#!/usr/bin/env python3

import time
import subprocess
import sys

def read_file(filename):
    with open(filename) as f:
        return f.read()

def read_cpu_idle_jiffys(procstat):
    line = procstat.split("\n")[0]
    fields = line.split()
    return int(fields[4])

def count_cpus(procstat):
    count = -1
    for line in procstat.split("\n"):
        if line.startswith("cpu"):
            count += 1
    return count

def read_cpu_percent():
    procstat = read_file("/proc/stat")
    num_cpus = count_cpus(procstat)

    tstart = time.time()
    idle_jiffy1 = read_cpu_idle_jiffys(procstat)
    time.sleep(0.1)
    idle_jiffy2 = read_cpu_idle_jiffys(read_file("/proc/stat"))
    tend = time.time()

    duration = tend - tstart
    idle_jiffys_per_second = (idle_jiffy2 - idle_jiffy1) / duration

    idle_jiffys_per_cpu_second = idle_jiffys_per_second / num_cpus

    # One jiffy is 10ms, so we can get the percentage very easily!
    return 100 - idle_jiffys_per_cpu_second

def read_mem_percent():
    meminfo = read_file("/proc/meminfo")

    d = {}
    for line in meminfo.strip().split("\n"):
        key, value = line.split()[:2]
        d[key] = int(value)

    mem_total = d["MemTotal:"]
    mem_free = d["MemAvailable:"]
    mem_used = mem_total - mem_free

    return mem_used / mem_total * 100

def read_battery_percent():
    args = ["upower", "--show-info", "/org/freedesktop/UPower/devices/DisplayDevice"]
    with subprocess.Popen(args, stdout=subprocess.PIPE) as process:
        upower_data, _ = process.communicate()
        if process.poll() != 0:
            return

    for line in upower_data.decode("ascii").split("\n"):
        line = line.strip()
        if line.startswith("percentage:"):
            percent_str = line.split()[1]
            return int(percent_str.replace("%", ""))

def write(s):
    sys.stdout.write(s)

def print_percent(name, units, value, color_map):
    if value is None:
        return

    value = round(value)

    for low, high, color in color_map:
        if value >= low and value <= high:
            break
    else:
        color = "black"

    write(
        "%s <span color='%s'>%s</span>%s  " %
        (name, color, value, units)
    )

def main():
    write("<txt>")

    print_percent(
        "cpu", "%",
        read_cpu_percent(),
        color_map=[(50, 100, "red"), (0, 5, "green")],
    )

    print_percent(
        "mem", "%",
        read_mem_percent(),
        color_map=[(70, 100, "red")],
    )

    print_percent(
        "batt", "%",
        read_battery_percent(),
        color_map=[(0, 25, "red")],
    )

    write("</txt>")

if __name__ == "__main__":
    main()