Implement Ruleset configuration in logranger

Added a Ruleset configuration to the logranger application, along with associated error handling. The code now loads a ruleset file from configuration, checks for duplicate rules, and logs each rule as it is found. The ruleset is also integrated within the server setup. The PIDFile now includes a default RuleFile reference in config.go.

config.go

@@ -20,7 +20,8 @@ import (
 type Config struct {
 	// Server holds server specific configuration values
 	Server struct {
-		PIDFile string `fig:"pid_file" default:"/var/run/logranger.pid"`
+		PIDFile  string `fig:"pid_file" default:"/var/run/logranger.pid"`
+		RuleFile string `fig:"rule_file" default:"etc/logranger.rules.toml"`
 	}
 	Listener struct {
 		ListenerUnix struct {

rule.go

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2023 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
+package logranger
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"github.com/kkyr/fig"
+)
+
+type Ruleset struct {
+	Rule []struct {
+		ID     string         `fig:"id" validate:"required"`
+		Regexp *regexp.Regexp `fig:"regexp" validate:"required"`
+	} `fig:"rule"`
+}
+
+func NewRuleset(c *Config) (*Ruleset, error) {
+	rs := &Ruleset{}
+	p := filepath.Dir(c.Server.RuleFile)
+	f := filepath.Base(c.Server.RuleFile)
+	_, err := os.Stat(fmt.Sprintf("%s/%s", p, f))
+	if err != nil {
+		return rs, fmt.Errorf("failed to read config: %w", err)
+	}
+
+	if err = fig.Load(rs, fig.Dirs(p), fig.File(f), fig.UseStrict()); err != nil {
+		return rs, fmt.Errorf("failed to load ruleset: %w", err)
+	}
+
+	rna := make([]string, 0)
+	for _, r := range rs.Rule {
+		for _, rn := range rna {
+			if strings.EqualFold(r.ID, rn) {
+				return nil, fmt.Errorf("duplicate rule found: %s", r.ID)
+			}
+		}
+		rna = append(rna, r.ID)
+	}
+
+	return rs, nil
+}

server.go

@@ -35,6 +35,8 @@ type Server struct {
 	log *slog.Logger
 	// parser is a parsesyslog.Parser
 	parser parsesyslog.Parser
+	// ruleset is a pointer to the ruleset
+	ruleset *Ruleset
 	// wg is a sync.WaitGroup
 	wg sync.WaitGroup
 }
@@ -55,11 +57,22 @@ func (s *Server) Run() error {
 	if err != nil {
 		return err
 	}
+
 	p, err := parsesyslog.New(s.conf.internal.ParserType)
 	if err != nil {
 		return fmt.Errorf("failed to initialize syslog parser: %w", err)
 	}
 	s.parser = p
+
+	rs, err := NewRuleset(s.conf)
+	if err != nil {
+		return fmt.Errorf("failed to read ruleset: %w", err)
+	}
+	s.ruleset = rs
+	for _, r := range rs.Rule {
+		s.log.Debug("found rule", slog.String("ID", r.ID))
+	}
+
 	return s.RunWithListener(l)
 }
 
@@ -159,7 +172,8 @@ ReadLoop:
 		s.log.Debug("log message successfully received",
 			slog.String("message", lm.Message.String()),
 			slog.String("facility", lm.Facility.String()),
-			slog.String("severity", lm.Severity.String()))
+			slog.String("severity", lm.Severity.String()),
+			slog.Time("server_time", lm.Timestamp))
 	}
 }