// Copyright 2021, johan@nosd.in
//go:build freebsd
// +build freebsd

//
// godit is a search tool for BSM audit trails used by FreeBSD auditd
//

/*
% time praudit -l /home/yo/Dev/go/godit/20211228134923.20211228151348 > praudit.log
101.728u 7.315s 1:49.09 99.9%   10+167k 0+191152io 0pf+0w

% time ./godit 20211228134923.20211228151348 > godit.log
11.599u 38.235s 0:48.25 103.2%  1045+553k 1+2262168io 4pf+0w
% ./godit -V
Godit v0.03

% time ./godit 20211228134923.20211228151348 > 20211228134923.20211228151348.godit3
7.183u 19.590s 0:25.98 103.0%   1038+559k 0+2262168io 0pf+0w
% ./godit -V
Godit v0.4.3
*/

package main

import (
	"io"
	"os"
	"fmt"
	"sync"
	"bufio"
	"strings"
	"syscall"
	"os/signal"
	"github.com/spf13/pflag"
)

const (
	version = "0.6.3"
)

var (
	randFlag    bool
	showVersion bool

	// Default delimiter
	delimiter = ","

	Writer *bufio.Writer
)

func NewWriter(file string) (*bufio.Writer, *os.File, error) {
	if len(file) > 0 {
		var f *os.File
		var err error

		f, err = os.OpenFile(file, os.O_CREATE|os.O_RDWR|os.O_APPEND, 0640)
		if err != nil {
			return nil, nil, err
		}
		Writer = bufio.NewWriter(f)
		return Writer, f, nil
	} else {
		Writer = bufio.NewWriter(os.Stdout)
		return Writer, nil, nil
	}
}

func main() {
	var flags int
	var oneLine bool
	var noUserResolve bool
	var syslog23 bool
	var json bool
	var outputFile string
	// Output file mutex
	var outfMtx sync.Mutex
	var outFile *os.File

	pflag.BoolVarP(&oneLine, "oneline", "l", false, "Prints the entire record on the same line")
	pflag.BoolVarP(&noUserResolve, "numeric", "n", false, "Do not convert user and group IDs to their names but leave in their numeric forms")
	pflag.BoolVarP(&json, "json", "j", false, "Print compact json")
	pflag.BoolVarP(&syslog23, "syslog23", "s", false, "Print time as \"2006-01-02T15:04:05.000Z07:00\", RFC339 with ms, also used on RSYSLOG_SyslogProtocol23Format. \"msec\" field will not be print in json output")
	pflag.StringVarP(&outputFile, "out", "o", "", "Output to file, overwrite existing. File will be re-opened receiving SIGUSR1.")
	pflag.BoolVarP(&showVersion, "version", "V", false, "Show version and exit")

	var Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of \"%s [opts] auditfile\":\n", os.Args[0])
		pflag.PrintDefaults()
		fmt.Fprintf(os.Stderr, "Set auditfile to \"-\" to read stdin\n")
	}
	pflag.Usage = Usage

	pflag.Parse()

	if showVersion {
		fmt.Printf("Godit v%s\n", version)
		return
	}
	if oneLine {
		flags = flags + PRT_ONELINE
	}
	if noUserResolve {
		flags = flags + PRT_NORESOLVE_USER
	}
	if syslog23 {
		flags = flags + PRT_TIMESYSLOG23
	}
	if json {
		flags |= PRT_JSON
	}

	args := os.Args
	if len(os.Args) < 2 {
		pflag.Usage()
		os.Exit(1)
	}
	filename := args[len(args)-1]

	// Get a writer, file or stdout
	_, outFile, err := NewWriter(outputFile)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%v\n", err)
		os.Exit(1)
	}
	if len(outputFile) > 0 {
		// Manage output file rotation when receiving SIGUSR1
		sig := make(chan os.Signal)
		signal.Notify(sig, syscall.SIGUSR1)
		go func() {
			for {
				<-sig
				outfMtx.Lock()
				fmt.Println("SIGUSR1 received, recreating output file")
				outFile.Close()
				_, outFile, err = NewWriter(outputFile)
				if err != nil {
					outfMtx.Unlock()
					fmt.Fprintf(os.Stderr, "%v\n", err)
					os.Exit(1)
				}
				outfMtx.Unlock()
			}
		}()
	}

	var f *os.File
	var r *bufio.Reader
	if len(filename) > 0 {
		// If arg is "-", open stdin to read content
		if true == strings.EqualFold(filename, "-") {
			r = bufio.NewReader(os.Stdin)
		} else {
			f, err = os.Open(filename)
			if err != nil {
				fmt.Fprintf(os.Stderr, "Impossible d'ouvrir le fichier %s\n", filename)
				os.Exit(-1)
			}
			r = bufio.NewReader(f)
		}

		for {
			rec, err := readRecordToStruct(r)
			if err != nil {
				if err != io.EOF {
					fmt.Printf("Erreur : %v\n", err)
				} else { // v.0.4.2 : Continue on error
					return
				}
			}
			if len(outputFile) > 0 {
				outfMtx.Lock()
				rec.Print(Writer, ",", flags)
				Writer.Flush()	// Performance ?
				outfMtx.Unlock()
			} else {
				// No need for mutex with stdout
				rec.Print(Writer, ",", flags)
			}
		}
	}

	if len(outputFile) > 0 && outFile != nil {
		outfMtx.Lock()
		outFile.Close()
		outfMtx.Unlock()
	}
}