chore: Add simple parsers for journald and tail files

internal/parser/journald.go

@@ -0,0 +1,41 @@
+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
+}