// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2015 BMW Car IT GmbH
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <bpf/libbpf.h>
#include <bpf/bpf.h>

#define MAX_ENTRIES     20
#define MAX_CPU         4
#define MAX_STARS       40

struct cpu_hist {
        long data[MAX_ENTRIES];
        long max;
};

static struct cpu_hist cpu_hist[MAX_CPU];

static void stars(char *str, long val, long max, int width)
{
        int i;

        for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
                str[i] = '*';
        if (val > max)
                str[i - 1] = '+';
        str[i] = '\0';
}

static void print_hist(void)
{
        char starstr[MAX_STARS];
        struct cpu_hist *hist;
        int i, j;

        /* clear screen */
        printf("\033[2J");

        for (j = 0; j < MAX_CPU; j++) {
                hist = &cpu_hist[j];

                /* ignore CPUs without data (maybe offline?) */
                if (hist->max == 0)
                        continue;

                printf("CPU %d\n", j);
                printf("      latency        : count     distribution\n");
                for (i = 1; i <= MAX_ENTRIES; i++) {
                        stars(starstr, hist->data[i - 1], hist->max, MAX_STARS);
                        printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
                                (1l << i) >> 1, (1l << i) - 1,
                                hist->data[i - 1], MAX_STARS, starstr);
                }
        }
}

static void get_data(int fd)
{
        long key, value;
        int c, i;

        for (i = 0; i < MAX_CPU; i++)
                cpu_hist[i].max = 0;

        for (c = 0; c < MAX_CPU; c++) {
                for (i = 0; i < MAX_ENTRIES; i++) {
                        key = c * MAX_ENTRIES + i;
                        bpf_map_lookup_elem(fd, &key, &value);

                        cpu_hist[c].data[i] = value;
                        if (value > cpu_hist[c].max)
                                cpu_hist[c].max = value;
                }
        }
}

int main(int argc, char **argv)
{
        struct bpf_link *links[2];
        struct bpf_program *prog;
        struct bpf_object *obj;
        char filename[256];
        int map_fd, i = 0;

        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
        obj = bpf_object__open_file(filename, NULL);
        if (libbpf_get_error(obj)) {
                fprintf(stderr, "ERROR: opening BPF object file failed\n");
                return 0;
        }

        /* load BPF program */
        if (bpf_object__load(obj)) {
                fprintf(stderr, "ERROR: loading BPF object file failed\n");
                goto cleanup;
        }

        map_fd = bpf_object__find_map_fd_by_name(obj, "my_lat");
        if (map_fd < 0) {
                fprintf(stderr, "ERROR: finding a map in obj file failed\n");
                goto cleanup;
        }

        bpf_object__for_each_program(prog, obj) {
                links[i] = bpf_program__attach(prog);
                if (libbpf_get_error(links[i])) {
                        fprintf(stderr, "ERROR: bpf_program__attach failed\n");
                        links[i] = NULL;
                        goto cleanup;
                }
                i++;
        }

        while (1) {
                get_data(map_fd);
                print_hist();
                sleep(5);
        }

cleanup:
        for (i--; i >= 0; i--)
                bpf_link__destroy(links[i]);

        bpf_object__close(obj);
        return 0;
}