from __future__ import absolute_import, unicode_literals

import time

from django.template.loader import render_to_string
from django.utils.translation import ugettext_lazy as _

from debug_toolbar.panels import Panel

try:
    import resource     # Not available on Win32 systems
except ImportError:
    resource = None


class TimerPanel(Panel):
    """
    Panel that displays the time a response took in milliseconds.
    """

    def nav_subtitle(self):
        stats = self.get_stats()
        if hasattr(self, '_start_rusage'):
            utime = self._end_rusage.ru_utime - self._start_rusage.ru_utime
            stime = self._end_rusage.ru_stime - self._start_rusage.ru_stime
            return _("CPU: %(cum)0.2fms (%(total)0.2fms)") % {
                'cum': (utime + stime) * 1000.0,
                'total': stats['total_time']
            }
        elif 'total_time' in stats:
            return _("Total: %0.2fms") % stats['total_time']
        else:
            return ''

    has_content = resource is not None

    title = _("Time")

    template = 'debug_toolbar/panels/timer.html'

    @property
    def content(self):
        stats = self.get_stats()
        rows = (
            (_("User CPU time"), _("%(utime)0.3f msec") % stats),
            (_("System CPU time"), _("%(stime)0.3f msec") % stats),
            (_("Total CPU time"), _("%(total)0.3f msec") % stats),
            (_("Elapsed time"), _("%(total_time)0.3f msec") % stats),
            (_("Context switches"), _("%(vcsw)d voluntary, %(ivcsw)d involuntary") % stats),
        )
        return render_to_string(self.template, {'rows': rows})

    def process_request(self, request):
        self._start_time = time.time()
        if self.has_content:
            self._start_rusage = resource.getrusage(resource.RUSAGE_SELF)

    def generate_stats(self, request, response):
        stats = {}
        if hasattr(self, '_start_time'):
            stats['total_time'] = (time.time() - self._start_time) * 1000
        if hasattr(self, '_start_rusage'):
            self._end_rusage = resource.getrusage(resource.RUSAGE_SELF)
            stats['utime'] = 1000 * self._elapsed_ru('ru_utime')
            stats['stime'] = 1000 * self._elapsed_ru('ru_stime')
            stats['total'] = stats['utime'] + stats['stime']
            stats['vcsw'] = self._elapsed_ru('ru_nvcsw')
            stats['ivcsw'] = self._elapsed_ru('ru_nivcsw')
            stats['minflt'] = self._elapsed_ru('ru_minflt')
            stats['majflt'] = self._elapsed_ru('ru_majflt')
            # these are documented as not meaningful under Linux.  If you're running BSD
            # feel free to enable them, and add any others that I hadn't gotten to before
            # I noticed that I was getting nothing but zeroes and that the docs agreed. :-(
            #
            #        stats['blkin'] = self._elapsed_ru('ru_inblock')
            #        stats['blkout'] = self._elapsed_ru('ru_oublock')
            #        stats['swap'] = self._elapsed_ru('ru_nswap')
            #        stats['rss'] = self._end_rusage.ru_maxrss
            #        stats['srss'] = self._end_rusage.ru_ixrss
            #        stats['urss'] = self._end_rusage.ru_idrss
            #        stats['usrss'] = self._end_rusage.ru_isrss

        self.record_stats(stats)

    def _elapsed_ru(self, name):
        return getattr(self._end_rusage, name) - getattr(self._start_rusage, name)