"""Displays info about zpools present on the system

Parameters:
   * zpool.list: Comma-separated list of zpools to display info for. If empty, info for all zpools
                 is displayed. (Default: '')
   * zpool.format: Format string, tags {name}, {used}, {left}, {size}, {percentfree}, {percentuse},
                   {status}, {shortstatus}, {fragpercent}, {deduppercent} are supported.
                   (Default: '{name} {used}/{size} ({percentfree}%)')
   * zpool.showio: Show also widgets detailing current read and write I/O (Default: true)
   * zpool.ioformat: Format string for I/O widget, tags {ops} (operations per seconds) and {band}
                     (bandwidth) are supported. (Default: '{band}')
   * zpool.warnfree: Warn if free space is below this percentage (Default: 10)
   * zpool.sudo: Use sudo when calling the `zpool` binary. (Default: false)

Option `zpool.sudo` is intended for Linux users using zfsonlinux older than 0.7.0: In pre-0.7.0
releases of zfsonlinux regular users couldn't invoke even informative commands such as
`zpool list`. If this option is true, command `zpool list` is invoked with sudo. If this option
is used, the following (or ekvivalent) must be added to the `sudoers(5)`:

```
<username/ALL> ALL = (root) NOPASSWD: /usr/bin/zpool list
```

Be aware of security implications of doing this!
"""

import time
import logging
from pkg_resources import parse_version

log = logging.getLogger(__name__)

import core.module
import core.widget

import util.cli
import util.format

class Module(core.module.Module):
    def __init__(self, config):
        super().__init__(config, [])

        self._includelist = set(filter(lambda x: len(x) > 0,
                                       util.format.aslist(self.parameter('list', default=''))))
        self._format = self.parameter('format', default='{name} {shortstatus} {used}/{size} ' +
                                                        '({percentfree}%)')
        self._usesudo = util.format.asbool(self.parameter('sudo', default=False))
        self._showio = util.format.asbool(self.parameter('showio', default=True))
        self._ioformat = self.parameter('ioformat', default='{band}')
        self._warnfree = int(self.parameter('warnfree', default=10))

    def update(self):
        widgets = self.widgets()
        zfs_version_path = '/sys/module/zfs/version'
        # zpool list -H: List all zpools, use script mode (no headers and tabs as separators).
        try:
            with open(zfs_version_path, 'r') as zfs_mod_version:
                zfs_version = zfs_mod_version.readline().rstrip().split('-')[0]
        except IOError:
            # ZFS isn't installed or the module isn't loaded, stub the version
            zfs_version = '0.0.0'
            logging.error('ZFS version information not found at {}, check the module is loaded.'.format(zfs_version_path))

        raw_zpools = util.cli.execute(('sudo ' if self._usesudo else '') + 'zpool list -H').split('\n')

        for widget in widgets:
            widget.set('visited', False)

        for raw_zpool in raw_zpools:
            try:
                # Ignored fields (assigned to _) are 'expandsz' and 'altroot', also 'ckpoint' in ZFS 0.8.0+
                if parse_version(zfs_version) < parse_version('0.8.0'):
                    name, size, alloc, free, _, frag, cap, dedup, health, _ = raw_zpool.split('\t')
                else:
                    name, size, alloc, free, _, _, frag, cap, dedup, health, _ = raw_zpool.split('\t')
                cap = cap.rstrip('%')
                percentuse=int(cap)
                percentfree=100-percentuse
                # There is a command, zpool iostat, which is however blocking and was therefore
                # causing issues.
                # Instead, we read file `/proc/spl/kstat/zfs/<poolname>/io` which contains
                # cumulative I/O statistics since boot (or pool creation). We store these values
                # (and timestamp) during each widget update, and during the next widget update we
                # use them to compute delta of transferred bytes, and using the last and current
                # timestamp the rate at which they have been transferred.
                with open('/proc/spl/kstat/zfs/{}/io'.format(name), 'r') as f:
                    # Third row provides data we need, we are interested in the first 4 values.
                    # More info about this file can be found here:
                    # https://github.com/zfsonlinux/zfs/blob/master/lib/libspl/include/sys/kstat.h#L580
                    # The 4 values are:
                    # nread, nwritten, reads, writes
                    iostat = list(map(int, f.readlines()[2].split()[:4]))
            except (ValueError, IOError):
                # Unable to parse info about this pool, skip it
                continue

            if self._includelist and name not in self._includelist:
                continue

            widget = self.widget(name)
            if not widget:
                widget = core.widget.Widget(name=name)
                widget.set('last_iostat', [0, 0, 0, 0])
                widget.set('last_timestamp', 0)
                widgets.append(widget)

            delta_iostat = [b - a for a, b in zip(iostat, widget.get('last_iostat'))]
            widget.set('last_iostat', iostat)

            # From docs:
            #   > Note that even though the time is always returned as a floating point number, not
            #   > all systems provide time with a better precision than 1 second.
            # Be aware that that may affect the precision of reported I/O
            # Also, during one update cycle the reported I/O may be garbage if the system time
            # was changed.
            timestamp = time.time()
            delta_timestamp = widget.get('last_timestamp') - timestamp
            widget.set('last_timestamp', time.time())

            # abs is there because sometimes the result is -0
            rate_iostat = [abs(x / delta_timestamp) for x in delta_iostat]
            nread, nwritten, reads, writes = rate_iostat

            # theme.minwidth is not set since these values are not expected to change
            # rapidly
            widget.full_text(self._format.format(name=name, used=alloc, left=free, size=size,
                                                 percentfree=percentfree, percentuse=percentuse,
                                                 status=health,
                                                 shortstatus=self._shortstatus(health),
                                                 fragpercent=frag, deduppercent=dedup))
            widget.set('state', health)
            widget.set('percentfree', percentfree)
            widget.set('visited', True)

            if self._showio:
                wname, rname = [name + x for x in ['__write', '__read']]
                widget_w = self.widget(wname)
                widget_r = self.widget(rname)
                if not widget_w or not widget_r:
                    widget_r = core.widget.Widget(name=rname)
                    widget_w = core.widget.Widget(name=wname)
                    widgets.extend([widget_r, widget_w])
                for w in [widget_r, widget_w]:
                    w.set('theme.minwidth', self._ioformat.format(ops=9999,
                                                                  band=util.format.bytefmt(999.99*(1024**2))))
                    w.set('visited', True)
                widget_w.full_text(self._ioformat.format(ops=round(writes),
                                                         band=util.format.bytefmt(nwritten)))
                widget_r.full_text(self._ioformat.format(ops=round(reads),
                                                         band=util.format.bytefmt(nread)))

        for widget in widgets:
            if widget.get('visited') is False:
                widgets.remove(widget)
        self.widgets(widgets)

    def state(self, widget):
        if widget.name.endswith('__read'):
            return 'poolread'
        elif widget.name.endswith('__write'):
            return 'poolwrite'

        state = widget.get('state')
        if state == 'FAULTED':
            return [state, 'critical']
        elif state == 'DEGRADED' or widget.get('percentfree') < self._warnfree:
            return [state, 'warning']

        return state

    @staticmethod
    def _shortstatus(status):
        # From `zpool(8)`, section Device Failure and Recovery:
        # A pool's health status is described by one of three states: online, degraded, or faulted.
        # An online pool has all devices operating normally.  A degraded pool is one in which one
        # or more devices have failed, but the data is still available due to a redundant
        # configuration.  A faulted pool has corrupted metadata, or one or more faulted devices, and
        # insufficient replicas to continue functioning.
        shortstate = {
            'DEGRADED': 'DEG',
            'FAULTED': 'FLT',
            'ONLINE': 'ONL',
        }
        try:
            return shortstate[status]
        except KeyError:
            return ''

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