check.go

package main

import (
	"bytes"
	"crypto/sha256"
	"fmt"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"strings"

	"github.com/mackerelio/checkers"
	"github.com/monitoring-forge/saferio"
)

func (opt *Opt) cmd(file *os.File) error {
	cmd := exec.Command(opt.Command, opt.Args...)
	var stderr bytes.Buffer
	cmd.Stdout = file
	cmd.Stderr = &stderr
	if err := cmd.Start(); err != nil {
		return err
	}
	err := cmd.Wait()
	if err != nil {
		return fmt.Errorf("%w - %s", err, stderr.String())
	}
	return nil
}

func (opt *Opt) check() *checkers.Checker {

	hasher := sha256.New()
	fmt.Fprintf(hasher, "%s\x00%s\x00%s", opt.Identifier, opt.Command, strings.Join(opt.Args, "\x00"))

	curUser, err := user.Current()
	if err != nil {
		return checkers.Critical(err.Error())
	}

	prevFileName := fmt.Sprintf("check-diff-%s-%x", curUser.Uid, hasher.Sum(nil))
	newFile, err := os.CreateTemp(opt.Workdir, "check-diff-")
	if err != nil {
		return checkers.Critical(err.Error())
	}

	defer func() {
		_ = newFile.Close()
		_ = os.Remove(newFile.Name())
	}()

	err = opt.cmd(newFile)
	if err != nil {
		return checkers.Critical(err.Error())
	}

	err = newFile.Close()
	if err != nil {
		return checkers.Critical(err.Error())
	}

	if !saferio.FileExists(opt.Workdir, prevFileName) {
		err = os.Rename(newFile.Name(), filepath.Join(opt.Workdir, prevFileName))
		if err != nil {
			return checkers.Critical(err.Error())
		}
		if len(opt.Args) > 0 {
			return checkers.Ok(fmt.Sprintf("first time execution command: '%s %s'", opt.Command, strings.Join(opt.Args, " ")))
		}
		return checkers.Ok(fmt.Sprintf("first time execution command: '%s'", opt.Command))
	}

	textdiff := ""
	var errDiff error
	if opt.JSON {
		textdiff, errDiff = diffJson(filepath.Join(opt.Workdir, prevFileName), newFile.Name(), opt.jq)
		if errDiff != nil {
			return checkers.Critical(errDiff.Error())
		}
	} else {
		textdiff, errDiff = diff(filepath.Join(opt.Workdir, prevFileName), newFile.Name())
		if errDiff != nil {
			return checkers.Critical(errDiff.Error())
		}
	}

	err = os.Rename(newFile.Name(), filepath.Join(opt.Workdir, prevFileName))
	if err != nil {
		return checkers.Critical(err.Error())
	}

	if textdiff == "" {
		msg, err := buildNoDifferenceMsg(filepath.Join(opt.Workdir, prevFileName))
		if err != nil {
			return checkers.Critical(err.Error())
		}
		return checkers.Ok(msg)
	}

	diffMsg := buildDiffMsg(textdiff)
	if opt.Warn {
		return checkers.Warning(diffMsg)
	}
	return checkers.Critical(diffMsg)
}