feat: add rule-based log syntax highlighter and tests

pkg/utils/logs.go

@@ -0,0 +1,41 @@
+package utils
+
+import (
+	"regexp"
+	"strings"
+)
+
+var (
+	errRegex   = regexp.MustCompile(`(?i)\b(error|err|critical|fatal)\b`)
+	warnRegex  = regexp.MustCompile(`(?i)\b(warning|warn)\b`)
+	infoRegex  = regexp.MustCompile(`(?i)\b(info)\b`)
+	debugRegex = regexp.MustCompile(`(?i)\b(debug)\b`)
+
+	timestampRegex = regexp.MustCompile(`\b\d{4}-\d{2}-\d{2}[T ]\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+-]\d{2}:?\d{2})?\b`)
+)
+
+// ColoriseLog applies basic ANSI syntax highlighting to typical log statements.
+func ColoriseLog(line string) string {
+	if strings.Contains(line, "\x1b[") {
+		return line
+	}
+
+	line = timestampRegex.ReplaceAllStringFunc(line, func(ts string) string {
+		return "\x1b[90m" + ts + "\x1b[0m"
+	})
+
+	line = errRegex.ReplaceAllStringFunc(line, func(match string) string {
+		return "\x1b[31;1m" + match + "\x1b[0m"
+	})
+	line = warnRegex.ReplaceAllStringFunc(line, func(match string) string {
+		return "\x1b[33;1m" + match + "\x1b[0m"
+	})
+	line = infoRegex.ReplaceAllStringFunc(line, func(match string) string {
+		return "\x1b[32m" + match + "\x1b[0m"
+	})
+	line = debugRegex.ReplaceAllStringFunc(line, func(match string) string {
+		return "\x1b[34m" + match + "\x1b[0m"
+	})
+
+	return line
+}

pkg/utils/logs_test.go

@@ -0,0 +1,41 @@
+package utils
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestColoriseLog(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		contains []string
+	}{
+		{
+			name:     "Highlight error log level",
+			input:    "ERROR: database failed to connect",
+			contains: []string{"\x1b[31;1mERROR\x1b[0m"},
+		},
+		{
+			name:     "Highlight warning log level",
+			input:    "[WARN] deprecation warning",
+			contains: []string{"\x1b[33;1mWARN\x1b[0m"},
+		},
+		{
+			name:     "Highlight timestamp",
+			input:    "2026-06-04T12:00:00Z something happened",
+			contains: []string{"\x1b[90m2026-06-04T12:00:00Z\x1b[0m"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := ColoriseLog(tt.input)
+			for _, c := range tt.contains {
+				if !strings.Contains(got, c) {
+					t.Errorf("expected %q to contain %q, but it was %q", got, c, got)
+				}
+			}
+		})
+	}
+}