// Package ldap 目录服务集成（go-ldap，实现模式参考 LokiStack）。
package ldap

import (
	"crypto/tls"
	"fmt"
	"net"
	"strings"
	"time"

	"github.com/go-ldap/ldap/v3"
)

// Entry LDAP 用户条目
type Entry struct {
	DN          string `json:"dn"`
	Username    string `json:"username"`
	DisplayName string `json:"displayName"`
	Email       string `json:"email"`
}

// Dial 连接并完成管理员 Bind（5s 拨号 / 10s 操作超时）
func Dial(host string, port int, useSSL bool, bindDN, bindPassword string) (*ldap.Conn, error) {
	scheme := "ldap"
	if useSSL {
		scheme = "ldaps"
	}
	url := fmt.Sprintf("%s://%s:%d", scheme, host, port)
	conn, err := ldap.DialURL(url,
		ldap.DialWithDialer(&net.Dialer{Timeout: 5 * time.Second}),
		ldap.DialWithTLSConfig(&tls.Config{InsecureSkipVerify: true}),
	)
	if err != nil {
		return nil, fmt.Errorf("无法连接 LDAP 服务器 %s: %v", url, err)
	}
	conn.SetTimeout(10 * time.Second)
	if err := conn.Bind(bindDN, bindPassword); err != nil {
		conn.Close()
		return nil, fmt.Errorf("管理员绑定失败（检查 Bind DN/密码）: %v", err)
	}
	return conn, nil
}

func normalizeFilter(f, def string) string {
	if strings.TrimSpace(f) == "" {
		f = def
	}
	if !strings.HasPrefix(f, "(") {
		f = "(" + f + ")"
	}
	return f
}

// SearchUsers 按 BaseDN/过滤器搜索用户（sizeLimit 截断）
func SearchUsers(host string, port int, useSSL bool, bindDN, bindPassword, baseDN, userFilter, usernameAttr, nameAttr, emailAttr string, sizeLimit int) ([]Entry, error) {
	conn, err := Dial(host, port, useSSL, bindDN, bindPassword)
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	if usernameAttr == "" {
		usernameAttr = "uid"
	}
	if nameAttr == "" {
		nameAttr = "displayName"
	}
	if emailAttr == "" {
		emailAttr = "mail"
	}
	req := ldap.NewSearchRequest(baseDN, ldap.ScopeWholeSubtree, ldap.NeverDerefAliases,
		sizeLimit, 0, false, normalizeFilter(userFilter, "(objectClass=inetOrgPerson)"),
		[]string{"dn", usernameAttr, nameAttr, "cn", emailAttr}, nil)
	res, err := conn.Search(req)
	if err != nil {
		return nil, fmt.Errorf("搜索失败: %v", err)
	}
	seen := map[string]bool{}
	var out []Entry
	for _, e := range res.Entries {
		username := e.GetAttributeValue(usernameAttr)
		if username == "" {
			continue // 跳过 OU 等非用户条目
		}
		if seen[e.DN] {
			continue
		}
		seen[e.DN] = true
		name := e.GetAttributeValue(nameAttr)
		if name == "" {
			name = e.GetAttributeValue("cn")
		}
		out = append(out, Entry{
			DN: e.DN, Username: username, DisplayName: name, Email: e.GetAttributeValue(emailAttr),
		})
	}
	return out, nil
}

// SearchOne 按用户名搜索单个条目（登录用，EscapeFilter 防注入）
func SearchOne(host string, port int, useSSL bool, bindDN, bindPassword, baseDN, userFilter, usernameAttr, username string) (*Entry, error) {
	conn, err := Dial(host, port, useSSL, bindDN, bindPassword)
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	if usernameAttr == "" {
		usernameAttr = "uid"
	}
	filter := fmt.Sprintf("(&%s(%s=%s))", normalizeFilter(userFilter, "(objectClass=inetOrgPerson)"),
		usernameAttr, ldap.EscapeFilter(username))
	req := ldap.NewSearchRequest(baseDN, ldap.ScopeWholeSubtree, ldap.NeverDerefAliases,
		2, 0, false, filter, []string{"dn", usernameAttr, "displayName", "cn", "mail"}, nil)
	res, err := conn.Search(req)
	if err != nil {
		return nil, err
	}
	if len(res.Entries) == 0 {
		return nil, fmt.Errorf("用户不存在")
	}
	if len(res.Entries) > 1 {
		return nil, fmt.Errorf("LDAP 中存在多个匹配的用户")
	}
	e := res.Entries[0]
	name := e.GetAttributeValue("displayName")
	if name == "" {
		name = e.GetAttributeValue("cn")
	}
	return &Entry{DN: e.DN, Username: e.GetAttributeValue(usernameAttr), DisplayName: name, Email: e.GetAttributeValue("mail")}, nil
}

// BindAsUser 用用户自己的 DN+密码直连校验（密码不落库）
func BindAsUser(host string, port int, useSSL bool, userDN, password string) error {
	scheme := "ldap"
	if useSSL {
		scheme = "ldaps"
	}
	conn, err := ldap.DialURL(fmt.Sprintf("%s://%s:%d", scheme, host, port),
		ldap.DialWithDialer(&net.Dialer{Timeout: 5 * time.Second}),
		ldap.DialWithTLSConfig(&tls.Config{InsecureSkipVerify: true}),
	)
	if err != nil {
		return err
	}
	defer conn.Close()
	return conn.Bind(userDN, password)
}