package slug

import (
	"crypto/rand"
	"regexp"
	"strconv"
	"strings"
	"time"
	"unicode"

	"github.com/rs/zerolog/log"
	"golang.org/x/text/runes"
	"golang.org/x/text/transform"
	"golang.org/x/text/unicode/norm"
)

func Generate(text string) string {
	log.Debug().
		Str("service", "slugService").
		Str("action", "generate_slug_started").
		Str("input_text", text).
		Msg("starting slug generation")
	text = strings.ToLower(text)
	t := transform.Chain(norm.NFD, runes.Remove(runes.In(unicode.Mn)), norm.NFC)
	text, _, _ = transform.String(t, text)

	text = strings.Replace(text, " ", "-", -1)
	text = strings.Replace(text, "_", "-", -1)

	reg := regexp.MustCompile(`[^a-z0-9-]+`)
	text = reg.ReplaceAllString(text, "")

	reg = regexp.MustCompile(`-+`)
	text = reg.ReplaceAllString(text, "-")

	text = strings.Trim(text, "-")

	if len(text) > 100 {
		log.Debug().
			Str("service", "slugService").
			Str("action", "slug_truncated").
			Int("original_length", len(text)).
			Msg("slug exceeded 100 characters and was truncated")
		text = text[:100]
		text = strings.TrimRight(text, "-")
	}

	if text == "" {
		log.Warn().
			Str("service", "slugService").
			Str("action", "empty_slug_generated").
			Str("input_text", text).
			Msg("slug is empty after sanitization; generating random fallback")
		text = "tenant" + generateRandomString(8)
	}

	return text

}

func GenerateUnique(base string, exists func(string) bool) string {
	log.Debug().
		Str("service", "slugService").
		Str("action", "generate_unique_slug_started").
		Str("base", base).
		Msg("generating unique slug")

	slug := Generate(base)

	if !exists(slug) {
		log.Debug().
			Str("service", "slugService").
			Str("action", "unique_slug_available").
			Str("slug", slug).
			Msg("slug is available without modification")
		return slug
	}

	for i := 2; i < 1000; i++ {
		candidate := slug + "-" + strconv.Itoa(i)
		if !exists(candidate) {
			log.Info().
				Str("service", "slugService").
				Str("action", "unique_slug_generated_with_suffix").
				Str("slug", candidate).
				Int("attempt", i-1).
				Msg("slug collision resolved with numeric suffix")
			return candidate
		}
	}
	fallback := slug + "-" + strconv.Itoa(int(time.Now().Unix()))
	log.Warn().
		Str("service", "slugService").
		Str("action", "unique_slug_fallback_timestamp").
		Str("slug", fallback).
		Msg("exhausted 1000 attempts; using timestamp fallback")

	return fallback
}

func generateRandomString(length int) string {
	log.Debug().
		Str("service", "slugService").
		Str("action", "generate_random_string").
		Int("length", length).
		Msg("generating random slug string")
	const charset = "abcdefghijklmopqrstuvwxyz0123456789"
	randBytes := make([]byte, length)
	if _, err := rand.Read(randBytes); err != nil {
		log.Error().
			Str("service", "slugService").
			Str("action", "rand_read_failed").
			Err(err).
			Msg("falling back to time-based random string")
		return strconv.FormatInt(time.Now().UnixNano(), 36)[:length]
	}
	result := make([]byte, length)
	for i := 0; i < length; i++ {
		result[i] = charset[randBytes[i]%byte(len(charset))]
	}
	str := string(result)
	log.Debug().
		Str("service", "slugService").
		Str("action", "random_string_generated").
		Str("value", str).
		Msg("random slug string generated")
	return str
}