#
# Copyright (C) 2017-2018 Marko Myllynen <myllynen@redhat.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
""" PCP BCC PMDA sysfork module """

# pylint: disable=invalid-name

from ctypes import c_int

from bcc import BPF

from pcp.pmapi import pmUnits
from cpmapi import PM_TYPE_U64, PM_SEM_COUNTER, PM_COUNT_ONE
from cpmda import PMDA_FETCH_NOVALUES

from modules.pcpbcc import PCPBCCBase

#
# BPF program
#
bpf_src = "modules/sysfork.bpf"

#
# PCP BCC PMDA constants
#
MODULE = 'sysfork'
METRIC = 'proc.sysfork'
units_count = pmUnits(0, 0, 1, 0, 0, PM_COUNT_ONE)

#
# PCP BCC Module
#
class PCPBCCModule(PCPBCCBase):
    """ PCP BCC sysfork module """
    def __init__(self, config, log, err, _):
        """ Constructor """
        PCPBCCBase.__init__(self, MODULE, config, log, err)

        self.value = 0

        self.log("Initialized.")

    def metrics(self):
        """ Get metric definitions """
        name = METRIC
        self.items.append(
            # Name - reserved - type - semantics - units - help
            (name, None, PM_TYPE_U64, PM_SEM_COUNTER, units_count, 'fork rate'),
        )
        return False, self.items

    def compile(self):
        """ Compile BPF """
        try:
            self.bpf = BPF(src_file=bpf_src)
            self.bpf.attach_kprobe(event="sched_fork", fn_name="do_count")
            self.log("Compiled.")
        except Exception as error: # pylint: disable=broad-except
            self.bpf = None
            self.err(str(error))
            self.err("Module NOT active!")
            raise

    def refresh(self):
        """ Refresh BPF data """
        if self.bpf is None:
            return

        self.value = self.bpf["stats"][c_int(1)].value

    def bpfdata(self, item, inst):
        """ Return BPF data as PCP metric value """
        try:
            return [self.value, 1]
        except Exception: # pylint: disable=broad-except
            return [PMDA_FETCH_NOVALUES, 0]