/*
 * Copyright (C) 2014
 *     Olivier Gayot <ogayot@baylibre.com>
 *     Bartosz Golaszewski <bgolaszewski@baylibre.com>
 *     Olivier Gayot <olivier.gayot@sigexec.com>
 *
 * 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This software is based on Andy Green's test-server available here
 * http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/
 */

#include <libwebsockets.h>

#include <stdio.h>
#include <stdbool.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sysexits.h>
#include <getopt.h>
#include <limits.h>
#include <errno.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <time.h>

#include "misc.h"
#include "log.h"

#define DEFAULT_PORT            8080
#define DEFAULT_PAGES_DIR       "/var/www/"
#define DEFAULT_HOMEPAGE        "index.html"
#define DEFAULT_CONFIG_FILE     "/etc/caod/config.cfg"
#define DEFAULT_SAMPLING_RATE   1 /* one ms */

#define DEFAULT_CLIENT_REFRESH_RATE 100 /* in ms */

#define USER_DATA_BUFSIZE  1048576

struct per_session_data_cao_prot {
    bool handshake_ok: 1;

    /*
     * libwebsockets requires a padding before and after the buffer.
     * Since we want to be able to use sizeof(buffer) anyway, we will
     * make a packed structure containing the buffer and its padding.
     */
    struct {
        unsigned char _pre_padding[LWS_SEND_BUFFER_PRE_PADDING];
        unsigned char buffer[USER_DATA_BUFSIZE];
        unsigned char _post_padding[LWS_SEND_BUFFER_POST_PADDING];
    };

    unsigned short len;

    struct {
        unsigned short sps; /* snaps per second */
    } params;
};

struct mime_type {
    char *ext;
    size_t ext_len;
    char *type;
};

struct pws_event {
    bool set;
    int probe_id;
    int state;
};

static bool daemonize_g = false;
static int verbosity_g = 0;
static volatile bool asked_to_quit_g = false;
static const char *pages_dir_g = DEFAULT_PAGES_DIR;
static const char *homepage_g = DEFAULT_HOMEPAGE;
static const char *config_file_g = DEFAULT_CONFIG_FILE;
static struct lws_context *context_g;

#define MIME_EXT_ARGS(_ext)  _ext, (sizeof(_ext) - 1)

static struct mime_type mimes_g[] = {
    { MIME_EXT_ARGS(".ico"),     "image/x-icon", },
    { MIME_EXT_ARGS(".png"),     "image/png" },
    { MIME_EXT_ARGS(".html"),    "text/html" },
    { MIME_EXT_ARGS(".css"),     "text/css" },
    { MIME_EXT_ARGS(".js"),      "application/javascript" },
#define SHORTEST_MIME_EXT 3 /* size of the shortest extension (incl. the dot) */
};

#undef MIME_EXT_ARGS

/* return a string describing the mime type if supported, otherwise NULL */
static const char *get_mimetype(const char *filename)
{
    int n, i;

    n = strlen(filename);
    if (n < SHORTEST_MIME_EXT + 1)
        return NULL;

    for (i = 0; i < countof(mimes_g); ++i) {
        const struct mime_type *mimep = &mimes_g[i];

        if (!strcmp(&filename[n - mimep->ext_len], mimep->ext)) {
            return mimep->type;
        }
    }

    return NULL;
}

static int callback_http_only(struct lws *wsi,
        enum lws_callback_reasons reason, void *user UNUSED_PARAM,
        void *in, size_t len)
{
    const char *mimetype;
    static char path[PATH_MAX];
    static char real_path[PATH_MAX];
    size_t path_len;
    size_t def_path_len;

    switch (reason) {
        case LWS_CALLBACK_HTTP:

            if (len < 1) {
                lws_return_http_status(wsi,
                        HTTP_STATUS_BAD_REQUEST, NULL);
                return -1;
            }

            /* serve either the specified page or the default one */
            if (strcmp(in, "/") != 0) {
                snprintf(path, sizeof(path), "%s/%s", pages_dir_g,
                        (char *)in);
            } else {
                snprintf(path, sizeof(path), "%s/%s", pages_dir_g,
                        homepage_g);
            }

            /*
             * avoid a security issue: "jail" inside pages_dir_g
             * XXX: beware, a race condition might occur between realpath() and
             * open() which is called by lwss_serve_http_file()
             */
            if (realpath(path, real_path) == NULL) {
                lws_return_http_status(wsi,
                        HTTP_STATUS_NOT_FOUND, NULL);
                return -1;
            }
            path_len = strlen(real_path);
            def_path_len = strlen(pages_dir_g);
            if (path_len <= def_path_len ||
                    strncmp(real_path, pages_dir_g, def_path_len) != 0)
            {
                lws_return_http_status(wsi,
                        HTTP_STATUS_FORBIDDEN, NULL);

                return -1;
            }

            /* check if the mimetype if supported */
            mimetype = get_mimetype(path);
            if (mimetype == NULL) {
                caod_err("Unknown mimetype for %s", path);
                lws_return_http_status(wsi,
                        HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE, NULL);

                return -1;
            }

            if (lws_serve_http_file(wsi, path, mimetype, NULL, 0))
            {
                /*
                 * close the socket if either an error occured or the file has
                 * been sent completely
                 */
                return -1;
            }

            break;
        case LWS_CALLBACK_HTTP_BODY:
            break;
        case LWS_CALLBACK_HTTP_BODY_COMPLETION:
            break;
        case LWS_CALLBACK_HTTP_FILE_COMPLETION:
            break;
        case LWS_CALLBACK_HTTP_WRITEABLE:
            break;
        case LWS_CALLBACK_FILTER_NETWORK_CONNECTION:
            break;
        default:
            break;
    }

    return 0;
}

static void set_shunt_vals(int *vals)
{
    FILE *shfd;
    int numvals = 8;
    int i;
    FILE *chfd;
    char channels[8];
    int hwind = 1;
    ssize_t rd;

    chfd = fopen("/etc/caod/channels", "r");
    if (!chfd)
        goto err;

    shfd = fopen("/etc/caod/shunt_vals", "w");
    if (!shfd)
        goto err;

    for (i = 0; i < numvals; i++) {
        if (vals[i] > 0) {
            fprintf(shfd, "%d\n", vals[i]);
        }
    }
    fclose(shfd);

    rd = fread(channels, 1, sizeof(channels), chfd);
    if (rd != sizeof(channels)) {
        goto err;
    }
    fclose(chfd);

    for (i = 0; i < numvals; i++) {
        if (channels[i] == 'I') {
            char cmd[256];

            snprintf(cmd, sizeof(cmd),
                     "/root/cao-suite/scripts/cao_ctl.py set_shunt %d %d %d",
                     hwind, i+1, vals[i]);
            caod_info("Executing: %s", cmd);
            system(cmd);
            hwind++;
        } else if (channels[i] == 'T') {
            hwind++;
        }
    }

    sync();

    return;

err:
    caod_err("Error setting shunt values");
}

static int callback_cao_prot(struct lws *wsi UNUSED_PARAM,
        enum lws_callback_reasons reason,
        void *user, void *in UNUSED_PARAM, size_t len UNUSED_PARAM)
{
    struct per_session_data_cao_prot *user_data = user;

    switch (reason) {
            case LWS_CALLBACK_ESTABLISHED:
                    user_data->params.sps = 0;
                    user_data->handshake_ok = false;
                break;
            case LWS_CALLBACK_CLOSED:
                break;
            case LWS_CALLBACK_SERVER_WRITEABLE:
                break;
            case LWS_CALLBACK_RECEIVE:
                set_shunt_vals(in);
                break;
            case LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION:
                break;
            default:
                break;
        }

        return 0;
}

static struct lws_context_creation_info info_g = {
    .port = DEFAULT_PORT,
    .iface = NULL,
    /* list the protocols available */
    .protocols = (struct lws_protocols[]) {
        {
            .name = "http-only", /* name */
            .callback = callback_http_only,
            .per_session_data_size = 0,
        }, {
            .name = "cao-prot",
            .callback = callback_cao_prot,
            .per_session_data_size =
                sizeof(struct per_session_data_cao_prot),
        }, { /* empty field needed at the end */
            .name = NULL,
            .callback = NULL,
            .per_session_data_size = 0,
        },
    },
    .options = 0,
};

/* display an usage message and exit */
NORETURN static void usage(const char *progname)
{
    fprintf(stderr, "Usage: %s [OPTIONS]\n"
            "\n"
            "-p - override the default port (%d),\n"
            "-h - display this help and exit,\n"
            "-d - fork in the background,\n"
            "-v - increase verbosity (1-info, 2-debug),\n"
            "-w - set the path to the WWW directory (default: '%s'),\n"
            "-H - set the filename of the homepage in the www directory\n"
            "-c - specify a custom path to the config file (default: '%s'),"
            " (default: '%s').\n",
            progname,
            DEFAULT_PORT,
            DEFAULT_PAGES_DIR,
            DEFAULT_HOMEPAGE,
            DEFAULT_CONFIG_FILE);

    exit(EX_USAGE);
}

static void errmsg_and_usage(const char *progname, const char *fmt, ...)
{
    va_list va;

    va_start(va, fmt);
    vfprintf(stderr, fmt, va);
    fprintf(stderr, "\n");
    va_end(va);

    usage(progname);
}

/*
 * search options passed to the program and handle them
 * argc will be modified accordingly
 * argv will be returned shifted accordingly
 */
static char **parse_opt(int *argc, char *argv[])
{
    int opt;
    char *errptr;

    while ((opt = getopt(*argc, argv, "v:hdp:w:H:c:")) != -1) {
        switch (opt) {
            case 'p':
                /* change the default port */
                info_g.port = strtol(optarg, &errptr, 10);

                if (*errptr != '\0') {
                    usage(argv[0]);
                }

                break;
            case 'h':
                /* display the help (and exit) */
                usage(argv[0]);
                break;
            case 'd':
                /* fork on the background */
                daemonize_g = true;
                break;
            case 'v':
                /* increase verbosity */
                if ((strcmp(optarg, "1") == 0) || (strcmp(optarg, "2") == 0))
                    verbosity_g = atoi(optarg);
                else
                    errmsg_and_usage(argv[0], "Invalid verbosity level\n");
                break;
            case 'w':
                if (optarg[0] != '/')
                    errmsg_and_usage(argv[0],
                            "Must specify an absolute path for -D\n");
                pages_dir_g = optarg;
                break;
            case 'H':
                homepage_g = optarg;
                break;
            case 'c':
                config_file_g = optarg;
                break;
            default:
                /* noreturn */
                usage(argv[0]);
        }
    }

    *argc -= optind;

    return &(argv[optind]);
}

static void handle_signal(int sig)
{
    switch (sig) {
        case SIGINT:
        case SIGTERM:
            asked_to_quit_g = true;
            break;
    }
}

static int callback_http_on_bug(struct lws *wsi,
        enum lws_callback_reasons reason,
        void *user UNUSED_PARAM, void *in UNUSED_PARAM, size_t len)
{
    char path[256];

    memset(path, 0, sizeof(path));
    snprintf(path, sizeof(path), "%s/error.html", pages_dir_g);

    switch (reason) {
        case LWS_CALLBACK_HTTP:

            if (len < 1) {
                lws_return_http_status(wsi, HTTP_STATUS_BAD_REQUEST, NULL);
                return -1;
            }

            if (lws_serve_http_file(wsi, path, "text/html", NULL, 0)) {
                /*
                 * close the socket if either an error occured or the file has
                 * been sent completely
                 */
                return -1;
            }

            break;
        default:
            break;
    }

    return 0;
}

static struct lws_context_creation_info info_bug = {
    .port = DEFAULT_PORT,
    .iface = NULL,
    /* list the protocols available */
    .protocols = (struct lws_protocols[]) {
        {
            .name = "http-only", /* name */
            .callback = callback_http_on_bug,
            .per_session_data_size = 0,
        }, { /* empty field needed at the end */
            .name = NULL,
            .callback = NULL,
            .per_session_data_size = 0,
        },
    },
    .options = 0,
};

/*
 * If an error happened - let this function run eternally to inform users
 * about the bug via HTTP on default port.
 */
static void bug_on(void)
{
    struct lws_context *context;

    if ((context = lws_create_context(&info_bug)) == NULL) {
        caod_err("lws init failed");
        abort();
    }

    caod_err("Entering bug_on state...");
    while (!asked_to_quit_g) {
        if (lws_service(context, 5) < 0) {
        caod_err("lws_service() returned with an error");
        }
    }
}

/*
 * The general idea is to read the configuration and create the data model,
 * then create a pipe and fork. The child process will then try to stick to
 * the given sampling rate and perform the measurements on time, feeding all
 * the results into the pipe, while the parent will read from it, store these
 * values in a buffer and send them periodically to the client.
 *
 * The buffer size should be (client_refresh_rate / sampling_rate). The buffer
 * is only allocated in the parent process, although both processes share
 * the rest of the data model.
 */
int main(int argc, char *argv[])
{
    const char *progname = argv[0];
    int ret = EXIT_SUCCESS;
    int dbglvl;

    argv = parse_opt(&argc, argv);
    /* XXX argc and argv have been shifted */

    /* no argument are accepted for now on */
    if (argc > 0) {
        usage(progname);
    }

    if (daemonize_g && lws_daemonize("/tmp/.caod-lock") != 0) {
        caod_err("failed to daemonize");
        return -1;
    }

    caod_setup_logs();
    dbglvl = LLL_ERR | LLL_WARN | LLL_NOTICE;

    switch (verbosity_g) {
        case 2: dbglvl |= LLL_DEBUG; /* Fall through. */
        case 1: dbglvl |= LLL_INFO;
    }

    lws_set_log_level(dbglvl, &caod_log_hook);

    signal(SIGINT, &handle_signal);
    signal(SIGTERM, &handle_signal);

    if ((context_g = lws_create_context(&info_g)) == NULL) {
        caod_err("lws init failed");
        ret = EXIT_FAILURE;
        return ret;
    }

    while (!asked_to_quit_g) {
        if (lws_service(context_g, 5) < 0) {
            caod_err("lws_service() returned with an error");
            ret = EXIT_FAILURE;
            break;
        }
    }

    lws_context_destroy(context_g);

    return ret;
}