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

package ldap

import (
	"crypto/tls"
	"fmt"
	"net/http"
	"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 LdapDiagnosticImpl struct {
	config func() *model.Config
	logger mlog.LoggerIFace
}

func NewLdapDiagnosticInterface(config func() *model.Config, logger mlog.LoggerIFace) einterfaces.LdapDiagnosticInterface {
	return &LdapDiagnosticImpl{
		config: config,
		logger: logger,
	}
}

func (ld *LdapDiagnosticImpl) getSettings() *model.LdapSettings {
	return &ld.config().LdapSettings
}

// RunTest runs a basic LDAP connection test
func (ld *LdapDiagnosticImpl) RunTest(rctx request.CTX) *model.AppError {
	return ld.RunTestConnection(rctx, *ld.getSettings())
}

// GetVendorNameAndVendorVersion retrieves LDAP server vendor info
func (ld *LdapDiagnosticImpl) GetVendorNameAndVendorVersion(rctx request.CTX) (string, string, error) {
	settings := ld.getSettings()

	conn, err := ld.connect(settings)
	if err != nil {
		return "", "", err
	}
	defer conn.Close()

	if err := conn.Bind(*settings.BindUsername, *settings.BindPassword); err != nil {
		return "", "", err
	}

	// Query root DSE for vendor info
	searchRequest := ldapv3.NewSearchRequest(
		"",
		ldapv3.ScopeBaseObject,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		"(objectClass=*)",
		[]string{"vendorName", "vendorVersion", "supportedLDAPVersion"},
		nil,
	)

	sr, err := conn.Search(searchRequest)
	if err != nil {
		return "Unknown", "Unknown", nil
	}

	if len(sr.Entries) == 0 {
		return "Unknown", "Unknown", nil
	}

	entry := sr.Entries[0]
	vendorName := entry.GetAttributeValue("vendorName")
	vendorVersion := entry.GetAttributeValue("vendorVersion")

	if vendorName == "" {
		vendorName = "Unknown"
	}
	if vendorVersion == "" {
		vendorVersion = "Unknown"
	}

	return vendorName, vendorVersion, nil
}

// RunTestConnection tests LDAP connectivity with given settings
func (ld *LdapDiagnosticImpl) RunTestConnection(rctx request.CTX, settings model.LdapSettings) *model.AppError {
	conn, err := ld.connect(&settings)
	if err != nil {
		return model.NewAppError("LdapDiagnostic.RunTestConnection", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	// Test bind
	if err := conn.Bind(*settings.BindUsername, *settings.BindPassword); err != nil {
		return model.NewAppError("LdapDiagnostic.RunTestConnection", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusUnauthorized)
	}

	// Test search
	searchRequest := ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeBaseObject,
		ldapv3.NeverDerefAliases,
		0, 0, false,
		"(objectClass=*)",
		[]string{"dn"},
		nil,
	)

	_, err = conn.Search(searchRequest)
	if err != nil {
		return model.NewAppError("LdapDiagnostic.RunTestConnection", "api.ldap.search_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	return nil
}

// RunTestDiagnostics runs detailed diagnostic tests
func (ld *LdapDiagnosticImpl) RunTestDiagnostics(rctx request.CTX, testType model.LdapDiagnosticTestType, settings model.LdapSettings) ([]model.LdapDiagnosticResult, *model.AppError) {
	conn, err := ld.connect(&settings)
	if err != nil {
		return nil, model.NewAppError("LdapDiagnostic.RunTestDiagnostics", "api.ldap.connection_error.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	defer conn.Close()

	if err := conn.Bind(*settings.BindUsername, *settings.BindPassword); err != nil {
		return nil, model.NewAppError("LdapDiagnostic.RunTestDiagnostics", "api.ldap.bind_error.app_error", nil, err.Error(), http.StatusUnauthorized)
	}

	var results []model.LdapDiagnosticResult

	switch testType {
	case model.LdapDiagnosticTestTypeFilters:
		results = ld.testFilters(conn, &settings)
	case model.LdapDiagnosticTestTypeAttributes:
		results = ld.testAttributes(conn, &settings)
	case model.LdapDiagnosticTestTypeGroupAttributes:
		results = ld.testGroupAttributes(conn, &settings)
	default:
		return nil, model.NewAppError("LdapDiagnostic.RunTestDiagnostics", "api.ldap.invalid_test_type.app_error", nil, "", http.StatusBadRequest)
	}

	return results, nil
}

func (ld *LdapDiagnosticImpl) connect(settings *model.LdapSettings) (*ldapv3.Conn, error) {
	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,
		}
		conn, err = ldapv3.DialTLS("tcp", address, tlsConfig)
	case model.ConnSecurityStarttls:
		conn, err = ldapv3.Dial("tcp", address)
		if err != nil {
			return nil, 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, err
	}

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

	return conn, nil
}

func (ld *LdapDiagnosticImpl) testFilters(conn *ldapv3.Conn, settings *model.LdapSettings) []model.LdapDiagnosticResult {
	var results []model.LdapDiagnosticResult

	// Test user filter
	userFilter := *settings.UserFilter
	if userFilter == "" {
		userFilter = "(objectClass=person)"
	}

	userResult := model.LdapDiagnosticResult{
		TestName:  "User Filter",
		TestValue: userFilter,
	}

	sr, err := conn.Search(ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		100, 0, false,
		userFilter,
		[]string{"dn"},
		nil,
	))
	if err != nil {
		userResult.Error = err.Error()
	} else {
		userResult.TotalCount = len(sr.Entries)
		userResult.Message = fmt.Sprintf("Found %d users", len(sr.Entries))

		// Sample results
		maxSamples := 5
		if len(sr.Entries) < maxSamples {
			maxSamples = len(sr.Entries)
		}
		for i := 0; i < maxSamples; i++ {
			userResult.SampleResults = append(userResult.SampleResults, model.LdapSampleEntry{
				DN: sr.Entries[i].DN,
			})
		}
	}
	results = append(results, userResult)

	// Test group filter
	if *settings.GroupFilter != "" {
		groupResult := model.LdapDiagnosticResult{
			TestName:  "Group Filter",
			TestValue: *settings.GroupFilter,
		}

		sr, err := conn.Search(ldapv3.NewSearchRequest(
			*settings.BaseDN,
			ldapv3.ScopeWholeSubtree,
			ldapv3.NeverDerefAliases,
			100, 0, false,
			*settings.GroupFilter,
			[]string{"dn"},
			nil,
		))
		if err != nil {
			groupResult.Error = err.Error()
		} else {
			groupResult.TotalCount = len(sr.Entries)
			groupResult.Message = fmt.Sprintf("Found %d groups", len(sr.Entries))
		}
		results = append(results, groupResult)
	}

	return results
}

func (ld *LdapDiagnosticImpl) testAttributes(conn *ldapv3.Conn, settings *model.LdapSettings) []model.LdapDiagnosticResult {
	var results []model.LdapDiagnosticResult

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

	// Get sample users
	sr, err := conn.Search(ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		100, 0, false,
		userFilter,
		[]string{"*"},
		nil,
	))
	if err != nil {
		return []model.LdapDiagnosticResult{{
			TestName: "Attributes",
			Error:    err.Error(),
		}}
	}

	totalUsers := len(sr.Entries)

	// Test each configured attribute
	attrs := map[string]string{
		"ID Attribute":        *settings.IdAttribute,
		"Username Attribute":  *settings.UsernameAttribute,
		"Email Attribute":     *settings.EmailAttribute,
		"First Name Attr":     *settings.FirstNameAttribute,
		"Last Name Attr":      *settings.LastNameAttribute,
		"Nickname Attribute":  *settings.NicknameAttribute,
		"Position Attribute":  *settings.PositionAttribute,
	}

	for name, attr := range attrs {
		if attr == "" {
			continue
		}

		result := model.LdapDiagnosticResult{
			TestName:   name,
			TestValue:  attr,
			TotalCount: totalUsers,
		}

		count := 0
		for _, entry := range sr.Entries {
			if entry.GetAttributeValue(attr) != "" {
				count++
			}
		}
		result.EntriesWithValue = count
		result.Message = fmt.Sprintf("%d/%d users have this attribute", count, totalUsers)

		results = append(results, result)
	}

	return results
}

func (ld *LdapDiagnosticImpl) testGroupAttributes(conn *ldapv3.Conn, settings *model.LdapSettings) []model.LdapDiagnosticResult {
	var results []model.LdapDiagnosticResult

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

	sr, err := conn.Search(ldapv3.NewSearchRequest(
		*settings.BaseDN,
		ldapv3.ScopeWholeSubtree,
		ldapv3.NeverDerefAliases,
		100, 0, false,
		groupFilter,
		[]string{"*"},
		nil,
	))
	if err != nil {
		return []model.LdapDiagnosticResult{{
			TestName: "Group Attributes",
			Error:    err.Error(),
		}}
	}

	totalGroups := len(sr.Entries)

	// Test group attributes
	attrs := map[string]string{
		"Group ID Attribute":      *settings.GroupIdAttribute,
		"Group Display Name Attr": *settings.GroupDisplayNameAttribute,
	}

	for name, attr := range attrs {
		if attr == "" {
			continue
		}

		result := model.LdapDiagnosticResult{
			TestName:   name,
			TestValue:  attr,
			TotalCount: totalGroups,
		}

		count := 0
		for _, entry := range sr.Entries {
			if entry.GetAttributeValue(attr) != "" {
				count++
			}
		}
		result.EntriesWithValue = count
		result.Message = fmt.Sprintf("%d/%d groups have this attribute", count, totalGroups)

		results = append(results, result)
	}

	return results
}