package processor

import (
	"math"
	"regexp"
	"spider/internal/extractor"
	"spider/internal/model"
	"strings"
)

// BlacklistResult holds the outcome of blacklist filtering.
type BlacklistResult struct {
	Passed  []model.MerchantRaw
	Blocked []FilteredMerchant
}

// FilteredMerchant pairs a raw merchant with its rejection status.
type FilteredMerchant struct {
	Raw    model.MerchantRaw
	Status string // bot / invalid
}

var systemBots = []string{
	"telegram", "telegramhints", "gif", "pic", "bing", "vid",
	"bold", "vote", "like", "sticker", "music",
	"channel_bot", "botfather", "spambot",
	// Common false positives from HTML/code extraction
	"github", "gmail", "email", "admin", "login", "signup",
	"about", "contact", "support", "https", "style",
	"script", "header", "footer", "button", "input",
	"image", "video", "media", "share", "click",
	"undefined", "object", "string", "number", "function",
	"return", "const", "class", "export", "import",
	"ssage", "messages", "channel", "username",
}

var reBase64 = regexp.MustCompile(`^[A-Za-z0-9_-]{16,24}$`)

// FilterBlacklist applies blacklist rules to raw merchants.
func FilterBlacklist(raws []model.MerchantRaw) BlacklistResult {
	var result BlacklistResult
	for _, raw := range raws {
		status := checkBlacklist(raw)
		if status != "" {
			result.Blocked = append(result.Blocked, FilteredMerchant{Raw: raw, Status: status})
		} else {
			result.Passed = append(result.Passed, raw)
		}
	}
	return result
}

func checkBlacklist(raw model.MerchantRaw) string {
	username := strings.ToLower(raw.TgUsername)

	// System bot names
	for _, b := range systemBots {
		if username == b {
			return "bot"
		}
	}

	// xxxbot suffix
	if strings.HasSuffix(username, "bot") && len(username) > 3 {
		return "bot"
	}

	// Invite link hash (16-24 char base64 with high entropy)
	if len(raw.TgUsername) >= 16 && len(raw.TgUsername) <= 24 {
		if reBase64.MatchString(raw.TgUsername) && entropy(raw.TgUsername) > 3.5 {
			return "invalid"
		}
	}

	// Original text non-Chinese: only filter if text is long and has NO Chinese at all
	// Short texts and mixed-language texts are allowed
	if len(raw.OriginalText) > 200 && !extractor.ContainsChinese(raw.OriginalText, 0) {
		return "invalid"
	}

	return ""
}

func entropy(s string) float64 {
	freq := map[rune]int{}
	for _, r := range s {
		freq[r]++
	}
	n := float64(len(s))
	h := 0.0
	for _, count := range freq {
		p := float64(count) / n
		h -= p * math.Log2(p)
	}
	return h
}