package ldap

import (
	"errors"
	"fmt"

	ber "github.com/go-asn1-ber/asn1-ber"
)

// Change operation choices
const (
	AddAttribute       = 0
	DeleteAttribute    = 1
	ReplaceAttribute   = 2
	IncrementAttribute = 3 // (https://tools.ietf.org/html/rfc4525)
)

// PartialAttribute for a ModifyRequest as defined in https://tools.ietf.org/html/rfc4511
type PartialAttribute struct {
	// Type is the type of the partial attribute
	Type string
	// Vals are the values of the partial attribute
	Vals []string
}

func (p *PartialAttribute) encode() *ber.Packet {
	seq := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "PartialAttribute")
	seq.AppendChild(ber.NewString(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, p.Type, "Type"))
	set := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSet, nil, "AttributeValue")
	for _, value := range p.Vals {
		set.AppendChild(ber.NewString(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, value, "Vals"))
	}
	seq.AppendChild(set)
	return seq
}

// Change for a ModifyRequest as defined in https://tools.ietf.org/html/rfc4511
type Change struct {
	// Operation is the type of change to be made
	Operation uint
	// Modification is the attribute to be modified
	Modification PartialAttribute
}

func (c *Change) encode() *ber.Packet {
	change := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "Change")
	change.AppendChild(ber.NewInteger(ber.ClassUniversal, ber.TypePrimitive, ber.TagEnumerated, uint64(c.Operation), "Operation"))
	change.AppendChild(c.Modification.encode())
	return change
}

// ModifyRequest as defined in https://tools.ietf.org/html/rfc4511
type ModifyRequest struct {
	// DN is the distinguishedName of the directory entry to modify
	DN string
	// Changes contain the attributes to modify
	Changes []Change
	// Controls hold optional controls to send with the request
	Controls []Control
}

// Add appends the given attribute to the list of changes to be made
func (req *ModifyRequest) Add(attrType string, attrVals []string) {
	req.appendChange(AddAttribute, attrType, attrVals)
}

// Delete appends the given attribute to the list of changes to be made
func (req *ModifyRequest) Delete(attrType string, attrVals []string) {
	req.appendChange(DeleteAttribute, attrType, attrVals)
}

// Replace appends the given attribute to the list of changes to be made
func (req *ModifyRequest) Replace(attrType string, attrVals []string) {
	req.appendChange(ReplaceAttribute, attrType, attrVals)
}

// Increment appends the given attribute to the list of changes to be made
func (req *ModifyRequest) Increment(attrType string, attrVal string) {
	req.appendChange(IncrementAttribute, attrType, []string{attrVal})
}

func (req *ModifyRequest) appendChange(operation uint, attrType string, attrVals []string) {
	req.Changes = append(req.Changes, Change{operation, PartialAttribute{Type: attrType, Vals: attrVals}})
}

func (req *ModifyRequest) appendTo(envelope *ber.Packet) error {
	pkt := ber.Encode(ber.ClassApplication, ber.TypeConstructed, ApplicationModifyRequest, nil, "Modify Request")
	pkt.AppendChild(ber.NewString(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, req.DN, "DN"))
	changes := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "Changes")
	for _, change := range req.Changes {
		changes.AppendChild(change.encode())
	}
	pkt.AppendChild(changes)

	envelope.AppendChild(pkt)
	if len(req.Controls) > 0 {
		envelope.AppendChild(encodeControls(req.Controls))
	}

	return nil
}

// NewModifyRequest creates a modify request for the given DN
func NewModifyRequest(dn string, controls []Control) *ModifyRequest {
	return &ModifyRequest{
		DN:       dn,
		Controls: controls,
	}
}

// Modify performs the ModifyRequest
func (l *Conn) Modify(modifyRequest *ModifyRequest) error {
	msgCtx, err := l.doRequest(modifyRequest)
	if err != nil {
		return err
	}
	defer l.finishMessage(msgCtx)

	packet, err := l.readPacket(msgCtx)
	if err != nil {
		return err
	}

	if packet.Children[1].Tag == ApplicationModifyResponse {
		err := GetLDAPError(packet)
		if err != nil {
			return err
		}
	} else {
		return fmt.Errorf("ldap: unexpected response: %d", packet.Children[1].Tag)
	}

	return nil
}

// ModifyResult holds the server's response to a modify request
type ModifyResult struct {
	// Controls are the returned controls
	Controls []Control
	// Referral is the returned referral
	Referral string
}

// ModifyWithResult performs the ModifyRequest and returns the result
func (l *Conn) ModifyWithResult(modifyRequest *ModifyRequest) (*ModifyResult, error) {
	msgCtx, err := l.doRequest(modifyRequest)
	if err != nil {
		return nil, err
	}
	defer l.finishMessage(msgCtx)

	result := &ModifyResult{
		Controls: make([]Control, 0),
	}

	l.Debug.Printf("%d: waiting for response", msgCtx.id)
	packet, err := l.readPacket(msgCtx)
	if err != nil {
		return nil, err
	}

	switch packet.Children[1].Tag {
	case ApplicationModifyResponse:
		if err = GetLDAPError(packet); err != nil {
			result.Referral = getReferral(err, packet)

			return result, err
		}
		if len(packet.Children) == 3 {
			for _, child := range packet.Children[2].Children {
				decodedChild, err := DecodeControl(child)
				if err != nil {
					return nil, errors.New("failed to decode child control: " + err.Error())
				}
				result.Controls = append(result.Controls, decodedChild)
			}
		}
	}
	l.Debug.Printf("%d: returning", msgCtx.id)
	return result, nil
}