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path: root/flood.go
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package main

import (
	"log"
	"math"
	"sort"
	"strings"

	irc "github.com/fluffle/goirc/client"
)

func Entropy(s string) (e float64) {
	n := make(map[rune]float64)
	for _, r := range s {
		n[r] += 1 / float64(len(s))
	}
	for _, v := range n {
		e -= v * math.Log2(v)
	}
	return
}

func Flood(s string) bool {
	if len(s) < 4 {
		return false
	}
	if v := strings.Fields(s); len(v) >= 6 {
		return CommonWord(v) >= 2*len(v)/3 || MedianLength(v) == 1
	}
	return Entropy(s) <= 1
}

func CommonWord(v []string) int {
	m := make(map[string]int)
	for _, w := range v {
		m[w]++
	}
	l := make([]int, len(m))
	for _, n := range m {
		l = append(l, n)
	}
	sort.Sort(sort.Reverse(sort.IntSlice(l)))
	return l[0]
}

func MedianLength(v []string) int {
	l := make([]int, len(v))
	for i, s := range v {
		l[i] = len(s)
	}
	sort.Sort(sort.IntSlice(l))
	return l[len(l)/2]
}

func DetectFlood(conn *irc.Conn, line *irc.Line) {
	if Flood(line.Text()) {
		log.Println("flood", line.Nick)
		conn.Kick(*room, line.Nick, "flood")
	}
}