try:
    import resource
except ImportError:
    pass # Will fail on Win32 systems
import time
from django.template.loader import render_to_string
from django.utils.translation import ugettext_lazy as _
from debug_toolbar.panels import DebugPanel

class TimerDebugPanel(DebugPanel):
    """
    Panel that displays the time a response took in milliseconds.
    """
    name = 'Timer'
    try: # if resource module not available, don't show content panel
        resource
    except NameError:
        has_content = False
        has_resource = False
    else:
        has_content = True
        has_resource = True

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

    def process_response(self, request, response):
        total_time = (time.time() - self._start_time) * 1000
        if self.has_resource:
            self._end_rusage = resource.getrusage(resource.RUSAGE_SELF)

        utime = 1000 * self._elapsed_ru('ru_utime')
        stime = 1000 * self._elapsed_ru('ru_stime')
        vcsw = self._elapsed_ru('ru_nvcsw')
        ivcsw = self._elapsed_ru('ru_nivcsw')
        minflt = self._elapsed_ru('ru_minflt')
        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. :-(
#
#        blkin = self._elapsed_ru('ru_inblock')
#        blkout = self._elapsed_ru('ru_oublock')
#        swap = self._elapsed_ru('ru_nswap')
#        rss = self._end_rusage.ru_maxrss
#        srss = self._end_rusage.ru_ixrss
#        urss = self._end_rusage.ru_idrss
#        usrss = self._end_rusage.ru_isrss

        self.stats = {
                'total_time': total_time,
                'utime': utime,
                'stime': stime,
                'vcsw': vcsw,
                'ivcsw': ivcsw,
                'minflt': minflt,
                'majflt': majflt,
#                'blkin': blkin,
#                'blkout': blkout,
#                'swap': swap,
#                'rss': rss,
#                'urss': urss,
#                'srss': srss,
#                'usrss': usrss,
                }

    def nav_title(self):
        return _('Time')

    def nav_subtitle(self):
        # TODO l10n
        if self.has_resource:
            utime = self._end_rusage.ru_utime - self._start_rusage.ru_utime
            stime = self._end_rusage.ru_stime - self._start_rusage.ru_stime
            return 'CPU: %0.2fms (%0.2fms)' % ((utime + stime) * 1000.0, self.stats['total_time'])
        else:
            return 'TOTAL: %0.2fms' % (self.stats[total_time])

    def title(self):
        return _('Resource Usage')

    def url(self):
        return ''

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

    def content(self):
        # TODO l10n on values
        rows = (
            (_('User CPU time'), '%0.3f msec' % self.stats['utime']),
            (_('System CPU time'), '%0.3f msec' % self.stats['stime']),
            (_('Total CPU time'), '%0.3f msec' % (self.stats['utime'] + self.stats['stime'])),
            (_('Elapsed time'), '%0.3f msec' % self.stats['total_time']),
            (_('Context switches'), '%d voluntary, %d involuntary' % (self.stats['vcsw'], self.stats['ivcsw'])),
#            ('Memory use', '%d max RSS, %d shared, %d unshared' % (self.stats['rss'], self.stats.['srss'],
#                                                                   self.stats['urss'] + self.stats['usrss'])),
#            ('Page faults', '%d no i/o, %d requiring i/o' % (self.stats['minflt'], self.stats['majflt'])),
#            ('Disk operations', '%d in, %d out, %d swapout' % (self.stats['blkin'], self.stats['blkout'], self.stats['swap'])),
        )

        context = self.context.copy()
        context.update({
            'rows': rows,
        })

        return render_to_string('debug_toolbar/panels/timer.html', context)