#include <stdio.h>
#include <unistd.h>

#include <assert.h>
#include <gst/gst.h>
#include <glib.h>
#include <string.h>

typedef struct _CustomData {
    GstElement *pipeline;
    GstElement *video_sink;
    GMainLoop *loop;

    gboolean playing; /* Playing or Paused */
    gdouble rate; /* Current playback rate (can be negative) */

    int count;
    int uri_count;
    char **uris;
} CustomData;

/* Send seek event to change rate */
static void send_seek_event(CustomData *data) {
    gint64 position;
    GstEvent *seek_event;

    /* Obtain the current position, needed for the seek event */
    if (!gst_element_query_position(data->pipeline, GST_FORMAT_TIME, &position)) {
        g_printerr("Unable to retrieve current position.\n");
        return;
    }

    seek_event = gst_event_new_seek(data->rate, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,
            GST_SEEK_TYPE_SET, position, GST_SEEK_TYPE_SET, -1);

    /* Send the event */
    gst_element_send_event(data->pipeline, seek_event);

    g_print("Current rate: %g\n", data->rate);
}

static void prepare_next_stream(GstElement *obj, gpointer userdata) {
    CustomData *data = (CustomData*) userdata;
    const char* next_uri = data->uris[(data->count + 1) % data->uri_count];
    g_print("about-to-finish %4d; setting next to %s\n",
            data->count, next_uri);
    g_object_set(G_OBJECT(data->pipeline), "uri", next_uri, NULL);

    data->count++;
}

/* Process keyboard input */
static gboolean handle_keyboard(GIOChannel *source, GIOCondition cond, CustomData *data) {
    gchar *str = NULL;

    if (g_io_channel_read_line(source, &str, NULL, NULL, NULL) != G_IO_STATUS_NORMAL) {
        return TRUE;
    }

    switch (g_ascii_tolower(str[0])) {
        case 'p':
            data->playing = !data->playing;
            gst_element_set_state(data->pipeline, data->playing ? GST_STATE_PLAYING : GST_STATE_PAUSED);
            g_print("Setting state to %s\n", data->playing ? "PLAYING" : "PAUSE");
            break;
        case 's':
            if (g_ascii_isupper(str[0])) {
                data->rate *= 1.1;
            } else {
                data->rate /= 1.1;
            }
            send_seek_event(data);
            break;
        case 'd':
            data->rate *= -1.0;
            send_seek_event(data);
            break;
        case 'n':
            if (data->video_sink == NULL) {
                /* If we have not done so, obtain the sink through which we will send the step events */
                g_object_get(data->pipeline, "video-sink", &data->video_sink, NULL);
            }

            gst_element_send_event(data->video_sink,
                    gst_event_new_step(GST_FORMAT_BUFFERS, 1, data->rate, TRUE, FALSE));
            g_print("Stepping one frame\n");
            break;
        case 'q':
            g_main_loop_quit(data->loop);
            break;
        default:
            break;
    }

    g_free(str);

    return TRUE;
}


int main(int argc, char *argv[]) {
    CustomData data;
    GIOChannel *io_stdin;

    /* Initialisation */
    gst_init(&argc, &argv);
    /* Initialize our data structure */
    memset(&data, 0, sizeof (data));

    data.loop = g_main_loop_new(NULL, FALSE);

    /* Check input arguments */
    if (argc < 2) {
        g_printerr("Usage: %s <list of space-delimited filenames or URLs>\n",
                argv[0]);
        return -1;
    }


    /* Print usage map */
    g_print(
            "USAGE: Choose one of the following options, then press enter:\n"
            " 'P' to toggle between PAUSE and PLAY\n"
            " 'S' to increase playback speed, 's' to decrease playback speed\n"
            " 'D' to toggle playback direction\n"
            " 'N' to move to next frame (in the current direction, better in PAUSE)\n"
            " 'Q' to quit\n");


    data.pipeline = gst_element_factory_make("playbin", "play");
    assert(data.pipeline != NULL);


    // Add watch for keyboard input
    io_stdin = g_io_channel_unix_new(fileno(stdin));
    g_io_add_watch(io_stdin, G_IO_IN, (GIOFunc) handle_keyboard, &data);

    /* Register about-to-finish callback to re-set the URI */
    data.count = 0;
    data.uris = &(argv[1]);
    data.uri_count = argc - 1;
    g_signal_connect(data.pipeline, "about-to-finish",
            G_CALLBACK(prepare_next_stream), &data);

    /* Set initial URI */
    g_object_set(G_OBJECT(data.pipeline), "uri", argv[1], NULL);
    g_print("Now playing: %s\n", argv[1]);
    gst_element_set_state(data.pipeline, GST_STATE_PLAYING);
    data.playing = TRUE;
    data.rate = 1.0;

    /* Iterate */
    g_print("Running...\n");
    g_main_loop_run(data.loop);

    /* since we loop endlessly, the follwing is never reached */

    /* Out of the main loop, clean up nicely */
    g_print("Returned, stopping playback\n");
    gst_element_set_state(data.pipeline, GST_STATE_NULL);

    g_print("Deleting pipeline\n");
    gst_object_unref(GST_OBJECT(data.pipeline));
    g_main_loop_unref(data.loop);


    return 0;
}