package userstore

import (
	"fmt"
	"regexp"
	"strings"
	"unicode"
)

var tenantSlugRe = regexp.MustCompile(`^[a-z][a-z0-9-]{1,31}$`)

// 路径段保留字：不可用作公司 slug（与后续 /{slug}/ 路由冲突）
var reservedTenantSlugs = map[string]struct{}{
	"api": {}, "ai": {}, "gateway": {}, "platform": {}, "_platform": {},
	"admin": {}, "assets": {}, "static": {}, "www": {}, "m": {}, "public": {},
	"health": {}, "ops": {}, "console": {}, "login": {}, "register": {},
	"favicon.ico": {}, "robots.txt": {},
}

// NormalizeTenantSlug 规范化公司路径 slug（全局唯一，用于 www.yuxinda.com/{slug}/）。
func NormalizeTenantSlug(raw string) (string, error) {
	s := strings.TrimSpace(strings.ToLower(raw))
	s = strings.ReplaceAll(s, "_", "-")
	s = strings.ReplaceAll(s, " ", "-")
	var b strings.Builder
	prevDash := false
	for _, r := range s {
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
			b.WriteRune(r)
			prevDash = false
			continue
		}
		if r == '-' {
			if b.Len() == 0 || prevDash {
				continue
			}
			b.WriteByte('-')
			prevDash = true
			continue
		}
		// 跳过其它字符（含中文）；中文名需用户另填 slug
	}
	s = strings.Trim(b.String(), "-")
	if s == "" {
		return "", fmt.Errorf("公司路径 slug 不能为空（请用英文/数字，如 aaa）")
	}
	if !tenantSlugRe.MatchString(s) {
		return "", fmt.Errorf("slug 须为 2–32 位，小写字母开头，仅含 a-z / 0-9 / -")
	}
	if _, bad := reservedTenantSlugs[s]; bad {
		return "", fmt.Errorf("slug %q 为系统保留字", s)
	}
	return s, nil
}

// SuggestTenantSlug 从公司名生成候选（中文名可能得不到可用 slug，需人工填写）。
func SuggestTenantSlug(name string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		return ""
	}
	// 纯 ASCII 名：直接规范化
	ascii := true
	for _, r := range name {
		if r > unicode.MaxASCII {
			ascii = false
			break
		}
	}
	if ascii {
		s, err := NormalizeTenantSlug(name)
		if err == nil {
			return s
		}
	}
	return ""
}