MyClub/internal/services/spam.go

package services

import (
	"regexp"
	"strings"
)

// Simple heuristics to evaluate spammy text. Returns score 0..1 and triggered rules.
func EvaluateSpamScore(s string) (float64, []string) {
	var rules []string
	content := strings.TrimSpace(s)
	if content == "" {
		return 1.0, []string{"empty"}
	}
	// Too short
	if len([]rune(content)) < 6 {
		rules = append(rules, "too_short")
	}
	// Excessive repeated characters like 'aaaaaa' or '!!!!'
	repeatRe := regexp.MustCompile(`([a-zA-Z!?.])\1{4,}`)
	if repeatRe.MatchString(content) {
		rules = append(rules, "repeated_chars")
	}
	// Low vowel ratio suggests gibberish in Czech/English latin text
	letters := regexp.MustCompile(`[A-Za-zÁáÉéĚěÍíÓóÚúŮůÝýŽžŠšČčŘřŤťŇňĎď]`).FindAllString(content, -1)
	if len(letters) >= 8 {
		vowels := regexp.MustCompile(`[AaEeIiOoUuYyÁáÉéĚěÍíÓóÚúŮůÝý]`).FindAllString(content, -1)
		ratio := float64(len(vowels)) / float64(len(letters))
		if ratio < 0.18 { // very low vowel ratio
			rules = append(rules, "low_vowel_ratio")
		}
	}
	// Too many links
	linkCount := len(regexp.MustCompile(`https?://`).FindAllStringIndex(content, -1))
	if linkCount >= 3 {
		rules = append(rules, "too_many_links")
	}
	// All-caps shouting
	if content == strings.ToUpper(content) && len(content) >= 8 {
		rules = append(rules, "all_caps")
	}
	// Compute score by rules weight
	weights := map[string]float64{
		"empty":           1.0,
		"too_short":       0.4,
		"repeated_chars":  0.3,
		"low_vowel_ratio": 0.3,
		"too_many_links":  0.5,
		"all_caps":        0.2,
	}
	score := 0.0
	for _, r := range rules { score += weights[r] }
	if score > 1.0 { score = 1.0 }
	return score, rules
}