/*
 * This file is part of Xfce (https://gitlab.xfce.org).
 *
 * zram monitor: local addition, not part of upstream.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES
 * ARE DISCLAIMED.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <glib.h>
#include <glib/gstdio.h>

#include "zram.h"

#ifdef __linux__

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
 * /sys/block/zramN/mm_stat is a single line of whitespace-separated numbers:
 *
 *   orig_data_size compr_data_size mem_used_total mem_limit mem_used_max
 *   same_pages pages_compacted huge_pages [huge_pages_since]
 *
 * All sizes are in bytes. Only the first three are needed here.
 *
 * The file exists only while the device is initialised; an allocated but
 * unused zramN has no mm_stat, so a failed read is normal, not an error.
 */
static gboolean
read_one_device (const gchar *devname, guint64 *orig, guint64 *compr, guint64 *used)
{
    gchar *path = g_strdup_printf ("/sys/block/%s/mm_stat", devname);
    gchar *contents = NULL;
    gboolean ok = FALSE;

    if (g_file_get_contents (path, &contents, NULL, NULL))
    {
        guint64 o = 0, c = 0, u = 0;
        if (sscanf (contents, "%" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT,
                    &o, &c, &u) == 3)
        {
            *orig  = o;
            *compr = c;
            *used  = u;
            ok = TRUE;
        }
    }

    g_free (contents);
    g_free (path);
    return ok;
}

/* Walks /sys/block and sums mm_stat over every zram device. */
static gboolean
sum_devices (guint64 *orig, guint64 *compr, guint64 *used)
{
    GDir *dir = g_dir_open ("/sys/block", 0, NULL);
    if (dir == NULL)
        return FALSE;

    guint64 t_orig = 0, t_compr = 0, t_used = 0;
    gboolean found = FALSE;
    const gchar *name;

    while ((name = g_dir_read_name (dir)) != NULL)
    {
        if (!g_str_has_prefix (name, "zram"))
            continue;

        guint64 o = 0, c = 0, u = 0;
        if (read_one_device (name, &o, &c, &u))
        {
            t_orig  += o;
            t_compr += c;
            t_used  += u;
            found = TRUE;
        }
    }

    g_dir_close (dir);

    if (!found)
        return FALSE;

    *orig  = t_orig;
    *compr = t_compr;
    *used  = t_used;
    return TRUE;
}

static gulong
mem_total_kb (void)
{
    gchar *contents = NULL;
    gulong total = 0;

    if (g_file_get_contents ("/proc/meminfo", &contents, NULL, NULL))
    {
        const gchar *p = strstr (contents, "MemTotal");
        if (p != NULL)
            sscanf (p + strlen ("MemTotal"), ": %lu", &total);
    }

    g_free (contents);
    return total;
}

gulong
read_zram_phys (void)
{
    guint64 orig = 0, compr = 0, used = 0;

    if (!sum_devices (&orig, &compr, &used))
        return 0;

    return (gulong) (used / 1024);
}

gint
read_zram (gulong *zram, gulong *phys_kb, gulong *stored_kb, gdouble *ratio)
{
    guint64 orig = 0, compr = 0, used = 0;

    if (!sum_devices (&orig, &compr, &used))
        return -1;

    *phys_kb   = (gulong) (used / 1024);
    *stored_kb = (gulong) (orig / 1024);
    *ratio     = (compr > 0) ? ((gdouble) orig / (gdouble) compr) : 0.0;

    gulong total = mem_total_kb ();
    *zram = (total > 0) ? (*phys_kb * 100 / total) : 0;

    return 0;
}

gint
read_disk_swap (gulong *total_kb, gulong *used_kb)
{
    gchar *contents = NULL;

    if (!g_file_get_contents ("/proc/swaps", &contents, NULL, NULL))
        return -1;

    gulong total = 0, used = 0;
    gchar **lines = g_strsplit (contents, "\n", -1);

    /* Line 0 is the header: Filename Type Size Used Priority */
    for (guint i = 1; lines[i] != NULL; i++)
    {
        if (lines[i][0] == '\0')
            continue;

        gchar **f = g_strsplit_set (lines[i], " \t", -1);
        gchar **compact = g_new0 (gchar *, g_strv_length (f) + 1);
        guint n = 0;

        /* /proc/swaps is tab-padded, so collapse the empty fields */
        for (guint j = 0; f[j] != NULL; j++)
            if (f[j][0] != '\0')
                compact[n++] = f[j];

        /* Skip zram: its size is the uncompressed one and it costs no disk */
        if (n >= 4 && !g_str_has_prefix (compact[0], "/dev/zram"))
        {
            total += strtoul (compact[2], NULL, 10);
            used  += strtoul (compact[3], NULL, 10);
        }

        g_free (compact);
        g_strfreev (f);
    }

    g_strfreev (lines);
    g_free (contents);

    *total_kb = total;
    *used_kb  = used;
    return 0;
}

#else /* !__linux__ */

gulong
read_zram_phys (void)
{
    return 0;
}

gint
read_zram (gulong *zram, gulong *phys_kb, gulong *stored_kb, gdouble *ratio)
{
    *zram = 0;
    *phys_kb = 0;
    *stored_kb = 0;
    *ratio = 0.0;
    return -1;
}

gint
read_disk_swap (gulong *total_kb, gulong *used_kb)
{
    *total_kb = 0;
    *used_kb = 0;
    return -1;
}

#endif /* __linux__ */