from pymonitor import Metric
import re

memline_pattern = re.compile(r'^(?P<key>[^\\:]+)\:\s+(?P<value>[0-9]+)(\s(?P<unit>[a-zA-Z]+))?')

computed_fields = {
    "mempctused": lambda items: round((items["memtotal"] - items["memfree"]) / items["memtotal"], 5),
    "mempctfree": lambda items: 1 - round((items["memtotal"] - items["memfree"]) / items["memtotal"], 5),
    "mempctused_nocache": lambda items: round((items["memtotal"] - items["memfree"] - items["cached"]) /
                                              items["memtotal"], 5),
    "mempctfree_nocache": lambda items: 1 - round((items["memtotal"] - items["memfree"] - items["cached"]) /
                                                  items["memtotal"], 5),
    "swappctused": lambda items: round((items["swaptotal"] - items["swapfree"]) /
                                       items["swaptotal"] if items["swaptotal"] > 0 else 0.0, 5),
    "swappctfree": lambda items: 1 - round((items["swaptotal"] - items["swapfree"]) /
                                           items["swaptotal"] if items["swaptotal"] > 0 else 0.0, 5)
}


def meminfo(whitelist=[]):
    if not whitelist:
        whitelist = ["swaptotal", "swapfree", "swapcached",
                     "memtotal", "memfree", "cached",
                     "active", "inactive", ]

    result = {}
    with open("/proc/meminfo", "r") as f:
        for line in f.read().strip().split("\n"):
            matches = memline_pattern.match(line)

            value = int(matches.group("value"))
            unit = matches.group("unit")

            if unit:
                if unit == "kB":
                    value *= 1024
                else:
                    raise Exception("Unknown unit")

            name = ''.join(c for c in matches.group("key").lower() if 96 < ord(c) < 123)
            if name in whitelist:
                result[name] = value

        for key in computed_fields:
            result[key] = computed_fields[key](result)

    yield Metric(result)


mapping = {
    "swaptotal": {"type": "long"},
    "swapfree": {"type": "long"},
    "swapcached": {"type": "long"},
    "memtotal": {"type": "long"},
    "memfree": {"type": "long"},
    "memavailable": {"type": "long"},
    "cached": {"type": "long"},
    "active": {"type": "long"},
    "inactive": {"type": "long"},
    "mempctused": {"type": "double"},
    "mempctfree": {"type": "double"},
    "mempctused_nocache": {"type": "double"},
    "mempctfree_nocache": {"type": "double"},
    "swappctused": {"type": "double"},
    "swappctfree": {"type": "double"}
}


if __name__ == '__main__':
    for item in meminfo():
        print(item)