package main

import (
	"os"
	"strconv"
	"strings"
)

// Process contains an alias that will be returned when queries, and a process
// name to look for.
type Process struct {
	Alias   string `json:"alias"`
	Process string `json:"process"`
}

// ProcessesState is a map of processes' aliases and its statuses.
type ProcessesState map[string]bool

func GetProcessesState(procs *[]Process) (ps ProcessesState) {
	ps = make(ProcessesState)

	for _, proc := range *procs {
		pids, err := GetProcessPIDs(proc.Process)
		ps[proc.Alias] = err == nil && len(pids) > 0
	}

	return
}

// GetProcessPIDs returns a list of PIDs found for a process.
func GetProcessPIDs(name string) (pids []int, err error) {
	dir, err := os.ReadDir("/proc/")
	if err != nil {
		return nil, err
	}

	for _, entry := range dir {
		// This line demands a little clarification. Here we are making sure
		// that the first character of a directory name is numeric. In ASCII
		// all numerals are laying within 0x30-0x39 range.
		if entry.IsDir() && entry.Name()[0]>>0x4&0xf == 0x3 {
			cmdline, err := os.ReadFile("/proc/" + entry.Name() + "/cmdline")
			if err != nil {
				return nil, err
			}

			if strings.Contains(string(cmdline), name) {
				pid, err := strconv.Atoi(entry.Name())
				if err != nil {
					continue
				}
				pids = append(pids, pid)
			}
		}
	}

	return pids, nil
}