package ldap

import (
	"context"
	"strconv"
	"strings"

	"github.com/vjeantet/goldap/message"
	ldap "github.com/vjeantet/ldapserver"

	"github.com/netauth/ldap/internal/buildinfo"

	pb "github.com/netauth/protocol"
)

func (s *server) handleSearchDSE(w ldap.ResponseWriter, m *ldap.Message) {
	nc := strings.Join(s.nc, ", ")

	e := ldap.NewSearchResultEntry("")
	e.AddAttribute("vendorName", "NetAuth")
	e.AddAttribute("vendorVersion", message.AttributeValue(buildinfo.Version))
	e.AddAttribute("objectClass", "top", "extensibleObject")
	e.AddAttribute("supportedLDAPVersion", "3")
	e.AddAttribute("namingContexts", message.AttributeValue(nc))
	w.Write(e)

	res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultSuccess)
	w.Write(res)
}

// objectClasses are the structural classes advertised on every entry.
// NetAuth has no schema, so entries are presented as the least
// surprising generic classes.
var objectClasses = []message.AttributeValue{"top", "extensibleObject"}

// handleSearchEntry answers a base-object search addressed at a single
// entity or group DN. Some clients (HashiCorp Vault among them) read
// the attributes of one known entry with a base-scope
// "(objectClass=*)" search instead of a subtree search, and NetAuth
// has no per-entry lookup, so the entry is fetched by its ID or name
// and then checked against the filter.
func (s *server) handleSearchEntry(w ldap.ResponseWriter, m *ldap.Message) {
	ctx, cancel := context.WithTimeout(context.Background(), rpcTimeout)
	defer cancel()

	if !s.bound(m) {
		s.l.Warn("Search from an unauthenticated connection")
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultInsufficientAccessRights)
		res.SetDiagnosticMessage("a bind is required before searching")
		w.Write(res)
		return
	}

	r := m.GetSearchRequest()
	dn := string(r.BaseObject())
	ref, err := s.entryFromDN(r.BaseObject())
	if err != nil {
		s.l.Debug("Base scope search for something we do not have", "dn", dn)
		writeSearchDone(w, ldap.LDAPResultNoSuchObject,
			"only entity and group DNs can be searched directly, e.g. uid=<name>,ou=entities,"+strings.Join(s.nc, ","))
		return
	}

	entry, found, err := s.fetchEntry(ctx, ref, dn, r.Attributes())
	if err != nil {
		s.l.Warn("NetAuth entry lookup failed", "dn", dn, "error", err)
		writeSearchDone(w, ldap.LDAPResultOperationsError, err.Error())
		return
	}
	if !found {
		writeSearchDone(w, ldap.LDAPResultNoSuchObject, "")
		return
	}

	match, err := entryFilterMatches(r.Filter(), ref.name)
	if err != nil {
		s.l.Warn("Unsupported filter on a base scope search", "dn", dn, "error", err)
		writeSearchDone(w, ldap.LDAPResultUnwillingToPerform, "Filter type not supported")
		return
	}
	// RFC 4511: a base-object search whose entry does not match the
	// filter succeeds and returns zero entries.
	if !match {
		writeSearchDone(w, ldap.LDAPResultSuccess, "")
		return
	}

	w.Write(entry)
	writeSearchDone(w, ldap.LDAPResultSuccess, "")
}

// writeSearchDone terminates a search operation.
func writeSearchDone(w ldap.ResponseWriter, code int, diagnostic string) {
	res := ldap.NewSearchResultDoneResponse(code)
	if diagnostic != "" {
		res.SetDiagnosticMessage(diagnostic)
	}
	w.Write(res)
}

// fetchEntry looks up a single entity or group in NetAuth and renders
// it under the exact DN the client asked for. The boolean reports
// whether NetAuth knows the name at all.
func (s *server) fetchEntry(ctx context.Context, ref *entryRef, dn string, attrs message.AttributeSelection) (message.SearchResultEntry, bool, error) {
	switch ref.kind {
	case kindEntity:
		expr, err := mapToBleveStringQuery("uid", ref.name)
		if err != nil {
			return message.SearchResultEntry{}, false, err
		}
		ents, err := s.c.EntitySearch(ctx, expr)
		if err != nil {
			return message.SearchResultEntry{}, false, err
		}
		for i := range ents {
			if !strings.EqualFold(ents[i].GetID(), ref.name) {
				continue
			}
			entry, err := s.entityAttributes(ctx, ents[i], dn, attrs)
			return entry, err == nil, err
		}
	case kindGroup:
		expr, err := mapToBleveStringQuery("cn", ref.name)
		if err != nil {
			return message.SearchResultEntry{}, false, err
		}
		grps, err := s.c.GroupSearch(ctx, expr)
		if err != nil {
			return message.SearchResultEntry{}, false, err
		}
		for i := range grps {
			if !strings.EqualFold(grps[i].GetName(), ref.name) {
				continue
			}
			entry, err := s.groupAttributes(ctx, grps[i], dn, attrs)
			return entry, err == nil, err
		}
	}
	return message.SearchResultEntry{}, false, nil
}

// entryFilterMatches reports whether a search filter selects a single
// entry whose identifying attribute has the given name. Only the
// filter forms this bridge models are evaluated; anything else is an
// error so that a client is never handed a wrong answer instead.
func entryFilterMatches(f message.Filter, name string) (bool, error) {
	switch f := f.(type) {
	case message.FilterPresent:
		switch strings.ToLower(string(f)) {
		case "objectclass", "uid", "cn":
			return true, nil
		}
		return false, errUnsupportedFilter
	case message.FilterEqualityMatch:
		value := string(f.AssertionValue())
		switch strings.ToLower(string(f.AttributeDesc())) {
		case "uid", "cn":
			return strings.EqualFold(value, name), nil
		case "objectclass":
			return strings.EqualFold(value, "top") || strings.EqualFold(value, "extensibleObject"), nil
		}
		return false, errUnsupportedFilter
	case message.FilterAnd:
		for _, sub := range f {
			ok, err := entryFilterMatches(sub, name)
			if err != nil || !ok {
				return false, err
			}
		}
		return true, nil
	case message.FilterOr:
		for _, sub := range f {
			ok, err := entryFilterMatches(sub, name)
			if err != nil {
				return false, err
			}
			if ok {
				return true, nil
			}
		}
		return false, nil
	case message.FilterNot:
		ok, err := entryFilterMatches(f.Filter, name)
		return !ok, err
	}
	return false, errUnsupportedFilter
}

func (s *server) handleSearchEntities(w ldap.ResponseWriter, m *ldap.Message) {
	ctx, cancel := context.WithTimeout(context.Background(), rpcTimeout)
	defer cancel()
	s.l.Debug("Search Entities")

	if !s.bound(m) {
		s.l.Warn("Search from an unauthenticated connection")
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultInsufficientAccessRights)
		res.SetDiagnosticMessage("a bind is required before searching")
		w.Write(res)
		return
	}

	r := m.GetSearchRequest()
	expr, err := s.buildBleveQuery(r.Filter())
	if err != nil {
		// If err is non-nil at this point it must mean that
		// the above match didn't find a supported filter.
		s.l.Warn("Unsupported Search Filter, this is a bug, please file a report", "filter", r.Filter())
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultUnwillingToPerform)
		res.SetDiagnosticMessage("Filter type not supported")
		w.Write(res)
		return
	}

	s.l.Debug("Searching entities", "query", expr)

	ents, err := s.c.EntitySearch(ctx, expr)
	if err != nil {
		s.l.Warn("NetAuth entity search failed", "query", expr, "error", err)
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultOperationsError)
		res.SetDiagnosticMessage(err.Error())
		w.Write(res)
		return
	}

	for i := range ents {
		e, err := s.entitySearchResult(ctx, ents[i], r.BaseObject(), r.Attributes())
		if err != nil {
			res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultOperationsError)
			res.SetDiagnosticMessage(err.Error())
			w.Write(res)
			return
		}
		w.Write(e)
	}

	s.l.Debug("Entities", "res", ents)

	res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultSuccess)
	w.Write(res)
}

// entitySearchResult maps an entity from a subtree search onto a
// SearchResultEntry, deriving the entry DN from the search base.
func (s *server) entitySearchResult(ctx context.Context, e *pb.Entity, dn message.LDAPDN, attrs message.AttributeSelection) (message.SearchResultEntry, error) {
	return s.entityAttributes(ctx, e, "uid="+e.GetID()+","+string(dn), attrs)
}

// entityAttributes maps an entity onto a SearchResultEntry at the
// given full DN. The extra lookup needed to populate memberOf is only
// performed when the client asked for that attribute, since it costs
// one NetAuth round trip per entity.
func (s *server) entityAttributes(ctx context.Context, e *pb.Entity, dn string, attrs message.AttributeSelection) (message.SearchResultEntry, error) {
	res := ldap.NewSearchResultEntry(dn)
	res.AddAttribute("objectClass", objectClasses...)
	res.AddAttribute("uid", message.AttributeValue(e.GetID()))
	res.AddAttribute("uidNumber", message.AttributeValue(strconv.Itoa(int(e.GetNumber()))))

	if !attributeRequested(attrs, "memberOf") {
		return res, nil
	}

	grps, err := s.c.EntityGroups(ctx, e.GetID())
	if err != nil {
		return res, err
	}

	memberOf := []message.AttributeValue{}
	for i := range grps {
		g := "cn=" + grps[i].GetName() + ",ou=groups," + strings.Join(s.nc, ",")
		memberOf = append(memberOf, message.AttributeValue(g))
	}
	res.AddAttribute("memberOf", memberOf...)

	return res, nil
}

func (s *server) handleSearchGroups(w ldap.ResponseWriter, m *ldap.Message) {
	ctx, cancel := context.WithTimeout(context.Background(), rpcTimeout)
	defer cancel()
	s.l.Debug("Search Groups")

	if !s.bound(m) {
		s.l.Warn("Search from an unauthenticated connection")
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultInsufficientAccessRights)
		res.SetDiagnosticMessage("a bind is required before searching")
		w.Write(res)
		return
	}

	r := m.GetSearchRequest()

	expr, err := s.buildBleveQuery(r.Filter())
	if err != nil {
		// If err is non-nil at this point it must mean that
		// the above match didn't find a supported filter.
		s.l.Warn("Unsupported Search Filter, this is a bug, please file a report", "filter", r.Filter())
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultUnwillingToPerform)
		res.SetDiagnosticMessage("Filter type not supported")
		w.Write(res)
		return
	}

	s.l.Debug("Searching groups", "expr", expr)

	groups, err := s.c.GroupSearch(ctx, expr)
	if err != nil {
		s.l.Warn("NetAuth group search failed", "query", expr, "error", err)
		res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultOperationsError)
		res.SetDiagnosticMessage(err.Error())
		w.Write(res)
		return
	}

	for i := range groups {
		s.l.Debug("Found group", "group", groups[i].GetName())
		e, err := s.groupSearchResult(ctx, groups[i], r.BaseObject(), r.Attributes())
		if err != nil {
			res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultOperationsError)
			res.SetDiagnosticMessage(err.Error())
			w.Write(res)
			return
		}
		w.Write(e)
	}

	res := ldap.NewSearchResultDoneResponse(ldap.LDAPResultSuccess)
	w.Write(res)
}

// groupSearchResult maps a group from a subtree search onto a
// SearchResultEntry, deriving the entry DN from the search base.
func (s *server) groupSearchResult(ctx context.Context, g *pb.Group, dn message.LDAPDN, attrs message.AttributeSelection) (message.SearchResultEntry, error) {
	return s.groupAttributes(ctx, g, "cn="+g.GetName()+","+string(dn), attrs)
}

// groupAttributes maps a group onto a SearchResultEntry at the given
// full DN. The extra lookup needed to populate member is only
// performed when the client asked for that attribute, since it costs
// one NetAuth round trip per group.
func (s *server) groupAttributes(ctx context.Context, g *pb.Group, dn string, attrs message.AttributeSelection) (message.SearchResultEntry, error) {
	res := ldap.NewSearchResultEntry(dn)
	res.AddAttribute("objectClass", objectClasses...)
	res.AddAttribute("cn", message.AttributeValue(g.GetName()))
	res.AddAttribute("gidNumber", message.AttributeValue(strconv.Itoa(int(g.GetNumber()))))

	if !attributeRequested(attrs, "member") {
		return res, nil
	}

	members, err := s.c.GroupMembers(ctx, g.GetName())
	if err != nil {
		return res, err
	}

	memberList := []message.AttributeValue{}
	for i := range members {
		g := "uid=" + members[i].GetID() + ",ou=entities," + strings.Join(s.nc, ",")
		memberList = append(memberList, message.AttributeValue(g))
	}
	res.AddAttribute("member", memberList...)

	return res, nil
}