#include <pulse/pulseaudio.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/signal.h>
#include <limits.h>

#define ERROR(...) fprintf(stderr, "error: " __VA_ARGS__)

typedef struct {
    size_t pid;
    unsigned int signum;
} TargetData;

static void sink_info_callback(pa_context *ctx, const pa_sink_info *info,
                               int eol, TargetData *target) {
    if (info && kill(target->pid, target->signum) < 0) {
        ERROR("terget process died\n");
        exit(1);
    }
}

static void server_info_callback(pa_context *ctx, const pa_server_info *info,
                                 TargetData *target) {
    pa_operation *op = pa_context_get_sink_info_by_name(
            ctx,
            info->default_sink_name,
            (pa_sink_info_cb_t) sink_info_callback,
            target);
    pa_operation_unref(op);
}

static void subscribe_callback(pa_context *ctx,
                               pa_subscription_event_type_t type, uint32_t idx,
                               TargetData *target) {
    unsigned int facility = type & PA_SUBSCRIPTION_EVENT_FACILITY_MASK;
    pa_operation *op = NULL;
    switch (facility) {
    case PA_SUBSCRIPTION_EVENT_SINK:
        op = pa_context_get_sink_info_by_index(ctx,
                                               idx,
                                               (pa_sink_info_cb_t) sink_info_callback,
                                               target);
        break;
    }
    if (op) {
        pa_operation_unref(op);
    }
}

static void state_callback(pa_context *ctx, TargetData *target) {
    pa_operation *op;
    switch (pa_context_get_state(ctx)) {
    case PA_CONTEXT_READY:
        op = pa_context_get_server_info(ctx,
                                        (pa_server_info_cb_t) server_info_callback,
                                        target);
        pa_operation_unref(op);
        pa_context_set_subscribe_callback(ctx,
                                          (pa_context_subscribe_cb_t) subscribe_callback,
                                          target);
        op = pa_context_subscribe(ctx, PA_SUBSCRIPTION_MASK_SINK, NULL, NULL);
        pa_operation_unref(op);
        break;
    case PA_CONTEXT_FAILED:
        if (kill(target->pid, target->signum) < 0) {
            ERROR("terget process died\n");
            exit(1);
        }
        break;
    default:
        break;
    }
}

int main(int argc, const char **argv) {
    if (argc < 2) {
        ERROR("no pid\n");
        return 1;
    }
    char *endptr = NULL;
    unsigned int signum = SIGRTMIN + 1;
    if (argc >= 3 && argv[1][0] == '-') {
        const char *signumstr = argv[1] + 1;
        unsigned long num = strtoul(signumstr, &endptr, 10);
        if (num > (SIGRTMAX - SIGRTMIN) + 1) {
            ERROR("signal out of range: %lu\n", num);
            return 1;
        }
        signum = SIGRTMIN + num;
        ++argv;
    }
    endptr = NULL;
    errno = 0;
    unsigned long pid = strtoul(argv[1], &endptr, 10);
    if (argv[1][0] == '-' || errno == ERANGE) {
        ERROR("pid out of range: \"%s\"\n", argv[1]);
        return 1;
    }
    pa_mainloop *mainloop = pa_mainloop_new();
    if (!mainloop) {
        ERROR("could not create pulse mainloop\n");
        return 1;
    }
    pa_mainloop_api *api = pa_mainloop_get_api(mainloop);
    if (!api) {
        ERROR("could not create pulse mainloop api\n");
        return 1;
    }
    pa_context *context = pa_context_new(api, "dwmblocks-listener");
    if (!context) {
        ERROR("could not create pulse context\n");
        return 1;
    }
    TargetData target = { pid, signum };
    pa_context_set_state_callback( context,
                                  (pa_context_notify_cb_t)&state_callback,
                                  &target);
    if (pa_context_connect(context, NULL, PA_CONTEXT_NOAUTOSPAWN, NULL) < 0) {
        ERROR("could not connect to pulse");
        return 1;
    }
    pa_mainloop_run(mainloop, NULL);
    return 0;
}