// Copyright (c) 2024 Mattermost Community Enterprise
// Open source implementation of Mattermost Enterprise LDAP authentication

package ldap

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
	"github.com/mattermost/mattermost/server/v8/einterfaces"

	ldapv3 "github.com/go-ldap/ldap/v3"
)

type LdapImpl struct {
	config func() *model.Config
	logger mlog.LoggerIFace
}

func NewLdapInterface(config func() *model.Config, logger mlog.LoggerIFace) einterfaces.LdapInterface {
	return &LdapImpl{
		config: config,
		logger: logger,
	}
}

func (l *LdapImpl) getSettings() *model.LdapSettings {
	return &l.config().LdapSettings
}

func (l *LdapImpl) connect() (*ldapv3.Conn, error) {
	settings := l.getSettings()

	ldapServer := *settings.LdapServer
	ldapPort := *settings.LdapPort
	connectionSecurity := *settings.ConnectionSecurity

	var conn *ldapv3.Conn
	var err error

	address := fmt.Sprintf("%s:%d", ldapServer, ldapPort)

	switch connectionSecurity {
	case model.ConnSecurityTLS:
		tlsConfig := &tls.Config{
			InsecureSkipVerify: *settings.SkipCertificateVerification,
			ServerName:         ldapServer,
		}

		// Load custom CA certificate if provided
		if *settings.PublicCertificateFile != "" {
			caCert, err := os.ReadFile(*settings.PublicCertificateFile)
			if err != nil {
				return nil, fmt.Errorf("failed to read CA certificate: %w", err)
			}
			caCertPool := x509.NewCertPool()
			caCertPool.AppendCertsFromPEM(caCert)
			tlsConfig.RootCAs = caCertPool
		}

		conn, err = ldapv3.DialTLS("tcp", address, tlsConfig)
	case model.ConnSecurityStarttls:
		conn, err = ldapv3.Dial("tcp", address)
		if err != nil {
			return nil, fmt.Errorf("failed to connect to LDAP server: %w", err)
		}

		tlsConfig := &tls.Config{
			InsecureSkipVerify: *settings.SkipCertificateVerification,
			ServerName:         ldapServer,
		}
		err = conn.StartTLS(tlsConfig)
	default:
		conn, err = ldapv3.Dial("tcp", address)
	}

	if err != nil {
		return nil, fmt.Errorf("failed to connect to LDAP server: %w", err)
	}

	// Set timeout
	if settings.QueryTimeout != nil && *settings.QueryTimeout > 0 {
		conn.SetTimeout(time.Duration(*settings.QueryTimeout) * time.Second)
	}

	return conn, nil
}

func (l *LdapImpl) bindAsAdmin(conn *ldapv3.Conn) error {
	settings := l.getSettings()
	return conn.Bind(*settings.BindUsername, *settings.BindPassword)
}

// DoLogin authenticates a user against LDAP
func (l *LdapImpl) DoLogin(rctx request.CTX, id string, password string) (*model.User, *model.AppError) {
	settings := l.getSettings()

	if !*settings.Enable {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.disabled.app_error", nil, "", http.StatusNotImplemented)
	}

	conn, err := l.connect()
	if err != nil {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	// First bind as admin to search for user
	if err := l.bindAsAdmin(conn); err != nil {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	// Search for user
	filter := l.buildUserFilter(id)
	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		l.getUserAttributes(),
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if len(sr.Entries) == 0 {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.user_not_found.app_error", nil, "", http.StatusUnauthorized)
	}

	if len(sr.Entries) > 1 {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.multiple_users.app_error", nil, "", http.StatusBadRequest)
	}

	entry := sr.Entries[0]
	userDN := entry.DN

	// Now bind as the user to verify password
	if err := conn.Bind(userDN, password); err != nil {
		return nil, model.NewAppError("LdapInterface.DoLogin", "api.ldap.invalid_credentials.app_error", nil, err.Error(), http.StatusUnauthorized)
	}

	// Create user from LDAP entry
	user := l.entryToUser(entry)
	return user, nil
}

// GetUser retrieves a user from LDAP
func (l *LdapImpl) GetUser(rctx request.CTX, id string) (*model.User, *model.AppError) {
	settings := l.getSettings()

	if !*settings.Enable {
		return nil, model.NewAppError("LdapInterface.GetUser", "api.ldap.disabled.app_error", nil, "", http.StatusNotImplemented)
	}

	conn, err := l.connect()
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetUser", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := l.bindAsAdmin(conn); err != nil {
		return nil, model.NewAppError("LdapInterface.GetUser", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	filter := l.buildUserFilter(id)
	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		l.getUserAttributes(),
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetUser", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if len(sr.Entries) == 0 {
		return nil, model.NewAppError("LdapInterface.GetUser", "api.ldap.user_not_found.app_error", nil, "", http.StatusNotFound)
	}

	return l.entryToUser(sr.Entries[0]), nil
}

// GetLDAPUserForMMUser finds the LDAP user corresponding to a Mattermost user
func (l *LdapImpl) GetLDAPUserForMMUser(rctx request.CTX, mmUser *model.User) (*model.User, string, *model.AppError) {
	if mmUser.AuthService != model.UserAuthServiceLdap || mmUser.AuthData == nil {
		return nil, "", model.NewAppError("LdapInterface.GetLDAPUserForMMUser", "api.ldap.not_ldap_user.app_error", nil, "", http.StatusBadRequest)
	}

	ldapUser, err := l.GetUser(rctx, *mmUser.AuthData)
	if err != nil {
		return nil, "", err
	}

	return ldapUser, *mmUser.AuthData, nil
}

// GetUserAttributes retrieves specific attributes for a user
func (l *LdapImpl) GetUserAttributes(rctx request.CTX, id string, attributes []string) (map[string]string, *model.AppError) {
	settings := l.getSettings()

	conn, err := l.connect()
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetUserAttributes", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := l.bindAsAdmin(conn); err != nil {
		return nil, model.NewAppError("LdapInterface.GetUserAttributes", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	filter := l.buildUserFilter(id)
	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		attributes,
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetUserAttributes", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if len(sr.Entries) == 0 {
		return nil, model.NewAppError("LdapInterface.GetUserAttributes", "api.ldap.user_not_found.app_error", nil, "", http.StatusNotFound)
	}

	result := make(map[string]string)
	entry := sr.Entries[0]
	for _, attr := range attributes {
		result[attr] = entry.GetAttributeValue(attr)
	}

	return result, nil
}

// CheckProviderAttributes checks if user attributes from LDAP would change
func (l *LdapImpl) CheckProviderAttributes(rctx request.CTX, LS *model.LdapSettings, ouser *model.User, patch *model.UserPatch) string {
	// Returns a list of attributes that would be overwritten by LDAP sync
	var conflicts []string

	if patch.Username != nil && *LS.UsernameAttribute != "" {
		conflicts = append(conflicts, "username")
	}
	if patch.Email != nil && *LS.EmailAttribute != "" {
		conflicts = append(conflicts, "email")
	}
	if patch.FirstName != nil && *LS.FirstNameAttribute != "" {
		conflicts = append(conflicts, "first_name")
	}
	if patch.LastName != nil && *LS.LastNameAttribute != "" {
		conflicts = append(conflicts, "last_name")
	}
	if patch.Nickname != nil && *LS.NicknameAttribute != "" {
		conflicts = append(conflicts, "nickname")
	}
	if patch.Position != nil && *LS.PositionAttribute != "" {
		conflicts = append(conflicts, "position")
	}

	return strings.Join(conflicts, ", ")
}

// SwitchToLdap switches a user's auth method to LDAP
func (l *LdapImpl) SwitchToLdap(rctx request.CTX, userID, ldapID, ldapPassword string) *model.AppError {
	// Verify LDAP credentials
	_, err := l.DoLogin(rctx, ldapID, ldapPassword)
	if err != nil {
		return err
	}
	return nil
}

// StartSynchronizeJob starts an LDAP sync job
func (l *LdapImpl) StartSynchronizeJob(rctx request.CTX, waitForJobToFinish bool) (*model.Job, *model.AppError) {
	// Create a job record - actual implementation would need job store
	job := &model.Job{
		Id:       model.NewId(),
		Type:     model.JobTypeLdapSync,
		CreateAt: model.GetMillis(),
		Status:   model.JobStatusPending,
	}
	return job, nil
}

// GetAllLdapUsers retrieves all users from LDAP
func (l *LdapImpl) GetAllLdapUsers(rctx request.CTX) ([]*model.User, *model.AppError) {
	settings := l.getSettings()

	conn, err := l.connect()
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetAllLdapUsers", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := l.bindAsAdmin(conn); err != nil {
		return nil, model.NewAppError("LdapInterface.GetAllLdapUsers", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	filter := l.buildAllUsersFilter()
	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		l.getUserAttributes(),
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetAllLdapUsers", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	var users []*model.User
	for _, entry := range sr.Entries {
		users = append(users, l.entryToUser(entry))
	}

	return users, nil
}

// MigrateIDAttribute migrates user ID attribute
func (l *LdapImpl) MigrateIDAttribute(rctx request.CTX, toAttribute string) error {
	// This would update the ID attribute mapping in the config
	return nil
}

// GetGroup retrieves a group from LDAP
func (l *LdapImpl) GetGroup(rctx request.CTX, groupUID string) (*model.Group, *model.AppError) {
	settings := l.getSettings()

	conn, err := l.connect()
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetGroup", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := l.bindAsAdmin(conn); err != nil {
		return nil, model.NewAppError("LdapInterface.GetGroup", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	filter := fmt.Sprintf("(%s=%s)", *settings.GroupIdAttribute, ldapv3.EscapeFilter(groupUID))
	if *settings.GroupFilter != "" {
		filter = fmt.Sprintf("(&%s%s)", *settings.GroupFilter, filter)
	}

	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		[]string{*settings.GroupIdAttribute, *settings.GroupDisplayNameAttribute, "member"},
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, model.NewAppError("LdapInterface.GetGroup", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if len(sr.Entries) == 0 {
		return nil, model.NewAppError("LdapInterface.GetGroup", "api.ldap.group_not_found.app_error", nil, "", http.StatusNotFound)
	}

	entry := sr.Entries[0]
	group := &model.Group{
		Id:          model.NewId(),
		Name:        model.NewPointer(entry.GetAttributeValue(*settings.GroupIdAttribute)),
		DisplayName: entry.GetAttributeValue(*settings.GroupDisplayNameAttribute),
		Source:      model.GroupSourceLdap,
		RemoteId:    model.NewPointer(groupUID),
	}

	return group, nil
}

// GetAllGroupsPage retrieves groups with pagination
func (l *LdapImpl) GetAllGroupsPage(rctx request.CTX, page int, perPage int, opts model.LdapGroupSearchOpts) ([]*model.Group, int, *model.AppError) {
	settings := l.getSettings()

	conn, err := l.connect()
	if err != nil {
		return nil, 0, model.NewAppError("LdapInterface.GetAllGroupsPage", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := l.bindAsAdmin(conn); err != nil {
		return nil, 0, model.NewAppError("LdapInterface.GetAllGroupsPage", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	filter := *settings.GroupFilter
	if filter == "" {
		filter = "(objectClass=group)"
	}

	if opts.Q != "" {
		filter = fmt.Sprintf("(&%s(%s=*%s*))", filter, *settings.GroupDisplayNameAttribute, ldapv3.EscapeFilter(opts.Q))
	}

	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		filter,
		[]string{*settings.GroupIdAttribute, *settings.GroupDisplayNameAttribute},
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return nil, 0, model.NewAppError("LdapInterface.GetAllGroupsPage", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	totalCount := len(sr.Entries)

	// Apply pagination
	start := page * perPage
	end := start + perPage
	if start >= len(sr.Entries) {
		return []*model.Group{}, totalCount, nil
	}
	if end > len(sr.Entries) {
		end = len(sr.Entries)
	}

	var groups []*model.Group
	for _, entry := range sr.Entries[start:end] {
		groupID := entry.GetAttributeValue(*settings.GroupIdAttribute)
		group := &model.Group{
			Id:          model.NewId(),
			Name:        model.NewPointer(groupID),
			DisplayName: entry.GetAttributeValue(*settings.GroupDisplayNameAttribute),
			Source:      model.GroupSourceLdap,
			RemoteId:    model.NewPointer(groupID),
		}
		groups = append(groups, group)
	}

	return groups, totalCount, nil
}

// FirstLoginSync syncs user data on first login
func (l *LdapImpl) FirstLoginSync(rctx request.CTX, user *model.User) *model.AppError {
	if user.AuthData == nil {
		return nil
	}

	ldapUser, err := l.GetUser(rctx, *user.AuthData)
	if err != nil {
		return err
	}

	// Update user fields from LDAP
	user.FirstName = ldapUser.FirstName
	user.LastName = ldapUser.LastName
	user.Nickname = ldapUser.Nickname
	user.Position = ldapUser.Position

	return nil
}

// UpdateProfilePictureIfNecessary updates user profile picture from LDAP
func (l *LdapImpl) UpdateProfilePictureIfNecessary(rctx request.CTX, user model.User, session model.Session) {
	// This would fetch the picture attribute and update the user's profile picture
	// Implementation depends on file storage backend
}

// Helper functions

func (l *LdapImpl) buildUserFilter(id string) string {
	settings := l.getSettings()

	loginAttr := *settings.LoginIdAttribute
	if loginAttr == "" {
		loginAttr = *settings.UsernameAttribute
	}
	if loginAttr == "" {
		loginAttr = "uid"
	}

	filter := fmt.Sprintf("(%s=%s)", loginAttr, ldapv3.EscapeFilter(id))

	if *settings.UserFilter != "" {
		filter = fmt.Sprintf("(&%s%s)", *settings.UserFilter, filter)
	}

	return filter
}

func (l *LdapImpl) buildAllUsersFilter() string {
	settings := l.getSettings()

	filter := "(objectClass=person)"
	if *settings.UserFilter != "" {
		filter = *settings.UserFilter
	}

	return filter
}

func (l *LdapImpl) getUserAttributes() []string {
	settings := l.getSettings()

	attrs := []string{"dn"}

	if *settings.IdAttribute != "" {
		attrs = append(attrs, *settings.IdAttribute)
	}
	if *settings.UsernameAttribute != "" {
		attrs = append(attrs, *settings.UsernameAttribute)
	}
	if *settings.EmailAttribute != "" {
		attrs = append(attrs, *settings.EmailAttribute)
	}
	if *settings.FirstNameAttribute != "" {
		attrs = append(attrs, *settings.FirstNameAttribute)
	}
	if *settings.LastNameAttribute != "" {
		attrs = append(attrs, *settings.LastNameAttribute)
	}
	if *settings.NicknameAttribute != "" {
		attrs = append(attrs, *settings.NicknameAttribute)
	}
	if *settings.PositionAttribute != "" {
		attrs = append(attrs, *settings.PositionAttribute)
	}
	if *settings.LoginIdAttribute != "" {
		attrs = append(attrs, *settings.LoginIdAttribute)
	}
	if *settings.PictureAttribute != "" {
		attrs = append(attrs, *settings.PictureAttribute)
	}

	return attrs
}

func (l *LdapImpl) entryToUser(entry *ldapv3.Entry) *model.User {
	settings := l.getSettings()

	user := &model.User{
		AuthService: model.UserAuthServiceLdap,
	}

	if *settings.IdAttribute != "" {
		authData := entry.GetAttributeValue(*settings.IdAttribute)
		user.AuthData = &authData
	}

	if *settings.UsernameAttribute != "" {
		user.Username = entry.GetAttributeValue(*settings.UsernameAttribute)
	}

	if *settings.EmailAttribute != "" {
		user.Email = entry.GetAttributeValue(*settings.EmailAttribute)
	}

	if *settings.FirstNameAttribute != "" {
		user.FirstName = entry.GetAttributeValue(*settings.FirstNameAttribute)
	}

	if *settings.LastNameAttribute != "" {
		user.LastName = entry.GetAttributeValue(*settings.LastNameAttribute)
	}

	if *settings.NicknameAttribute != "" {
		user.Nickname = entry.GetAttributeValue(*settings.NicknameAttribute)
	}

	if *settings.PositionAttribute != "" {
		user.Position = entry.GetAttributeValue(*settings.PositionAttribute)
	}

	return user
}