// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package main

import (
  "fmt"
  "strings"
  "regexp"
  "io/ioutil"
  "strconv"
)

// Proc is a struct with process information
type Proc struct {
  Pid int
  CmdLine string
  Swap int
}

// NewProc initialize a new Proc struct
func NewProc(pid int) *Proc {
  proc := new(Proc)
  proc.Pid = pid
  proc.CmdLine = CmdLine(pid)
  proc.Swap = Swap(pid)

  return proc
}

// CmdLine return the command line for a process
func CmdLine(pid int) string {
  data, err := ioutil.ReadFile(fmt.Sprintf("/proc/%d/cmdline", pid))
  if err != nil {
    return ""
  }
  cmdline := strings.Replace(string(data), "\x00", " ", -1)

  return cmdline
}

// Swap return the swap usage for a process
func Swap(pid int) int {
  data, err := ioutil.ReadFile(fmt.Sprintf("/proc/%d/status", pid))
  if err != nil {
    return 0
  }

  r := regexp.MustCompile(`VmSwap:\s+(\d+) kB`)
  match := r.FindSubmatch(data)
  if len(match) == 0 {
    return 0
  }

  swap, err := strconv.Atoi(string(match[1]))
  if err != nil {
    return 0
  }

  return swap
}