#!/usr/bin/env python3

import sys

def read_meminfo():
    f = open("/proc/meminfo")
    result = {}
    for line in f:
        key, value, *_ = line.split()
        key = key.strip(":")
        result[key] = int(value) * 1024
    return result

def read_zfs_arcstats():
    try:
        f = open("/proc/spl/kstat/zfs/arcstats")
    except FileNotFoundError:
        return {}

    # skip first two lines
    f.readline()
    f.readline()

    result = {}
    for line in f:
        key, _, value = line.split()
        result[key] = int(value)
    return result

def print_template(first, *rest):
    sys.stdout.write(first.ljust(7))
    for x in rest:
        sys.stdout.write(x.rjust(12))
    sys.stdout.write("\n")

def main():
    meminfo = read_meminfo()
    arcstats = read_zfs_arcstats()

    mem_total = meminfo["MemTotal"]
    mem_free = meminfo["MemFree"]
    mem_cached = meminfo["Cached"] + meminfo["SReclaimable"]
    mem_buffers = meminfo["Buffers"]
    mem_shared = meminfo["Shmem"]
    mem_available = meminfo["MemAvailable"]

    swap_total = meminfo["SwapTotal"]
    swap_free = meminfo["SwapFree"]

    arc_total = arcstats.get("c_max", 0)
    arc_used = arcstats.get("size", 0)

    calc_used = mem_total - mem_free - mem_cached - mem_buffers - arc_used
    calc_cache = mem_buffers + mem_cached + arc_used
    calc_available = mem_available + arc_used

    def fmt(x):
        return str(round(x/1024/1024))

    print_template("", "total", "used", "free", "shared", "buff/cache", "available")

    print_template(
        "Mem:",
        fmt(mem_total),
        fmt(calc_used),
        fmt(mem_free),
        fmt(mem_shared),
        fmt(calc_cache),
        fmt(calc_available),
    )
    print_template(
        "Swap:",
        fmt(swap_total),
        fmt(swap_total - swap_free),
        fmt(swap_free),
    )
    if arcstats:
        print_template(
            "ZFS:",
            fmt(arc_total),
            fmt(arc_used),
        )

if __name__ == "__main__":
    main()