package handler

import (
	"encoding/json"
	"fmt"
	"net"
	"net/http"
	"strings"
	"time"

	"sql-platform/internal/handler/resp"
	"sql-platform/internal/middleware"
	"sql-platform/internal/model"

	"github.com/gin-gonic/gin"
	"github.com/go-ldap/ldap/v3"
	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
)

// POST /api/v1/auth/login
// Strategy: local account first, then LDAP fallback
func Login(c *gin.Context) {
	var req model.LoginRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		resp.BadRequest(c, "username and password required")
		return
	}

	var user model.User
	err := model.DB.Where("username = ?", req.Username).First(&user).Error

	// ── 登录失败锁定检查 ──
	if err == nil && user.LockedUntil != nil && user.LockedUntil.After(time.Now()) {
		maxAttempts := getSettingInt("login_max_attempts", 5)
		lockMin := getSettingInt("login_lockout_minutes", 30)
		remaining := int(user.LockedUntil.Sub(time.Now()).Minutes()) + 1
		resp.TooManyRequests(c, fmt.Sprintf("账号已锁定，连续 %d 次登录失败，请 %d 分钟后重试", maxAttempts, lockMin), remaining)
		return
	}
	// Lock expired → reset
	if err == nil && user.LockedUntil != nil && !user.LockedUntil.After(time.Now()) {
		user.FailedLoginAttempts = 0
		user.LockedUntil = nil
		model.DB.Save(&user)
	}

	if err == nil {
		// ── 本地用户存在 ──
		if user.IsActive != nil && !*user.IsActive {
			resp.Forbidden(c, "Account is disabled")
			return
		}

		// Try local password first
		passOk := bcrypt.CompareHashAndPassword([]byte(user.HashedPassword), []byte(req.Password)) == nil

		if !passOk {
			// Local password failed — try LDAP fallback for LDAP-imported users (password == "-")
			_, ldapInfo, ldapErr := tryLDAPAuth(req.Username, req.Password)
			if ldapErr != nil || ldapInfo == nil {
				// Both local and LDAP failed → record failed attempt
				handleFailedLogin(&user)
				resp.Unauthorized(c, "Invalid username or password")
				return
			}
			// LDAP OK — update local user info
			if ldapInfo != nil {
				updates := map[string]interface{}{}
				if ldapInfo.DisplayName != "" && ldapInfo.DisplayName != user.DisplayName {
					updates["display_name"] = ldapInfo.DisplayName
				}
				if ldapInfo.Email != nil && *ldapInfo.Email != "" {
					updates["email"] = *ldapInfo.Email
				}
				if len(updates) > 0 {
					model.DB.Model(&user).Updates(updates)
				}
			}
		}
	} else if err == gorm.ErrRecordNotFound {
		// ── 本地不存在该用户，尝试 LDAP 认证 ──
		_, ldapInfo, ldapErr := tryLDAPAuth(req.Username, req.Password)
		if ldapErr != nil || ldapInfo == nil {
			resp.Unauthorized(c, "Invalid username or password")
			return
		}
		// LDAP 认证成功，自动创建或恢复本地用户
		isActive := true
		defaultRole := "developer"
		if ldapInfo.DisplayName == "" {
			ldapInfo.DisplayName = ldapInfo.Username
		}
		newUser := model.User{
			Username:       ldapInfo.Username,
			DisplayName:    ldapInfo.DisplayName,
			Email:          ldapInfo.Email,
			HashedPassword: "-", // LDAP 用户不存本地密码
			AuthSource:     "ldap",
			Role:           defaultRole,
			IsActive:       &isActive,
		}
		// FirstOrCreate: 不存在则创建，已存在则获取（避免 uniqueIndex 冲突）
		result := model.DB.Where("username = ?", ldapInfo.Username).FirstOrCreate(&newUser)
		if result.Error != nil {
			resp.InternalErr(c, result.Error)
			return
		}
		// 更新已有用户的 display_name / email（LDAP 信息可能变更）
		if newUser.ID != 0 {
			updates := map[string]interface{}{
				"display_name": ldapInfo.DisplayName,
				"auth_source":  "ldap",
				"is_active":    true,
			}
			if ldapInfo.Email != nil {
				updates["email"] = *ldapInfo.Email
			}
			model.DB.Model(&newUser).Updates(updates)
		}
		user = newUser
	} else {
		resp.InternalMsg(c, "Database error")
		return
	}

	// ── 生成 Token ──
	// Login success → reset failed attempts
	user.FailedLoginAttempts = 0
	user.LockedUntil = nil
	token, err := middleware.GenerateToken(&user)
	if err != nil {
		resp.InternalMsg(c, "Failed to generate token")
		return
	}

	now := time.Now()
	user.LastLogin = &now
	model.DB.Save(&user)

	// 签发 refresh token（失败不阻塞登录，仅记录）
	refreshToken, refreshErr := middleware.GenerateRefreshToken(user.ID)
	if refreshErr != nil {
		fmt.Printf("generate refresh token failed: %v\n", refreshErr)
	}

	c.JSON(http.StatusOK, model.LoginResponse{
		AccessToken:  token,
		RefreshToken: refreshToken,
		TokenType:    "bearer",
		User:         user,
	})
}

// POST /api/v1/auth/refresh — 用 refresh_token 轮换新的 token 对
func RefreshToken(c *gin.Context) {
	var req struct {
		RefreshToken string `json:"refresh_token" binding:"required"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		resp.BadRequest(c, "refresh_token required")
		return
	}
	user, newRefresh, err := middleware.ConsumeRefreshToken(req.RefreshToken)
	if err != nil {
		resp.Fail(c, http.StatusUnauthorized, "登录已过期，请重新登录")
		return
	}
	access, err := middleware.GenerateToken(user)
	if err != nil {
		resp.InternalErr(c, err)
		return
	}
	c.JSON(http.StatusOK, gin.H{
		"access_token":  access,
		"refresh_token": newRefresh,
		"token_type":    "bearer",
	})
}

// POST /api/v1/auth/logout — 撤销当前用户全部 refresh token
func Logout(c *gin.Context) {
	userID, _, _ := middleware.GetCurrentUser(c)
	middleware.RevokeUserRefreshTokens(userID)
	resp.Message(c, "Logged out")
}

// LDAPAuthInfo holds extracted user info from LDAP
type LDAPAuthInfo struct {
	Username    string
	DisplayName string
	Email       *string
}

// tryLDAPAuth attempts LDAP bind for the given username/password.
// Returns (ldapConn, userInfo, error). Caller does NOT need to close conn.
func tryLDAPAuth(username, password string) (*ldap.Conn, *LDAPAuthInfo, error) {
	// 1. Load LDAP config from DB
	var cfg model.LDAPConfig
	if err := model.DB.Order("id").First(&cfg).Error; err != nil {
		return nil, nil, fmt.Errorf("no LDAP config")
	}
	if cfg.LDAPHost == "" {
		return nil, nil, fmt.Errorf("LDAP not configured")
	}

	// 2. Connect to LDAP server
	protocol := "ldap"
	if cfg.UseLDAPS != nil && *cfg.UseLDAPS {
		protocol = "ldaps"
	}
	uri := fmt.Sprintf("%s://%s:%d", protocol, cfg.LDAPHost, 389)
	if cfg.LDAPPort != nil && *cfg.LDAPPort > 0 {
		uri = fmt.Sprintf("%s://%s:%d", protocol, cfg.LDAPHost, *cfg.LDAPPort)
	}

	dialer := &net.Dialer{Timeout: 3 * time.Second}
	conn, err := ldap.DialURL(uri, ldap.DialWithDialer(dialer))
	if err != nil {
		return nil, nil, fmt.Errorf("LDAP connect failed: %w", err)
	}
	defer conn.Close()

	// 3. Admin bind to search user (decrypt password first)
	adminPw, _ := decryptPassword(cfg.AdminPassword)
	if err := conn.Bind(cfg.AdminDN, adminPw); err != nil {
		return nil, nil, fmt.Errorf("LDAP admin bind failed: %w", err)
	}

	// 4-5. 多轮过滤器搜索用户(OpenLDAP + AD 兜底,借鉴 aiops)
	entry, err := ldapSearchFirstUser(conn, &cfg, username)
	if err != nil {
		return nil, nil, err
	}
	userDN := entry.DN

	// 6. Verify password by binding as user
	if err := conn.Bind(userDN, password); err != nil {
		return nil, nil, fmt.Errorf("LDAP user bind failed: %w", err)
	}

	// 7. Extract user info using mapping
	userMapping := map[string]string{
		"username":     "uid",
		"email":        "mail",
		"display_name": "cn",
	}
	if cfg.UserMapping != nil && *cfg.UserMapping != "" {
		json.Unmarshal([]byte(*cfg.UserMapping), &userMapping)
	}

	// 7. 属性回退链提取身份(OpenLDAP 与 AD 字段差异由 ldapEntryAttr 抹平)
	identUser, identName, identEmail := ldapIdentityFromEntry(entry, username)

	info := &LDAPAuthInfo{
		Username:    identUser,
		DisplayName: identName,
	}
	if identEmail != "" {
		info.Email = &identEmail
	}

	return nil, info, nil // conn already closed by defer
}

// GET /api/v1/auth/me
func GetMe(c *gin.Context) {
	userID, _, _ := middleware.GetCurrentUser(c)
	var user model.User
	if err := model.DB.First(&user, userID).Error; err != nil {
		resp.NotFound(c, "User not found")
		return
	}
	c.JSON(http.StatusOK, user)
}

// GET /api/v1/users
func ListUsers(c *gin.Context) {
	var users []model.User
	model.DB.Order("id").Find(&users)
	c.JSON(http.StatusOK, users)
}

// POST /api/v1/users
func CreateUser(c *gin.Context) {
	var input struct {
		Username    string  `json:"username" binding:"required"`
		DisplayName string  `json:"display_name" binding:"required"`
		Password    string  `json:"password" binding:"required"`
		Email       *string `json:"email"`
		Phone       *string `json:"phone"`
		Role        string  `json:"role" binding:"required"`
	}
	if err := c.ShouldBindJSON(&input); err != nil {
		resp.BadRequest(c, err.Error())
		return
	}

	hashed, err := bcrypt.GenerateFromPassword([]byte(input.Password), bcrypt.DefaultCost)
	if err != nil {
		resp.InternalMsg(c, "Failed to hash password")
		return
	}

	isActive := true
	user := model.User{
		Username:       input.Username,
		DisplayName:    input.DisplayName,
		HashedPassword: string(hashed),
		Email:          input.Email,
		Phone:          input.Phone,
		Role:           input.Role,
		IsActive:       &isActive,
	}

	if err := model.DB.Create(&user).Error; err != nil {
		if strings.Contains(err.Error(), "UNIQUE") || strings.Contains(err.Error(), "duplicate") {
			resp.BadRequest(c, "Username already exists")
		} else {
			resp.InternalErr(c, err)
		}
		return
	}

	c.JSON(http.StatusCreated, user)
}

// PUT /api/v1/users/:id
func UpdateUser(c *gin.Context) {
	id := c.Param("id")
	var user model.User
	if err := model.DB.First(&user, id).Error; err != nil {
		resp.NotFound(c, "User not found")
		return
	}

	var input map[string]interface{}
	if err := c.ShouldBindJSON(&input); err != nil {
		resp.BadRequest(c, err.Error())
		return
	}

	if pw, ok := input["password"].(string); ok && pw != "" {
		hashed, _ := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.DefaultCost)
		input["hashed_password"] = string(hashed)
	}
	delete(input, "password")

	if err := model.DB.Model(&user).Updates(input).Error; err != nil {
		resp.InternalErr(c, err)
		return
	}

	model.DB.First(&user, id)
	c.JSON(http.StatusOK, user)
}

// DELETE /api/v1/users/:id
func DeleteUser(c *gin.Context) {
	id := c.Param("id")
	// Protect admin (id=1) and dba (id=2) from being deleted
	if id == "1" || id == "2" {
		resp.Forbidden(c, "Cannot delete system reserved users")
		return
	}
	if err := model.DB.Delete(&model.User{}, id).Error; err != nil {
		resp.InternalErr(c, err)
		return
	}
	c.JSON(http.StatusOK, gin.H{"message": "User deleted"})
}

// handleFailedLogin records a failed login attempt and locks the account if threshold is reached.
func handleFailedLogin(user *model.User) {
	maxAttempts := getSettingInt("login_max_attempts", 5)
	lockMinutes := getSettingInt("login_lockout_minutes", 30)

	user.FailedLoginAttempts++
	if user.FailedLoginAttempts >= maxAttempts {
		lockedUntil := time.Now().Add(time.Duration(lockMinutes) * time.Minute)
		user.LockedUntil = &lockedUntil
	}
	model.DB.Save(user)
}