package parser

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"regexp"
)

func ParseJournald(unit string) (Parser, error) {
	if unit == "" {
		return Parser{}, errors.New("unit name cannot be empty")
	}

	validUnitName := regexp.MustCompile(`^[a-zA-Z0-9:_\.\-@]+$`)
	if !validUnitName.MatchString(unit) {
		return Parser{}, fmt.Errorf("invalid systemd unit name: %s", unit)
	}

	cmd := exec.Command("journalctl", "-u", unit, "-f", "-n", "0", "-o", "short", "--no-pager")

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return Parser{}, fmt.Errorf("stdout pipe error: %w", err)
	}

	if err := cmd.Start(); err != nil {
		return Parser{}, fmt.Errorf("failed to start journalctl: %w", err)
	}

	p := Parser{
		parser: bufio.NewScanner(stdout),
		ch:     make(chan string, 100),
		cmd:    cmd,
		file:   nil,
	}

	return p, nil
}