"""Read-only local telemetry; no dependency on the monitoring application."""
import re
import shutil
import subprocess
import time
from pathlib import Path


class LocalState:
    def __init__(self):
        self.previous_cpu=None
        self.network_at=float('-inf')
        self.network={'kind':'NET','metric':'--','ip_label':'IP4','ip':'NO IP'}

    def cpu(self):
        values=list(map(int,Path('/proc/stat').read_text().splitlines()[0].split()[1:9]))
        current=(sum(values),values[3]+values[4]);previous=self.previous_cpu;self.previous_cpu=current
        if previous is None:return None
        total=current[0]-previous[0]
        return max(0,min(100,100*(1-(current[1]-previous[1])/total))) if total>0 else None

    @staticmethod
    def memory():
        values={line.split(':')[0]:int(line.split()[1]) for line in Path('/proc/meminfo').read_text().splitlines()}
        return 100*(1-values['MemAvailable']/values['MemTotal'])

    @staticmethod
    def disk():
        usage=shutil.disk_usage('/')
        return 100*usage.used/usage.total

    @staticmethod
    def read_network():
        for family,address,label in [('-4','1.1.1.1','IP4'),('-6','2606:4700:4700::1111','IP6')]:
            # Route lookup only: does not send packets or change network configuration.
            result=subprocess.run(['ip',family,'route','get',address],capture_output=True,text=True,timeout=1)
            dev=re.search(r'\bdev\s+(\S+)',result.stdout);src=re.search(r'\bsrc\s+(\S+)',result.stdout)
            if not dev:continue
            iface=dev.group(1);wireless=Path('/sys/class/net',iface,'wireless').exists();metric='--'
            if wireless:
                for line in Path('/proc/net/wireless').read_text().splitlines():
                    if line.lstrip().startswith(iface+':'):metric=str(float(line.split()[3].rstrip('.')));break
            else:
                try:metric=Path('/sys/class/net',iface,'speed').read_text().strip()
                except OSError:metric='UP'
            return {'kind':'WIF' if wireless else 'ETH','metric':metric,'ip_label':label,'ip':src.group(1) if src else 'NO IP'}
        return {'kind':'NET','metric':'DOWN','ip_label':'IP4','ip':'NO IP'}

    def sample(self):
        system={};errors={}
        for name,reader in [('cpu_percent',self.cpu),('memory_percent',self.memory),('disk_percent',self.disk),
                            ('temperature_c',lambda:float(Path('/sys/class/thermal/thermal_zone0/temp').read_text())/1000)]:
            try:system[name]=reader()
            except (OSError,ValueError,KeyError,IndexError,ZeroDivisionError) as exc:system[name]=None;errors[name]=str(exc)
        if time.monotonic()-self.network_at>=5:
            try:self.network=self.read_network()
            except (OSError,ValueError,subprocess.SubprocessError) as exc:
                self.network={'kind':'NET','metric':'--','ip_label':'IP4','ip':'UNKNOWN'};errors['network']=str(exc)
            self.network_at=time.monotonic()
        return {'system':system,'network':dict(self.network)},errors