package config

import (
	"testing"
)

// FuzzParseTopics tests topic parsing doesn't panic on arbitrary input
func FuzzParseTopics(f *testing.F) {
	// Normal cases
	f.Add("alerts")
	f.Add("alerts,updates")
	f.Add("alerts, updates, notifications")
	f.Add("")

	// Edge cases
	f.Add(",,,")
	f.Add("  ,  ,  ")
	f.Add("a]topic-with-special_chars.123")
	f.Add("\x00\x00\x00")
	f.Add("topic\nwith\nnewlines")

	f.Fuzz(func(t *testing.T, input string) {
		// Simulate topic parsing logic
		if input == "" {
			return
		}

		topics := make([]string, 0)
		for _, topic := range splitAndTrim(input) {
			topics = append(topics, topic)
		}

		// Accessing results should not panic
		_ = len(topics)
	})
}

// splitAndTrim mimics the topic parsing in Load()
func splitAndTrim(s string) []string {
	if s == "" {
		return nil
	}
	var result []string
	start := 0
	for i := 0; i < len(s); i++ {
		if s[i] == ',' {
			part := trimSpace(s[start:i])
			if part != "" {
				result = append(result, part)
			}
			start = i + 1
		}
	}
	// Last part
	part := trimSpace(s[start:])
	if part != "" {
		result = append(result, part)
	}
	return result
}

func trimSpace(s string) string {
	start := 0
	end := len(s)
	for start < end && (s[start] == ' ' || s[start] == '\t' || s[start] == '\n' || s[start] == '\r') {
		start++
	}
	for end > start && (s[end-1] == ' ' || s[end-1] == '\t' || s[end-1] == '\n' || s[end-1] == '\r') {
		end--
	}
	return s[start:end]
}