/*
 * Copyright (C) 2003-2017 Bastien Nocera <hadess@hadess.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>

#include "bacon-message-connection.hh"

#ifndef UNIX_PATH_MAX
#define UNIX_PATH_MAX 108
#endif

struct BaconMessageConnection {
    /* A server accepts connections */
    gboolean is_server;

    /* The socket path itself */
    char *path;

    /* File descriptor of the socket */
    int fd;
    /* Channel to watch */
    GIOChannel *chan;
    /* Event id returned by g_io_add_watch() */
    int conn_id;

    /* Connections accepted by this connection */
    GSList *accepted_connections;

    /* callback */
    void (*func) (const char *message, gpointer user_data);
    gpointer data;
};

static gboolean
test_is_socket (const char *path)
{
    struct stat s;

    if (stat (path, &s) == -1)
        return false;

    if (S_ISSOCK (s.st_mode))
        return true;

    return false;
}

static gboolean
is_owned_by_user_and_socket (const char *path)
{
    struct stat s;

    if (stat (path, &s) == -1)
        return false;

    if (s.st_uid != geteuid ())
        return false;

    if ((s.st_mode & S_IFSOCK) != S_IFSOCK)
        return false;

    return true;
}

static gboolean server_cb (GIOChannel *source,
                           GIOCondition condition, gpointer data);

static gboolean
setup_connection (BaconMessageConnection *conn)
{
    g_return_val_if_fail (conn->chan == NULL, false);

    conn->chan = g_io_channel_unix_new (conn->fd);
    if (!conn->chan) {
        return false;
    }
    g_io_channel_set_line_term (conn->chan, "\n", 1);
    conn->conn_id = g_io_add_watch (conn->chan, G_IO_IN, server_cb, conn);

    return true;
}

static void
accept_new_connection (BaconMessageConnection *server_conn)
{
    BaconMessageConnection *conn;
    int alen;

    g_return_if_fail (server_conn->is_server);

    conn = g_new0 (BaconMessageConnection, 1);
    conn->is_server = false;
    conn->func = server_conn->func;
    conn->data = server_conn->data;

    conn->fd = accept (server_conn->fd, NULL, (guint *)&alen);

    server_conn->accepted_connections =
            g_slist_prepend (server_conn->accepted_connections, conn);

    setup_connection (conn);
}

static gboolean
server_cb (GIOChannel *source, GIOCondition, gpointer data)
{
    BaconMessageConnection *conn = reinterpret_cast<BaconMessageConnection *>(data);
    char *message, *subs, buf;
    int cd, rc, offset;
    gboolean finished;

    offset = 0;
    if (conn->is_server && conn->fd == g_io_channel_unix_get_fd (source)) {
        accept_new_connection (conn);
        return true;
    }
    message = (char *)(g_malloc (1));
    cd = conn->fd;
    rc = read (cd, &buf, 1);
    while (rc > 0 && buf != '\n')
    {
        message = (char *)(g_realloc (message, rc + offset + 1));
        message[offset] = buf;
        offset = offset + rc;
        rc = read (cd, &buf, 1);
    }
    if (rc <= 0) {
        g_io_channel_shutdown (conn->chan, false, NULL);
        g_io_channel_unref (conn->chan);
        conn->chan = NULL;
        close (conn->fd);
        conn->fd = -1;
        g_free (message);
        conn->conn_id = 0;

        return false;
    }
    message[offset] = '\0';

    subs = message;
    finished = false;

    while (finished == false && *subs != '\0')
    {
        if (conn->func != NULL)
            (*conn->func) (subs, conn->data);

        subs += strlen (subs) + 1;
        if (subs - message >= offset)
            finished = true;
    }

    g_free (message);

    return true;
}

static char *
find_file_with_pattern (const char *dir, const char *pattern)
{
    GDir *filedir;
    char *found_filename;
    const char *filename;
    GPatternSpec *pat;

    filedir = g_dir_open (dir, 0, NULL);
    if (filedir == NULL)
        return NULL;

    pat = g_pattern_spec_new (pattern);
    if (pat == NULL)
    {
        g_dir_close (filedir);
        return NULL;
    }

    found_filename = NULL;

    while ((filename = g_dir_read_name (filedir)))
    {
        if (g_pattern_match_string (pat, filename))
        {
            char *tmp = g_build_filename (dir, filename, NULL);
            if (is_owned_by_user_and_socket (tmp))
                found_filename = g_strdup (filename);
            g_free (tmp);
        }

        if (found_filename != NULL)
            break;
    }

    g_pattern_spec_free (pat);
    g_dir_close (filedir);

    return found_filename;
}

static char *
socket_filename (const char *prefix)
{
    char *pattern, *newfile, *path, *filename;
    const char *tmpdir;

    pattern = g_strdup_printf ("%s.%s.*", prefix, g_get_user_name ());
    tmpdir = g_get_tmp_dir ();
    filename = find_file_with_pattern (tmpdir, pattern);
    if (filename == NULL)
    {
        newfile = g_strdup_printf ("%s.%s.%u", prefix,
                                   g_get_user_name (), g_random_int ());
        path = g_build_filename (tmpdir, newfile, NULL);
        g_free (newfile);
    } else {
        path = g_build_filename (tmpdir, filename, NULL);
        g_free (filename);
    }

    g_free (pattern);
    return path;
}

static gboolean
try_server (BaconMessageConnection *conn)
{
    struct sockaddr_un uaddr;

    uaddr.sun_family = AF_UNIX;
    strncpy (uaddr.sun_path, conn->path,
             MIN (strlen(conn->path)+1, UNIX_PATH_MAX));
    conn->fd = socket (PF_UNIX, SOCK_STREAM, 0);

    if(conn->fd == -1)
        return false;

    if (bind (conn->fd, (struct sockaddr *) &uaddr, sizeof (uaddr)) == -1)
    {
        // conn->fd = -1;
        return false;
    }
    listen (conn->fd, 5);

    if (!setup_connection (conn))
        return false;
    return true;
}

static gboolean
try_client (BaconMessageConnection *conn)
{
    struct sockaddr_un uaddr;

    uaddr.sun_family = AF_UNIX;
    strncpy (uaddr.sun_path, conn->path,
             MIN(strlen(conn->path)+1, UNIX_PATH_MAX));
    conn->fd = socket (PF_UNIX, SOCK_STREAM, 0);
    if(conn->fd == -1)
        return false;

    if (connect (conn->fd, (struct sockaddr *) &uaddr,
                 sizeof (uaddr)) == -1)
    {
        //conn->fd = -1;
        return false;
    }

    return setup_connection (conn);
}

BaconMessageConnection *
bacon_message_connection_new (const char *prefix)
{
    BaconMessageConnection *conn;

    g_return_val_if_fail (prefix != NULL, NULL);

    conn = g_new0 (BaconMessageConnection, 1);
    conn->path = socket_filename (prefix);

    if (test_is_socket (conn->path) == false)
    {
        if (!try_server (conn))
        {
            bacon_message_connection_free (conn);
            return NULL;
        }

        conn->is_server = true;
        return conn;
    }

    if (try_client (conn) == false)
    {
        unlink (conn->path);
        try_server (conn);
        if (conn->fd == -1)
        {
            bacon_message_connection_free (conn);
            return NULL;
        }

        conn->is_server = true;
        return conn;
    }

    conn->is_server = false;
    return conn;
}

void
bacon_message_connection_free (BaconMessageConnection *conn)
{
    GSList *child_conn;

    g_return_if_fail (conn != NULL);
    /* Only servers can accept other connections */
    g_return_if_fail (conn->is_server != false ||
            conn->accepted_connections == NULL);

    child_conn = conn->accepted_connections;
    while (child_conn != NULL) {
        bacon_message_connection_free (reinterpret_cast<BaconMessageConnection *>(child_conn->data));
        child_conn = g_slist_next (child_conn);
    }
    g_slist_free (conn->accepted_connections);

    if (conn->conn_id) {
        g_source_remove (conn->conn_id);
        conn->conn_id = 0;
    }
    if (conn->chan) {
        g_io_channel_shutdown (conn->chan, false, NULL);
        g_io_channel_unref (conn->chan);
    }

    if (conn->is_server != false) {
        unlink (conn->path);
    }
    if (conn->fd != -1) {
        close (conn->fd);
    }

    g_free (conn->path);
    g_free (conn);
}

void
bacon_message_connection_set_callback (BaconMessageConnection *conn,
                                       BaconMessageReceivedFunc func,
                                       gpointer user_data)
{
    g_return_if_fail (conn != NULL);

    conn->func = func;
    conn->data = user_data;
}

void
bacon_message_connection_send (BaconMessageConnection *conn,
                               const char *message)
{
    g_return_if_fail (conn != NULL);
    g_return_if_fail (message != NULL);

    g_io_channel_write_chars (conn->chan, message, strlen (message),
                              NULL, NULL);
    g_io_channel_write_chars (conn->chan, "\n", 1, NULL, NULL);
    g_io_channel_flush (conn->chan, NULL);
}

gboolean
bacon_message_connection_get_is_server (BaconMessageConnection *conn)
{
    g_return_val_if_fail (conn != NULL, false);

    return conn->is_server;
}

