package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"strings"
)

// Map to hold a list of "currently running" processes.
var processes = make(map[string]string)

// Build a map of userid to username
var userMap = make(map[string]string)
func buildUserIdMap() {
	passwdContents, err := ioutil.ReadFile("/etc/passwd")
	if err != nil {
		return
	}
	lines := strings.Split(string(passwdContents), "\n")
	for _, line := range lines {
		if len(line) < 5 {
			continue
		}
		elements := strings.Split(line, ":")
		name := elements[0]
		uid := elements[2]
		userMap[uid] = name
	}
}

// Function to check for new processes.
func checkForNewProcesses() (newProcesses, processOwners map[string]string) {

	// Get a list of all files/dirs inside /proc
	files, err := ioutil.ReadDir("//proc")
	if err != nil {
		log.Fatal(err)
	}

	// Create a map to hold new process info
	newProcesses = make(map[string]string)
	processOwners = make(map[string]string)

	// Iterate through the list of files/dirs
	for _, file := range files {
		// If this is a directory try to process it
		if file.IsDir() {
			name := file.Name()

			// Does it already exist in the list of processes we've seen?
			if _, ok := processes[name]; ok {
				continue
			}
			// If not add it to the list of new processes
			cmdline, err := ioutil.ReadFile(fmt.Sprintf("//proc//%s//cmdline", name))
			if err != nil {
				continue
			}

			// Split into strings whenever we find a null byte
			parts := make([]string,0)
			start := 0
			for i := 0; i < len(cmdline); i++ {
				if cmdline[i] == 0x00 {
					parts = append(parts, string(cmdline[start:i]))
					start = i
				}
			}

			processArgs := strings.Join(parts, " ")
			newProcesses[name] = processArgs
			processes[name] = processArgs //TODO: With the way this is currently used could just be a slice

			// Try to get owner info
			statusline, err := ioutil.ReadFile(fmt.Sprintf("//proc//%s//status", name))
			if err != nil {
				continue
			}

			lines := strings.Split(string(statusline), "\n")
			uid := strings.Split(lines[8], "\t")[1]
			processOwners[name] = userMap[uid]
		}
	}
	return
}

func main() {

	// Build the map to translate uid to a friendly name
	buildUserIdMap()

	for {
		newProcesses, processOwners := checkForNewProcesses()
		for key, value := range newProcesses {
			log.Printf("[%5s]\t%s [owner=%s]\n", key, value, processOwners[key])
		}
	}
}