// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */

#include <vmlinux.h>
#include <string.h>
#include <stdbool.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"

#define ENTRIES 128

char _license[] SEC("license") = "GPL";

__u64 callback_scheduled = 0;
__u64 callback_success = 0;
__u64 schedule_error = 0;
__u64 delete_success = 0;

struct elem {
        __u32 count;
        struct bpf_task_work tw;
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(map_flags, BPF_F_NO_PREALLOC);
        __uint(max_entries, ENTRIES);
        __type(key, int);
        __type(value, struct elem);
} hmap SEC(".maps");

static int process_work(struct bpf_map *map, void *key, void *value)
{
        __sync_fetch_and_add(&callback_success, 1);
        return 0;
}

SEC("syscall")
int schedule_task_work(void *ctx)
{
        struct elem empty_work = {.count = 0};
        struct elem *work;
        int key = 0, err;

        key = bpf_ktime_get_ns() % ENTRIES;
        work = bpf_map_lookup_elem(&hmap, &key);
        if (!work) {
                bpf_map_update_elem(&hmap, &key, &empty_work, BPF_NOEXIST);
                work = bpf_map_lookup_elem(&hmap, &key);
                if (!work)
                        return 0;
        }
        err = bpf_task_work_schedule_signal(bpf_get_current_task_btf(), &work->tw, &hmap,
                                            process_work);
        if (err)
                __sync_fetch_and_add(&schedule_error, 1);
        else
                __sync_fetch_and_add(&callback_scheduled, 1);
        return 0;
}

SEC("syscall")
int delete_task_work(void *ctx)
{
        int key = 0, err;

        key = bpf_get_prandom_u32() % ENTRIES;
        err = bpf_map_delete_elem(&hmap, &key);
        if (!err)
                __sync_fetch_and_add(&delete_success, 1);
        return 0;
}