package helpers

import (
	"errors"

	"forge.redroom.link/yves/meowlib"
	"forge.redroom.link/yves/meowlib/client"
	"google.golang.org/protobuf/proto"
)

// InvitationStep3ProcessAnswer is called by the initiator's background service when a
// step-2 answer (invitee's ContactCard) arrives via the invitation server poll.
// It decrypts the answer, calls InvitationStep3 to generate the initiator's full keypairs,
// and returns the peer and the initiator's ContactCard ready for STEP_3_SEND.
func InvitationStep3ProcessAnswer(invitation *meowlib.Invitation) (*client.Peer, *meowlib.ContactCard, string, error) {
	var invitationAnswer meowlib.PackedUserMessage
	if err := proto.Unmarshal(invitation.Payload, &invitationAnswer); err != nil {
		return nil, nil, "InvitationStep3ProcessAnswer: Unmarshal PackedUserMessage", err
	}

	peer := client.GetConfig().GetIdentity().Peers.GetFromInvitationId(invitation.Uuid)
	if peer == nil {
		return nil, nil, "InvitationStep3ProcessAnswer: peer not found", errors.New("no peer for invitation uuid " + invitation.Uuid)
	}
	// Guard against duplicate delivery (e.g., same answer from multiple servers).
	if peer.InvitationKp == nil {
		return nil, nil, "", nil
	}

	// Decrypt invitee's ContactCard using the initiator's temporary InvitationKp.
	usermsg, err := peer.ProcessInboundStep2UserMessage(&invitationAnswer, invitation.From)
	if err != nil {
		return nil, nil, "InvitationStep3ProcessAnswer: ProcessInboundStep2UserMessage", err
	}

	var inviteeCC meowlib.ContactCard
	if err := proto.Unmarshal(usermsg.Invitation.Payload, &inviteeCC); err != nil {
		return nil, nil, "InvitationStep3ProcessAnswer: Unmarshal ContactCard", err
	}

	myCC, peer, err := client.GetConfig().GetIdentity().InvitationStep3(&inviteeCC)
	if err != nil {
		return nil, nil, "InvitationStep3ProcessAnswer: InvitationStep3", err
	}
	client.GetConfig().GetIdentity().Save()
	return peer, myCC, "", nil
}

// InvitationStep3Message builds and returns the packed server messages that send the
// initiator's full ContactCard to the invitee through the invitee's servers (STEP_3_SEND).
func InvitationStep3Message(invitationId string) ([][]byte, string, error) {
	id := client.GetConfig().GetIdentity()
	peer := id.Peers.GetFromInvitationId(invitationId)
	if peer == nil {
		return nil, "InvitationStep3Message: peer not found", errors.New("no peer for invitation id " + invitationId)
	}

	step3msg, err := peer.BuildInvitationStep3Message(peer.GetMyContact())
	if err != nil {
		return nil, "InvitationStep3Message: BuildInvitationStep3Message", err
	}
	// Step-3 must NOT use DR or sym layers: the invitee hasn't received those
	// keys yet (they are carried inside this very message).  Use plain asym only.
	serialized, err := peer.SerializeUserMessage(step3msg)
	if err != nil {
		return nil, "InvitationStep3Message: SerializeUserMessage", err
	}
	enc, err := peer.AsymEncryptMessage(serialized)
	if err != nil {
		return nil, "InvitationStep3Message: AsymEncryptMessage", err
	}
	packedMsg := peer.PackUserMessage(enc.Data, enc.Signature)

	var results [][]byte
	for _, srvUid := range peer.ContactPullServers {
		srv, err := id.MessageServers.LoadServer(srvUid)
		if err != nil {
			continue
		}
		toSrvMsg := srv.BuildToServerMessageFromUserMessage(packedMsg)
		bytemsg, err := srv.ProcessOutboundMessage(toSrvMsg)
		if err != nil {
			continue
		}
		results = append(results, bytemsg)
	}
	if len(results) == 0 {
		return nil, "InvitationStep3Message: no reachable invitee server", errors.New("could not build message for any invitee server")
	}
	return results, "", nil
}

// InvitationStep4ProcessStep3 is called by the invitee's message processing when a UserMessage
// with invitation.step==3 is received. It finalizes the initiator's peer entry.
func InvitationStep4ProcessStep3(usermsg *meowlib.UserMessage) (*client.Peer, string, error) {
	if usermsg.Invitation == nil || usermsg.Invitation.Step != 3 {
		return nil, "InvitationStep4ProcessStep3: unexpected step", errors.New("expected invitation step 3")
	}
	var initiatorCC meowlib.ContactCard
	if err := proto.Unmarshal(usermsg.Invitation.Payload, &initiatorCC); err != nil {
		return nil, "InvitationStep4ProcessStep3: Unmarshal ContactCard", err
	}
	// Patch the invitation ID from the outer message in case it was not set in the CC.
	if initiatorCC.InvitationId == "" {
		initiatorCC.InvitationId = usermsg.Invitation.Uuid
	}
	if err := client.GetConfig().GetIdentity().InvitationStep4(&initiatorCC); err != nil {
		return nil, "InvitationStep4ProcessStep3: InvitationStep4", err
	}
	client.GetConfig().GetIdentity().Save()
	peer := client.GetConfig().GetIdentity().Peers.GetFromInvitationId(initiatorCC.InvitationId)
	return peer, "", nil
}

// InvitationStep4Message builds and returns the packed server messages that send the
// invitee's confirmation to the initiator through the initiator's servers (STEP_4).
func InvitationStep4Message(invitationId string) ([][]byte, string, error) {
	id := client.GetConfig().GetIdentity()
	peer := id.Peers.GetFromInvitationId(invitationId)
	if peer == nil {
		return nil, "InvitationStep4Message: peer not found", errors.New("no peer for invitation id " + invitationId)
	}

	step4msg, err := peer.BuildInvitationStep4Message()
	if err != nil {
		return nil, "InvitationStep4Message: BuildInvitationStep4Message", err
	}
	packedMsg, err := peer.ProcessOutboundUserMessage(step4msg)
	if err != nil {
		return nil, "InvitationStep4Message: ProcessOutboundUserMessage", err
	}

	var results [][]byte
	for _, srvUid := range peer.ContactPullServers {
		srv, err := id.MessageServers.LoadServer(srvUid)
		if err != nil {
			continue
		}
		toSrvMsg := srv.BuildToServerMessageFromUserMessage(packedMsg)
		bytemsg, err := srv.ProcessOutboundMessage(toSrvMsg)
		if err != nil {
			continue
		}
		results = append(results, bytemsg)
	}
	if len(results) == 0 {
		return nil, "InvitationStep4Message: no reachable initiator server", errors.New("could not build message for any initiator server")
	}
	return results, "", nil
}