const std = @import("std");
const gst = @cImport({ // glib-object for g_object_* functions
    @cInclude("glib-object.h");
    @cInclude("gst.h");
    @cInclude("gstappsrc.h");
    @cInclude("glib.h"); // and glib for other g_* functions
});

pub const GstError = error {
    EmptySample,
    EmptyBuffer,
    EmptyBufferMap,
};


pub fn get_buffer(app_sink: gst.GstElement) !*gst.GstBuffer {
    const sample: *gst.GstSample = undefined;
    var buffer: ?*gst.GetBuffer = undefined;

    std.debug.print("pulling sample\n", .{});
    sample = gst.gst_app_sink_pull_sample(@ptrCast(app_sink));
    std.debug.print("Pulled appsink sample\n", .{});

    const sample_info = gst.gst_sample_get_info(sample);
    if (sample_info != null) {
        const si_string = gst.gst_structure_to_string(sample_info);
        std.debug.print("Sample info retrieved {s}\n", .{ si_string });
        gst.g_free(si_string);
    } else {
        std.debug.print("Got sample with no info!\n", .{});
        return GstError.EmptySample;
    }
    defer gst.gst_sample_unref(sample);

    const s_caps: ?*gst.GstCaps = gst.gst_sample_get_caps(sample);
    if (s_caps != null) {
        const cap_str = gst.gst_caps_to_string(s_caps);
        std.debug.print("Got sample with caps {s}\n", .{ cap_str });
        gst.g_free(cap_str);
    }

    buffer = gst.gst_sample_get_buffer(sample);
    std.debug.print("Got buffer from sample!\n", .{});

    var map: *gst.GstMapInfo = undefined;

    defer gst.gst_buffer_unmap(buffer, &map);

    if (buffer == null || !gst.gst_buffer_map(buffer, &map, gst.GST_MAP_READ)) {
        std.debug.print("Failed to get buffer or buffer map!\n", .{});
        if (buffer == null) {
            return GstError.EmptyBuffer;
        } else {
            return GstError.EmptyBufferMap;
        }
    }

    const len = map.size;
    std.debug.print("map size is: {d}\n", .{ len });


    return buffer;
}