *hash += (*hash <<  3);
    *hash ^= (*hash >> 11);
    *hash += (*hash << 15);
}

static uint32_t hash_addrpair(patty_ax25_addr *local,
                              patty_ax25_addr *remote) {
    uint32_t hash;

    hash_init(&hash);

    hash_addr(&hash, local);
    hash_addr(&hash, remote);

    hash_end(&hash);

    return hash;
}

static patty_ax25_sock *sock_by_fd(patty_dict *dict,
                                   int fd) {
    return patty_dict_get(dict,
                          NULL + fd,
                          sizeof(fd));
}

static patty_ax25_sock *sock_by_addr(patty_dict *dict,
                                     patty_ax25_addr *addr) {
    patty_dict_slot *slot;

    uint32_t hash;

    hash_init(&hash);
    hash_addr(&hash, addr);
    hash_end(&hash);

    if ((slot = patty_dict_slot_find(dict, hash)) == NULL) {
        errno = EEXIST;

        goto error_dict_slot_find;
    }

    return (patty_ax25_sock *)slot->value;

error_dict_slot_find:
    return NULL;
}

static patty_ax25_sock *sock_by_addrpair(patty_dict *dict,
                                         patty_ax25_addr *local,
                                         patty_ax25_addr *remote) {
    patty_dict_slot *slot;

    uint32_t hash = hash_addrpair(local, remote);

    if ((slot = patty_dict_slot_find(dict, hash)) == NULL) {
        errno = EEXIST;

        goto error_dict_slot_find;
    }

    return (patty_ax25_sock *)slot->value;

error_dict_slot_find:
    return NULL;
}

static int sock_save_by_fd(patty_dict *dict, patty_ax25_sock *sock) {
    if (patty_dict_set(dict,
                       NULL + sock->fd,
                       sizeof(sock->fd),
                       sock) == NULL) {
        goto error_dict_set;
    }

    return sock->fd;

error_dict_set:
    return -1;
}

static int sock_save_by_addr(patty_dict *dict,
                             patty_ax25_sock *sock,
                             patty_ax25_addr *addr) {
    uint32_t hash;

    hash_init(&hash);
    hash_addr(&hash, addr);
    hash_end(&hash);

    if (patty_dict_set_with_hash(dict,
                                 addr,
                                 sizeof(*addr),
                                 sock,
                                 hash) == NULL) {
        goto error_dict_set_with_hash;
    }
    
    return 0;

error_dict_set_with_hash:
    return -1;
}

static int sock_save_by_addrpair(patty_dict *dict,
                                 patty_ax25_sock *sock,
                                 patty_ax25_addr *local,
                                 patty_ax25_addr *remote) {
    uint32_t hash = hash_addrpair(local, remote);

    if (patty_dict_set_with_hash(dict,
                                sock,
                                sizeof(*sock),
                                sock,
                                hash) == NULL) {
        goto error_dict_set_with_hash;
    }
    
    return 0;

error_dict_set_with_hash:
    return -1;
}

static int server_connect(patty_ax25_server *server,
                          int socket,
                          patty_ax25_addr *addr) {
    patty_ax25_sock *sock;

    if ((sock = sock_by_fd(server->socks_by_fd, socket)) == NULL) {
        goto error_sock_by_fd;
    }

    if (sock->remote.callsign[0] != '\0') {
        errno = EEXIST;

        goto error_exists;
    }

    memcpy(&sock->remote, addr, sizeof(*addr));

    return 0;

error_exists:
error_sock_by_fd:
    return -1;
}

int patty_ax25_server_add_if(patty_ax25_server *server,
                             patty_ax25_if *iface) {
    int fd;

    if ((fd = patty_kiss_tnc_fd(iface->tnc)) >= 0) {
        FD_SET(fd, &server->fds_watch);

        if (server->fd_max < fd + 1) {
            server->fd_max = fd + 1;
        }
    }

    if (patty_dict_set(server->socks_by_fd, NULL + fd, sizeof(fd), iface) == NULL) {
        goto error_dict_set;
    }

    if (patty_list_append(server->ifaces, iface) == NULL) {
        goto error_list_append;
    }

    return 0;

error_list_append:
error_dict_set:
    return -1;
}

int patty_ax25_server_delete_if(patty_ax25_server *server,
                                patty_ax25_if *iface) {
    patty_list_item *item = server->ifaces->first;

    int fd, i = 0;

    while (item) {
        if (item->value == iface) {
            if (patty_list_splice(server->ifaces, i) == NULL) {
                goto error_list_splice;
            }

            return 0;
        }

        item = item->next;
        i++;
    }

    if ((fd = patty_kiss_tnc_fd(iface->tnc)) >= 0) {
        FD_CLR(fd, &server->fds_watch);

        if (server->fd_max == fd) {
            server->fd_max--;
        }

        if (patty_dict_delete(server->socks_by_fd, NULL + fd, sizeof(fd)) == NULL) {
            goto error_dict_delete;
        }
    }

    return 0;

error_dict_delete:
error_list_splice:
    return -1;
}

patty_ax25_if *patty_ax25_server_get_if(patty_ax25_server *server,
                                        const char *name) {
    patty_list_iterator *iter;
    patty_ax25_if *iface;

    if ((iter = patty_list_start(server->ifaces)) == NULL) {
        goto error_list_start;
    }

    while ((iface = patty_list_next(iter)) != NULL) {
        if (strncmp(iface->name, name, sizeof(iface->name)) == 0) {
            patty_list_finish(iter);

            return iface;
        }
    }

    patty_list_finish(iter);

error_list_start:
    return NULL;
}

int patty_ax25_server_each_if(patty_ax25_server *server,
                              int (*callback)(patty_ax25_if *, void *),
                              void *ctx) {
    patty_list_iterator *iter;
    patty_ax25_if *iface;

    if ((iter = patty_list_start(server->ifaces)) == NULL) {
        goto error_list_start;
    }

    while ((iface = patty_list_next(iter)) != NULL) {
        if (callback(iface, ctx) < 0) {
            goto error_callback;
        }
    }

    patty_list_finish(iter);

    return 0;

error_callback:
    patty_list_finish(iter);

error_list_start:
    return -1;
}

static int server_socket(patty_ax25_server *server,
                         int client) {
    patty_ax25_call_socket_request request;
    patty_ax25_call_socket_response response;

    patty_ax25_sock *sock;

    if ((sock = malloc(sizeof(*sock))) == NULL) {
        goto error_malloc_sock;
    }

    sock_init(sock, request.type);

    if ((sock->fd = open("/dev/null", O_RDWR)) < 0) {
        goto error_io;
    }

    if (read(client, &request, sizeof(request)) < 0) {
        goto error_io;
    }

    response.ret = sock->fd;
    response.eno = 0;

    if (sock_save_by_fd(server->socks_by_fd, sock) < 0) {
        response.ret = -1;
        response.eno = errno;

        goto error_sock_save_by_fd;
    }

error_sock_save_by_fd:
    if (write(client, &response, sizeof(response)) < 0) {
        goto error_io;
    }

    return 0;

error_io:
    free(sock);

error_malloc_sock:
    return -1;
}

static int server_bind(patty_ax25_server *server,
                       int client) {
    patty_ax25_call_bind_request request;
    patty_ax25_call_bind_response response;

    patty_ax25_sock *sock;

    if (read(client, &request, sizeof(request)) < 0) {
        goto error_io;
    }

    if ((sock = sock_by_fd(server->socks_by_fd, request.socket)) == NULL) {
        response.ret = -1;
        response.eno = EBADF;

        goto error_sock_by_fd;
    }

    /*
     * If there is already a local address associated with this socket, then
     * that's a problem.
     */
    if (sock->local.callsign[0] != '\0') {
        response.ret = -1;
        response.eno = EINVAL;

        goto error_bound;
    }

    if (patty_dict_get(server->socks_bound,
                       &sock->local,
                       sizeof(sock->local))) {
        response.ret = -1;
        response.eno = EADDRINUSE;

        goto error_inuse;
    }

    memcpy(&sock->local, &request.peer, sizeof(request.peer));

    if (patty_dict_set(server->socks_bound,
                       &sock->local,
                       sizeof(sock->local),
                       sock) == NULL) {
        goto error_dict_set;
    }

    if (write(client, &response, sizeof(response)) < 0) {
        goto error_io;
    }

    response.ret = 0;
    response.eno = 0;

error_inuse:
error_bound:
error_sock_by_fd:
    return 0;

error_dict_set:
error_io:
    return -1;
}

static int server_listen(patty_ax25_server *server,
                         int client) {
    patty_ax25_call_listen_request request;
    patty_ax25_call_listen_response response;

    patty_ax25_sock *sock;

    if (read(client, &request, sizeof(request)) < 0) {
        goto error_io;
    }

    if ((sock = sock_by_fd(server->socks_by_fd, request.socket)) == NULL) {
        response.ret = -1;
        response.eno = EBADF;

        goto error_sock_by_fd;
    }

    if (sock->local.callsign[0] == '\0') {
        response.eno = EINVAL;

        goto error_invalid_fd;
    }

    sock->status = PATTY_AX25_SOCK_LISTENING;

    response.ret = 0;
    response.eno = 0;

error_invalid_fd:
error_sock_by_fd:
    if (write(client, &response, sizeof(response)) < 0) {
        goto error_io;
    }

    return 0;

error_io:
    return -1;
}

static int server_accept_pty(patty_ax25_server *server,
                             patty_ax25_call_accept_response *response,
                             patty_ax25_sock *sock) {
    if ((sock->fd = open("/dev/ptmx", O_RDWR)) < 0) {
        goto error_open;
    }

    if (grantpt(sock->fd) < 0) {
        goto error_grantpt;
    }

    if (unlockpt(sock->fd) < 0) {
        goto error_unlockpt;
    }

    if (ptsname_r(sock->fd, response->path, PATTY_AX25_SOCK_PATH_SIZE) < 0) {
        goto error_ptsname_r;
    }

    response->ret = sock->fd;
    response->eno = 0;

    return 0;

error_ptsname_r:
error_unlockpt:
error_grantpt:
    close(sock->fd);

error_open:
    return -1;
}

static int server_accept_unix(patty_ax25_server *server,
                              patty_ax25_call_accept_response *response,
                              patty_ax25_sock *sock) {
    struct sockaddr_un addr;

    if ((sock->fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
        goto error_socket;
    }

    if (snprintf(response->path, PATTY_AX25_SOCK_PATH_SIZE, "/var/run/patty/%d.sock", sock->fd) < 0) {
        goto error_snprintf;
    }

    memset(&addr, '\0', sizeof(addr));
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, response->path, sizeof(addr.sun_path));

    if (bind(sock->fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        goto error_bind;
    }

    response->ret = sock->fd;
    response->eno = 0;

    return 0;

error_bind:
error_snprintf:
    close(sock->fd);

error_socket:
    return -1;
}

static int server_accept(patty_ax25_server *server,
                         int client) {
    patty_ax25_call_accept_request request;
    patty_ax25_call_accept_response response;

    patty_ax25_sock *local,
                    *remote;

    if (read(client, &request, sizeof(request)) < 0) {
        goto error_io;
    }

    if ((local = sock_by_fd(server->socks_by_fd, request.socket)) == NULL) {
        response.ret = -1;
        response.eno = EBADF;

        goto error_sock_by_fd;
    }

    if ((remote = malloc(sizeof(*remote))) == NULL) {
        goto error_malloc_remote;
    }

    sock_init(remote, local->type);

    if (local->type & PATTY_AX25_SOCK_PTY) {
        if (server_accept_pty(server, &response, remote) < 0) {
            goto error_server_accept_pty;
        }
    } else {
        if (server_accept_unix(server, &response, remote) < 0) {
            goto error_server_accept_unix;
        }
    }

error_sock_by_fd:
    if (write(client, &response, sizeof(response)) < 0) {
        goto error_io;
    }

    return 0;

error_server_accept_unix:
error_server_accept_pty:
    free(remote);

error_malloc_remote:
error_io:
    return -1;
}