package handler

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

	"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 {
		c.JSON(http.StatusBadRequest, gin.H{"detail": "username and password required"})
		return
	}

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

	if err == nil {
		// ── 本地用户存在 ──
		if user.IsActive != nil && !*user.IsActive {
			c.JSON(http.StatusForbidden, gin.H{"detail": "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 {
				c.JSON(http.StatusUnauthorized, gin.H{"detail": "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 {
			c.JSON(http.StatusUnauthorized, gin.H{"detail": "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 {
			c.JSON(http.StatusInternalServerError, gin.H{"detail": "Failed to create LDAP user: " + result.Error.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 {
		c.JSON(http.StatusInternalServerError, gin.H{"detail": "Database error"})
		return
	}

	// ── 生成 Token ──
	token, err := middleware.GenerateToken(&user)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"detail": "Failed to generate token"})
		return
	}

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

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

// 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. Build search filter
	userFilter := ""
	baseFilter := "(objectClass=inetOrgPerson)"
	if cfg.SearchFilter != nil && *cfg.SearchFilter != "" {
		sf := *cfg.SearchFilter
		if strings.Contains(sf, "%s") {
			userFilter = strings.ReplaceAll(sf, "%s", ldap.EscapeFilter(username))
		} else {
			baseFilter = sf
			userFilter = fmt.Sprintf("(&%s(uid=%s))", baseFilter, ldap.EscapeFilter(username))
		}
	} else {
		userFilter = fmt.Sprintf("(&%s(uid=%s))", baseFilter, ldap.EscapeFilter(username))
	}

	// 5. Search user
	searchReq := ldap.NewSearchRequest(
		cfg.BaseDN,
		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases,
		1, 10, false,
		userFilter,
		[]string{"uid", "cn", "mail", "telephoneNumber"},
		nil,
	)
	sr, err := conn.Search(searchReq)
	if err != nil || len(sr.Entries) == 0 {
		return nil, nil, fmt.Errorf("user not found in LDAP")
	}
	entry := sr.Entries[0]
	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)
	}

	getAttr := func(key string) string {
		if v := entry.GetAttributeValue(key); v != "" {
			return v
		}
		return ""
	}

	info := &LDAPAuthInfo{
		Username:    getAttr(userMapping["username"]),
		DisplayName: getAttr(userMapping["display_name"]),
	}
	if email := getAttr(userMapping["email"]); email != "" {
		info.Email = &email
	}
	if info.Username == "" {
		info.Username = username
	}

	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 {
		c.JSON(http.StatusNotFound, gin.H{"detail": "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 {
		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
		return
	}

	hashed, err := bcrypt.GenerateFromPassword([]byte(input.Password), bcrypt.DefaultCost)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"detail": "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") {
			c.JSON(http.StatusBadRequest, gin.H{"detail": "Username already exists"})
		} else {
			c.JSON(http.StatusInternalServerError, gin.H{"detail": err.Error()})
		}
		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 {
		c.JSON(http.StatusNotFound, gin.H{"detail": "User not found"})
		return
	}

	var input map[string]interface{}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"detail": 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 {
		c.JSON(http.StatusInternalServerError, gin.H{"detail": err.Error()})
		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" {
		c.JSON(http.StatusForbidden, gin.H{"detail": "Cannot delete system reserved users"})
		return
	}
	if err := model.DB.Delete(&model.User{}, id).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"detail": err.Error()})
		return
	}
	c.JSON(http.StatusOK, gin.H{"message": "User deleted"})
}